NWS Forecast Discussion

398
FXUS63 KMPX 182323
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
523 PM CST Sat Jan 18 2020

.UPDATE...For 00Z Aviation discussion below

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 217 PM CST Sat Jan 18 2020

An arctic cold front moved across Minnesota, and through western
Wisconsin this morning. Temperatures fell 10 to 20 degrees in less
than 2 hours as this front moved across the area. Once ample
mixing in the boundary layer developed this morning, wind speeds
strengthened across the southern half of Minnesota, with blizzard
conditions in the west and south by noon. Although area webcams,
and observations didn`t support a full blizzard, MnDOT plows
allowed to see the worst conditions just outside towns, and in
open country. Several of the cams suggested surface visibilities
near 1/4 of mile at times. Wind gusts were in the 40s where the
blizzard warning was in effect. Outside the blizzard warnings,
wind speeds still averaged around 25 to 35 mph, with significant
blowing and drifting snow.

Although the wind speeds will diminish tonight, there could still
be near blizzard conditions in the west/southwest, and south
central part of the state until winds decrease significantly. We
still expect the blizzard warnings & winter storm warnings to
expire at 6 pm. However, please be aware that areas of blowing and
drifting snow will continue through the evening. The other aspect
to this departing storm, and the arctic air mass that has been
replaced, wind chill values will drop to very cold values where
exposed skin could easily freezing in a minute or two. We will be
issuing a wind chill advisory for all of central/southern
Minnesota, as well as west central Wisconsin as wind chill values
drop to around -30F. Some areas in west central Minnesota could
approach -35F for an hour or two during the morning hours.

Another upper level short wave is forecast to move southward
across Minnesota Sunday, with a sharper short wave moving
through the Upper Midwest Sunday night. Both of these waves will
be capable of producing light snow or flurries. However, the air
mass is very dry, so any accumulations will be minor and under an
inch.

.LONG TERM...(Monday through Saturday)
Issued at 217 PM CST Sat Jan 18 2020

The period will commence with arctic high pressure (1045mb)
centered over eastern SD and encompassing much of the CONUS east
of the Rockies. Aloft, a compact positively-tilted shortwave
trough will be dropping through the region with a ridge axis
aligned over the Rockies and a longwave trough over the eastern
CONUS.

With the upper trough disturbance dropping south through the
region early Monday, clouds will remain in place to start the day
but with significantly drier air moving through the lower levels,
no precipitation is expected. The trough will drop all the way to
Missouri by late afternoon while the surface high center moves
into Iowa, thus some clearing can be expected by late in the day.
The surface high will then maintain its influence across the area
Monday night through Wednesday morning while the western ridge
axis moves across the central CONUS. This will allow for mostly
clear skies through Tuesday afternoon. Clouds return Tuesday night
into Wednesday ahead of a broad north-south oriented surface
trough over the lee of the Rockies. This system is expected to be
a slow-moving system during the latter half of the week while a
cutoff low deepens over the Plains into the Mid-Mississippi River
Valley. With the surface system not all that organized, the upper
level forcing plus fairly deep moisture will be enough to produce
scattered showers Wednesday through Friday. Due to appreciable
warm air advection during the early portion of the week, pushing
max temps into the mid 30s Wed-Fri, showers will be mainly -SN but
will have some -RA mixed in for southern and eastern areas for a
few daytime periods. Overall, no significant snowfall expected
through the upcoming week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 524 PM CST Sat Jan 18 2020

Brisk northwest winds will yield areas of blowing snow and MVFR
visibility reductions this eve, with improvement overnight as
winds slightly decline. Ceilings will continue to scatter out to
bring mostly VFR conditions, but MVFR ceilings are expected to
redevelop in eastern MN and western WI on Sunday morning under
cyclonic flow. Northwest winds will persist through the period,
but gusts should diminish Sunday morning.

KMSP...
Expect the stratus deck to scatter out this evening, but then
build back in overnight through Sunday morning.

/OUTLOOK FOR KMSP/
Mon...VFR. Wind W at 5kts.
Tue...VFR. Wind SW at 15kts.
Wed...VFR. Chc -SN/MVFR cigs/vsby late. Wind SSW 10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning until 6 PM CST this evening for WIZ014>016-
     023>028.

     Wind Chill Advisory from midnight tonight to 9 AM CST Sunday for
     WIZ026-028.

MN...Wind Chill Advisory until noon CST Sunday for MNZ041-042-047>049-
     054>058-064>067-073>076-082>085-091>093.

     Blizzard Warning until 6 PM CST this evening for MNZ047-048-
     054>057-064-065-067-073>076-082>085-091>093.

     Winter Storm Warning until 6 PM CST this evening for MNZ041>045-
     049>053-058>063-066-068>070-077-078.

     Wind Chill Advisory from midnight tonight to 9 AM CST Sunday for
     MNZ059-060-068>070-077-078.

&&

$$

SHORT TERM...JLT
LONG TERM...JPC
AVIATION...LS

NWS MPX Office Area Forecast Discussion

Script by Ken True @Saratoga-Weather.org