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
