Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KARX 231930

Area Forecast Discussion
National Weather Service La Crosse WI
230 PM CDT Fri Mar 23 2018

.SHORT TERM...(This evening through Saturday)
Issued at 230 PM CDT Fri Mar 23 2018

Forecast focus through the short term period is on the winter storm
tonight into Saturday over parts of the area. Main changes today
were to slow down the arrival of precip into the area and trim
amounts on the eastern and northern edges of the band.

Early this afternoon, the area remained under the influence of a dry
sprawling high pressure system across Canada with some increase in
mid/high level moisture. Precip was beginning to develop westward
across southwest Minnesota and northwest Iowa where mid level
frontogenesis/warm advection is maximized.

Late today and tonight, a shortwave trough currently over the
central Rockies will eject out towards the Upper MS Valley.
Precipitation will begin to increase in coverage and gradually
spread eastward in response to the upper wave and frontal lift as
deep moisture increases. Given the initial very dry airmass, it will
take some time to completely saturate, so much of the evening should
be dry before the arrival of the precip.  It still looks like there will
be a sharp gradient on the north and eastern edge of the heaviest
snow given focused frontal forcing and the dry environment to the
east. Have attempted to tighten up the snowfall gradient this
afternoon. As a result, removed the MN counties adjacent to the MS
River from the advisory and converted Fillmore and Dodge counties
to a Winter Weather Advisory. The highest potential for 5-10+
inches of snow looks to be from south central Minnesota through
parts of northeast Iowa. There are still some differences in the
global/high res models exactly where the gradient sets up (notably
the HRRR/RAP keep the highest amounts southwest of the area), so
will have to monitor trends over the next several hours. In
addition, winds will become gusty from the east through tonight in
response to a tightening gradient as low pressure tracks across
the Mid MS Valley.

The snow, or mixed rain/snow, will be winding down by Saturday
afternoon as mid-level ridging begins to work in from the west.

.LONG TERM...(Saturday night through Friday)
Issued at 230 PM CDT Fri Mar 23 2018

As the upper shortwave trough pulls into the Ohio Valley Saturday
night and Sunday, the persistent strong surface high over eastern
Canada and mid-level ridging will exert influence over the area with
dry and seasonable conditions. Temps will be cooler on Sunday though
for areas that receive heavier snow tonight into Sunday.

Southwest flow aloft returns for early next week with another low
pressure system expected to eject out of the plains. This system
will draw northward more moisture and warmth, with precipitable
water values climbing up to near an inch over parts of the area.
Although initial precip may begin as a mix Sunday night into
Monday, overall more of a rain event is expected. There are some
differences in the models with the overall upper air pattern, with
the 23.12Z GFS favoring a slower solution, hanging on to precip
chances through Tues night.

Behind the system, the upper flow transitions back to west to north
westerly, with fairly seasonable temps and generally quieter weather
for the second half of the week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1129 AM CDT Fri Mar 23 2018

VFR conditions are expected through the rest of the day. A storm
system will bring snow into the area from the west tonight into
Saturday. Continued to mention some snow at KRST, but delayed the
onset time. Confidence is somewhat low on the eastward extent of
precip, which will impact ceilings/visibilities at KRST. IFR or
LIFR conditions are expected within heavier snow bands, though. Farther
east, mainly VFR conditions are expected at KLSE, with much of
the snow remaining west. Gusty easterly winds are expected this
evening into Saturday, especially at KRST.


WI...Winter Weather Advisory from 1 AM to noon CDT Saturday for

MN...Winter Storm Warning from 10 PM this evening to noon CDT
     Saturday for MNZ094.

     Winter Weather Advisory from 1 AM to noon CDT Saturday for

IA...Winter Storm Warning from 10 PM this evening to noon CDT
     Saturday for IAZ008>010-018-019-029-030.

     Winter Weather Advisory from 1 AM to noon CDT Saturday for



AVIATION...JM is the U.S. government's official web portal to all federal, state and local government web resources and services.