The November Gloom Continues

Public weather briefing

After a generally cloudy Tuesday, clouds will stick around all week with slight chances of light snow Wednesday night and Friday. Temperatures will be warmer than they have been most of the month, but will remain below average for the work week. Thanksgiving will be much colder than normal, as temperatures will be in the lower 20's. Milder weather can be expected for game day on Saturday with temperatures around 40 degrees.

Forecast 

Tonight. Overcast conditions continue with some spotty clearing. Winds become calm. Low in the lower teens. 

Wednesday. Generally cloudy skies with a high in the upper 20's. Light winds around 5 mph.

Wednesday night. Slight chance of snow showers with accumulations of less than one half inch. Low in the middle teens. Winds increasing to around 10 mph.

Thursday. Mostly sunny skies with a high in the lower 20's. Winds around 5 mph.

Friday. Cloudy skies with a slight chance of snow. High in the lower 30's. Winds around 10 mph.

Outlook for Saturday through Monday. Cloudy skies will remain in place with highs consistently in the upper 20's to low 30's except for a brief warm up to 40 degrees on Saturday which will make for a decent game day. Winds 5-15 mph throughout the weekend into Monday.

[CONFIDENCE: MEDIUM]

Forecast Discussion

The cyclone located in the northern plains will dominate our weather moving through the middle of the work week as it propagates to the southeast through Iowa, Missouri, and Tennessee. Cold air advection and some vorticity advection will lead to snow Wednesday night. Strong cold air advection will lead to a cold day on Thursday while warm air advection makes its way into our area on Saturday with the associated cyclone. A chance of snow on Friday is associated with low amounts of vorticity advection. High pressure will dominate our area over the weekend although a few low pressure systems will be in our vicinity.

Brandon Lipp

Josh Weber

 

Less Cold, But Still Cold...

Public weather briefing

After a snowy Monday, clouds will stick around all week but we will remain dry. Temperatures will be warmer than they have been most of the month, but will remain below average for the work week. Thanksgiving will be much colder than normal, as temperatures may not break 20 degrees. Milder weather can be expected for the weekend and temperatures will be near 40 and may briefly be above average. 

Forecast 

Tonight. Snow will continue into the overnight hours with new accumulation less than one inch. Winds will be out of the northwest around 10 mph. Low in the upper teens.

Tuesday. Snow will end around 6 am, but skies will remain overcast. Winds will be northwesterly around 5 mph. High in the mid 20s. 

Tuesday night. Overcast conditions continue. Winds become calm. Low in the mid teens. 

Wednesday. Skies will remain cloudy. Winds will be variable around 5 mph. High around 30.

Thursday. More clouds. Temperatures get significantly with high temperatures around 20.

Outlook for Friday through Sunday.  Clouds skies will remain all weekend, and there will be a slight chance of precipitation each day. Temperatures will be mild. Highs in the lower 30s for Friday before climbing near 40 on Saturday, then dropping back down to to the 30s for Sunday. Lows will be in the teens Friday morning and  in the mid 20s Saturday and Sunday.  [CONFIDENCE: MEDIUM]

Forecast Discussion

The influence of the cyclone in Ontario weakens Monday night as snow moves out of the area. Cold air advection on Tuesday will keep temperatures cold. Cyclonic flow from a low pressure system in the great plains will provide some temporary warm air advection Wednesday, but the flow will again become northwesterly and cold air advection will dominate on Thursday. There will be relatively little vertical motion until Friday, when weak vorticity advection will bring a chance for a flurry. There will be additional periods of vorticity advection Saturday and Sunday that may result in a shower or flurry respectively.

Brandon Lipp
Josh Weber

Bundle Up For Badger Football

Public weather briefing

The weather heading into this weekend will leave you digging through storage to find your winter jacket and gloves. An unseasonably cold air mass from the north is here to stay, and will cause temperatures over the weekend to plummet below freezing. This air mass closely resembles the pattern that dominated last winter and caused perpetual frigid conditions through much of January. Intermittent snow overnight Saturday and into Sunday morning will accompany these chilly conditions, with accumulation ranging from 1"-2", and looks give way to light flurrying conditions through Monday. Winds look to be moderate out of the north and west. Kickoff temperatures on Saturday will near 30 degrees. 

Forecast 

Tonight. Continuing slight chance of flurries early in the evening. Cloudy overnight. Low of 18 with light winds from the northwest.

Friday. Mix of sun and clouds with high temperatures nearing 30 degrees. 

Friday Night. Clouds roll in overnight. Winds light ant from the northwest. Low of 19. 

Saturday. Bundle up for Badger Football! Slight chance of snow later in the afternoon/evening. Accumulation nearing 1". 

Sunday. Accumulating snow (up to 1") through the morning will give way to cloudy skies in the afternoon. Highs nearing the middle to upper 20s.

Outlook for Sunday through Tuesday. Cold temperatures persist and don't look to reach above freezing through the early part of next week. Slight chance of flurries late Monday night. [CONFIDENCE: MEDIUM]

Forecast Discussion

A maturing surface cyclone centered east of the Great Lakes will continue to advect cold air into our area through the rest of the week, at which point flows become more zonal. The upper trough seen in the GFS at 700mb made its way through southern Wisconsin over Wednesday night and into Thursday morning,, causing flurries throughout the afternoon with little accumulation. This can be attributed to a very slight amount of positive vorticity advection from the plains.

 

Late Thursday into Friday, the 700mb vertical velocity switches to negative over our area. This subsiding air will keep conditions dry into Friday, at which point an arctic air mass to our west will drop night time temperatures below 20.

 

Come Saturday, slight warm air advection from the Great Plains can be noted as well as increased increased vertical motion at 18Z Saturday. The models are in moderate agreement, hence our medium forecast confidence. GFS and NAM both suggest snow falls nearing 2 inches, while the Canadian model only 1. By Sunday, the 500mb trough axis will move on east from our area. Slight vertical motion at 700mb over the area at 6Z and 9Z Sunday suggest more flurries which taper off later through the night.

 

The beginning of the week unfortunately will be marred with more wind out of the northwest and thus cold temps. The 850mb at 18Z Monday shows Wisconsin situated between a in geopotential minimum northeast of the Great Lakes and a ridge to our southwest. No indication of instability, vertical motion, or precipitation early next week.

 

All in all, Arctic air continues to slam the forecast are over the weekend with weak favorable dynamic conditions for measurable snow Saturday into Sunday.

Rebecca Schultz

Daniel Knuth

Time to Find Your Parka

Public weather briefing

The weather over the weekend just may rationalize the playing of Christmas music in the middle of November. An unseasonably cold air mass from the north will give conditions more like mid to late December for the forecast period. This feature closely resembles the one which led to the extremely cold weather in the U.S. last winter. Intermittent snow on Saturday and Sunday morning (totals near 1 inch) will give way to light flurrying conditions through Monday. Winds will continue to be moderate out of the north and west. But the highlight (more like a lowlight) will be the cold temperatures, which aren't expected to rise above 30 over the forecast period.

Forecast 

Tonight. Chance of flurries with winds 5-10mph out of the northwest. Low of 20.

 

Thursday. Slight chance of flurries in the morning with moderate winds around 10mph. High of 30.

 

Thursday night. Potential light flurries early in the evening then becoming cloudy. Light winds from the northwest and low of 18.

 

Friday. Mix of sun and clouds with high temperatures flirting around 30 degrees.

 

Saturday. Bundle up for Badger football! Slight chance of snow and highs again near 30 degrees.

 

Outlook for Sunday through Tuesday. Chances for snow through Saturday night and Sunday morning totalling roughly an inch. Cold temps persist, rarely reaching the 30s. [CONFIDENCE: MEDIUM]

 

 

Forecast Discussion

A maturing surface cyclone centered east of the Great Lakes will continue to advect cold air into our area through the rest of the week, at which point flows become more zonal. An upper trough seen in the GFS at 700mb will make its way through southern Wisconsin over Wednesday night, which may give rise to light flurries which will continue into Thursday. This can be attributed to a very slight amount of positive vorticity advection from the plains.

 

Late Thursday into Friday, the 700mb vertical velocity switches to negative over our area. This subsiding air will keep conditions dry into Friday, at which point an arctic air mass to our west will drop night time temperatures below 20.

 

Come Saturday, slight warm air advection from the Great Plains can be noted as well as increased increased vertical motion at 18Z Saturday. The models are in moderate agreement, hence our medium forecast confidence. GFS and NAM both suggest snow falls nearing 2 inches, while the Canadian model only 1. By Sunday, the 500mb trough axis will move on east from our area. Slight vertical motion at 700mb over the area at 6Z and 9Z Sunday suggest more flurries which taper off later through the night.

 

The beginning of the week unfortunately will be marred with more wind out of the northwest and thus cold temps. The 850mb at 18Z Monday shows Wisconsin situated between a in geopotential minimum northeast of the Great Lakes and a ridge to our southwest. No indication of instability, vertical motion, or precipitation early next week.

 

All in all, Arctic air continues to slam the forecast are over the weekend with weak favorable dynamic conditions for measurable snow Saturday into Sunday.

Daniel Knuth

Rebecca Schultz

Special Update: Significant winter weather event for northern WI, unseasonable cold mid-to-late week statewide

Public weather briefing

The winter weather event highlighted in last week's blog posts is emerging to be a threat for northern Wisconsin. As of Sunday evening, it appears that southern Wisconsin will not see much in the way of snow.  The northern half of the state could see snowfall approaching a foot by Tuesday evening.

Light snow and rain will develop over southern Wisconsin tonight and change to all rain in the early morning hours before tapering off in the mid-morning. With air temperatures at or above freezing and the ground still relatively warm, snow accumulation overnight in the southern half of the state is unlikely. Snow will develop in the far north by early morning and continue through most of Monday.  Driving in northern Wisconsin will likely become difficult with time by early afternoon. 

As a cyclone develops to our southwest on Monday afternoon and moves northeast - passing just south of Madison, another round of precipitation is possible Tuesday morning.  At that time, with falling temperatures, a brief period of light snow is possible.  

Significantly below normal temperatures (15F to 20F below normal) are expected for the latter half of the week into the weekend as a cold anticyclone slowly moves into the upper Midwest.  The next chance for measurable precipitation (likely in the form of snow) is for Saturday.

Forecast 

Tonight. Cloudy with light rain and drizzle. Light northeast winds before midnight, becoming easterly by dawn. Lows near freezing.

Monday. Cloudy with rain and rain showers ending early. Less than 0.03" liquid equivalent during the day. Winds east-southeast 10-15 mph. High 50.

Monday night. Cloudy with rain and rain showers, especially north of Madison.  Less than 0.05" liquid equivalent. Temperatures slowly falling from the mid-40's into the 30's by dawn.

Tuesday. Rain changing over to snow during the morning with little or no accumulation. Less than 0.1" liquid equivalent. Winds southwest shifting to northwest at 10 to 15 mph with temperatures falling from the 40's back into the lower 30's by mid-afternoon.   Low 15-19.

Wednesday. Mostly cloudy with a few sunny breaks. Snow showers possible. High 25-28F. Low 15F

Outlook for Thursday through Saturday. Partly cloudy Thursday and Friday. Light snow possible on Saturday.  Highs in the mid 20's Thursday, upper 20's to near 30 on Friday and in mid 30's on Saturday. Low's in the teens through the period. [CONFIDENCE: HIGH]

Forecast Discussion

A cold front will stall just south of Madison tonight before gradually retreating northward as a warm front early tomorrow morning.  Prior to the front's northward movement, a broad deformation pattern will begin to tighten the thermal gradient associated with the front.  The thermally direct circulation about the intensifying front will be associated with a band of light rain and snow starting over the southern half of the state overnight. 

The forecast challenge for tomorrow is the position of this front during the day as a surface and lower tropospheric cyclone develops to our southwest. North of the front, cold dry air will be advected southward. This dry air and associated evaporational cooling will thwart significant motion of the surface front northward. At the surface, significant warm advection ahead of the developing cyclone will push temperatures above 50F in southeastern WI. Aloft, all of sourthern WI will be in the warm sector of the 850 hPa cyclone. As a consequence, warm advection will push the 850 hPa 0C isotherm well north and east of the Dells making the largest threat for significant frozen or perhaps freezing precipitation likely in the northwestern and north-central parts of the state. The 0000 UTC 10 November NAM and 1800 UTC 9 November GFS are similar in this scenario, with the more recent run of the NAM more aggressive in bringing the warm air into the southern half of the state.

Following the passage of the cyclone on Tuesday, an arctic anticyclone will slowly build southward into the upper Midwest. Cold advection on the periphery of the anticyclone will keep temperatures well below average for the week. Broad cyclonic flow aloft will support the development and maintenance of low clouds on Wednesday. Significant precipitation is not anticipated for the latter half of the week.

Michael C. Morgan

Coldest Air Of The Season On The Way But, Possible Accumulating Snow First

Public weather briefing

Much cooler weather has settled into southern Wisconsin and it's here to stay. Winds will die down tonight and skies will clear allowing for good radational cooling conditions. Friday should start out sunny, but it will become mostly cloudy with a chance of showers late at night. Below normal temperatures are still excepted for the weekend with highs only in the 40s. Saturday looks to be the best day, but cool. Clouds will once again increase Sunday as attention turns to possible accumulating snow for Monday into Tuesday. Look for much colder conditions by Wednesday, With snow cover and an arctic airmass in place, highs Wednesday and Thursday may struggle to reach 30.

Forecast 

Tonight. Becoming mostly clear. Low around 26. Light winds.

Friday. Partly sunny, then becoming cloudy by afternoon. High around 42. Light wind becoming south around 5 to 10 mph.

Friday night. Mostly Cloudy. A chance of showers. Low around 36. South winds 5-10 mph turning northwest after midnight. Chance of rain 40%. Rainfall less than a tenth of an inch.

Saturday. Mostly cloudy skies early giving way to mostly sunny skies. High near 41. Breezy. Northwest winds 15-20 mph, with gusts to 30, mainly before noon.

Sunday. Partly sunny. High around 47. Low around 30. Southwest winds 10 to 15 mph shifting to the north late.

Outlook for Monday through Wednesday. Monday, snow developing by noon possibly becoming mixed with rain late. Highs on Monday in the low 30s. Veterans Day, light snow early giving way to partly cloudy skies and cooler with highs only around 30 and lows around 20. Wednesday, Mostly sunny, continued cool. Highs in the upper 20s and lows in the upper teens. [CONFIDENCE: LOW TO MEDIUM]

Forecast Discussion

Overnight: Subsidence and decreasing winds behind departing cyclone, will make for good radiational cooling conditions. 850 mb temperatures will hover around -5C allowing lows to dip to around 25. 

Friday and Saturday night: Friday will start out mostly sunny, but increasing warm air advection ahead of the next shortwave will increase clouds as the day wears on. 850 mb temperatures rise to 4 to 6 C and 925 mb temps rise to around 3 C. With decent  mixing, highs on Friday should rise into the low 40s. Only a slight chance of rain Friday night as both the NAM and the GFS have a cold front pushing through after midnight Friday night. The new 00Z NAM shows continued warm air advection and positive vorticity advection as well as moderate Q-vector convergence right along the front. 18Z GFS showing positive vorticity advection and warm air advection, but not as much as the NAM. After frontal passage, clouds will clear by midday Saturday along with subsidence behind shortwave to make for a cool and breezy day. Winds will gust to 30 mph behind front then subside by late afternoon on Saturday. Weak warm air advection develops Saturday night ahead of yet another weak shortwave.

Sunday through Veterans Day: Sunday looks to be the warmest of the next 5 days as weak warm air advection coninues with southwest winds. New NAM and GFS disagree on tuning of weak cold front for Sunday. GFS has it coming through in the morning, while the NAM has it coming though later in the afternoon. If earlier frontal passage occurs, temperatures will be cooler then current forecast. Monday and Tuesday the forecast is tricky. 18Z GFS run came into agreement with its last run and sets up a baroclinic zone just to our south. A rather potent shortwave will move along this zone causing a 850mb cyclone to develop ahead of it and move it northeast to over the area by 06Z Tuesday. Warm air advection along with positive vorticity advection will help cause vertical motion along this zone. GFS has precip in the form of snow to develop by 18Z Monday and continue Tuesday morning before tapering off. Liquid estimates are between .3 and .5 inches which would be about 4-5 inches. The ECMWF shows a much bigger storm system with a well organized surface cyclone passing south of the area across northern Illinois. This is a favored track for significant snow for southern Wisconsin if gulf of mexico moisture can get tapped. This run was similar to the 12Z run on Tuesday placed the surface cyclone in almost the same spot. After the storm exits, an arctic airmass will drop into the northern plains and upper midwest with 850 temps dropping to -12 to -14. Highs on Tuesday and Wednesday may struggle to reach 30 especially with a fresh snow pack. 

Ross Braatz   

Cooler Weather on the Way with Chances for Snow?

Public weather briefing

Rain showers will continue for the overnight hours. Turning cooler Thursday morning as winds pick up from the north and the precipitation could end as some flurries or flurries/drizzle. Staying cloudy most of the day and winds will ease as the day wears on. Next chance of precipitation comes Friday night as a cold front passes through area late in the evening with only a moderate chance of light showers. Another cold arctic airmass plunges in behind the frontal passage on strong north winds and below normal temperatures Saturday and Sunday. Highs running around 8 degrees below normal for the weekend. Attention then turns to possible storm system/frontal boundary for Monday into Veterans Day.  

Forecast 

Tonight. Showers likely, mainly before 3 am. Lows around 37. South winds around 10 mph shifting to the northwest late. Chance of precipitation 80%. Rainfall amounts less than a tenth of an inch. 

Thursday. Chance of rain and snow in the morning, then cloudy. High around 41. Breezy, with a north wind 15-20 mph, with gusts to 30, mainly before noon. Chance of precipitation 50%. Rainfall amounts less then a tenth of an inch. Little or no snow accumulation expected.  

Thursday night. Clearing. Lows around 26. Light northwest wind. 

Friday. Sunny in the morning, then turning partly sunny in the afternoon. Highs around 43. Light winds becoming south in the afternoon.  

Saturday. A slight chance of showers early, becoming mostly sunny in the afternoon. Highs in the lower 40s. Breezy early. North winds 15-20 mph. Chance of rain 20%. Rainfall amounts less than a tenth of an inch.

Outlook for Sunday through Veterans Day. Sunday mostly sunny, slight chance of rain at nigh. Highs in the lower 40s and lows in the lower to mid 30s. Monday chance of rain and snow. Highs in the lower to mid 40s. Veterans day mostly cloudy. Cooler highs in the low 30s. [CONFIDENCE: LOW TO MEDIUM]

Forecast Discussion

Overnight: Rain showers will overspread the area from the southwest with the approaching cyclone from the west within an area of moderate upward vertical motion in association with warm air advection at 850 mb. 850 mb temperatures hovering between 2 and 4 degrees C will drop to below 0 by 12Z changing an light rain or drizzle to flurries with little or no accumulation excepted. 

Thursday thru Friday Night: As the surface cyclone mentioned above passes to the east, it will deepen slightly producing a strong pressure gradient between it and the surface anticyclone building into the central plains. Strong cold air advection will cause highs Thursday to be cooler then today. Only low 40s excepted with 925mb temps only around -2 C. Dryer air an subsistence behind the shortwave will clear things out Thursday night into Friday. Clouds will increase Friday afternoon with southerly winds and warm air advection ahead of the next shortwave diving in from the northwest. NAM and GFS are in very good agreement in bringing a cold front though the area after midnight Friday night. There is positive vorticity advection with neutral temperature advection seen on both NAM and, to a lesser extent, the GFS, at 06Z Saturday, so chance of rain will be in the forecast late Friday night.

Saturday and beyond: Negative vorticity advection occurs Saturday as low levels dry out on breezy northwest winds and cold air advection producing downward vertical motion and an end to any precipitation. 850 mb temps drop to -8C on the NAM and -6 on the GFS. A blend will be perferred for highs on Saturday. Sunday looks to be sunny but cool with slightly warmer temperatures at 925mb climb to around 2C so will lean highs around 40. Monday is interesting because the GFS and the ECMWF diverge with the evolution of a winter event. 18Z run of the GFS has a baroclinic zone setting up just south of the area and a weak low pressure moves northeast along this boundary and produces an area of light snow with the 5400 m thickness line right overhead. The 12Z ECMWF run however, shows a well organized surface cyclone moving in from the central plains. ECMWF is a little warmer than the previous day's run so low confidence in this system. Will lean toward ECMWF because of the run to run consistently. After that, strong cold air advection ensues after departing surface cyclone or baroclinic zone depending on model. Coldest air of the season to be seen after Monday system as 850mb temps drop to -14 to -16 on GFS and -12 on ECMWF. Highs on Veterans day may struggle to reach 30 with some wind to put even more of a chill in the air. Stay tuned.     

Winter-like Pattern Setting Up

Public weather briefing

Diminishing clouds during the afternoon will lead to a cool night across the area tonight.  Temperatures drop back into the mid 30's with clear skies and light winds out of the southwest. Attention turns to a developing area of low pressure currently entering the US in northern Montana.  This system will continue to dive southeastward Wednesday night into Thursday.  The precipitation will begin as rain mainly after 6pm tomorrow, but should transition over to a wintry mix overnight, with a chance for snow showers by Thursday morning as the system passes to our east.  Highs Thursday will be significantly cooler, struggling to reach 40 with brisk northwesterly winds approaching 20mph.  A relatively dry cold front moves in Saturday morning, accompanied by well below normal temperatures, with highs in the upper 30's both Saturday and Sunday. Significant winter weather is possible as we head into the next work week.

Forecast

Tonight. Mostly Clear.  Low 35.  Southwest winds at 5 to 10 mph.

Wednesday. Increasing clouds. PM rain showers.  High 55.  Southerly winds around 10 mph.

Wednesday Night. Rain, changing to a wintry mix. Low 35. South wind 5-10mph, shifting westerly during the overnight. Precipitation amounts around a tenth of an inch.  Little snow accumulation expected. 

Thursday. Morning show showers.  Cloudy skies, high around 40.  Gusty winds out of the north at 15 to 25 mph.

Friday. A few passing clouds. High around 43. Winds light and variable

Outlook for Saturday through Monday.  Slight chance of precipitation Friday night into Saturday.  Unseasonably cold Saturday and Sunday, highs around 40. A strong area of low pressure looks to impact the Great Lakes Monday into Tuesday, with accumulating snow possible. [CONFIDENCE: LOW]

Forecast Discussion

Clear skies expected tonight. Dew points sit around 36 degrees, which should allow lows to fall back into the mid 30 overnight. Winds out of the southwest allow for warm air advection during the afternoon.  Increasing clouds throughout the day should suppress daytime heating, even with a 850mb temperature around 6C. 

The next significant cyclone pushes in for Wednesday into Thursday as a strengthening area of low pressure drifts southeast from southern Canada. Localized warm air advection ahead of the system will warm us up into the mid 50's and suggest upward vertical motion.  The GFS is outputting significant Q vector convergence along the track of the system.  Consequently, vertical motion can be expected and is forecasted by both the NAM and GFS.  Both models have a chance of showers late Wednesday evening ahead of the passing cyclone. As the cyclone pulls away from Southern Wisconsin, cold air advection will result from the shifting of winds on the back side. While there is cold air advection, it is not localized. A significant amount of positive vorticity advection is forecasted by the NAM and GFS, which will spawn the chance of snow showers with light accumulations, as 850mb temperatures are below zero and 1000-500mb thickness values drop to 5340 meters. The GFS plots upward vertical motion directly over Madison Thursday morning.  

Models generally agree on the extent of the cold for Saturday and Sunday behind a cold front expected to pass through the area Saturday morning. Cold weather can be expected with highs in the upper 30's to around 40.  The average temperature over this period is 48.

Significant forecast challenges exist at the end of the forecast period. The ECMWF shows a full blown winter storm with a sea level pressure of below 998mb and half a foot of snow.  Meanwhile, the GFS plots a similar system but passed the surface low pressure north of Madison, giving northern Wisconsin several inches of snow.  This system bears watching.

Below is a plot from The College of DuPage.  It shows the significant winter storm forecast by the EURO model Tuesday morning, and substantial cold air advection on the back side of the cyclone as the pushes east.

Furthermore, here is the 12z ECMWF snow output for the Monday possible winter storm, can we all gasp out a collect "WOW":

And the 18z GFS:

Courtesy of Weather bell.

Morning Showers Clearing for your Election Day

Public weather briefing

Scattered showers move in for the overnight associated with a cold front that will pass through around 3:00am or 4:00am Tuesday morning.  A couple tenths of an inch of rain can be expected, with rain coming to an end around the time the polls open Tuesday morning.  The winds shift to a more northerly component following the passing of the front, ushering in cooler, drier air.  Winds could gust as high as 20 to 30 mph, with sustained winds around 10mph. A few breaks in the clouds can be expected during the afternoon hours.  Attention turns to a developing area of low pressure currently located just off the coast of British Columbia.  This system will dive southeastward Wednesday night into Thursday, bringing a chance for snow showers Thursday morning as the system passes to our east.  Highs Thursday will be noticeably cooler, reaching only the mid forty's with brisk northwesterly winds approaching 20mph sustained.  A relatively dry cold front moves in Friday night into Saturday,
accompanied by well below normal temperatures, with highs in the 30's both Saturday and Sunday.

Forecast 

Tonight. Showers, low 49.  Winds out of the south shifting to the west, 10 to 15 mph. Total precipitation 0.20 inches.

Tuesday. Decreasing clouds.  High 54.  Winds northwest at 10 to 15 mph.

Tuesday night. Mostly Clear.  Low 35.  West winds at 5 to 10 mph.

Wednesday. Increasing clouds. PM rain showers.  High 56.  Southerly winds around 10 mph.

Thursday. Morning wintery mix.  Cloudy skies, high around 45.  Gusty winds out of the north at 15 to 25 mph.

Outlook for Friday through Sunday.  Cool temperatures Friday with highs in the mid 40's.  Chance of precipitation Friday night with a better chance as we head into Monday.  Unseasonably cold Saturday and Sunday, highs in the 30's. [CONFIDENCE: MEDIUM]

Forecast Discussion

A surface cyclone will pass to our north tonight with a strong cold front pushing through southern Wisconsin around 3:00 or 4:00am tonight. A linear band of showers accompanied by a line of baroclinicity and positive vorticty advection will affect the area through about 4am, according the hrrr and hi-res NAM. As the cyclone passes to the east, cold air advection will ensue with northwesterly winds. An area of high pressure and subsidence will push into the area for Tuesday into Wednesday.

The next significant cyclone pushes in for Wednesday into Thursday as a strengthening area of low pressure drifts southeast from southern Canada. Localized warm air advection ahead of the system will warm us up into the mid 50's and suggests upward vertical motion. The GFS and NAM both have a chance of showers late Wednesday evening ahead of the passing cyclone. As the cyclone pulls away from Southern Wisconsin, cold air advection will result from the shifting of winds on the back side. While there is cold air advection, it is not localized. A significant amount of positive vorticity advection is forecasted by the NAM and GFS, which will spawn the chance of snow showers with light accumulations, as 850mb temperatures are below zero and 1000-500mb thickness values drop to 5340 meters. The GFS plots vertical motion directly over Madison Thursday morning. A dusting to maybe an inch of snow is possible early in the morning Thursday. The image below is a plot from the 18 UTC GFS initialized November 3rd, 2014, valid 06 November at 18 UTC. It shows the chance of snow showers behind clipper. The NAM lags the system relative to the GFS by about 18 hours.

 

Joe Nettesheim
Tanner Verstegen