Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 292349

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
549 PM CST Tue Nov 29 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 215 PM CST Tue Nov 29 2016

Early afternoon water vapor imagery together with GFS 500mb heights
and surface obs show a broad upper level trough across the central
Conus, with the center of an upper level low across central
Minnesota. Over the next 36 hours this upper level low will slowly
meander to the east southeast. Areas of enhanced vorticity will lead
to widespread light precipitation. Forecast soundings show deep
saturation and no elevated warm layer, so the precipitation type
will depend solely on the boundary and surface layer temps, and for
that reason expecting a rain/snow mix. The best forcing for ascent
will be along the Minnesota River valley and I-90, so have increased
pops considerably for those locations. QPF amounts are less than a
tenth of an inch over 6 hours, so snowfall amounts will also be
light, with western Minnesota seeing the maybe a couple of inches.
Areas in eastern Minnesota and western Wisconsin will see little if
any precipitation.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 215 PM CST Tue Nov 29 2016

The longer term trends are continuing to indicate a more active
pattern developing mainly later in the weekend into next week.

In the interim...we have the Wednesday night upper low to spread
east taking the light snow...drizzle/flurries with it through
Thursday morning. It does look like clouds will remain through
Thursday and into Friday. Temperatures should remain above normal
through this period...with small diurnal change continuing.

The next threat of snow arrive Sunday as another weak wave moves
east in the northern stream. Critical thickness values for this
period do increase there remains the potential for a
rain/snow mix. The various deterministic runs diverge some on
timing of this wave and what follows into early next week. We do
see some consensus developing for a significant trough developing
over the western CONUS by midweek as cold Canadian air drops
south over the rockies. This aids in the development of what could
be a significant winter storm for the Great Lakes/Upper Midwest
region by Wed/Thu 12.07 through 12.09. Both the 12z GFS and ECMWF
show the potential for a deep TX/OK panhandle low developing and
ejecting northeast across IA/SRN MN/WI region. It does appear that
it should be mainly snow as enough cold air is in place initially.
We will need to monitor this model trend closely the next few days
to see if it continues.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 549 PM CST Tue Nov 29 2016

Vertically stacked low pressure over MN will drift slowly east
into WI during the TAF period. Extensive MVFR/IFR ceilings will
prevail through the period. In addition, MVFR/IFR visibilities in
-ra/sn will be common as well, working from western MN this
evening into eastern MN and western WI during the overnight hours.
Winds ahead of the low will be light SSE while behind the low it
will turn WNW.

KMSP...Ceilings will slowly deteriorate tonight as surface low
pressure near KSTC reaches the Twin Cities by daybreak Wednesday.
Some -RA will occur this evening, mixing with -sn late. A period
of -SN is possible Wednesday morning but little or no
accumulation is expected with surface temperatures at the airfield
not dropping below 34 degrees. S winds near 10 knots this evening
veering to the WNW by Wednesday morning and then more NW Wednesday

Thu...MVFR. Wind NW 5-10 kts.
Fri...MVFR. Wind NW 5-10 kts.
Sat...VFR with MVFR possible. Wind W at 10 kts




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