Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 132337
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Fri Apr 13 2018

.SHORT TERM...(This evening through Saturday)
Issued at 351 PM CDT Fri Apr 13 2018

A very complex storm system continues to take shape for tonight
through the weekend with precip types/amounts a tough forecast.

Still anticipate widespread rain/embedded storms developing through
the evening/overnight into Saturday morning with moisture
transport/warm advection north of the surface warm front. The
surface warm front does look to be stuck a little farther south
across southeast Iowa, which may end up focusing precip right
across our area. Confidence is lower into north-central Wisconsin
with how far north precip reaches tonight. A few hail producing
storms are possible this evening with the low freezing levels and
elevated instability. Strong, gusty east to northeast winds will
also gust up to around 45 mph.

As for precip types, as temps slowly fall tonight, a trend towards a
wintry mix from north to south is expected, with freezing
rain/rain/sleet possible, and some snow possible in north-central
WI. South of I-90, mostly rain would be expected, although with
convective potential, some sleet is possible. Expect some icing
concerns, especially on elevated surfaces with temps near
freezing.

As the upper trough approaches through the day Saturday, expect
more precip to develop. With surface temps clinging close to
freezing, remaining warm aloft into southwest Wisconsin, and some
potential for convective elements given steep lapse rates, a
wintry mix of precip types remains likely, with more snow from
southeast MN into north-central WI. As the def zone precip
overspreads the area Sat night into Sun, a general transition
towards snow is expected, although some mixed precip could
persist. Residual light snow will diminish later Sunday into
Sunday night.

As for headlines, messaging and impacts, it`s a difficult system
to deal with. Brought A Winter Weather Advisory southward tonight
to account for some icing, possibly light snow over north-central
Wisconsin. Did adjust total event ice amounts down to the 1/10 to
1/4 inch range. With the wave of precip Sat afternoon into Sunday
more likely to be snow with 6+ inches a decent bet from parts of
southeast Minnesota through north- central Wisconsin, converted
the advisory to a warning in these areas into Sunday, with the
advisory remaining farther south. As mentioned, the freezing rain
impacts are expected to be greatest on elevated surfaces, but with
surface temps playing a key role on roads. The highest snow
impacts are expected over southeast Minnesota into north-central
Wisconsin, where some areas may see 8+ inches. Blowing snow is
also possible in open areas Sat/Sat night. Will have to monitor
short term trends and make any adjustments as necessary.

.LONG TERM...(Saturday night through Friday)
Issued at 351 PM CDT Fri Apr 13 2018

Surface ridging passes over the Upper Midwest Monday into Tuesday
with a respite from the precipitation. A fairly vigorous upper
trough and surface low are expected to lift towards the Great
Lakes Tuesday night and Monday with another shot at some wintry
precip, including some snow. A quieter late week stretch is
anticipated behind this system, although model guidance in general
indicates the potential for another system to possibly impact the
area next weekend. Temps should stay below seasonal norms through
the next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Apr 13 2018

Next round of precipitation developing right now across the area
and that will continue through roughly 04-06Z before we catch
another break in the action the second half of tonight. Most of
the precipitation should be just rain, but with some embedded
convective elements, could see not only a little lightning but
also some sleet or small hail along with very heavy rains for
brief periods. Given continued fetch of drier air into the area,
ceilings may hang right around the IFR/MVFR range for RST but
mainly MVFR for LSE, probably actually rising after 06Z tonight as
much of the precipitation briefly ends.

That break in precipitation should hold through mid to late
morning Saturday, though can`t rule out some drizzle or light rain
at times. Will be closely watching surface temperatures as we
will continue to see readings slide toward the freezing mark, and
likely below at RST very late tonight or into Saturday morning.
Should that occur, can`t totally rule out some light freezing rain
or drizzle for RST, though per the latest trends, it appears any
precipitation from about 06Z tonight through 18Z Saturday will be
very light. Thereafter, our next round of heavier precipitation
still looks on track into Saturday afternoon and evening, with
much of that likely falling as snow and/or sleet, perhaps heavy at
times with accumulation likely for LSE and RST. Winds will become
increasingly gusty from the northeast tonight into Saturday
morning, with a few gusts nearing 40 knots not out of the question
at RST.

&&

.HYDROLOGY...
Issued at 351 PM CDT Fri Apr 13 2018

Additional precipitation amounts of 1 to 2 inches are expected
through Sunday, in addition to the 0.50 to locally greater than 1
inch amounts that fell over parts of the region. By Saturday night
much of the precipitation is expected to be snow. Soils remain at
least partially frozen, especially north of I-90, or are wet from
recent snowmelt. Due to this, a higher than normal percentage of
the rainfall expected to runoff, producing ponding of water in low
spots and cause river rises. Flooding remains a concern later
today thru the weekend into early next week on some area rivers
and streams. Please continue to monitor forecasts closely,
especially if you have interests along or live near a river or
stream.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 1 PM Saturday to 7 PM CDT Sunday
     for WIZ061.

     Winter Weather Advisory from 7 AM Saturday to 7 PM CDT Sunday
     for WIZ053>055.

     Winter Weather Advisory from 1 AM Saturday to 7 PM CDT Sunday
     for WIZ041>044.

     Winter Weather Advisory from 1 AM to 1 PM CDT Saturday for
     WIZ032.

     Winter Storm Warning from 1 PM Saturday to 1 PM CDT Sunday for
     WIZ032.

     Winter Weather Advisory from 1 AM to 4 PM CDT Saturday for
     WIZ017-029-033-034.

     Winter Storm Warning from 4 PM Saturday to 7 PM CDT Sunday for
     WIZ017-029-033-034.

MN...Winter Weather Advisory from 7 AM Saturday to 7 PM CDT Sunday
     for MNZ094>096.

     Winter Weather Advisory from 1 AM to 1 PM CDT Saturday for
     MNZ079-086>088.

     Winter Storm Warning from 1 PM Saturday to 1 PM CDT Sunday for
     MNZ079-086>088.

IA...Winter Weather Advisory from 1 PM Saturday to 7 PM CDT Sunday
     for IAZ018-019-029-030.

     Winter Weather Advisory from 7 AM Saturday to 7 PM CDT Sunday
     for IAZ008>011.

&&

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION...Lawrence
HYDROLOGY...JM/RRS



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