Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231043
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
543 AM CDT Wed Aug 23 2017

.UPDATE...For 12z Aviation discussion below

&&

.SHORT TERM...(Today and tonight)
Issued at 407 AM CDT Wed Aug 23 2017

The main change to the short-term portion of the forecast was to
slow down timing for precipitation associated with the shortwave
dropping southeast from Manitoba. We do look to see an increase in
700-500mb humidity ahead of this feature today, particularly east of
the MN River valley. Therefore increased cloud cover a bit, and also
raised POPS slightly given the progged burst of healthy 600-700mb
Omega that drops south across the area this evening and overnight.

Given high pressure ridging at the surface, winds will be lighter
today, and temperatures still a bit below normal. Expect highs to
range through the 70s, and lows from 45 to 55 degrees.

.LONG TERM...(Thursday through Tuesday)
Issued at 407 AM CDT Wed Aug 23 2017

It looks like a rather unsettled pattern this weekend, with future
Tropical Storm or Hurricane Harvey potentially playing an indirect
role from the Gulf Coast.

A short wave will continue diving southeast Thursday morning with
a northwest to southeast oriented band of showers ongoing from the
Twin Cities area and southeast. This should exit the region fairly
quickly within the fast northwest flow with clearing skies by
afternoon. The respite from rain will be short-lived as moisture
increases from the southwest Friday. A persistent 25-35 kt LLJ
will be in place Friday and Friday night with a warm front
situated roughly along the Minnesota River across southwest
Minnesota. This should allow for continued development of showers
north of the boundary and cool temperatures. Instability looks
meager overall with drier southeast surface flow, but we certainly
could get a storm or two near the deeper moisture over the
eastern Dakotas.

That deeper moisture will shift east for Saturday with the parent
system while Harvey makes landfall somewhere over the western
Gulf Coast. Lower level flow (850-925 mb) is favorable to advect
some of Harvey`s moisture northward across the Plains, but a
the trough to the east may entrain some drier air in that flow. At
this point, a predecessor rain event (PRE) looks unlikely here given
the 700 mb trough across the east and northwest flow locally (the
trough is about 180 degrees out of phase for a favorable setup).
The eastern trough will leave Harvey without much steering flow
though and there is quite a bit of uncertainty with the track.
Multiple feet of rain are possible somewhere across Texas and
Louisiana and we will need need to watch how the low level flow
influences moisture advection up this way.

Continued with the high chance to likely probabilities through
Sunday with a few showers possibly lingering into Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 543 AM CDT Wed Aug 23 2017

Mid level clouds will increase throughout the day ahead of a
disturbance that will bring scattered showers tonight. Have
included VCSH/Prob30s for now given relatively low
coverage anticipated. Timing has slowed down by about 6 hours, and
it now looks to be more overnight. VFR conditions should still
prevail. Winds will be lighter today, starting out northwest then
becoming east/southeast this eve. Speeds in the 6-10 knot range.


KMSP...
VFR is expected through the period. Small chance of some
isolated/scattered showers moving close to MSP around/after 06z
Thursday .

/OUTLOOK FOR KMSP/
Thu...VFR with MVFR possible. Wind SE at 10 kts.
Fri...VFR with MVFR/-SHRA possible. Wind SE at 10 kts.
Sat...VFR with MVFR/-SHRA possible. Wind S at 10G20 kts.

&&

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

$$

SHORT TERM...LS
LONG TERM...BORGHOFF
AVIATION...LS



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