Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231119

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
519 AM CST Mon Jan 23 2017

Issued at 519 AM CST Mon Jan 23 2017

Updated to include 12Z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 315 AM CST Mon Jan 23 2017

Things look to remain somewhat murky, but otherwise quiet
weatherwise for today and most of tonight. We`ll remain in somewhat
of a col in the sea level pressure pattern today, but should begin
to see some return flow kick in across the western portion of the
forecast area by later tonight as the upcoming system begins to work
out into the southern Plains. Some isentropic ascent and deeper
moistening is suggested across the far west by most of the guidance
by 12Z, so included some chance PoPs for snow in that area late
tonight. Otherwise, look for cloud skies to persist across the area
today and tonight, with light winds. Areas of fog this morning,
along with some patchy drizzle, should slowly slide east and/or
dissipate by this afternoon, although some localized fog will
certainly still be possible, particularly across the east.

.LONG TERM...(Tuesday through Sunday)
Issued at 315 AM CST Mon Jan 23 2017

The main forecast concern in the longer term remains development
of winter storm in the Tuesday/Wednesday time frame. We will
continue the winter storm watch for 18z Tuesday through Wednesday
Afternoon for this forecast.

Models have begun to shift slightly to the north...with the 08z
Nam-wrf showing the greatest shift from yesterday. This trend will
have to be monitored as a northward shift in the overall heavy
snow band is a possibility. The 00z ECMWF continued it slightly
more southern track and a bit slower in lifting the snow into
southern MN. Forecast QPF has increased a bit with some
deterministic models indicating totals around 1 inch possible to
the southwest. This seems a bit overdone but the 0.80 inch totals
look more likely. The 00z GEFS probabilities are still showing a
bullseye over the southern third of the state...with totals of 3
to 5 inches across the metro. And this followed well with the SREF
snow accumulation`s as well. We considered lifting the watch
another tier of counties north...but held off because of the
large spread in overall guidance. The trough is just now coming
ashore over the southwest and we should get increased confidence
in overall forecast with the 12z model run.

The system spreads east Wednesday with snow tapering and ending
from west to east during the day. Still could see an inch or two
to the east during this period. Flow aloft becomes more northwest
and drags slightly cooler air along with the continuation of
clouds through much of the remainder of the period. Some small
chances for light snow or flurries into Thursday with generally
dry thereafter until chances return for more snow late in the
weekend or early next week.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 519 AM CST Mon Jan 23 2017

Similar story, different day, with low clouds and fog through the
period. The fog shouldn`t be as widespread or dense today and
tonight, but will still be an issue, particularly this morning
along with some drizzle. But, we look to maintain low ceilings
with minimal low level advection to move anything out of the area,
and clouds extending well the west and southwest. Some snow may
start to move into the southwest portion of the forecast area
toward the end of the period, and the large scale forcing
associated with that should work to actually raise ceilings some.

KMSP...Main area of uncertainty is with visibilities and ceilings
this morning, particularly in terms of how quickly and how much
they will improve. Stuck close to previous forecast, which is
slightly more optimistic than the LAMP guidance, although still
fairly close to that.

Tuesday afternoon...MVFR expected, IFR possible with snow likely.
East wind 5 to 15 kt.
Tuesday night...IFR expected. Snow. Northeast wind 10 to 15 kt.
Wednesday...IFR expected, MVFR possible in the afternoon. Snow
likely. Northeast wind 10 to 20 kt becoming northwest 15 to 25
Wednesday night...MVFR expected. Chance of snow. Northwest wind 15
to 25 kt.
Thursday...MVFR possible. Chance of snow. Northwest wind 10 to 20


MN...Winter Storm Watch from Tuesday afternoon through Wednesday
     afternoon for MNZ073>078-082>085-091>093.



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