Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 202330
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
630 PM CDT Thu Apr 20 2017

.SHORT TERM...(This evening through Friday)
Issued at 306 PM CDT Thu Apr 20 2017

This afternoon, the departing surface low was centered over the
Great Lakes at the surface, but the large upper level trough
enveloped most of the upper midwest with the trough axis over
eastern MN/western WI.  The widespread stratocu shield will
gradually begin to erode this evening, with diminishing cloud cover
expected from west to east overnight.  Some scattered low clouds may
linger into tomorrow morning.  But, ultimately as the upper trough
shifts east tonight, a ridge will push in from the west, leading to
widespread subsidence across the region, and clearing skies.

Meanwhile, surface high pressure will strengthen overnight across,
centered across western MN.  With the lack of wind and clearing
skies there, have included fog overnight and into tomorrow morning.
Farther east, thinking that the scattered clouds and more wind will
prevent much fog from developing tonight.  For tomorrow, the high
will slowly push across north central MN to the east.  We will see
mostly sunny skies and generally north winds of 5 to 10 MPH.  Highs
will be in the upper 50s to near 60.

.LONG TERM...(Friday night through Thursday)
Issued at 306 PM CDT Thu Apr 20 2017

The weather this upcoming weekend continues to look great for being
outdoors. However a much more active weather pattern will develop
early next week with several strong storm systems expected to move
across the Midwest. Confidence is fairly high that this active
weather pattern will come to fruition since it will be driven by
strong Pacific jet upstream that will come crashing on shore and
break down into several shortwave troughs.

In the meantime, a cool dry Canadian air mass will remain across
Minnesota and Wisconsin in the wake of the cold front that pushed
through the region overnight. This seasonably dry air mass will make
for a sunny weekend, but it will also have implications on the
weather for Monday. The first of a series of PV Anomalies will
develop a surface low over Minnesota and Wisconsin. The wind shear
profile favors organized storms and severe weather, but the boundary
layer is very dry and is not able to recover ahead of the cold
front. For that reason there is not instability, and may see the
cold front pass through dry on Monday. Areas across northern
Minnesota and Wisconsin will have a much higher chance of seeing
precipitation than areas to the south.

Looking ahead, the is a tremendous amount of energy associated with
the aforementioned upper level jet. The models show considerable
disagreement on how they handle this energy. For example, the GFS
and ECMWF 20.12 bring another shortwave and surface low across
the region, and this one is further south which would mean a
better chance of precipitation. Later next week a stronger system
should develop across the Midwest, but at this point it is beyond
our forecast period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 630 PM CDT Thu Apr 20 2017

Isolated showers will end early this evening across eastern MN and
western WI. However, MVFR ceilings will be slow to lift in western
WI due to the cyclonic low level flow. This will eventually change
during the night as high pressure builds in from the Dakotas. Some
MVFR BR possible around daybreak Friday under the ridge axis in
western MN. Although the axis of high pressure will be over the
TAF sites on Friday, the CU rule is rather negative in the morning,
likely leading to SCT CU forming before fading away in the
afternoon. NW winds 12 knots gusting to 18 knots this evening,
diminishing to less than 10 knots overnight, then becoming
northeast Friday afternoon.

KMSP...VCSH for the first hour this evening as a surface trough
pushes south of the airfield. VFR through the period with SCT
conditions overnight and Friday. Winds similar to those described
above.

/OUTLOOK FOR KMSP/
Sat...VFR. Wind W 5 kts.
Sun...VFR. Wind NE 5 kts becoming E.
Mon...VFR. ISO SHRA. Wind SE 10 kts becoming S 15-20 kts.

&&

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

$$

SHORT TERM...SPD
LONG TERM...JRB
AVIATION...RAH



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