Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 110807

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
307 AM CDT Wed Oct 11 2017

.SHORT TERM...(Today and tonight)
Issued at 300 AM CDT Wed Oct 11 2017

Surface analysis early this morning shows extensive high pressure
across the region from the Upper Midwest through the central Plains.
Aloft, a ridge axis sits over northern WI through southern MN into
northern KS. Associated with a potent upper level low over moving
onshore the Pacific Northwest, a low pressure center in southern
Alberta with a trailing cold front through northern California will
move in conjunction with each other east over the next 24 hours. The
main surface low will move into central Manitoba by daybreak
Thursday morning with the cold front sagging south through the
central Dakotas then southwest into WY/CO. The upper Mississippi
River Valley will remain generally in the warm sector of this system
which will allow for a warming trend of temperatures through
tomorrow. However, due to a rotating deep upper level ridge over the
southeastern CONUS, a pronounced plume of Gulf of Mexico moisture
will be advected northward into the mid-Mississippi River Valley.
Just enough mid-to-upper level moisture will make it as far north as
MN/WI such that clouds will be on the increase today through
tonight. In addition, a very weak buckling in the prevailing
southwest flow aloft may allow for isolated rain showers to develop
mainly after midnight in far eastern MN into western WI. There may
also be some patchy fog and/or drizzle in southeastern MN overnight
as the lower level moisture fills in south of I-94 (and closer to I-
90). As alluded to earlier, the more southerly flow available for
this region today will make for highs roughly 5-10 degrees warmer
today than what was experienced yesterday and this trend will
continue into Thursday. Lows this morning in the lower 30s to lower
40s will rise nearly 15 degrees warmer this time tomorrow.

.LONG TERM...(Thursday through Tuesday)
Issued at 300 AM CDT Wed Oct 11 2017

The main long term concerns remain timing of cold front Friday and
development/movement of the weekend system.

There may be some drizzle/light rain across eastern portions of
the area Thursday morning as low level waa and moisture are driven
east ahead of the next frontal system over the Dakotas. Clouds
are expected to clear west to east during the day. Depending on
timing of clearing, temperatures should warm through the 60s.

The cold front is progged to move into eastern areas Friday
afternoon. By that time, a strong 130 kt 300 hPa jet will be
streaking southwest/northeast across southern Minnesota and will
enhance strong mid level F-gen across mainly the southeast cwa. We
will continue the higher end PoPs for that region. This system
exits Friday night ahead of the next incoming trough.

The deterministic 00Z GFS switched to the previous 00Z ECMWF
handling of the weekend trough. It is now deeper than the ECMWF.
However, forcing with either model solution should be strong
enough to generate widespread rains over the region Saturday
night into Sunday. The 00Z GEFS ensembles continues to focus the
higher QPF off just to the southeast of our cwa during this

Following this system we will see some brief cooling with
temperatures moderating quickly as the upper flow becomes a bit
more zonal into the first part of the week.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1056 PM CDT Tue Oct 10 2017

Rain showers have shifted well south and east of the area at TAF
issuance, and now the next concern shifts to the potential for
MVFR ceilings to lift north into the area by daybreak Wednesday.
The Nam12 seems to be handling the current MVFR cigs over Iowa
better than other guidance, so have leaned toward that. This would
bring MVFR cigs into KMKT/KMSP/KRNH/KEAU between 12z and 15z,
reaching KSTC during the early afternoon. Think this scenario
seems reasonable, with the exception of not confident we will see
IFR cigs (sub-1000ft) as it indicates. So, have kept cigs in the
1500-2000ft range for most of Wed/Wed eve. Light and variable
winds overnight increase from the southeast on Wednesday
afternoon to sustained speeds 10-15 knots. Gusts to 25 knots
possible at KAXN.

Much more pessimistic about cigs this issuance. Higher confidence
that we will see an MVFR deck by 17z. Could possibly go lower
than 2kft during the afternoon.

Thu...VFR. Wind S 10 kts.
Fri...Mainly VFR. MVFR late with p.m. SHRA likely. Wind N 5 kts
becoming NE.
Sat...Mainly VFR. MVFR late with p.m. SHRA expected. Wind
ENE 5 kts.




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