NWS-La Crosse Forecast Discussion

 

						FXUS63 KARX 181733
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1133 AM CST Sat Jan 18 2020

.SHORT TERM...(Today and tonight)
Issued at 315 AM CST Sat Jan 18 2020

Latest water vapor satellite imagery shows upper level low over the
Northern Plains with a couple of shortwave troughs rotating
around upper level low into the region. Latest 08z surface
analysis indicated a cold front extending from northwest Minnesota
to western Iowa. Out ahead of the cold front freezing drizzle was
falling and light snow was falling behind the front...per latest
mosaic radar and metars.

Concern today is the potential of blowing and drifting of snow in
open areas of southeast Minnesota and northeast Iowa. Surface front
is expected to move across the forecast area. Tight pressure
gradient behind the front will increase the winds out of the
northwest to 20 to 30 mph with gusts up to 40 mph. The
combination of subsidence/greatest pressure rises southwest of the
forecast area and a layer of ice crust on top of the recent snow
due to freezing drizzle overnight...may prohibit blowing and
drifting snow in open areas of southeast Minnesota and northeast
Iowa. At this time...not looking at any widespread
blowing snow across the forecast and continue mention of patchy
to areas of blowing/drifting snow in open areas.

With the surface frontal passage...colder airmass advects into the
forecast area and temperatures during the day will fall into the
single digits to the teens by early this evening. Strong winds and
temperatures falling into the single digits below zero tonight will
produce wind chill values in the minus 15 to minus 30 range. Wind
chill advisories most likely will be needed tonight into Sunday
morning.

.LONG TERM...(Sunday through Friday)
Issued at 315 AM CST Sat Jan 18 2020

Sunday into Monday...Arctic surface ridge builds into the area.
Colder airmass remains entrenched over the forecast area...with
925mb temperatures progged to be minus 10 to minus 20 degrees
celsius. Low temperatures Sunday morning are expected to drop into
the single digits below zero...and combined with the winds. Wind
chill values Sunday morning will be in the minus 15 to minus 25
range across the forecast area. Weak shortwave embedded in the
northwesterly flow aloft tracks into the Northern Plains Sunday
night into Monday morning. The 18.00z GFS/NAM indicate the deeper
lift/saturation remains west of the forecast area. The 18.00z
deterministic models bufkit soundings show saturation through the
atmosphere column and the potential is there for flurries Sunday
night into Monday. Have introduced flurries during this time
frame.

Main forecast concerns Tuesday night into Friday are
precipitation chances through the period. The latest 18.00z
GFS/ECMWF/GEM are in decent agreement with breaking down shortwave
ridging over the Upper Great Lakes Region and cut off upper level
low over the central United States middle of next week. Pieces of
energy ejecting out/rotating around the closed upper level low
into the Upper Midwest will produce chances of precipitation
middle to late next week. Precipitation type will be an issue...as
the deterministic models are suggesting temperatures rising into
the 30s/above freezing middle of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1133 AM CST Sat Jan 18 2020

Windy conditions will continue across the region through this
evening, with northwest breezes of 15-25 knots gusting up to 40
knots at times before gradually subsiding later tonight into
Sunday morning. Those winds will lead to widespread blowing snow
at RST, with visibility down to 1/4-1/2SM at times, while LSE
shouldn't see any blowing snow impacts due to its more sheltered
location. Occasional flurries will also continue for most of the
area into the afternoon, with MVFR ceilings gradually lifting to
VFR for a time tonight before again returning to MVFR levels
toward or after 09Z as additional moisture works back into the
area.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST this evening for
     WIZ041>044-053>055-061.

     Winter Storm Warning until 6 PM CST this evening for WIZ017-029-
     032>034.

MN...Blizzard Warning until 6 PM CST this evening for MNZ086-087-094-
     095.

     Winter Weather Advisory until 6 PM CST this evening for MNZ096.

     Winter Storm Warning until 6 PM CST this evening for MNZ079-088.

IA...Blizzard Warning until 6 PM CST this evening for IAZ008-009-018-
     019.

     Winter Weather Advisory until 6 PM CST this evening for IAZ011.

     Winter Storm Warning until 6 PM CST this evening for IAZ010-029-
     030.

&&

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...Lawrence