Area Forecast Discussion
Issued by NWS Twin Cities, MN

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594
FXUS63 KMPX 041236
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
636 AM CST Sun Dec 4 2016

.UPDATE...
Issued at 622 AM CST Sun Dec 4 2016

Updated to include 12z aviation discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 410 AM CST Sun Dec 4 2016

Surface analysis this morning depicts a surface low over
southwestern Manitoba with a southward-sagging surface trough
draped over the central Dakotas through the central Plains.
Surface high pressure is prevailing over the Rockies and over the
Ohio Valley. Aloft, a deep longwave trough from central Canada
digs into the deep South. Plenty of moisture is being shunted
northward just in advance of both trough features, at the surface
and aloft, and the upper level feature is pivoting, taking on a
more negative orientation. Per model initialization soundings,
much of the moisture is found within the DGZ, helping to make for
efficient snow development over central portions of the WFO MPX
coverage area overnight. Bands of moderate-heavy snow have been
evident on KMPX radar and since midnight our office has picked up
about 1" of snow with roughly 0.05" liquid equivalent, making for
a 20:1 ratio, which is pretty decent for air temperatures of about
30 degrees (keeping in mind, it is a relatively small sample).
Have nudged up snow amounts slightly which will make for minor
accumulating snows from eastern MN through western WI.
Specifically, 1-2" can be expected through this afternoon in and
around the Twin Cities metro and up/down the I-35 corridor then
amounts will range 2-4" in western Wisconsin, highest in Chippewa
and Eau Claire counties where we have issued a Winter Weather
Advisory. Counties just to the west (Rusk & Pepin) will be close
to that mark as well, especially should the this same mesoscale
setup shift just to the east and persist. We will monitor and
adjust the advisory if/as needed, but regardless if there is an
advisory or not, travel may still be hazardous due to the wet
slippery nature of the snow. Most affected would be portions of
I-94 along with other highways in parts of western WI. The snow
will taper off from west to east during the afternoon and evening
hours with no additional snowfall expected from midnight onward.
Before the precipitation ends in eastern MN, there may even be a
brief mixing with rain should temperatures increase to the 36-37
degree mark but that`s about as high as the max temperatures would
be for today. Highs will generally run 32-36, keeping the
prevailing p-type as snow. Clouds will still be prevalent across
the area tonight as both trough features complete their
progression over the coverage area, making their way into the
Great Lakes by daybreak Monday morning. The lack of airmass change
plus the blanket of clouds will keep lows early Monday morning
from becoming too cold, only dropping to the mid-upper 20s.

.LONG TERM...(Monday through Saturday)
Issued at 410 AM CST Sun Dec 4 2016

The upcoming cool down is the main topic of interest in the long
term forecast period. Little has changed with the going forecast.

Starting out on Monday, a deepening surface low will be slowly
moving east along the Canadian/North Dakota border which places us
in a decent southerly flow and warm air advection regime. With
ample low level moisture, expected continued cloud cover and and
light precipitation will be possible. Temperatures will climb into
the mid 30s to low 40s across southern MN and west central WI, so
the precipitation will be a mix of rain and snow. Accumulations
will be very light.

Meanwhile the jet stream will be diving south as a large upper low
sags  south through western Canada. The surface cold front will
reach western MN Monday night and move east through the remainder
of the area by Tuesday morning and northwesterly winds will usher
cooler air into the region. Cold air advection will continue as
northwesterly flow persists. Did raise winds above guidance each
day from Tuesday through Thursday, roughly about 5mph. This was
consistent from the previous forecast. In addition, increased and
expanded pops on Thursday as the main upper low moves through.
With the cold advection and the upper low overhead, its plausible
to see light snow develop Thursday.

Highs will only be in the teens across most of the area Wednesday
and Thursday, around 10 degrees below normal.  A slight moderation
is expected toward the weekend, but not much.  There is some
agreement that potent shortwave will move through the Midwest next
weekend, hence the chance of snow in the forecast.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 622 AM CST Sun Dec 4 2016

Swath of light-mod snow continues to erode to the east, with the
western edge nearly aligned along the I-35 corridor at
initialization time. Snow will continue moving east with the WI
TAF sites having to deal with accumulating -SN likely into the
afternoon hours. IFR conditions will be prevalent through late
afternoon at all sites with improvement into VFR for western MN
late this afternoon then in eastern MN this evening. Ceilings may
attempt to drop back into MVFR by Monday morning but confidence
isn`t entirely solid on that scenario as VFR ceilings may be able
to hold.

KMSP...IFR conditions expected to persist through the first couple
hours of the 05/12z TAF then improvement is expected to bump
visibility into MVFR range as the snow diminishes. However. IFR
ceilings are still expected to prevail through mid-afternoon with
slow improvement thereafter. VFR conditions are then expected
thereafter. Little additional snowfall accumulation is expected
from this point with the snow shield moving east.

/OUTLOOK FOR KMSP/
Tue...MVFR. Chc -SN early. Wind W 15g25kts.
Wed...MVFR. Wind WNW 15g25kts.
Thu...MVFR. Chc -SN. Wind WNW 15g25kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 3 PM CST this afternoon for WIZ027-
     028.

MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...JPC
LONG TERM...SPD
AVIATION...JPC



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