Tuesday, February 10, 2015

Arctic Cold, cold, COLD!!!!

Public weather briefing

After a somewhat mild day with snow showers moving through, look for cloudy conditions with patchy freezing drizzle/flurries to continue through the night. Much colder weather is in store for the rest of the forecast period as arctic air funnels in from the north. Not much in the way of precipitation, except a small chance on Friday with a weak clipper system passing through. Temperatures then plummet Friday night into the extended with cold wind chills Saturday morning.


Tonight. Mainly cloudy. A slight chance of freezing drizzle or flurries. Nearly steady temperature around 29. Southeast wind shifting to west after midnight.

Wednesday. Mostly cloudy. Early highs around 28, then falling though the rest of the day. Blustery. Northwest winds 10-20 mph, with gusts to 30 mph.  

Wednesday night. Mostly cloudy. A slight chance of snow showers. Low around 4. Continued breezy. Northwest winds 10-20 mph, with gusts to 30 mph. Wind chills around 10 below.  

Thursday. Partly cloudy and cold. High around 10 and low around 2. Wind chills between 5 and 15 below. 

Friday. Not as cold. Slight chance of snow showers. Highs in the low 20s. Lows near 0. Southwest winds shifting to the northwest late in the night.

Outlook for the Weekend and Monday. Saturday looks to be very cold with bitterly cold wind chills approaching advisory criteria of 25 below in the morning. Highs around 5 and lows in the mid teens below. Sunday, continued cold. Highs around 10 with a slight chance of snow showers. Monday. Not as cold with highs in the low 20s. [CONFIDENCE: MEDIUM TO HIGH]

Forecast Discussion

Tonight thru Wednesday night. Initial 500 mb vorticity maximum to move northeast of the area as the next one comes in late tonight. The area will remain under a cyclonic flow during this time keeping the clouds around and patchy freezing drizzle/snow showers into Wednesday. The pressure gradient tightens in response to the deepening cyclone to the east which will make for a breezy and colder day on Wednesday. Wind chills Wednesday night become a factor but should stay above advisory criteria. A third 500 mb vorticity maximum comes through wednesday night producing only a small chance of snow showers. 

Thursday. Skies should be clear in response to subsidence behind departing trough. 850 mb temperatures will start out around -20 C, then slowly moderate to -14 with weak warm air advection ahead of the next trough. This will make for a cold day with highs to struggle to reach 10. 

Friday through Monday. A northwest flow aloft will continue with a couple of vorticity maximums to note. The first to arrive early friday with a very slight chance of snow showers. This one will produce a cyclone and rapidly deepen it over the eastern US which will produce a strong pressure gradient over the area on saturday. 850 mb temperatures will plummet to around -28 C at 18Z Saturday and remain there with only a slight moderation into Sunday. Temperatures on Saturday could struggle to reach 5 with bitterly cold wind chills. Highs Sunday will be around 10 with lighter winds. Temperatures will moderate some what by Monday with highs in the 20s. 

Ross Braatz
Brandon Lipp


  1. Ross and Brandon, very nice first discussion. I appreciate the substantial dynamical discussions you provided, particularly in this forecast discussion. However, be careful when describing orientation, direction of motion, etc of upper level waves, or other phenomena. This is especially true if you do not provide any graphic to provide your audience with context. For example, in this forecast discussion, you mention that a vort max will move northeast of our area. Do you mean southwesterly flow, or that the position of the trough will be to our northeast? This is the sort of question your reader is left with if you don't use accurate descriptive language, which can ultimately diminish the quality of your discussion. As I said before, I appreciate the amount of dynamics you incorporated into your post, but take caution that your analysis isn't simply a narration of the model(s) you're using. If your audience wanted to see what the models were showing, they would look for themselves... but they came here to hear your opinion! All this being said, I am impressed with your first round and look forward to seeing what you put together for round two!

    QUESTION: We didn't quite get the freezing drizzle (as we discussed in class during your map discussion), but later in the evening around 9pm we did get some graupel-like precipitation. This was associated with a very small band of precipitation that extended southwest of the Madison area, west of the primary precipitation band that NEXRAD showed during your map discussion. Given our conversations during your map discussion on Tuesday, can you comment on where the small band could have come from since it was west of the primary precipitation band...in addition, what do you think was significant about the layer over Madison if graupel fell instead of freezing drizzle?

  2. For one thing, I did notice on my walk home after class (around 5:30) after our discussion, there was a tiny bit of graupel falling. The second band was what we expected to impact our area, but as flurries, not graupel. I'd venture a guess that some kind of wave structure, or perhaps conditional symmetric instability contributed to the formation of the two mostly parallel bands of precipitation. As for the reason that graupel fell instead of freezing rain, since we made the assumption that NEXRAD was picking up the melting level aloft in class, I figure that the drops fell at a slow enough speed to refreeze before hitting the ground.


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