Area Forecast Discussion
Issued by NWS Twin Cities, MN

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481
FXUS63 KMPX 272354
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
654 PM CDT TUE SEP 27 2016

.UPDATE...For 00z Aviation discussion below

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 321 PM CDT Tue Sep 27 2016

An area of stratiform rain will move across eastern MN and western
WI this afternoon and evening. Rainfall totals will generally be
less than a tenth. The rain is driven by a enhanced area of PV along
a shortwave trough rotating around a cut off upper level low. This
PV anomaly will rotate southeast, and the rain will gradually end
from north to south as it does so.

By Wednesday morning expect lingering clouds and northerly winds.
Forecast soundings show the clouds will be slow to dissipate in
central/eastern MN and western WI. Meanwhile western MN will have
clear skies. The breezy northwest winds will gradually become
northerly, and eventually northeasterly on Wednesday.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 321 PM CDT Tue Sep 27 2016

We are still anticipating nearly perfect fall weather through
Monday, with only one small tweak to the forecast for Saturday with
the next front of significance and chance for rain arriving Monday
of next week.

Main player for the weather through the weekend will be the upper
low currently over Lake Superior. This low will be cut off from the
main westerlies and drift down into eastern Kentucky/Tennessee by
Friday morning, at which point the GFS/ECMWF show this upper low
retracing its foot steps, ending up back over Michigan on Saturday.
Being northwest of the low, we will see pleasant and dry conditions
under the influence of high pressure Thursday and Friday, but as the
upper low moves into Michigan, it`s cyclonic flow and associated
cloud cover will start backing into our eastern areas. We have seen
the GFS trend west with the low, toward the ECMWF over the past
couple of runs, which has a couple of implications for the forecast.
One, increased cloud cover now shows up on Saturday as far west as
the Twin Cities, while a chance for showers has been brought into
western WI.

For next week, we are still seeing timing differences for when an
upper trough building over the Rockies this weekend begins moving
out into the Plains. The GFS continues to be the most progressive
with it, bringing this system in Monday night, with the ECMWF 12-18
hours behind. Given the strength of the upper ridge this weekend
over eastern Canada, the slower progression is likely the way to go.
As a result, we removed Pops from the forecast for Sunday night and
delayed how quickly they push east Monday into Monday night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 655 PM CDT Tue Sep 27 2016

Area of showers will exit TAF sites by 03z, and then MVFR level
clouds over northern MN/WI will filter south toward the TAF sites.
Model RH profiles show the thickest/lowest clouds will affect the
northern half of MN/WI, but still think STC-RNH-EAU will see an
MVFR deck this evening. KAXN and KMSP will be on the
western/southern fringes, but will also likely see a bkn020-025
deck. KRNH-KEAU may see sub-1000ft CIGs as well overnight. Clouds
slowly scatter out on Wednesday, but the MVFR deck will likely
linger through the morning. North winds prevail through the period
with gusts up to 20kts possible again during the day Wednesday.

KMSP...
Rain showers should end by 02z. The concern then becomes the
potential for low clouds this evening/overnight. Do expect
ceilings to dip to around 2500 ft, but current expectations are
that they will remain above 1800 ft tonight. Sct-bkn MVFR deck is
also expected to linger on Wednesday morning. Wind gusts diminish
this eve but pick up again by 16z Wed with speeds to around 18
kts.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind NE at 10kt
Fri...VFR. Wind NE at 05kt
Sat...VFR. Wind NE at 05kt.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$


SHORT TERM...JRB
LONG TERM...MPG
AVIATION...LS



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