Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 271634
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1134 AM CDT Wed Mar 27 2024

.KEY MESSAGES...

- A few snow showers/flurries with below normal temperatures
  today and tonight.

- Next chance for rain mainly Friday night with low chances for
  the weekend (10-30%).

- Seasonable temperatures for the holiday weekend.

- Unsettled Sunday night into early next week with chances for
  a wetting rain (10-30% for 0.10"+).

&&

.DISCUSSION...
Issued at 230 AM CDT Wed Mar 27 2024

Overview:

The 27.00Z MPX sounding was quite a bit colder with -13 deg C at
850mb, but an inversion at that layer warming to -9 deg C in that
saturated layer.  Precipitable water had dropped to 0.35". Latest
water vapor satellite imagery, heights, and lightning showed a broad
trough covering the central 2/3rds of the U.S. with an oblong
area of closed 500mb low centered northern Minnesota. The bulk
of the lightning was ahead of the trough from the Gulf of Mexico
toward the Southeast Atlantic States.

Recent nighttime microphysics satellite imagery and metars showed
the bulk of the stratus over the forecast area and to the east.
Upstream, there were severe band of stratus and several clear areas.
Flurries and light snow reports were common at many upstream
locations. The latest subjective surface analysis had the 994mb
low pressure system over the U.P. of Michigan with westerly
surface flow. Of note were the -15 to -18 deg C 850mb
temperatures over the area which would easily support flurries.
At the surface, temperatures had fallen to teens and 20s with
gusts of 20 to 35 mph continuing and local flurries.

A few snowshowers/flurries with below normal temperatures:

The closed low over Minnesota will track toward the U.P. and then on
to Ontario and Quebec today and Thursday.  The local area remains in
cyclonic flow with cold temperatures (850mb -12 to -18deg C today
and minus 1 to -12 Thursday) today and seasonal temperatures for
Thursday.  Forecast soundings show cool convective temperatures with
steep low level lapse rates, thus where temperatures are cold enough
and there is moisture, look for instability clouds/snow showers or
flurries.  Highs today mostly in the 20s and 30s and in the 30s and
40s for Thursday.  Lows Thursday morning drop back to 10 to 23 with
some single digit wind chills.  The blustery west winds continue
today with gusts mostly 20 to 25 mph and 10 to 20 mph Thursday.  The
wind gusts will drop off as surface high pressure builds in.

Friday through Tuesday:

Ridging then builds in for Friday as a warm front develops to the
south and lifts toward DBQ. Meanwhile, a trough swinging through
Canada and the Plains will begin to break down the ridge.  Warm
advection aloft begins Thursday night with stronger low level warm
advection Friday afternoon across Iowa shifting east Friday night.
Left front exit jet support occurs broadly within the steep lapse
rate environment with increasing moisture transport across Iowa. The
forcing is not coming together strongly, but enough to expect clouds
to be on the increase with the warm air advection and scattered
showers to develop.  A 40-50kt low level jet combined with the low
level moisture transport and 100-500J/kg instability to the south
should touch off some thunderstorms.  Unsure how far north these
storms will make it, but elevated instability is noted across the
southern part of the forecast area, thus left isolated thunder
in the forecast Friday night.

Seasonable temperatures for the weekend with highs in the 40s and
50s.  Mainly dry for Saturday with a weak trough aloft that keeps a
few more clouds and possibly a sprinkle in the area. Increasing
moisture in the zonal pattern aloft with 10-30% chances of
measurable precipitation for Easter Sunday.

A more active pattern Sunday night into Tuesday as an elongated
trough from Canada southwest to the Four Corners region
/southern California tracks east. The present pattern has the
forecast area on the cool side of the warm front, however
temperatures are mostly mild enough for rain. Current ensemble
probabilities for a wetting rain (0.10"+) are 30-40% Monday
with some low thunder probabilities across our south. The EC EFI
has 50 to 60 percent of the members with above the climate max
instability across our south and 50 to 60% above the climate max
qpf with a shift of tails of 0. The details in how the northern
trough and the southern portion of the trough phase are not in
agreement at this time, so check back as we refine the forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1134 AM CDT Wed Mar 27 2024

A field of somewhat diurnally-driven stratocumulus will persist
this afternoon, gradually scattering out through tonight.
Ceilings will slowly rise this afternoon, becoming mostly VFR
south of Interstate 94. However, smaller chances (20-40%) for
MVFR ceilings do persist through late afternoon, especially at
KRST, with a few flurries possible. Gusty west winds will
gradually diminish into the 5 to 10 kt range overnight into
Thursday.

&&

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

&&

$$

DISCUSSION...Zapotocny
AVIATION...JM


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