Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231747

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1147 AM CST Mon Jan 23 2017

.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 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1145 AM CST Mon Jan 23 2017

IFR/MVFR ceilings will continue through the forecast period. The
main forecast concern is late in the taf period with the
potential of LIFR -sn/fg. Ceilings have been struggling to rise
this morning with some areas actually lowering as very little
mixing in the boundary layer is noted. Will continue the same
trends of lifting ceilings to MVFR or high end IFR during the
afternoon, but remain at or below 2.5k. Ceilings will begin to
lower once again overnight along with vsby lowering to LIFR in
west central Wisconsin. The storm system that will bring snow to
southern Minnesota has slightly slowed in the past 24 hours based
on the latest model information. Therefore, the bulk of the lower
vsby will occur after 18z Tuesday.


May concern is whether 1.7k or higher ceilings develop this
afternoon as several locations have risen around the Twin Cities
area. However, as stated before, very little mixing in the
boundary layer, so kept ceilings near 1.2 to 1.5k thru 21z, then
lifting to 1.8k by 21z. Confidence remains low on ceilings rising
to 2.0k or higher this afternoon. Light and variable winds will
become east-southeast and increase Tuesday. IFR ceilings and vsby
are becoming more likely by the end of the taf period, especially
after 21z.


Tue night...IFR. SN. NE wind 10 to 15 kt.
Wed...IFR. SN early. MVFR late. NE wind 10-20G25 kts bcmg NW.
Thu...MVFR. Chc -SN. NW wind 10 to 20 kt.


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



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