Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 220023

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
623 PM CST Wed Feb 21 2018

.SHORT TERM...(This evening through Thursday)
Issued at 307 PM CST Wed Feb 21 2018

Surface high pressure shifts east of the area this evening and
allows weak warm air advection to ensue ahead of the next
approaching shortwave. This scenario will make for increasing
clouds overnight, along with temperatures reaching their minimums
overnight, then remaining steady or increasing toward daybreak.

Hi-resolution models indicate we will most likely stay dry in our
forecast area until after daybreak, although the I-90 corridor
should see snow shortly thereafter. Snow will then expand north
and east across the area during the afternoon hours. By Thursday evening,
much of the Minnesota portion of the forecast area should have 1-2
inches of new snow on the ground. This will quite likely hinder
the evening commute, especially since snow will be ongoing during
it. Have therefore issued a Winter Weather Advisory for most of
the MN portion of the area into northwest WI. Southeast of the
Twin Cities metro area and across west central WI (including Eau
Claire), given the precipitation onset is later and there`s more
uncertainty regarding precipitation type, will hold off on an
Advisory for now.

.LONG TERM...(Thursday night through Wednesday)
Issued at 307 PM CST Wed Feb 21 2018

Thursday night snow will be ongoing, with freezing drizzle
possible from south central MN into west central WI. By the time
the snow ends, the Advisory area can expect 2-4 inches with
isolated totals nearing 5 inches in central MN. Nearly the entire
area could see some freezing drizzle overnight into Friday morning
as we lose saturation in the dendritic layer.

Friday is our break between systems as surface high pressure
builds in. Given the pattern aloft, however, this break will be
short-lived. By Saturday afternoon, the 21.12Z GFS and ECMWF
solutions are now in pretty good agreement that a surface low
circa 995mb will be located over Iowa, and deepening as it heads
toward the Great Lakes. This feature is accompanied by a
negatively tilted mid-level trough, and most models yielding
0.25-0.50 inches of QPF. That being said, if this set-up were to
come to fruition, it would be a winter storm warning-worthy event
for our forecast area. Plenty of time and potential for shifting
at this point, but given models are already beginning to hone in
on a track, it bears close watching.

Sunday through the middle of next week we dry out as ridging
dominates for a few days. This will also yield near-normal temps
mostly in the 30s.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 623 PM CST Wed Feb 21 2018

Quiet weather until Thursday afternoon when snow arrives. NAM/GFS
have similar timing on snow pushing into southern MN around 15z.
There look to be 2 waves of precip, an initial light band of snow
moving through in the afternoon, with the heavier burst and
primary accums coming in around 00z and after. The first wave
looks to have vis down to 1sm at worst, but wave two will likely
produce 1/2sm to 3/4sm vis as it moves through. Also looks like
sub vfr cigs will be tied to falling snow.

KMSP...Snow may start as early as 18z, but looking at the lack of what
the HRRR as at 16z (end of the 22z run), it will probably be
closer to 20/21z before snow starts. First bit of snow looks
light, but 2nd round will likely have potential for 3/4" to 1" per
hour rates. Window for those types of rates looks to be between
1z and 7z Friday.

Fri...MVFR cigs in mrng. VFR in aftn. Wind W 5-10 kts.
Sat...VFR in mrng. MVFR or lower with SN in the afternoon.
      Significant accums possible Sat night. Wind E 5-10 kts.
Sun...MVFR early, VFR late. Wind W 10-15 kts.


WI...Winter Weather Advisory from noon Thursday to 6 AM CST Friday
     for WIZ014>016-023.

MN...Winter Weather Advisory from noon Thursday to 6 AM CST Friday
     for MNZ041>045-047>053-055-057>063-066-068>070-076-077-084-

     Winter Weather Advisory from noon Thursday to midnight CST
     Thursday night for MNZ054-056-064-065-067-075.

     Winter Weather Advisory from 9 AM Thursday to midnight CST
     Thursday night for MNZ073-074-082-083-091-092.



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