Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 032332

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
532 PM CST Sat Dec 3 2016

.UPDATE...For 00z Aviation discussion below


.SHORT TERM...(This evening through Sunday)
Issued at 314 PM CST Sat Dec 3 2016

Snow is now pushing into far southwest Minnesota from South
Dakota, Iowa, and Nebraska as a trough lifts northeast from the
central Plains. Visibility reductions have actually been quite
impressive already, falling to a mile and even 3/4 mile in western
Iowa. Not anticipating the snow to change much in intensity, but
it will become more widespread this evening as slightly better
moisture reaches eastern Minnesota and Wisconsin. Should see
several hours of light snow tonight and Sunday, persisting the
longest toward central Wisconsin where 3 to 4 inches are possible.
Most of the snow will fall late tonight and Sunday in those
locations, when temperatures may be warming into the low to mid
30s. Therefore, there shouldn`t be too much in the way of impacts
unless the snow falls moderately or heavily. For that reason, and
the current forecast calls for 3+ inches only in far eastern Eau
Claire and Chippewa counties, held off on an advisory. Elsewhere,
an inch is possible as far west as Alexandria, Willmar, and
Mankato with 2 inches near the WI border.

A few snow showers may remain into the afternoon over central MN
and western WI, but little in the way of accumulation will occur
after the morning hours with the best surge of moisture headed

.LONG TERM...(Sunday night through Saturday)
Issued at 314 PM CST Sat Dec 3 2016

Fairly quiet weather in the extended. The main changes to the
forecast was to increase winds on Tuesday above model guidance.
Gusts near 25 mph seem very reasonable. Also increased pops on
Thursday. There is an upper level wave dropping down which together
with the cold temperatures should produce some light snow showers.
Model QPF is quite low, but the synoptic environment supports
precipitation. Other than that no significant changes from model

Early afternoon water vapor imagery with GFS 500 mb heights and
winds showed a cutoff low across the Baja, with fast onshore flow
off the coast of Washington and Oregon. This zonal jet will prevent
the aforementioned southern stream low from affecting the Upper
Midwest. Instead a surface low will move along the international
border on Monday. Warm air advection ahead of this low will bring
Monday`s high near 40 across the region, which is around 10 degrees
above the seasonal average for early December. In addition, forecast
soundings show some lift, saturation, and precipitation late Monday
as the cold front moves through. Thermal profiles support a mix of
rain or snow.

Looking ahead, cold air advection will keep the boundary layer mixed
on Tuesday, so have increased winds during this time about 5 mph
above guidance. Seasonably cold air will remain over the Midwest
through the weekend. On Thursday the 03.12 models are in pretty good
agreement with a PV anomaly rotating down from Canada, so expanded
the chance for snow showers during this time. The GFS brings
accumulating snow across the region on Saturday...but the ECMWF is
considerably farther south near I-80. Do not have the confidence to
favor one solution over the other at this time.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 533 PM CST Sat Dec 3 2016

High confidence in the prevalence of MVFR cigs (or lower) through
the period, with reductions to IFR cigs/vsbys when the snow is
falling. The snow will be falling near TAF onset at
KAXN/KRWF, but will also shift east of there by midnight as it
settles in at the other sites. The duration of snow will linger
the longest at east central MN and west central WI sites (KMSP-
KRNH-KEAU), where snow will continue through Sunday morning.
Should start to see some improvement to VFR at KRWF toward the end
of the period (00z Mon), but MVFR cigs are expected through the
period at the rest of the sites.

Snow is expected to start around 04z, with the lowest visibilities
in snow occurring between 06z and 12z. Accumulations are not
expected to exceed 1/2 inch per hour. Cigs will be below 1800ft
during that timeframe, then come up to around 1800ft at 17z when
the snow ends. Expect to see some breaks in the MVFR deck by 21z.

Mon...VFR. MVFR with Chc -SN late. Wind SE 10-15kts.
Tue...MVFR. Chc -SN early. Wind W 15g25kts.
Wed...MVFR. Wind WNW 15-20kts.




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