Area Forecast Discussion
Issued by NWS Twin Cities, MN

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597
FXUS63 KMPX 261116
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
616 AM CDT Tue Sep 26 2017

.SHORT TERM...(Today and tonight)
Issued at 343 AM CDT Tue Sep 26 2017

Regional water vapor imagery/radar, and current trends of the short
term models, all support a sharp cutoff of the steadier
precipitation from southwest to northeast across southern Minnesota
this morning. This sharp cutoff is in response to the main short
wave moving across western Iowa early this morning, which is noted
from the sharper contrast in the water vapor imagery. Behind this
short wave, moisture depth becomes shallower and upper level support
ends.

There were two noted circulations /water vapor imagery/ in the
western Dakotas early this morning. As these weak circulations
rotate across the Dakotas, and into northern Minnesota this
afternoon, a few instability showers will be possible in central
Minnesota, but coverage will likely be too small to note in the
current forecast. Otherwise, skies will gradually clear tonight as
the main system moves off to the northeast. Due to ample boundary
layer moisture residing behind todays system, fog is possible once
skies clear in western Minnesota. I wouldn`t be surprised to see
localized dense fog where skies clear prior to Wednesday morning in
west central Minnesota.

.LONG TERM...(Wednesday through Monday)
Issued at 343 AM CDT Tue Sep 26 2017

The long term period looks mostly dry through at least Saturday as
Canadian high pressure fills in across the region in response to
subsidence on the downstream side of an amplified ridge advancing
east from the Pacific the next several days.  The next chance for
appreciable precipitation comes on the heels of said ridge, as a
trough looks to cut off and bring precip into the region in the
Sunday-Monday timeframe.

Expect that most of the cloud cover from today will have advected to
the east by tomorrow morning, with high pressure pushing in from the
west.  So, partly cloudy skies are expected from Wednesday through
the end of the week, but a shortwave trough will slide  southeast
from northern MN Thursday, bringing a few showers and a stray
thunderstorm or two to far eastern MN and western WI.  Otherwise
temps should be in the mid to upper 60s to finish out the week,
essentially normal for late September.  Really, Wednesday through
Saturday look to bring pleasant early fall conditions.

An upper trough on the backside of the aforementioned ridge will
begin to cut off on Sunday as a strong west to east jet streak noses
in from the Pacific.  This system will be the one to watch in the
long term.  We could see pretty warm conditions early next week in
the warm advection regime of this system, but also the opportunity
for showers and thunderstorms Sunday PM through Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 615 AM CDT Tue Sep 26 2017

Surface low moved over east central Minnesota over the past hour
and winds have begun to shift to the west/northwest across all of
Minnesota. It remained light and variable in west central
Wisconsin where cigs have dropped to 200` at KEAU. Elsewhere, cigs
remain in the LIFR or IFR range with isolated MVFR/VFR
conditions. Based on the continued ample moisture below 4k today,
and winds increasing from the west/northwest, both cigs
and vsbys will improve as good mixing develops. There will be
problems near KRWF/KEAU where airport minimum could develop
temporarily for an hour or two this morning. Otherwise, expected
cigs to slowly lift with MVFR cigs during the afternoon, and VFR
conditions developing overnight. Some fog is possible in west
central/central Minnesota where skies clear and surface winds
become light and variable by Wednesday morning.

KMSP...

IFR cigs will continue for the next few hours with improvements
during the afternoon/evening. The main concern is when cigs rise
above 1.7k, which doesn`t look likely until late morning/early
afternoon. Winds will slowly become west/northwest and increase
this morning. Some gusts of 16-18 kts are possible during the
afternoon.

/OUTLOOK FOR KMSP/

Wed...VFR. Winds WNW 5 kts.
Thu...VFR. Winds WNW bcmg NW 10 kts.
Fri...VFR. Winds N-NNE 5-10 kts.

&&

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

$$

SHORT TERM...JLT
LONG TERM...SPD
AVIATION...JLT



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