Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 221006

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
406 AM CST Sun Jan 22 2017

.SHORT TERM...(Today and tonight)
Issued at 330 AM CST Sun Jan 22 2017

Areas of fog will continue this morning, but visibilities will
slowly improve with time - they actually already have in many
locations. Clouds and light fog or mist will continue through the
short term with little temperature fluctuation.

A quick peek at the water vapor this morning clearly shows that
the most volatile weather is definitely not across the local
area. There is a sharp trough off the west coast and deepening
surface low over the Pacific Ocean that should drop below 970mb
today. Heavy precipitation and strong winds will impact California
and much of the western CONUS. There is severe weather in the
southeast US this morning with widespread wind advisories/warnings
across the Southern Plains associated with another system moving
across the south. Locally, we`re north of the Polar Jet and storm
track in an area of weak low pressure and a "baggy" pressure
gradient. The result is a light wind and a moist boundary layer -
thus all the fog, mist and drizzle over the past couple days. The
relatively high dewpoints helped by melting snow pack has
provided a continuous source of low level moisture to help fuel
the drizzle or light rain. While we don`t expect the skies to
clear today, we don`t think the fog will be quite as bad or
widespread tonight as it`s been - although we do expect some. A
slightly drier, weak northwest flow will likely keep MN/WI from
seeing widespread dense fog. It should be a bit cooler tonight as
a result of this as well. Speaking of the fog this morning, there
has been improvement in the visibility since about 2-3am. We
might be able to drop the dense fog advisory before the noon,
which was the original expiration time.

.LONG TERM...(Monday through Saturday)
Issued at 315 AM CST Sun Jan 22 2017

The forecast concern in the longer term remains the snow event
for the Tuesday/Wednesday time frame. There remains some model
differences but the overall forecast remains unchanged.

The overall development of the western conus trough remains the
the issue with eventual lee side cyclogenesis over eastern
Colorado by 12z Tuesday. It is progged to lift northeast across
Iowa into southern Wisconsin By 12z Wednesday. The Canadian and
Nam_wrf remain the farthest south with the system...but they seem
to be to compact with the upper low...thereby focusing the main
forcing/snow band well south. The GFS and ECMWF have been fairly
consistent with the system...driving the snow band north into the
southern third or so of Minnesota...which is climatologically
consistent with the forecast surface low track. The southern
third of Minnesota still looks to be our highest potential for
snowfall accumulations and matches well with the GEFS 12r
snow accumulation greater than than 2 inches showing probabilities
greater than than 50% across this region. There are even some
lower chance probabilities of greater than 6 inches across south
central MN. Looking at the CIPS analog for this shows
high probabilities of greater than 4 inches overall most of the
cwa. Overall lower level thermal profile continues to show mainly
snow for the P-type through the event...with SREF and GEFS
indicating this as well. At the moment we have a healthy advisory
event with 2 to 5 inches over the area...with the higher amounts
mainly along and south of the Minnesota River valley toward the
I90 corridor.

After this storm system moves off to our east during the day
Wednesday, the latter half of the week continues to point to
cooler temperatures with highs below freezing and lows in the
teens to lower 20s. Still above normal but overall a bit cooler.
We will have to monitor flow and see if we get some weak system
moving through the area in the faster northwest flow pattern. At
the moment timing would bring the threat later next weekend into
the following week.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 902 PM CST Sat Jan 21 2017

Forecast is essentially unchanged from earlier, with no reason to
argue with persistence at this point. Guidance remains quite
pessimistic. Some westerly flow works in on Sunday which should
help in improving visibilities, but IFR ceilings will likely
remain through the period.

KMSP...Main uncertainty continues to be with visibilities
overnight. Maintained the idea of them going down to around 1/2
mile and remaining there, but will certainly need to be watched.

Monday...MVFR possible early. West wind less than 10 kt.
Monday night...VFR. Variable wind less than 5 kt.
Tuesday...MVFR developing, IFR possible late. Chance of rain and
snow. East wind less than 10 kt becoming northeast 5 to 15 kt.
Tuesday night...MVFR expected, IFR possible. Snow likely, possibly
mixed with rain early. Northeast wind 10 to 20 kt becoming
Wednesday...MVFR expected, IFR possible. Snow likely early.
Northwest wind 15 to 25 kt.
Wednesday night and Thursday...MVFR possible with a chance of
light snow. Northwest wind 10 to 20 kt.


WI...Dense Fog Advisory until noon CST today for WIZ014>016-023>028.

MN...Dense Fog Advisory until noon CST today for MNZ041>045-047>070-



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