Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210046

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

Issued at 743 PM CDT Thu Oct 20 2016

Updated to include 00z aviation discussion below.


.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 00Z TAFS through 00Z Friday evening)
Issued at 743 PM CDT Thu Oct 20 2016

Mid-level stratus will fill in and persist for much of the night
before scattering out under high-level cirrostratus tomorrow, all
VFR. Winds will go light/variable overnight then pick up generally
5-10 kts from the southeast tomorrow.

KMSP...No other significant weather impacts expected.

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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