Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 202259
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
500 PM CST Tue Feb 20 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 216 PM CST Tue Feb 20 2018

20.20Z regional radars show the last bit of rain/freezing rain
moving east of the forecast area. Slippery conditions will
continue on untreated roads, sidewalks, and parking lots through
tonight, but with precipitation ending, cancelled the Winter
Weather Advisory at 2 PM.

For the rest of tonight, expect gradual clearing from west to east
with northwest breezes. Temperatures will fall into the single
digits to low teens above zero for most places.

A strong 1040 hPa surface high moves over the forecast area on
Wednesday, resulting in mostly sunny skies and light north-
northwest wind. With 925 hPa temperatures from -8 to -10 Celsius,
it will be on the chilly side with afternoon highs ranging from
the upper teens across the northwest to the upper 20s across the
southeast.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 216 PM CST Tue Feb 20 2018

Precipitation chances increase Thursday and Thursday night as a
weak short-wave lifts northeastward across the forecast area.
Increasing isentropic lift along the 280 to 290 K surfaces will
also enhance precipitation potential. GFS/NAM thermal/moisture
profiles suggest initial p-type will be snow, but decreasing cloud
ice from south to north and increasing maximum temperatures aloft
Thursday night should allow precipitation to change over to a
wintry mix or predominately freezing rain. Snow accumulations
before the change over look to be in the 1-2 inch range. Many
areas could also see a glaze of ice with some spots receiving up
to a tenth of an inch, especially south of I-90. Will fine-tune
these precipitation amounts as model QPF converges on a preferred
solution.

High pressure builds back across the region on Friday, resulting
in dry conditions and temperatures rising into the 30s. Still
watching the potential for a stronger winter storm Saturday
afternoon through early Sunday morning as a short-wave ejects
from the western CONUS trough and across the Upper Midwest. Still
differences in timing and storm track, but latest trends show the
surface low passing to our south, favoring colder temperatures and
mostly snow. Lots of details to iron out with subsequent forecasts,
but something to watch over the coming days.

An active 500 hPa wave train continues into early next week, but
poor agreement between individual models warrants low-end
consensus POPs at this time. Temperatures do appear to be warmer
with daily highs in the 30s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 500 PM CST Tue Feb 20 2018

Cigs: low mvfr cigs gradually exiting east this evening as parent
low pushes over the northern great lakes. Expecting skc conditions
after that with a sfc high moving in from the northern plains.

Winds: weakening pressure gradient will result in some decrease in
speeds Wed morning as the high moves in. Direction generally west to
north, then more light east/vrb for Wed night.

&&

.HYDROLOGY...
Issued at 208 PM CST Tue Feb 20 2018

Excessive runoff from rainfall this morning has caused elevated
river levels across portions of northeast Iowa and southwest
Wisconsin. No flooding is expected, except in southern Grant County
where a couple rivers (Grant River at Burton and Platte River at
Rockville) are above flood stage. Expect waters to slowly recede
this evening into tomorrow.

&&

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

$$

SHORT TERM...Rogers
LONG TERM...Rogers
AVIATION...Rieck
HYDROLOGY...MH



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