Area Forecast Discussion
Issued by NWS Twin Cities, MN

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261
FXUS63 KMPX 192350
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
650 PM CDT Wed Apr 19 2017

.SHORT TERM...(This evening through Thursday)
Issued at 358 PM CDT Wed Apr 19 2017

Early afternoon water vapor imagery together with RAP13 surface
analysis and obs identified an upper level wave across Nebraska with
an inverted surface trough extending into western Iowa. The warm
front associated with this surface trough was very evident via both
the surface obs and also the GOES16 satellite imagery. This warm
front tilted poleward with height, and an area of elevated showers
and thunderstorms was moving across the forecast area producing a
cool, light to moderate rain.

Expect a few hours of dry weather once this rain moves though, but
another round of precipitation will develop in the form of deep
convection in the warm sector of the aforementioned surface
trough/low. Supercells storms will quickly become severe across
Iowa, and a few of these storms could propagate north of the warm
front and produce a threat for large hail across the southern part
of our forecast area near I-90.

Cold air will rush in on Thursday as the parent cyclone quickly
matures. Forecast soundings show some instability atop the boundary
layer so have included chance of showers through Thursday afternoon
for the eastern part of the forecast area. Highs will struggle to
reach 50 for many locations.

.LONG TERM...(Thursday night through Wednesday)
Issued at 358 PM CDT Wed Apr 19 2017

Looking ahead, the weekend looks dry as high pressure builds across
the region. Precipitable water will drop below a quarter of an
inch. Expect light winds with seasonable temperatures. On Sunday
night an upper level wave will move across the high plains and
develop a compact surface low which will bring showers and
thunderstorms across the region. The mass fields in this system
appear quite similar to the storm system that is moving across
Iowa today, but the major difference is moisture content.

Next weeks storm will have lower dewpoints by about 10 to 15
degrees which means much less available potential energy and a
reduced severe threat. Could see some thunderstorms, but at this
point the instability is very marginal and the LCLs are too high
to merit more than a monitor phase. Cooler weather will follow in
the wake of this system, so could have a freeze concern in the
typical cold parts of the forecast area.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 650 PM CDT Wed Apr 19 2017

SHRA with embedded TSRA will push through east central and south
central MN and west central WI early this evening ahead of a low
pressure system headed northeast across IA. Pea to dime size hail
will occur with the stronger storms. SCT SHRA or even -RA will
occur for much of the night from KRWF on north through KSTC and
KAXN. Ceilings will be dropping precipitously this evening with
widespread MVFR/IFR becoming common by mid evening with IFR for
the late evening and overnight hours. Some IFR has already made
its way into the MN River Valley. The -RA will lift northeast of
the TAF sites early on Thursday with ceilings struggling to reach
MVFR by afternoon. NE winds tonight 10-15 knots becoming NW early
on Thursday at 12-16 knots gusting 20-25 knots.

KMSP...Worst of the TSRA now over and to the south of the
airfield. Several waves of moderate to heavy showers will move
through early this evening with a break in the steady rain
thereafter. Widespread IFR ceilings are still expected late
tonight and Thursday morning. MVFR for the afternoon and evening.
Winds similar to those described above.

/OUTLOOK FOR KMSP/
Fri...MVFR ceilings possible early then VFR. Wind NE 5 kts.
Sat...VFR. Wind light and variable.
Sun...VFR. Wind NE-E 5 kts.

&&

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

$$

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



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