Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 202103

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
403 PM CDT THU OCT 20 2016

.SHORT TERM...(This evening through Friday)
Issued at 403 PM CDT Thu Oct 20 2016

Extensive stratus has gradually been building south throughout the
day, but there have been recent signs of the southern edge
breaking up a bit as it approaches southern MN. As a trough axis
swings through, expecting these clouds to fill in to the south
this evening per much of the short range guidance. This should
keep temperatures milder with lows in the mid to upper 30s.

Clouds will persist into Friday, but southerly flow behind the
eastward shifting surface ridge axis will bring the next round of
WAA. Should see highs return to the lower 60s downwind of the
Buffalo Ridge, but mixing will be tougher to the east and highs
will be similar to today`s in the lower 50s north of I-94 and east
op I-35.

.LONG TERM...(Friday night through Thursday)
Issued at 403 PM CDT Thu Oct 20 2016

All still looks to remain quiet until Tuesday of next week, with the
only weather feature of significance till then a dry frontal passage
for the weekend.

Through the weekend, the amplification of troughs/closed upper lows
on either side of North America looks to leave us with ridging and
dry weather. A short wave will be rounding the top of the ridge
along the international border Saturday night, with its surface low
going across northern MN. Any precip with it will be staying
along/north of the international border, but it will swing a cold
front through here Saturday night/Sunday morning. Sunday afternoon
looks breezy with a well mixed CAA boundary layer, so we did
increase winds over what the central region SuperBlend guidance had.
Forecast soundings Sunday would support seeing NW winds gusting up
to around 30 mph by Sunday afternoon.

Early next week a short wave will get ejected from the western
trough and head out into the Plains. This will result in the
development of a warm front on Monday to our SW that will begin to
nudge toward southern MN Monday night. Both the GFS/ECMWF show
isentropic precip breaking out between 6z and 12z Tuesday. We have
seen some more trending toward agreement between the ECMWF and GFS
with what follows, with both developing a surface low and moving it
across Iowa Wednesday. The GFS is likely a bit too strong with the
system it develops and has its resultant precip too far south, but
both agree on the general idea that we should see a solid area of 1-
3 inches of rain develop to the north of the surface low where
frontogenetic forcing will be aided by upper diffluence in the exit
region of a 120+ kt jet streak that will be coming out of the
northern Rockies and across the northern Plains. Both models did
shift south some with where the heaviest rain will fall, so our
likely pops were trimmed toward the south and east as well in that
Tuesday night/Wednesday time frame. Along with the pop trimming,
also started to downplay the thunder mention, with the GFS now
showing best LIs just barely dipping to zero. Limited the thunder
mention to a slight chance and restricted it to the south/southeast
of the Twin Cities, closer to where the warm front and instability
will be. Finally if the clouds and precip materialize the way the
ECMWF and GFS say they will Tuesday and Wednesday, then our forecast
highs for both of those days could be a good 10 degrees too warm,
with highs in the 40s/50s more likely than the current 50s/60s if we
see some damp/gray days.

Behind this, we have some chance pops left over for Thursday, though
that is more of a relic of the previous run of the ECMWF which had a
warm front quickly lifting back into the area Thursday afternoon.
Though the current 20.12 models may say Thursday will be mainly dry,
we have been seeing enough changes in the models that far out to let
the blended forecast ride for now Thursday.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1256 PM CDT Thu Oct 20 2016

VFR stratus across the eastern Dakotas, northern MN and now
developing over western WI will fill in across central and
southern MN late this afternoon and evening. Winds will become
light and variable this evening, then south southeasterly winds
will take hold Friday.

KMSP...Stratus is most extensive just to the east, but it appears
likely by mid afternoon BKN-OVC cigs will return to MSP.

Sat...VFR. Wind light/variable.
Sun...VFR. MVFR cigs possible. Wind NW 10-20 kt.
Mon...VFR. Wind light/variable.


.MPX Watches/Warnings/Advisories...


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