Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230003

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
603 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 00Z TAFS through 00Z Friday evening)
Issued at 547 PM CST Thu Feb 22 2018

Snow has been battling the dry air this afternoon, hence it`s
later than advertised arrival, but the dry layer is quickly being
eaten away, with snow hitting the ground. Only had minor changes
to the going TAFs, with timing lined up similar to what the HRRR
is showing. Main change is looking at upstream obs, 3/4sm is the
prevailing vis, with some scattered 1/2sm vis, so trended the
TAFs that direction with prevailing 3/4sm and tempo 1/2sm vis.
Still expecting a widespread 3-5 inches, with snow mostly done by
12z. Lower confidence with cig trends behind the snow, but we
could certainly clear out faster than TAFs currently indicated,
but played the improvements a bit more conservative until we have
a better feel of how quickly skies will improve in the wake of the

KMSP...Based on the HRRR, looks like the vast majority of the
snow, along with the potential rates of around 3/4" per hour will
come between 4z and 7z. This is also the window where some vis
down to 1/2sm will be possible. Friday morning, skies may go VFR
shortly after the winds go SW and we could see VFR conditions as
early as 15z.

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.


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-

MN...Winter Weather Advisory until 6 AM CST Friday for MNZ041-042-

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

     Winter Weather Advisory until 9 AM CST Friday for MNZ043>045-050-

     Winter Weather Advisory until 3 AM CST Friday for MNZ054>056-064-

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



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