Area Forecast Discussion
Issued by NWS Twin Cities, MN

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952
FXUS63 KMPX 230538
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1138 PM CST Thu Feb 22 2018

.SHORT TERM...(This evening through Friday)
Issued at 327 PM CST Thu Feb 22 2018

Snow is advancing northeastward into southwestern Minnesota this
afternoon. It will reach just about all of the southern half of
Minnesota and western Wisconsin by 6 or 7 PM. Light to moderate
snow will persist area wide through midnight, then begin to end
from southwest to northeast. The steady snow will end in
southwest MN around 1 AM and the I-94 corridor by around 4 AM.
During this process of drying in the mid levels, there could be a
period of freezing drizzle following the end of accumulating snow
due to continued saturation in the low levels. However, this will
be brief and little or no ice accumulation is expected.

Models are in pretty good agreement with QPF tonight. There could
be some mesoscale banding in places and hi-res guidance is hinting
at streaks of higher QPF/snowfall. However, on a widespread basis
we should expect about 3 inches across southern MN where the
period of accumulating snow will be shortest, to 4 to 6 inches
across the remainder of the forecast area. The current Winter
Weather Advisory configuration looks good, so no changes were
needed to that.

Drier air will make for a relatively pleasant day Friday with
some decrease in clouds possible.

.LONG TERM...(Friday night through Thursday)
Issued at 327 PM CST Thu Feb 22 2018

Friday night and early Saturday look good, but the next system is
fast on the heels of tonight`s system and will begin arriving
Saturday afternoon. This system will be neutrally tilted to start
Friday night over the Plains, but will trend more negative
Saturday and Saturday night as it passes across the Upper Midwest.
This lends to a higher confidence event with widespread significant
snow accumulations. 12Z GFS is most bullish/quickest with the mid
level wave closing off and results in a strong cyclone centered
over the southeast corner of MN late Saturday evening. Models have
been slowly trending toward this solution. In addition, the GFS
deterministic run is right in the middle of the spread of SLP/QPF
in the GEFS solutions, with the lowest member still showing at
least 0.6" of QPF at MSP. Thus, confidence in 6 inch amounts is
pretty high from south central MN to northwest WI and totals could
approach 12 inches somewhere in that corridor. Snowfall rates will
be impressive with an inch or two per hour possible during the
height of the event. As for wind, the rapidly deepening low
center passing by could be occurring a little too late for the
wind to respond and increase to critical levels for blizzard
conditions. Therefore, blizzard conditions are still questionable,
but certainly not impossible if gusts can increase 5 to 10 mph
above what is currently forecast.

Given that we`re within a 48 hour window of the snow beginning,
and the degree of confidence present, have issued a Winter Storm
Watch for most of the CWA except for far western MN. It`s
possible those counties will be included later if confidence
increases for greater than 6 inches. All told, it`s likely most of
the CWA will see over 12 inches between tonight`s snow and
Saturday`s, and some could exceed 15 inches.

Much more tranquil weather follows for early next week, but there
are signs of another system for late next week that will need to
be watched.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1138 PM CST Thu Feb 22 2018

Few changes in the TAFs in terms of ongoing snowfall. Where there
is a lot of uncertainty is with how cigs will behave in the
morning in the wake of the snow. The RAP/HRRR shows cigs clearing
quickly this morning, but we`ll have plenty of moisture hanging
around to result in cloud patches hanging around. Followed closest
the RAP for showing some improvents given subsidence in the wake
of the snow that should help clear the clouds some.

KMSP...Confidence is high in the snow portion of the forecast, but
low confidence on cigs through the day. We could clear out by 15z
and stay VFR, clear out for a bit in the morning, but cloud back
in with afternoon mixing, or never lose the clouds.

/OUTLOOK FOR KMSP/
Sat...VFR early. Then IFR/SN with LIFR possible in aftn and
overnight. Significant snow accums possible. Wind ENE 5-15 kts.
Sun...CHC MVFR cigs. Wind W 10-20 kts.
Mon...VFR. Win SW 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from Saturday afternoon through late Saturday
     night for WIZ014>016-023>028.

     Winter Weather Advisory until 9 AM CST Friday for WIZ014>016-
     023>028.

MN...Winter Weather Advisory until 6 AM CST Friday for MNZ041-042-
     047>049-051-057>060-062-066>070-076>078-085.

     Winter Storm Watch from Saturday afternoon through late Saturday
     night for MNZ043>045-049>053-057>063-066>070-076>078-084-
     085-093.

     Winter Weather Advisory until 9 AM CST Friday for MNZ043>045-050-
     052-053-061-063.

     Winter Weather Advisory until 3 AM CST Friday for MNZ054>056-064-
     065-073>075-082>084-091>093.

     Winter Storm Watch from Saturday afternoon through late Saturday
     night for MNZ056-064-065-073>075-082-083-091-092.

&&

$$

SHORT TERM...BORGHOFF
LONG TERM...BORGHOFF
AVIATION...MPG



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