Area Forecast Discussion
Issued by NWS La Crosse, WI

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158
FXUS63 KARX 110802
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
302 AM CDT Sun Apr 11 2021

.SHORT TERM...(Today and tonight)
Issued at 249 AM CDT Sun Apr 11 2021

Forecast concerns in the short term will be wrap-around light rain
and drizzle today and tonight for some, temperatures, then light
rain re- developing late tonight into Monday.

April showers are bringing some much needed rain to the area.  Most
amounts over the last two days have been a quarter to three quarters
of an inch.  With this recent storm system, radar estimates shows
pockets of 1 to 1.5 inches for Clayton Co. with a trace to .4"
elsewhere.

The active weather pattern over the last few days will continue into
early next week. Water vapor satellite imagery shows the closed low
over central Illinois.  The fetch of moisture from the Gulf across
the Atlantic is feeding all the way toward Ohio into the Great Lakes
and the local area. The 00Z MPX sounding had dried out with
moisture to around 850mb and nearly 0.4 inches of precipitable
water.

The closed 500mb low will shift eastward today toward the Ohio River
Valley and then will slow down and meander toward western New York
Monday. Meanwhile, the trough from Saskatchewan to Montana will
swing southeast toward the Northern Plains today, becoming
elongated as trailing low pressure dumbbells on the backside,
gradually consolidating over Minnesota Monday. Moisture continues
to wrap around the storm system affecting parts of the forecast
area through Sunday night with rain. There is a break later Sunday
night into Monday morning for parts of the area, however that
next storm system is already moving into Minnesota. A 95kt upper
level jet dives into the Rockies Sunday and is heading toward
southern Minnesota and northern Iowa. Increasing upper level
divergence combines with positive vorticity advection to increase
shower activity north of I90. The brunt of the more organized
rainfall will spread across the northern half of Wisconsin and
gradually lift north. Frontogenesis bands are weaker today, but
re-develop Monday across MN into WI.  Rain should be spottier
farther south. Rain amounts are generally a trace to 0.1" with
.25" possible toward Clark Co. 850mb temperatures are around 4 to
5 degrees today, cooling tonight 0 to 3 degrees by Monday morning
and 0 to -1.5 Monday with northwest flow. High temperatures today
and Monday should mainly be in the 50s, however parts of Clark
Co. may hold in the 40s and warmer 60s may reach Floyd Co. in
northeast Iowa this afternoon. Did boost winds for Monday
afternoon. The HRRR/RAP show some 30 to 40kt winds over western
Minnesota spreading east with steep lapse rates in the low levels
and mixing., Did include some gusts around 30kts for parts of
southeast MN and northeast IA.

.LONG TERM...(Monday through Saturday)
Issued at 249 AM CDT Sun Apr 11 2021

A mid/upper level low across the Upper MS Valley is expected to
slowly migrate east across the Great Lakes through mid-week with
continued shower chances thanks to broad synoptic lift/mid-level
deformation Monday into perhaps Tuesday. The higher precip chances
look to be across southeast MN through central and northern WI.
Monday night into Tuesday will be the coolest period of the week
with overnight lows down into the low/mid 30s and highs only in
the 40s. Could see some snow mixed in with any rain during this
time, but chances for impactful accumulations are quite low. Drier
weather and gradually moderating temps through the 40s and 50s
are expected Wed/Thur under the influence of upper level ridging
and surface high pressure nosing in from Canada. Lower forecast
confidence persists by Friday into next weekend with the evolution
of a broad upper low over the western US in a muddled, blocky
flow pattern. As a result, just kept lower end NBM precip chances
at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1000 PM CDT Sat Apr 10 2021

Cigs: under the influence of an upper level low/troughs, along with
persistent low saturation, MVFR (IFR at times) cigs will hold
through much of Sun. Could see some improvement Sunday night, but
low cigs would likely return by Mon morning. The low cigs could then
stick around through Wed.

WX/vsby: rotating bands of -shra will continue to impact KLSE
tonight into Sun morning, but likely not make it far enough west to
fall across KRST. Some vsby impacts possible from time to time, but
overall VFR currently favored.

Winds: pressure gradient tightens up overnight as sfc low shifts
northeast toward the eastern great lakes. Northwest favored through
the forecast period, mostly  around/+10 kts sustained with higher
gusts around 20.


&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...JM
AVIATION...Rieck



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