Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 182334
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
634 PM CDT Tue Apr 18 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 249 PM CDT Tue Apr 18 2017

A busy weather day today with a low pressure system screaming east
through central MN.  Widespread showers and some thunderstorms have
come to an end, but more showers and thunderstorms will be on the
way tomorrow with the next system.

The winds will remain gusty through the daylight hours before
diminishing overnight.  The tough part of the forecast is whether or
not the low clouds hang around as high pressure builds in from the
northwest.  The clouds could become trapped under the inversion and
stratus linger all night.  On the flip side, the guidance has
repeatedly overdone low level moisture this spring, leading to a
more pessimistic forecast than reality has shown.  Leaning toward
mostly mid and high clouds, with fog possible when winds become
lighter overnight.

For tomorrow, more rain is forecast to move in, from the south this
time.  This next system will lift northeast out of Colorado with the
warm front advancing through much of Iowa.  Widespread rain to the
north of the front, along with weak elevated instability will lift
into southern MN in the afternoon.  Raised pops to near 100% in this
area where agreement is very high among the models.  Thunder should
be scattered or isolated and we do not expect severe weather at this
time.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 249 PM CDT Tue Apr 18 2017

The longer term concerns remain timing/development of the trough
through the region Wednesday night into Thursday. Then some threat
of frost later Thursday night over the northeast cwa and possibly
Sunday mornings well.

The longer term deterministic models drive the upper trough east
across the area into Thursday morning. This will promote categorical
PoPs across most of the area Wednesday night and trailing to the
east through Thursday morning. Clouds are expected to remain most of
the day to the east and will limit overall heating potential to the
east Thursday afternoon. Drier air works in then Friday night as
high pressure drops south. This should promote a clearing sky and
light winds. Temperatures should be able to cool to the lower 30s
across the north and east cwa by Friday morning with some frost
potential. Still have time to monitor model trends as the GFS is
trying to force a secondary wave dropping in behind the retreating
trough.

Following this system we should see dry and warmer conditions
developing into the weekend. The models continue to show a weak cold
front dropping into the region later Saturday night into Sunday but
it appears weak at this time. We retained the small chance of
showers over mainly across the northern cwa Saturday night and again
Sunday night. The next trough moves into the area Monday into
Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 634 PM CDT Tue Apr 18 2017

Low confidence forecast with regards to the dissipation of the
MVFR ceilings currently overhead. Short term guidance is backing
away from the clearing to our northwest making it much past
central MN during the night with MVFR ceilings being maintained
from the Twin Cities on east and south. This seems plausible when
looking at the RAP/NAM 0.5km condensation pressure deficits. The
NAM is more bullish on maintaining the MVFR longer than the RAP.
Another reason the ceilings may hold in there is that a ridge of
high pressure is quickly building in from the eastern Dakotas and
this may aid in trapping the low clouds under an inversion. For
now, went for a longer duration with the MVFR ceilings over the
previous package. This then leads into Wednesday on whether or not
any VFR will occur at all across southern MN and west central WI
as another low pressure system and warm front approach from the
central Plains. Confidence is high on showers spreading into KRWF
in the morning and then overrunning the remainder of the TAF sites
during the afternoon and continuing Wednesday night. MVFR or
lower ceilings and visibilities are likely. A few thunderstorms
can`t be ruled out for the Twin Cities as well as points east and
south late Wednesday afternoon and evening. NNW winds diminishing
quickly this evening and becoming light NNE overnight. E winds
10-15 knots on Wednesday with gusts to 20 knots.

KMSP...Kept the TAF MVFR through the period with confidence
lowering on clearing overnight. Some VFR is possible in the
morning before more MVFR ceilings/visibilities take hold for
Wednesday afternoon and night in showers/isolated TSRA.

/OUTLOOK FOR KMSP/
Thu...MVFR ceilings likely. CHC of SHRA early. Wind NW 10-15kts.
Fri...MVFR ceilings possible early then VFR. Wind NE 5kts.
Sat...VFR. Wind light and variable.

&&

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

$$

SHORT TERM...SPD
LONG TERM...DWE
AVIATION...RAH



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