Area Forecast Discussion
Issued by NWS Twin Cities, MN

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138
FXUS63 KMPX 250829
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
329 AM CDT SUN SEP 25 2016

.SHORT TERM...(Today and tonight)
Issued at 326 AM CDT Sun Sep 25 2016

Today and tonight...Surface analysis this morning shows a north-
south cold front along nearly the entire western MN/Dakotas
border with a slight warm sector holding strong in far SW MN.
The main surface low feature associated with these fronts is in
far southern Manitoba province. Aloft, deep southerly flow
continues to stream plenty of moisture into the area in advance
of a deep cutoff low over western North Dakota and this low is
maintained within a longwave trough emanating from north-central
Canada. Coverage thus far early this morning is not entirely
impressive but a pocket of low-level jetting, evidenced by a
small disturbance showing up on WV satellite imagery, is punching
north through eastern Nebraska and western Iowa. Better coverage
of precipitation is associated with the feature aloft but as the
overall pattern presses east, so will the better coverage of
precipitation. As such, aside from possibly an isolated pocket or
two of heavy rain, am not expecting much better coverage of
precipitation within the WFO MPX coverage area than currently
ongoing so am opting to discontinue the Flash Flood Watch prior
to 12z this morning. There is also quite the lack of instability
along with unimpressive lapse rates so am not looking for
anything in the way of strong thunderstorms. Even lightning is few
and far between with this activity. As this precipitation
moves east, a deep dry slot is still indicated on multiple
models immediately behind the cold front but in advance of the
upper level low. This will allow for some brief clearing, or at
least a rise in clouds to higher levels. As the upper level low
rotates northeast toward southeast Manitoba province, the trough
axis will open up and expand southward. The cooler core aloft
combined with trapped moisture within the base of the trough will
spark scattered rain showers moving in from the west and
northwest later this afternoon and evening. The showers will
linger over northern and eastern portions of the coverage area
through daybreak with low clouds also holding strong over much of
the area this evening through overnight tonight. Post-front,
temperatures today will be noticeably cooler and remain as such
through tonight. Highs today will only hit the 60-70 degree range,
which is some 15 degrees cooler than readings recorded over
western and southern Minnesota yesterday. Lows early Monday
morning will drop to the 45-50 degree range.

.LONG TERM...(Monday through Saturday)
Issued at 326 AM CDT Sun Sep 25 2016

Forecast concerns in the extended period deal with the evolution of
an Upper Low forecast to develop and intensify over the Great Lakes
early next week, and slowly drift southward.

Last week`s upper air pattern had been more progressive with a
fast southwest flow aloft and a very potent long wave trough
along the west coast. This long wave trough has progressed eastward
over the Rockies and into the plains, providing ample moisture to
the Upper Midwest overnight. Things will dramatically change over
the next two days as models continue to forecast an Upper Low
forming over the Great Lakes. This will lead to much cooler
conditions as the flow becomes northwest-north across the Upper
Midwest.

As an Upper Ridge forms north of this Upper Low, a blocking type
pattern will develop, leading to slow changes in the weather
department, especially over the Great Lakes. The GFS had been more
persistent in previous runs of this Upper Low development, and now
the latest EC/GEM have come more in line with this scenario.
Therefore, confidence has increased for this cooler pattern with
instability showers rotating around this Upper Low as it drifts to
the south next week and weakens. An Upper Ridge will slow begin to
build south and west across the Rockies by late in the week. This
ridge will build over the Upper Midwest next weekend. Therefore,
temperatures will slowly begin to modify with above normal
temperatures once again by next weekend. I don`t see any
widespread or organized precipitation pattern once todays system
moves off to the east-southeast.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1059 PM CDT Sat Sep 24 2016

A broken line of showers and thunderstorms extending all the way
from Texas up through Iowa will continue feeding north and
slightly east into the TAF area overnight. While the activity has
become a bit straggly this evening, expect it to become more
organized again over central MN into west central WI as a low
level jet of 40+ knots develops overnight. Have therefore retained
a mention SHRA/TS in the TAFs. MVFR and IFR conditions are
expected attendant with the shra/ts. Outside of the convective
activity, clouds will scatter out to yield VFR conditions
overnight at MN sites, but WI sites are expected to stay MVFR/IFR.
Low cigs are expected to redevelop by late Sunday morning under
the cold air advection regime with scattered showers possible.
South winds veer to west then northwest with the frontal passage.
Sustained 15-20 kt speeds with gusts between 25 and 30kts develop
by 18z Sun.

KMSP...Despite the absence of much activity on radar, do expect
more development as the low level jet strengthens overnight.
Attendant conditions with the SHRA/TS should be primarily MVFR but
temporary IFR conditions are possible. Clouds should scatter to
VFR in the wake of the convection, but MVFR cigs and possibly a
few scattered light rain showers redevelop by 18z Sun, along with
sustained west winds circa 18kts gusting to 25 kts.

/OUTLOOK FOR KMSP/
Mon...Chc MVFR/-SHRA. Wind WNW 15g25kts.
Tue...Chc MVFR early then VFR. Wind NW 5-10kts.
Wed...VFR. Wind N 5 kts.


&&

.MPX Watches/Warnings/Advisories...
WI...Flash Flood Watch until 10 AM CDT this morning for WIZ023>028.

MN...Flash Flood Watch until 10 AM CDT this morning for MNZ063-070-
     078.

     Flash Flood Watch until 7 AM CDT this morning for MNZ076-077-
     083>085-092-093.

&&

$$

SHORT TERM...JPC
LONG TERM...JLT
AVIATION...LS



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