Scientific Forecaster Discussion
fxus63 karx 110905
Area forecast discussion
National Weather Service La Crosse WI
304 am CST Wed Dec 11 2019
Short term...(today through Thursday night)
issued at 304 am CST Wed Dec 11 2019
GOES infrared/water vapor imagery showing a mid level wave pushing
southeast across Iowa. Light snow was falling across portions of
northwest into central Iowa with just some altocumulus across our
area, mainly south of I-94. Otherwise, temperatures as of 3 am this
morning ranged from -12 at Medford WI under clear skies, to 12 above
at Prairie Du Chien under the blanket of clouds.
Look for this mid-level wave to pass southeast of the area this
morning as high pressure builds in/drifts across the area. A mostly
sunny day is then on tap for today with increasing clouds late in
the afternoon ahead of incoming area of low pressure over the
Dakotas. Plan on another abnormally cold day with highs only in the
single digits/teens above zero. Will keep Wind Chill Advisory going
til noon today for areas along/north of I-94 as wind chills moderate
from early morning readings in the -25 to -35 range.
Attention then turns to accumulating snow late tonight into Thursday
as that aforementioned area of low pressure tracks southeast from
the Dakotas through our area. GFS/NAM showing a respectable push of
850mb transport and fairly strong isentropic upglide moving in after
midnight with forcing maximizing unfortunately during the morning
commute for areas mainly north of I-94. Right now, it looks like 2
to locally 5 inches of snow is possible north of I-94 with highest
amounts anticipated north of Highway 10 across Clark/Taylor
counties. Further south, down around the I-90 corridor, around of
inch of snow is expected. Will go ahead an Post a Winter Weather
Advisory for Clark and Taylor counties where 3-5 inches is expected
-in effect from midnight tonight through 3 PM Thursday. Otherwise,
plan on highs topping off in the 20s/across north central WI to the
mid/upper 30s across northeast Iowa into far southwest WI.
High pressure builds in Thursday night for a brief respite with
overnight lows falling into the teens/mid 20s.
Long term...(friday through tuesday)
issued at 304 am CST Wed Dec 11 2019
A slow moving/elongated area of low pressure will move through the
area Friday into Saturday for a prolonged bout of light snow
chances. Right now looks like there could be upwards of an inch or
two through this period along with perhaps some rain/snow mix at
times across portions of northeast Iowa/southwest WI. Highs Friday are
expected to top off in the mid 20s to mid 30s, turning colder
Saturday with readings in the mid teens to mid 20s.
Arctic air oozes back into the area Saturday night through Sunday.
Look for lows Saturday night in the single digits below and above
zero with highs Sunday in the single digits/teens above.
Modified Arctic airmass remains over the area through Tuesday. Will
have to keep an eye on cyclogenesis over the Southern Plains Monday.
Latest European model (ecmwf) keeps this low south of US but latest GFS wants to
graze our area with northwest periphery of the storm later Monday
into Tuesday. Highs Monday and Tuesday look to be in the teens to
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1015 PM CST Tue Dec 10 2019
Cigs/wx/vsby: upper level shortwave going to bring mid level deck of
VFR clouds to taf sites overnight, exiting around 12z Wed. Generally
sky clear/scattered through the day before another upper level trough returns a
mid deck to the region. Expecting a lowering of this deck for Thu
morning, along with some light pcpn chcs.
Winds: more southwest overnight, then west/northwest for Wed -
generally under 10 kts. Staying light but southeast Wed evening,
then increasing overnight as sfc pressure gradient tightens.
WI...Wind Chill Advisory until noon CST today for wiz017-029-032>034.
Winter Weather Advisory from midnight tonight to 3 PM CST
Thursday for wiz017-029.
Minnesota...Wind Chill Advisory until noon CST today for mnz079.