Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 242353

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
553 PM CST Sat Feb 24 2018

.SHORT TERM...(This evening through Sunday)
Issued at 326 PM CST Sat Feb 24 2018

Heavy snow is filling in rapidly across Minnesota, but one can
already see the back edge in the vicinity of Sioux Falls and
Brookings, SD. This clearing will make steady progress
northeastward through the evening hours, reaching western MN early
this evening, eastern MN late this evening, and western Wisconsin
shortly after midnight. Until that point, widespread expect heavy
snow to continue with 1 to 2 inch per hour rates.

Radar reflectivity is looking more convective across southern
Minnesota, which continues to lead to very high confidence in the
longevity of the intense snow rates. Still thinking there is some
chance of thundersnow across east central MN and western WI.

The snow outside of our office is pretty grainy as of 315 PM.
This may transition to pure dendrites, or it may remain a bit more
sleety into the evening. This could reduce the snow ratios some,
but hi-res models have increased the amount of QPF over the last
few runs so it may end up a wash in terms of final totals.

Wind will increase behind the snow overnight, leading to some
blowing and drifting. Forecast soundings are pretty impressive
with wind aloft, but the gusts are tempered by less than ideal
cold air advection/steep low level lapse rates. This should
prevent blizzard conditions from developing, but it will need to
be watched this evening.

.LONG TERM...(Sunday night through Saturday)
Issued at 326 PM CST Sat Feb 24 2018

The long term will commence with a slight incoming ridge aloft in
advance of a weak surface frontal system. The main surface low will
shift east while remaining north of the international border,
dragging its cold front through the region Monday night. Relatively
little moisture along with NVA will accompany the frontal passage,
resulting in nothing more than an increase in cloud cover. The
surface front will then settle to the south of the region, extending
southwest from the Great Lakes through Iowa into CO/KS, by Tuesday

While this occurs, a very potent upper level trough will drop south
along the western CONUS coast, with the trough aiding cyclogenesis
over the TX/OK Panhandles. Surface high pressure will then slide
across the region Tuesday and Tuesday night, washing out over the
eastern Great Lakes and not having much of an influence to move the
stalled front away from the area. The surface low over the
Panhandles will then shift northeast along the stalled front
Wednesday-Thursday, being nudged along by the sharp longwave trough
over the southwestern CONUS. As this system moves northeast, a
mixture of both Pacific and Deep South moisture again look to
converge over the Upper Midwest, available for this incoming system
to tap and effectively produce precipitation across much, if not all
of, the WFO MPX coverage area. The main issue then becomes
temperatures, as warmer air in advance of the system may make for a
mixture of rain/snow instead of solely snow. The upper low pivots
over the Central Plains on its way to the Great Lakes Wednesday
night through Thursday, bringing the system out of the area by
Thursday night, followed by surface high pressure and upper level
ridging for Friday.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 553 PM CST Sat Feb 24 2018

Not many changes to going TAFs when it comes to the current
snowfall. Back edge of the snow is already in SW MN and will
quickly shift north and east this evening. Like Thursday night,
the big question with this system is how quickly do skies clear
out behind the snow. Looking at satellite and upstream obs, we may
loose the sub VFR cigs a couple of hours after the snow shuts off,
with more sun than clouds expected tomorrow. Clouds will hang on
longest north of I-94. For cigs going to VFR, trended the timing
toward a blend of the fast RAP and slower LAV. For winds, as the
inverted trough swings through, there will be a rapid nearly 180
degree switch in directions from the east over to the west. Also,
we could see some wind gusts in MN up around 30 kts for the first
couple of hours post shift, but they should settle down to 20-25
kt gusts that will persist through Sunday.

KMSP...Heavy snow with 1/2sm and 1/4sm vis will dominate the first
3 hours of this TAF, but rapid improvements are still expected
after 3z, with the snow done by 6z. Lower confidence on cig trends
in the morning, but we should be mostly VFR by 16z, though could
happen much earlier than that.

Mon...VFR. Wind SW at 10-15kt.
Tue...VFR. Wind N at 5 kts.
Wed...MVFR with SN possible late. Wind E at 5 kts.


WI...Winter Storm Warning until 6 AM CST Sunday for WIZ023-024-026.

     Winter Storm Warning until 6 AM CST Sunday for WIZ014>016-025-

     Winter Weather Advisory until 6 AM CST Sunday for WIZ028.

MN...Winter Storm Warning until 6 AM CST Sunday for MNZ050-051-

     Winter Weather Advisory until 6 AM CST Sunday for MNZ041>043-048-

     Winter Storm Warning until 6 AM CST Sunday for MNZ044-045-052-

     Winter Weather Advisory until 3 AM CST Sunday for MNZ047-054>056-

     Winter Storm Warning until 3 AM CST Sunday for MNZ065-073>075-



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