Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 110356
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1056 PM CDT Tue Oct 10 2017

.UPDATE...For 06Z Aviation discussion below

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 346 PM CDT Tue Oct 10 2017

Early afternoon water vapor imagery together with GFS 500 mb
heights and winds identified a compact upper level low across
southern Iowa, with widespread synoptic ascent downstream across
eastern Iowa, southern Wisconsin, and northern Illinois. Regional
reflectivity with surface obs confirmed the precipitation, with a
few lighting strikes across the south where there was some
instability to go along with the forcing.

This precipitation will bring rain to the far southeast part of
the forecast area this afternoon and evening. Meanwhile areas to
the northwest had clear skies and light winds. This will set the
stage for another cool night across western and central Minnesota,
but have decided to discontinue frost/freeze headlines for this
region given that it is mid=October and most locations saw a
freezing temperatures last night.

Looking ahead, southerly winds will develop on Wednesday, and
forecast soundings show mid level clouds by mid afternoon across
eastern MN and western WI. Meanwhile western Minnesota should have
more sun. Highs on Wednesday will be in the upper 50s to near 60.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 346 PM CDT Tue Oct 10 2017

The main focus of the long term remains the west coast trough and
the expected precipitation with it as it progresses eastward through
the weekend.  At this time, Saturday night looks to be our best
chance of appreciable rainfall.

The aforementioned trough will be pushing onshore tonight, and by
tomorrow night it will be over Oregon and Washington.  A surface low
will already begin to develop across Montana/southern Canada by this
time, and locally we can expect increasing southerly winds for
Thursday as the pressure gradient pushes eastward.  Low level
moisture advection looks quite strong tomorrow night into Thursday,
so did include a mention of drizzle across far southern MN.

From Thursday into Friday, the surface low itself will deepen and
move northeast through much of Manitoba.  Meanwhile the west coast
trough will have another reinforcing shortwave form which will take
a more southern route and is the feature to watch for us.  Lead
energy looks to bring rain across our southeast Friday, but the main
system arrives Saturday afternoon/evening and we do anticipate
widespread rainfall Saturday night.

After that system departs, warmer temperatures should return with
the end of the period looking like highs in the 60s are a reasonable
expectation.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1056 PM CDT Tue Oct 10 2017

Rain showers have shifted well south and east of the area at TAF
issuance, and now the next concern shifts to the potential for
MVFR ceilings to lift north into the area by daybreak Wednesday.
The Nam12 seems to be handling the current MVFR cigs over Iowa
better than other guidance, so have leaned toward that. This would
bring MVFR cigs into KMKT/KMSP/KRNH/KEAU between 12z and 15z,
reaching KSTC during the early afternoon. Think this scenario
seems reasonable, with the exception of not confident we will see
IFR cigs (sub-1000ft) as it indicates. So, have kept cigs in the
1500-2000ft range for most of Wed/Wed eve. Light and variable
winds overnight increase from the southeast on Wednesday
afternoon to sustained speeds 10-15 knots. Gusts to 25 knots
possible at KAXN.

KMSP...
Much more pessimistic about cigs this issuance. Higher confidence
that we will see an MVFR deck by 17z. Could possibly go lower
than 2kft during the afternoon.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind S 10 kts.
Fri...Mainly VFR. MVFR late with p.m. SHRA likely. Wind N 5 kts
becoming NE.
Sat...Mainly VFR. MVFR late with p.m. SHRA expected. Wind
ENE 5 kts.


&&

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

$$

SHORT TERM...JRB
LONG TERM...SPD
AVIATION...LS



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