Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service La Crosse WI
457 am CST Fri Dec 13 2019
Short term...(today through Saturday night)
issued at 216 am CST Fri Dec 13 2019
Ridge of high pressure drifting across the region early this
morning. However, stratus is being stubborn, trapped under
subsidence inversion. Some pockets of clearing here and there were
noted but have a feeling there will be the possibility of some fog
formation in those area or stratus re-forming given the very moist
boundary layer in place. Otherwise, temperatures across the area
ranged from single digits/lower teens in the clearing to the lower 20s
under cloud cover.
For today into this evening will be watching an incoming mid-level
positive vorticity anomaly pushing in from the Dakotas along with
steepening mid-level lapse rates. This is expected to produce
scattered/periods of snow showers later this morning into early this
evening as the wave pushes through -latest WRF models/BUFKIT
soundings support this as well. Model soundings also show a loss of
cloud ice in stratus behind the wave this evening/overnight, so
could have a little freezing drizzle to contend with -at least
through the evening/very early morning hours with lingering albeit
weak lift. As far as snow amounts, looks like a dusting to an inch
of accumulation with highest amounts looking to be north of I-90.
Will have to keep an eye on this for possible travel impacts. Highs
today will be in the low 20s to low 30s with lows tonight falling
into the teens/lower 20s.
Colder/modified Arctic air filters into the areas Saturday on brisk
northwest winds. Look for highs not budging much from overnight lows.
Northwest winds 10-20 mph will produce wind chills in the single
digits below and above zero. Could also see some pockets of very
light snow east of the Mississippi River.
Long term...(sunday through thursday)
issued at 216 am CST Fri Dec 13 2019
Some pockets of clearing skies expected Saturday night with high
pressure building in. Otherwise, very cold with lows dipping down
into the single digits above and below zero.
Very cold conditions continue Sunday into Sunday night as high
pressure settles overhead. Plan on highs Sunday only in the single
digits and teens despite mostly sunny skies, and lows Sunday night
ranging from the single digits below to teens above.
A small chance of some light snow moves into portions of northeast
Iowa/far southern WI Monday as low pressure makes its way through the
Ohio River valley. Looks mostly cloudy for US otherwise with highs
in the teens/20s.
Tuesday looks dry but then a weak system in northwest flow aloft
will produce light snow chances mainly northeast of I-94 on
Wednesday. Colder than normal air remains over our region with highs
mainly in the teens/ lower 20s.
Thursday will see some mid-level ridge amplification across the
central Continental U.S. Into our area which looks to moderate temperatures
some/not much into the 20s/lower 30s.
Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 458 am CST Fri Dec 13 2019
Another day with lots of MVFR/IFR conditions for both airports. A
short wave trough will move across the region today with a band of
snow. The snow should be intense enough for a short period to
produce IFR conditions at both airports. Ahead of the snow, look
for the lower clouds with MVFR/IFR ceilings to remain in place.
Once the snow moves through, the visibility will improve but
little overall change in the ceilings are expected through the
night. In addition, there could be some on and off light freezing
drizzle through the night, but confidence in this occurring is not
high enough to include in the forecast at this time.