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071
FXUS63 KARX 191900
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
200 PM CDT Mon Apr 19 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 200 PM CDT Mon Apr 19 2021

Quite the change today from the weekend with a return to well below
average temps in the wake of last night`s strong frontal passage. An
intense shortwave trough seen in water vapor imagery continues to
rotate across the northern Great Lakes with plenty of post-frontal
cold advection stratocu and even some rain/snow showers across the
region this afternoon. Temps were mainly in the 30s and low 40s
early this afternoon...closer to average lows at this time of
year.

An unseasonably cool airmass will persist across the region through
Tuesday with upper troughing residing across the Upper Midwest.
Diurnally enhanced cu will likely gradually dissipate tonight
although some increase in mid/high cloud cover will occur from the
southwest ahead of a shortwave trough rotating through the
broader trough. The main story locally will be the cold temps with
lows falling into the 20s over most of the area tonight. The
airmass remains quite chilly on Tuesday with 925 mb temps hovering
a few degrees below 0C. Highs will remain mostly in the 40s with
diurnal cu developing thanks to cold mid-level temps/steep lapse
rates with cyclonic flow aloft. Moisture depth looks to be
lacking, but a few showers are possible in this environment. There
will also be continued mid/high cloud cover across portions of
the region associated with the wave passing to the south, but
precip with this system is expected to remain south.

.LONG TERM...(Tuesday night through Monday)
Issued at 200 PM CDT Mon Apr 19 2021

Not much change will occur in the overall pattern through mid-week
with an upper level trough and associated cool pool of air residing
over the area. With the dry, cool airmass beneath expansive high
pressure, lows Tuesday/Wednesday nights should again fall into the
20s, with highs Wednesday in the 40s. Continued steep lapse
rates/cold temps aloft in conjunction with a shortwave trough
passage could induce a few diurnal showers on Wednesday, but
soundings show a fairly dry profile.

The trough will finally be dislodged by Thursday as progressive
shortwave ridging spread across the area with temps recovering
back into the 50s. There is reasonable model consensus for a few
progressive shortwave troughs to pass across the region Friday
into Saturday. However, confidence in timing and coverage of
precip is relatively low given uncertainty in the shortwave
placement and models indicating little amplification/interaction
of the troughs at this point. GEFS/EPS members show variation in
precip amounts, but most ensemble members indicate 0.1 to 0.2" or
less for rain, so it`s not looking like a significant rainfall.

Behind this system, model guidance supports at least some degree of
ridge building into early next week across the central US as a
trough crashes ashore across the Pacific Northwest. This would
suggest warming temps into early next week, but EPS members show
very large spread in temps, so confidence all in all remains
tempered. Overall, dry/seasonably cool weather is expected to
dominate mid/late week through the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1145 AM CDT Mon Apr 19 2021

Cold/cyclonic flow was producing widespread (VFR) stratocumulus
over the area along with an isolated rain or snow shower. Plan on
this cloud cover to scatter out tonight with scattered to broken
altocumulus (VFR) cloud expected tonight into Tuesday morning.
Otherwise, look for the gusty northwest winds to taper off this
evening, but then picking up again Tuesday after sunrise.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION...DAS