Area Forecast Discussion
Issued by NWS Twin Cities, MN

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469
FXUS63 KMPX 031051
AFDMPX

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

.SHORT TERM...(Today and tonight)
Issued at 430 AM CST Sat Dec 3 2016

Early this morning, a subtle 700mb wave was moving through the
area producing a few areas of flurries or very light snow
despite high pressure at the surface. As expected the cloud cover
has held firm, but there is some erosion to the cloud deck across
portions of South Dakota. But, the last few satellite scans show
new stratus forming in northwest Iowa and expanding. So, we are
holding firm to the forecast for continued cloud cover this
period.

Early this morning, a mid level shortwave trough axis was apparent
on water vapor imagery pushing into the Dakotas from
Montana/Wyoming. This shortwave is expected to continue east
through the Dakotas this morning and begin spreading light snow
into western Minnesota this afternoon/evening. As the wave becomes
more negatively tilted and the PV feature pushes through late
tonight, isentropic lift (albeit not impressive) will coincide
with deeper moisture and produce up to an inch of snowfall across
far eastern MN and into west central WI by tomorrow morning.

Temperatures will continue to only vary by 5-10 degrees through as
skies remain mostly cloudy. We could see some brief breaks in the
clouds later today before the shortwave reaches us, but clouds
will fill back in tonight.

.LONG TERM...(Sunday through Friday)
Issued at 430 AM CST Sat Dec 3 2016

Sunday through Tuesday...The day will commence with a cold front
swinging through the region in conjunction with a modest longwave
trough axis. Light snow will likely be ongoing in far eastern MN
into western WI, and likely will continue in western WI through
much of the day. Its fast progression and far proximity from the
parent low (in south-central Canada) will mitigate any appreciable
snow accumulations so will only look for 1-2 inches in western WI
with less than an inch going into eastern MN. Some mixture with
-RA is possible in southeast MN as cold air advection will not
kick in until the start of the week, particularly with H5 heights
actually rising slightly on the backside of the departing ridge
for Monday. Highs will increase from the low-mid 30s on Sunday to
the mid 30s to lower 40s on Monday, even with plenty of cloud
cover still in place. A more potent but drier cold front will
swing through the region Monday night into early Tuesday and this
front will be the leading edge of a prolonged surge of colder air
which will last through the rest of the week. While some snow
showers are possible across the area, very limited moisture look
to keep accumulations minimal at worst, potentially an inch or
less. The main impact will be H85 temps in the -20 to -25 deg C
range starting to make their way down from northwestern Canada
atop dense high pressure oozing its way southeast. H5 heights
will also drop, shifting to a more west to northwest flow. As
such, highs are expected to only range 20-30 degrees.

Wednesday through Friday...Much colder temperatures will be the
main story with only minor spurts of -SN throughout the second
half of the week. The dense cold high pressure and deep northwest
flow will prevent any significant systems from impacting the
region, making for the first strong cold spell of the season. An
upper level trough will drop southeast through the region late
Wednesday into early Thursday, bringing some snow showers for
mainly northern and eastern portions of the WFO MPX coverage area
but with little to no snow accumulation. As alluded to,
temperatures will go on a very noticeable plunge to below normal
levels and this is even without any upstream snow cover to help
modify or enhance the colder air. Highs are expected to drop to
the teens while lows hit the single digits. Winds will also
increase in the mid-to-late week timeframe, which means wind
chills from Wednesday on through the rest of the week will
commonly run from zero to ten degrees below zero Fahrenheit.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1054 PM CST Fri Dec 2 2016

MVFR ceilings overnight in the 015-025 range. A few snow showers
can`t be ruled out from the Twin Cities on east and south due to a
mid level low pressure system near KRWF late this evening. This
feature is moving quickly eastward with weak WAA and some upglide
ahead of it. On Saturday, the low level high pressure system over
us will retreat to the east. LAMP probabilities continue to point
to ceilings becoming VFR during the late morning through early
afternoon hours from west to east. This seems plausible as the
low level wind field picks up from the SE on the backside of the
high. However, MVFR will return in the evening across western MN
along with a chance for MVFR/IFR visibilities in -sn as a large
scale trough approaches from the Dakotas. Light winds overnight
becoming SE 6-12 knots Saturday afternoon/evening.

KMSP...Ceilings near 020 overnight. Another small period of -sn
can`t be ruled out between 06z-09z due to the aforementioned wave
over SW MN. VCSH used. Confidence remains high that ceilings will
become VFR Saturday afternoon on the backside of the high. Chance
for light snow returns by midnight Saturday night due to the
approaching trough. A period of -SN is then expected between
04/08z-13z before ending. At this point, about a half inch of
snow accumulation is expected.

/OUTLOOK FOR KMSP/
Sun...MVFR/ifr. -SN ending in the mrng. Wind SW 10 kts.
Mon...VFR. Wind SE 10-15kts.
Tue...MVFR. -SHSN early. Wind NE 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...SPD
LONG TERM...JPC
AVIATION...RAH



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