Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 220857

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
357 AM CDT Wed Mar 22 2017

.SHORT TERM...(Today and tonight)
Issued at 357 AM CDT Wed Mar 22 2017

Cool, dry air continued to filter southward across the Upper Midwest
overnight. This dry air mass is evident at the surface as dew points
are in the single digits to lower teens across western Wisconsin,
and into southern Minnesota. This dry air mass will lead to problems
with precipitation reaching the ground across the state over the
next 24 hours.

The leading edge of a developing area of low pressure and moisture
advecting across the Dakotas, has led to precipitation to develop in
central South Dakota early this morning. However, the depth of the
moisture is rather shallow and most of the moisture advecting into
Minnesota this morning will be at mid levels. Therefore, if any
precipitation develops along the leading edge of the changing air
mass (warm air advection regime), will be sprinkles/flurries at
best. Even the H-res CAMS don`t support any precipitation reaching
the ground, with the exception of elevated returns. Once the
moisture return source comes from the gulf, or at least with the
thunderstorm activity in the lower Mississippi River Valley region,
will our region become moist enough to support precipitation
reaching the ground. This is not likely until after tonight.

No changes in the current temperatures as highs today will be
similar to yesterday with readings in the 30s, to lower 40s. Tonight
will be warmer with lows only dropping a few degrees from afternoon

.LONG TERM...(Thursday through Tuesday)
Issued at 357 AM CDT Wed Mar 22 2017

The concern in the long term is the parade of short waves/low
pressure systems that will push into the western CONUS and then
make their way out into the central/southern plains. There will be
four such systems in the next seven days. The first one will
consume the first several days of the long term due its slow
movement. This is partly tied to a large upper level low over
eastern Canada that will be hard to displace due to a rex block
developing over the eastern Atlantic/western Europe.

One thing noted with the current deterministic runs is that the
GFS has shown a trend of pushing the heaviest part of the
precipitation axis well south of our forecast area. This is a
trend that has been occurring over the past day or so. This is
supported by the MPX-WRFARW LH and NLH runs, 18z MPAS and to
some degree the 00z HOPWRF-TS 24km ARW.

On the other hand, the Canadian and ECMWF keep the main
precipitation axis right across our CWA, arching from Sioux Falls
through the Twin Cities to north of Green Bay. One to two inches
of QPF is forecast from Thursday through Friday, while the GFS
locally is less than a quarter inch increasing to near an inch in
far SE MN. The difference is tied to the upper low exiting the
southwestern U.S. being just a tad farther north on the
Canadian/ECMWF versus the GFS. This allows the right entrance
region of the upper jet to be north of the upper Great Lakes
instead of down across central MN. The GEFS plumes would have been
nice to see but they have been unavailable for the past 24 hours
due to the NAMv4 implementation. Hopefully the next cycle they
will be back.

Another concern is that PW on the GFS is forecast to increase to
over 1 inch from Thursday into Friday across about the southern
third of MN. This is at the top of the sounding climatology for
MPX. In addition, there is ample elevated instability Thursday
night across far southern MN, to the north of a developing warm
front. Therefore, given the above, likely to categorical pops
continued for the southern half of the forecast area for the late
week period along with thunder mentioned at this point for
Thursday night. A concern for later shifts is that our QPF will
be too light if the Canadian and ECMWF are correct. Chance pops
then linger for Saturday and Sunday as the upper low scoots by to
our southeast.

Beyond Sunday, divergence sets in with the handling of the
additional short waves. The GFS wants to keep the next two south,
while the ECMWF keeps the second short wave south of us but then
brings the third wave into our area late Tuesday into Wednesday.
For now, have held on to a dry forecast after seeing the problems
we have with the system Thursday and Friday.

Temperatures will be climbing back above normal for the duration
of the long term with highs 5 to 7 degrees above normal with lows
nearly 10 degrees above normal. This will easily erase our
negative departure on the monthly average temperature with what
looks like our 19th month in a row of above normal temperatures
for MSP.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1057 PM CDT Tue Mar 21 2017

No changes for the 06z TAFs, with dry high pressure keeping skies
clear tonight. NW to SE band of clouds from eastern Montana to
southwest Iowa will drift east across the area Wednesday, but
initial dry airmass will keep us dry, with clouds getting about
as low as 6k ft. Winds will increase tomorrow, with some gusts
into the mid 20s possible, though increasing cloud cover will
limit mixing on southeast winds that already tend to not be as
efficient at mixing down higher momentum air.

KMSP...No additional concerns with VFR conditions and southeast
winds throughout the period.

Thu...MVFR. Chc -RA in afternoon & night. Wind SSE 10-15 kt.
Fri...MVFR with -RA likely. Wind NE 5-10 kt.
Sat...Chance MVFR/-RASN. Wind NE 10-15 kt.




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