Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 212350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
550 PM CST Sun Jan 21 2018

.SHORT TERM...(This evening through Monday night)
Issued at 335 PM CST Sun Jan 21 2018

Hazardous to dangerous travel expected in heavy snow across much of
southeast Minnesota through northcentral Wisconsin. Wintry mix could
create travel difficulties further to the south.

A stronger winter storms will impact the region starting early
Monday morning and persisting through the day Monday into Monday
evening. Convective/intense snowfall is expected at times in the
heaviest band with snowfall rates of 2 inches per hour possible.
This may make it difficult for road crews to keep up with the
snow. A winter storm warning remains in effect for much of
southeast Minnesota through north central Wisconsin. A winter
weather advisory has been issued further south across portions of
northeast into west central Wisconsin where an occasional wintry
mix, or a switch over to snow at times, will create travel
concerns. Further to the south expect mainly rain where surface
temperatures and warm layer temperatures support all rain.
Isolated to perhaps scattered thunderstorms are possible tomorrow
as the strongest surge of warm air advection moves in. This looks
to occur in the 14Z to 19Z period. This is when the areas seeing
mainly rain could see a switch over to brief heavy snow mainly
along and north of I-90. Total snow accumulations of 6 to 12
inches are expected in the heaviest band with localized amounts of
13 to 15 inches possible. There may be some shifts in the
heaviest snow band, thanks to convection/thunderstorms occurring
to the south impacting the exact location of the band. Latest
mesoscale models suggest the band could edge just a little
southeast so continue to keep a close eye on the forecast. The
precipitation looks to lighten and switch over to drizzle or light
rain across portions of northeast Iowa into southwest Wisconsin
Monday afternoon. To the southeast of the heavy snow band a switch
over to freezing drizzle is possible Monday evening as colder air
works into the region. A gradual switch over to light snow is
then expected as the system winds down and exits the region late
Monday night into Tuesday morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 335 PM CST Sun Jan 21 2018

Behind the departing storm system, model guidance shows brief
upper-level ridging Tuesday, followed by a weak shortwave trough
late Tuesday into Wednesday. Cannot rule out some flurries
associated with the shortwave, but confidence is not high enough
to include a mention in the forecast at this time. Broad upper-
level ridging is then expected for Thursday into Friday, allowing
temperatures to rise well above normal. Models have been
consistent with bringing a deepening trough across the central
CONUS late Friday into Sunday. Precipitation could begin as early
as Friday afternoon over our area as strong warm-air advection
commences. Precipitation would likely start as rain with a change
over to snow as a cold front moves through. The GFS/GEM/ECMWF all
track the associated surface low towards Lake Superior, which
would result in a shorter-duration, lower-impact event. This
system will bear watching, though.


&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 550 PM CST Sun Jan 21 2018

Cigs: lowering cloud deck this evening, eventually IFR/LIFR by 06z
or so. Low cigs will hold fast through the day Monday, with probably
no improvement until Tue morning.

WX/vsby: drizzle starting to blossom across northeast IA/southwest
WI in a region of increasing low level saturation/low level thermal
dynamics. Trends and meso models support bringing this to KLSE and
KRST this evening - likely KLSE first. Gradually, the saturation
should deepen enough overnight for ice to be introduced into the
cloud, and pcpn more of a rain or snow question. Have a threat for
freezing rain as sfc temps will be near freezing - moreso KRST.
Going to keep it rain/snow for now. Track of the storm system`s low
would keep KRST under mostly snow, while KLSE will likely stay on
the rain side. That said, some convective elements hinted at for
Monday, which could result in dynamically forced rain to snow, in
additional to pushing 2-3" per hour rates. Complex scenario.

Vsbys are expected to gradually drop into IFR range, holding there
for the better part of Monday. Expect 1/2sm in the heavier snows at
KRST. In addition, despite the expected wet nature of the snow, 20
mph winds at KRST could blow/drift what falls.

Winds: looking mostly northeast through the period, with increasing
speeds at the low approaching from the southwest - around 20 kts
sustained at KRST for the better part of Mon. Winds will stay up
into Tue morning, decreasing later Tue afternoon. LLWS an issue for
KLSE Mon morning, blowing around 50kts by 2kft.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning from 3 AM Monday to midnight CST Monday
     night for WIZ017-029-032>034.

     Winter Weather Advisory from 3 AM Monday to midnight CST Monday
     night for WIZ041-042.

MN...Winter Storm Warning from 3 AM Monday to midnight CST Monday
     night for MNZ079-086>088-094-095.

     Winter Weather Advisory from 3 AM Monday to midnight CST Monday
     night for MNZ096.

IA...Winter Weather Advisory from 3 AM Monday to midnight CST Monday
     night for IAZ008>010.

&&

$$

SHORT TERM...Wetenkamp
LONG TERM...MH
AVIATION...Rieck


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