FXUS63 KMPX 180028

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
628 PM CST Fri Jan 17 2020

.SHORT TERM...(This evening through Saturday night)
Issued at 230 PM CST Fri Jan 17 2020

Nice snow banding has developed across southern Minnesota in the past
couple of hours as seen by enhanced satellite imagery (Day-Cloud-
Phase) and regional radar. Snowfall rates under these intense snow
bands are likely in the 1-2 inch per hour range. A few reports in
southwest Minnesota has already indicated that morning snowfall has
exceeded 3 to 4 inches. These snowfall rates will likely continue
through the late afternoon before shifting north across central
Minnesota, and into western Wisconsin by the early evening. Farther
to the west/southwest, overall snowfall rates will decrease as the
mid level forcing abates. However, I wouldn't be surprised to see
snowfall rates across southern Minnesota, north of the Minnesota
River, around 1/2 inch per hour until early evening. In addition to
the banding noted on the satellite imagery, there is a pronounced
area of a shallower cloud deck which is a good indication of mainly
supercooled water droplets vs. ice clouds in southeast South
Dakota/northeast Nebraska. Therefore, as this area of supercooled
water droplet (clouds) move into southern Minnesota, a mix of
freezing drizzle will be possible during the late afternoon/early
evening. I wouldn't expect much in ice accumulations but it needs to
be watched.

The main upper level trough will still be west of Minnesota through
this evening. This trough will hold onto large scale lift, but the
amount of ice cloud seeding may be limited to central Minnesota. I
wouldn't rule out a couple more inches of snow as the main upper
trough moves across the Upper Midwest overnight. The main concern by
Saturday morning is the strength of the surface winds as the surface
low moves across Iowa, and into the Great Lakes. Significant
pressure falls behind the surface low will create strong winds, with
blizzard conditions likely in western/southwest/south central
Minnesota. Current blizzard warning looks reasonable based on
typical areas that receive blizzard conditions with wide open
country and the speed of the surface winds. These surface winds will
slowly abate by the late afternoon and into Saturday evening. Thus,
blizzard warnings should be allowed to expire at that time. There
will still be areas of blowing and drifting snow, but the worst
surface visibilities will have ended.

Not much change in the forecast Saturday night as wind speeds abate,
but wind chill values will likely drop into the 20s and 30s below
zero range.

.LONG TERM...(Sunday through Friday)
Issued at 225 PM CST Fri Jan 17 2020

The long range period will start off cold and dry, with temperature
slowly moderating back to above freezing as the week progresses. We
will be watching the possibility of another strong system
approaching the area late in the week.

Strong high pressure begins to build southwest out of Canada on
Saturday, and into the Dakotas on Sunday, setting the stage for a
couple of cold, Highs on Sunday will range from the low single
digits below zero in the west to single digits above zero for most
of the rest of the forecast area. There will be some highs in the
low teens in the far eastern portions of our forecast area.

After a cold morning in the single digits below zero, high
temperatures on Monday will rise a few degrees from Sunday's highs.
On Tuesday high pressure will move off to the southeast and
temperatures will rebound into the 20s with the return flow. On
Wednesday highs will warm up to freezing or a little above. Moisture
will surge northeast out of Texas with the flow and could start to
affect the area later on Wednesday. Long range models are showing a
system coming together somewhere in the south-central US, but there
is not much agreement beyond that. We will continue to carry
light POPs from Wednesday on.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 627 PM CST Fri Jan 17 2020

Main change with 00z TAFs deals with dry slot moving in that is
quickly cutting down on snow rates. We have seen FZDZ make it all
the way up to Watertown, SD, so expanded mention of FZDZ up into
MSP and EAU for a couple of hours this evening. Timing for end of
snow has not changed much, but will end rapidly as winds switch
over to the northwest. For winds Saturday, went a bit above LAMP
guidance given mixing potential seen in BUFKIT with the GFS/NAM.
As temperatures crash Saturday, expect skies to clear out as the
moisture bearing cloud layer sees temps drop below -20C, though
timing of that clearing will need more refinement.

KMSP...Based on obs in southwest MN, confidence is increasing
that we will lose cloud ice, with FZDZ showing up between 3z and
8z. As this dry slot moves east, we'll see snow fill back in, with
mainly 1sm to 3sm snow the rest of the event. Snow end time right
now looks to come between 11z and 14z.

Sun...VFR. Wind NW at 10G20kts.
Mon...VFR. Wind W at 5kts.
Tue...VFR. Wind SW at 15kts.


WI...Winter Storm Warning until 6 PM CST Saturday for WIZ014>016-

MN...Winter Storm Warning until 6 PM CST Saturday for MNZ041>045-

Winter Storm Warning until 6 AM CST Saturday for MNZ047-048-

Blizzard Warning from 6 AM to 6 PM CST Saturday for MNZ047-048-



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