Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 161947
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
247 PM CDT Mon Apr 16 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 247 PM CDT Mon Apr 16 2018

An area of high pressure currently stretching north/south through
the Missouri River Valley will gradually slide east toward the
Great Lakes through Tuesday. The high will provide a brief break
with the recent wintry precipitation by giving the area dry
weather Tuesday with some sunshine. Temperatures will remain below
normal with highs in the middle 30s to middle 40s.

.LONG TERM...(Tuesday night through Monday)
Issued at 247 PM CDT Mon Apr 16 2018

Water vapor satellite this afternoon shows a short wave trough
moving onshore over northern California. This wave will advance
quickly east through the Rockies Tuesday and form a cut off low
over the Dakotas Tuesday night. This low will have a negative
tilt to it as it moves east/southeast toward the lower Great Lakes
through Wednesday night. With this path it is expected to bring
strong and deep lift across the area moderate to strong pv
advection in the 500-300 mb layer Wednesday along with moderate to
strong qg convergence in the 850-300 mb layer. There also looks to
be a round of strong frontogenesis in the 750-550 mb layer that
will move quickly across the area Wednesday. The best isentropic
upglide will occur late Tuesday night into Wednesday morning with
2 to 4 ubar/s expected on the 280K surface. This may linger
through Wednesday afternoon and possibly into the evening with the
development of a trowal as the warm conveyor belt gets wrapped
around the north side of the mid level low.

With all of this forcing, confident that precipitation will
develop and impact a good share of the area Wednesday. Some
concern initially as to what type of precipitation it will be. The
warm air advection ahead of the system will bring a warm layer
aloft over the southern half of the area that would suggest the
potential for some freezing rain. However, it looks like that most
of the precipitation will be in the deformation zone of the low
level low to the point that the warm layer aloft should be gone
and not much of a concern. This should make snow the dominant
precipitation type with this system, with maybe some very light
freezing rain/drizzle on the leading edge. With this in mind, if
there is going to be any icing, it should primarily be across
northeast Iowa Tuesday night and Wednesday morning from central
Wisconsin into northeast Iowa until the warm nose aloft is pushed
out. The snowfall amounts of 4 to 7 inches still look possible
over all of southeast Minnesota into the first tier of counties
across northeast Iowa. Will expand the winter storm watch a little
and add in Wabasha, Winona, Houston and Winneshiek Counties.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1208 PM CDT Mon Apr 16 2018

MVFR stratocumulus clouds expected to erode/scatter out this
evening, becoming VFR through the remainder of the period as high
pressure builds in. Look for northwest winds to diminish this
evening as well.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Watch from late Tuesday night through late
     Wednesday night for MNZ079-086>088-094>096.

IA...Winter Storm Watch from late Tuesday night through late
     Wednesday night for IAZ008>010-018-019.

&&

$$

SHORT TERM...04
LONG TERM...04
AVIATION...DAS



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