Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 150437
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1137 PM CDT Sat Apr 14 2018

.SHORT TERM...(This evening through Sunday)
Issued at 330 PM CDT Sat Apr 14 2018

The significant late season winter storm continues through Sunday.
In addition to the expansion of the Winter Storm Warnings across
southeast Minnesota and parts of northeast Iowa earlier today,
also expanded the Winter Storm Warning from Houston County, MN
through La Crosse/Vernon Counties eastward into central
Wisconsin.

Water vapor imagery early this afternoon showed the upper low
over northern Kansas with the upper jet core punching northeast on
the east side of the circulation and implied upper difluence
downstream over the Upper MS Valley indicative of increasing
synoptic ascent.

The strong synoptic lift and frontogenetical lift in the deformation
zone will lead to increasing coverage of precip through the rest of
the afternoon and tonight. Within the deformation zone, it looks
like snow should be the predominant precip type given sufficient
moisture depth. Snowfall amounts were nudged upwards into central
Wisconsin given expectation of less freezing rain potential and a
bit higher QPF tonight, hence the expansion of the Warning in
this area. With some embedded convective elements aided by steep
mid-level lapse rates and a lingering warm nose into southwest WI
into early evening, some sleet is also possible. Any freezing
rain/drizzle threat should be mainly over northeast IA/southwest
WI, and this will be dependent on moisture depth. The heaviest
snowfall is expected late this afternoon and tonight, with rates
possibly exceeding 1 inch/hour at times, especially when
convectively enhanced. With the surface low only moving slowly
northeast through Sunday, the well-developed def zone precip will
be slow to erode on Sunday, but gradually diminishing through the
day.

Additional snowfall accumulations through Sunday currently are
forecast to be 6 to 12 inches near and north of I-90, tapering to
2 to 6 inches over parts of northeast Iowa into southwest
Wisconsin. Expect some blowing and drifting snow with the strong
east to northeast winds, especially across open areas west of the
Mississippi with gusty east winds, which could create near
whiteout conditions at times. Deteriorating conditions are
expected into tonight as precip increases and as temps cool with
loss of daylight, leading to difficult/hazardous travel.

.LONG TERM...(Sunday night through Saturday)
Issued at 330 PM CDT Sat Apr 14 2018

An active and cooler than normal pattern still looks to persist
through the coming week. Surface ridging will build across the
region later Monday into Tuesday providing at least a short break
from the unsettled weather. However, global models continue to
indicate an intense upper shortwave trough and surface low
crossing the region Tuesday night through Wednesday night. There
are some timing differences between the GFS/ECMWF but once again
there is potential for accumulating snow with this system. It will
bear close watching early in the coming week. Mid-level ridging
will develop behind this system for late week with a return to
quiet weather and daytime highs mainly in the 40s to low 50s.
There has been a consistent signal for another upper trough to
lift into the plains next weekend, but confidence is very low on
how this system will evolve.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1137 PM CDT Sat Apr 14 2018

Bands of snow continue to work across the LSE airport but may end
for a time the next few hours as drier air works into western
Wisconsin. Meanwhile, RST continues to sit in some very light snow
along with blowing snow at times, though overall winds continue to
decrease. As we head through the morning hours, snowfall should
increase in coverage once again across much of the area (for both
LSE and RST), with several more inches possible. Could even see
some brief intervals of heavier snow, though we`ll have to wait to
see exactly where any heavier snow bands line up through the
morning. Regardless, overall conditions within the snow should
remain IFR but with a gradual return to MVFR criteria as snow
lightens in intensity later in the day and into the evening.

&&

.HYDROLOGY...
Issued at 330 PM CDT Sat Apr 14 2018

Precipitation amounts of 1 to locally 2.5 inches were common along
the Interstate 90 corridor through this morning, with lower amounts
over parts of northeast IA/southwest WI and in north-central WI.
Additional precipitation amounts of 0.5 to locally greater than 1
inch are expected through Sunday, mostly falling as wintry mix or
snow. Rises will continue on some area rivers/streams over the
coming days from rainfall runoff and then snowmelt, with minor
flooding along a few rivers. 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 until 7 PM CDT Sunday for WIZ054-055-061.

     Winter Storm Warning until 7 PM CDT Sunday for WIZ017-029-
     032>034-041>044-053.

MN...Winter Storm Warning until 7 PM CDT Sunday for MNZ079-086>088-
     094>096.

IA...Winter Weather Advisory until 7 PM CDT Sunday for IAZ010-011-019-
     029-030.

     Winter Storm Warning until 7 PM CDT Sunday for IAZ008-009-018.

&&

$$

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



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