Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250357

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1057 PM CDT Wed May 24 2017

.UPDATE...For 06z Aviation discussion below


.SHORT TERM...(This evening through Thursday)
Issued at 335 PM CDT Wed May 24 2017

The afternoon surface analysis indicated a surface ridge centered
across Minnesota with northeast winds across eastern Minnesota,
and east/southeast winds in the west.

The main concern over the next 24 hours is whether enough
moisture will allow for some showers to develop in west
central/central Minnesota during the afternoon.

Although models have been consistently moving a frontal boundary
across the Dakotas by late Thursday afternoon, moisture depth
remain limited in the southern half of Minnesota and upper level
energy is confined to northern Minnesota where better jet energy
exists. Only weak instability may be ample enough to generate a
few showers late Thursday afternoon in west central, and central
Minnesota. Otherwise, mid level cloudiness will increase with
temperatures rising into the 60s and lower 70s. This could be one
of the warmer days in the next seven as the extended period
remains cool.

.LONG TERM...(Thursday night through Wednesday)
Issued at 315 PM CDT Wed May 24 2017

Main points of discussion in the long term are the frontal passage
Friday as light precipitation is possible along the front, and for
the development of a longwave trough over central North America.

By tomorrow evening, the strong low pressure system of interest for
the long term period will be moving east across southern
Saskatchewan into southern Manitoba and the trailing cold front
draped to the south through the Dakotas.  There have been timing
differences in when this front will make its way through our region
but confidence is increasing that the front will reach the Minnesota
border overnight (early Friday A.M.) and work eastward through MN
during the day, and in western WI in the late afternoon to Friday
night.  The GFS remains the fastest with this idea, but the suite of
available guidance at least has more tightly packed than in previous
runs.  The Canadian is still much slower and is a significant
outlier in timing of the front, so leaned to a blend of
GFS/NAM/ECMWF.  Showers and a few rumbles of thunder will be
possible along and ahead of the front, especially in eastern MN and
western WI based during the afternoon as lapse rates steepen.

The parent upper trough with this system will slow down and
basically sit to our north in southern Canada and repeatedly send
shortwave energy down in cyclonic flow of and on through the
weekend, leading to a forecast that is littered with chances for
showers and limited chances for thunder as well as temepratures near
to below normal and northwest surface winds persisting for days.

Early next week, the upper ridge over the west coast amplifies, so
our upper trough will follow suit and deepen while holding steady
over our area.  Persistent northwest flow will continue with
temperatures looking cooler for Monday and Tuesday, and could see
diurnally driven scattered showers continuing through this period.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1057 PM CDT Wed May 24 2017

VFR conditions are prevailing now but MVFR ceilings are inching in
from the west now that low level winds are shifting to easterly in
direction. Expect the MVFR ceilings to reach KRNH and KEAU, but
will more likely be of a scattered nature to the west at KMSP.
There could also be IFR/LIFR visibility restrictions due to
BR/fog (primarily at KRNH/KEAU). After 18z Thursday isolated
showers will be possible (primarily in western MN), with the
slight chances expanding eastward during the afternoon.

Still do not think MVFR ceilings look quite as likely as they did
for Wednesday morning, so have kept it at a FEW-SCT mention. Any
broken layer would more likely be above 1800 ft. Winds veer to
southeasterly overnight with some gusts into the mid teens (knots)
developing by late morning Thursday. Isolated showers could near
the field by 00z Friday, but the probability/coverage is too low
to warrant inclusion in the TAF at this point.

Sat...Mainly VFR. Slgt chc P.M. -SHRA/-TSRA. Wind W 5-10 kts.
Sun...Mainly VFR. Chc -SHRA/-TSRA. Wind NW 5-10 kts.
Mon...MVFR possible. Chc -SHRA/-TSRA. Wind NW 5-10 kts.




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