Area Forecast Discussion
Issued by NWS Twin Cities, MN

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805
FXUS63 KMPX 140331
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1031 PM CDT Fri Oct 13 2017

.UPDATE...For 06Z Aviation discussion below

&&

.SHORT TERM...(This evening through Saturday)
Issued at 149 PM CDT Fri Oct 13 2017

Surface analysis this afternoon puts a cold front emanating from
low pressure over Hudson Bay extending south into Lake Superior
then southwest through northwest Wisconsin into southeast
Minnesota and central Iowa. Weak high pressure over the Dakotas is
nudging east behind the front, contributing to clearing skies
slowly spreading east. Aloft, generally ENE-WSW flow is prevailing
while a longwave trough deepens over the Pacific Northwest and
subtropical ridging holds for over the southeastern CONUS. While
the ridge aloft is expected to remain in place through tomorrow
night, the trough will progress eastward over the Rockies and into
the Central Plains by tomorrow evening. The ridge will slow up the
progression of the front, allowing it to stall out from lower
Michigan through northern Missouri overnight. As the trough shifts
east, it will contribute to cyclogenesis over eastern Colorado.
The low is then expected to quickly move northeast along the
stalled front, moving to a position near the IA/MN/WI triple point
by tomorrow evening. A prolonged plume of deep South moisture will
be wrapped around the western periphery of the subtropical ridge
into the Upper Midwest, made available in advance of the
progression of the developing surface low for later tomorrow. This
combination of the approaching upper trough and surface low plus
the additional moisture will make for effective precipitation
generation tomorrow afternoon. Main difference from previous
forecasts is the timing as latest model runs have slowed the
spread of the rainfall from southwest to northeast. That said,
showers are still expected for much of the area by tomorrow
afternoon. As for temperatures, not much difference is expected
for highs tomorrow than from today, in the 50s area-wide. Lows
tonight behind the front will range from the mid 30s to lower 40s.

.LONG TERM...(Saturday night through Friday)
Issued at 357 PM CDT Fri Oct 13 2017

The area will start out cool and rainy Saturday night, with a transition
to dry and mild weather thereafter.

Models are in quite good agreement about the strong upper trough
arriving Saturday night and exiting Sunday morning. Cold advection
will be strongest Saturday evening, and south central MN will be
most susceptible to the strong wind, possibly seeing 20 knots
sustained as the surface low intensifies and departs to the
northeast.

Saturday evening, an axis of rainfall will be stretched out wsw-
ene across central MN into northwest WI, associated with a
deformation zone. Then another swath of rainfall will be to our
south and southeast. This means that southwest into east central
MN and west central WI may only see light rain tomorrow night,
where lift will not be as strong.

After this, upper flow turns northwest, and a weak short wave is
scheduled to arrive later Sunday. But this should only bring some
clouds from northern MN into western WI. But the northwest flow in
the wake of Saturday`s system means that max temperatures will be
5-8 degrees cooler than normal Sunday.

Once that goes by, the northern stream will remain north of our
area, with glancing blows from short waves and Pacific fronts
every couple of days. Monday through Friday should feature above
normal temperatures and dry weather. Toward the end of the week,
there seems to be reasonable agreement that another strong trough
will move into the middle to southern part of the west coast,
which could set the stage for an active pattern in this part of
the country a weekend from now. But that is beyond the time frame
in this forecast.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1032 PM CDT Fri Oct 13 2017

VFR conditions will continue through the overnight hours, with
scattered to broken clouds in the 12-15KFT range and light
east/northeast winds. Saturday clouds thicken and lower throughout
the day, with rain showers expected to spread across the area
after 17z. Expect cigs to follow suit and lower to MVFR during
the early to mid afternoon, with IFR possible by evening as rain
continues, especially over west central Wisconsin.

KMSP...
VFR will persist through Saturday morning, but MVFR will develop
around 19z-21z as rain moves in. Sub-1700ft cigs appear possible
for the evening push. Rain will continue through the evening. Rain
looks to shift east around 09z Sunday, with improvement in cigs as
winds become gusty from the northwest (around 25 knots).

/OUTLOOK FOR KMSP/
Sun...VFR. Wind NW 5-10 kts.
Mon-Thu...VFR. Wind SW 5-10 kts.

&&

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

$$

SHORT TERM...JPC
LONG TERM...TDK
AVIATION...LS



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