Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 260909
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
409 AM CDT Tue Mar 26 2024

.KEY MESSAGES...

- Rain transitions to wintry mix then light snow with falling
  temperatures and increasing northwest winds 20 to 35 mph.

- Most locations less than an inch. Probabilities for 1" or
  more of snow are greatest toward Dodge and Mondovi (50-70%).

- Precipitation chances return Friday and Sunday night into
  early next week.

&&

.DISCUSSION...
Issued at 345 AM CDT Tue Mar 26 2024

Overview:

The 26.00Z MPX sounding was saturated to above 700mb with 0.64" of
precipitable water and steep mid level lapse rates above 850mb.
Rainfall totals Monday varied quite a bit depending on where the
bands set up, with the .5"+ bands over the western and northern
halves of the forecast area. LSE had 0.28", Rochester 0.62" and
Charles City 0.96" through 06Z. Latest water vapor satellite
imagery, heights, and lightning showed the closed 500mb low was
centered over the Mid-Missouri River Valley and was part of a
larger trough that covered much of the western 2/3rds of the
U.S. The bulk of the lightning was ahead of the trough from the
Gulf of Mexico through the Tennessee River Valley toward the
Ohio River Valley.

At the surface, a 993mb low centered over central Iowa.  The warm
front was just south of La Crosse where there was a north wind
and 39 degrees, but it was 49 in Mauston, 45 at Preston, and 51
degrees at PDC. Most of Minnesota was on the cool side of the
front with rain transitioning to a wintry mix and snow with
temperatures in the mid 30s cooling to the mid 20s farther west.
It was interesting to note that here at the NWS office we were
45. 3hr pressure falls were 3 to 6 mb with the stronger falls
near Rockford.

Rain transitions to a wintry mix/light snow with falling
temperatures with increasing northwest winds:

Today, the mid tropospheric low/trough will track over the forecast
area and will head toward the U.P. Surface low pressure is expected
to take a similar track northeast through the forecast area.  Cold
air advection will increase as the surface low lifts northeast.
850mb temperatures at 26.12Z from 0 to +4 deg C. cooling to -9 deg C
to +2 deg C by 18Z and -12 to -9 deg C by 00Z.

The 07Z reflectivity has and expanding area of showers with 3hr
rainfall rates from 0.01 to 0.11". The farther west you go into
the cold air, the rain chances to a wintry mix and then snow.

The CAMs have a general idea of the greater precipitation coverage
lifting north at the beginning of the forecast period with the
colder air working into the west changing to a wintry mix and snow
with possibly a steadier band of snow could develop. Some low
CAPE values around 50 J/kg lift north and clip parts of
southwest or central WI today, but greater chances appear east
of the forecast area. Forecast soundings show a brief window
where mixed precipitation could occur and result in a glaze of
ice or wintry mix. The HREF ensemble max for any icing is
greater toward Dodge Co. With temperatures falling this morning
across Dodge Co. and the potential for light snow/wintry
mix/cold air moving in during the morning hours, did include
them in a winter weather advisory to match up with our
neighboring counties.The trend of the last five runs of the RAP
has been for less than an inch to some 1 to 3 inch snow amounts
for parts of west central WI. The last six HRRR runs have some
higher snow amounts for parts of Dodge Co. The HREF seems to
keep the higher snowfall rates to the west as well. As the
system translates east and the cold air arrives. Temperatures
are milder farther easter, but there is strong cold advection
with the precipitation gradually ending. Will need to monitor
how roads are responding to the cold air. Some light snow
flurries may continue into the evening hours.

Wednesday through Monday:

Surface high pressure will cover much of the region Wednesday
through Thursday night.  Ridging then builds in for Friday. A warm
front appears to develop to the south of the area as trough across
Canada and the Plains works into the Upper Mississippi Valley Friday
night.  The flow becomes more zonal for Easter weekend.  A more
active pattern develops Sunday night into early next week.

Mainly dry conditions are forecast Wednesday and Thursday, however
showers will return to the forecast Friday and Friday night. Mean
ensemble amounts are a trace to a tenth of an inch.  Sunday night
into early next weak looks a little more promising with the
potential for higher amounts and general ensemble means of 0.25 to
0.50.  Still a lot of details to work out as we get closer, but at
least we have a few more chances to pick up additional
precipitation. Highs remain below normal Wednesday and Thursday with
40s and 50s Friday into early next week.


&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1050 PM CDT Mon Mar 25 2024

A stalled surface warm front is draped across the region with
widely varying aviation conditions being observed. Patchy fog,
with locally dense areas, are expected to prevail through the
overnight period with visibilities expected to be the worst in
precipitation free areas with active snow cover along and north
of I90. As rain showers move through, expect temporary
improvement in the visibility overnight, but fog is expected to
redevelop after showers exit.

LIFR to IFR visibilities are expected to prevail through the
overnight hours, improving to VFR by Tuesday afternoon. LIFR to
IFR ceilings across the region will likely remain in IFR to
low-end MVFR through much of the TAF period across the region.
Expecting rain to persist through the overnight hours before
switching over to a light snow from west to east Tuesday
morning with minor accumulations expected. Winds will become
west northwest Tuesday with gusts up to 30kts.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Weather Advisory until 2 PM CDT this afternoon for
     MNZ086.
IA...None.

&&

$$

DISCUSSION...Zapotocny
AVIATION...JAW


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