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000
FXUS63 KARX 162350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
650 PM CDT Tue Apr 16 2024

.KEY MESSAGES...

- Severe weather potential continues into early evening. A
  tornado watch remains in effect for parts of northeast Iowa
  and southern Wisconsin.

- Potential for storm total rainfall of 1 to 2" continues. Even
  outside of storms, strong and gusty east winds 35 to 50 mph
  possible through this evening. Northwest gusts 25 to 35 mph
  Wednesday. A wind advisory continues for much of the area into
  the evening.

- Turning colder to end the week. Still have the potential for
  frost and freeze conditions Saturday morning. Some wind is
  expected, temperatures should get as cold as they could.

&&

.MESOSCALE...
Issued at 430 PM CDT Tue Apr 16 2024 Currently warm frontal
location at 400 PM is north of the Highway 20 corridor but bends
southeast near KDBQ. Area of storms on radar are on the front
with relatively rich low- level helicity band. This front will
continue to move north slowly and be the focal point for a small
tornado risk across southern Grant Co for the next hour. If the
front can get north, so will the tornado risk.

With the shear vector from 0-6km from south to north, and
parallel to the storm initiation orientation, rapid growth to
line segments is expected to continue which takes large hail
off the table for a risk. It is mainly a linear damaging wind
threat and isolated QLCS tornado threat at this time.
Probabilities are highest right near the warm front location and
with more vigorous updraft segments oriented west to east
perpendicular to the 0-3km bulk shear vector.

&&

.DISCUSSION...
Issued at 225 PM CDT Tue Apr 16 2024

Short term:

Latest water vapor satellite imagery shows upper level closed low
over eastern Nebraska. Pieces of energy wrapping around upper level
closed low is producing showers/storms mainly along and west of the
Mississippi River per latest mosaic radar. Ongoing showers/storms
will continue to pivot around the upper level closed low into the
forecast area this evening into tonight. Severe threat with the
storms will begin to diminish early this evening...as instability
diminishes across southern parts of the forecast area. Precipitable
water values of 0.75 of an inch to 1.25 will allow for some of the
showers/storms to produce an inch per hour rates through early this
evening. However...with strong low level flow and
aloft...showers/storms will track quickly over the region. Rainfall
amounts through Wednesday morning will be 1.25 to around 1.50
inches across the forecast area.

Upper level closed low lifts northward over the Upper Great Lakes
region tonight into Wednesday. Showers and a few storms will linger
over much of the forecast area. Colder air advects into the forecast
area on backside of the upper level closed low. Temperatures remain
nearly steady or slowly fall into the lower to middle 50s Wednesday
afternoon.

Extended:

Behind the storm system today, a large area of 500mb low pressure
will push across Manitoba and Ontario.  A shortwave trough with move
through the Plains into the Mid-Mississippi Valley.   Scattered
showers will push through with the precipitation ending before the
much colder air arrived.  Precipitation chances increase as you move
south of I90 toward DBQ and amounts increase as well from dry to a
wetting rain. Cold advection through the day Friday continues into
the weekend. The winds will remain elevated for Saturday morning, so
this should help mitigate temperatures pitting out. Frost/freeze
conditions still look possible for Saturday morning with lows in the
20s to lower 30s with some mid 30s. The GEFS/Canadian/EPS ensembles
show a  30 to 90% probability of 32 degrees or colder by 7am
Saturday. Cooler than normal temperatures are expected for Saturday
with seasonable temperatures forecast into early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 639 PM CDT Tue Apr 16 2024

Another round of showers will move east through the TAF sites
late this evening and overnight. There may be even some storms
between 17.03z and 17.07z at the TAF sites. Ceilings will be
VFR through much of the night and then become IFR/MVFR on
Wednesday morning and remain MVFR on Wednesday afternoon.

Winds will gradually weaken tonight. The east winds will shift
to the south and then west tonight. Sustained wind speeds will
then increase into the 15 to 25 knots and wind gusts will range
from 25 to 35 mph on Wednesday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory until 10 PM CDT this evening for WIZ017-029-
     032>034-041>044.
MN...Wind Advisory until 7 PM CDT this evening for MNZ079-086-087-
     094-095.
     Wind Advisory until 10 PM CDT this evening for MNZ088-096.
IA...Wind Advisory until 7 PM CDT this evening for IAZ008>010-018-
     019-029.

&&

$$

MESOSCALE...Baumgardt
DISCUSSION...DTJ/Zapotocny
AVIATION...Boyne