Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 240416
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1116 PM CDT Mon Oct 23 2017

.UPDATE...
Issued at 1037 PM CDT Mon Oct 23 2017

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 353 PM CDT Mon Oct 23 2017

A very powerful storm system will develop over the next 36 hours
across the Great Lakes region as a broad upper level trough with a
textbook PV signature merges with a cutoff low over the Tennessee
River Valley. Once this merger takes place, expect to see
bombogenesis take place with the surface low deepening from around
1008 mb this morning over western Indiana to 979 mb by Tuesday
morning over the eastern U.P. of Michigan. As this surface low
deepens, cold air advection will intensity across the Upper
Midwest and maintain an unstable boundary layer tonight. Forecast
soundings continue to indicate 45 kt winds toward the top of the
boundary layer, so while it isn`t likely to persist continuously,
occasional gusts of 45-50 mph are likely later tonight across much
of Minnesota, spreading eastward to Wisconsin for Tuesday. Issued
a Wind Advisory for MN Tonight/Tuesday and for Wisconsin Tuesday.

As the system develops this evening, some wrap around rain
showers may develop east of I-35. It doesn`t appear enough cold
air will be in place at the surface for much snow, but cannot rule
out a few flakes late tonight before drier air moves in Tuesday.

.LONG TERM...(Tuesday night through Monday)
Issued at 353 PM CDT Mon Oct 23 2017

Winds will quickly subside early Tuesday evening as surface
ridging briefly moves in. Another low pressure system developing
ahead of the next surge of cold air will pass east across the
northern Plains Wednesday night and northern Minnesota Thursday.
Western and southern Minnesota should reach the warm sector
Wednesday afternoon when temperatures may reach the low to mid
60s. Cold front will pass through Thursday with temperatures
tumbling by afternoon.

With the positively tilted trough axis deepening Thursday night,
the surface low should also deepen and slow somewhat over
Wisconsin. The GFS and ECMWF continue to advertise a good band of
wrap around precip accompanying this system, although the timing
between the two continues to be an issue with the ECMWF slowing
down several hours with the 12Z run. The NAM and Canadian keep
much of it to the north. Thus, consistency issues spatially and
temporally continue to degrade overall confidence. However, the
pattern is favorable for the first snowfall of the season for much
of the area and probabilities with the GEFS are fairly high. Some
areas could see an inch or two in a worst case scenario, with the
more likely bet being an inch or less if the period of snow does
materialize.

The northwest flow will persist into early next week, keeping
temperatures below normal. An even colder shot of air may spill
down by the middle of next week following a cold front Monday or
Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1037 PM CDT Mon Oct 23 2017

A weak upper level trough, behind the departing large low
pressure center over Michigan, will swing through the region
overnight. While any showers will be confined to east of the
Mississippi River, low VFR to possible upper-level MVFR ceilings
will be prevalent through late morning tomorrow. The lower clouds
will then dissipate, leaving FEW-SCT high clouds through the day.
The main issue will be strong NW winds, with sustained speeds
hitting the 20-25kt range with gusts of 30-40kts. Wind speeds will
diminish going into tomorrow evening.

KMSP...Ceilings are expected to remain within VFR levels but, if
anything, there is some potential for a few hours of MVFR ceilings
during the Tuesday morning push. Ceilings below 1700ft are not
expected. Otherwise, strong NW winds will be the main issue.
Directions will remain in the 310-330 range tonight through
Tuesday afternoon. Sustained speeds will remain around 20 knots
with gusts 30-35 knots. Not expecting gusts over 40 knots but an
occasional observation as such cannot be ruled out.

/OUTLOOK FOR KMSP/
Wed...VFR. Wind WNW 10 kts.
Thu...VFR with -SHRA/MVFR cigs late afternoon, becoming -SHSN Thu
eve. Wind W 10-15 kts becoming NW 20G35kts.
Fri...VFR. Wind NW at 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory from 7 AM to 6 PM CDT Tuesday for WIZ014>016-
     023>028.

MN...Wind Advisory until 6 PM CDT Tuesday for MNZ041>043-047>051-
     054>062-064>070-073>078-082>085-091>093.

     Wind Advisory from 7 AM to 6 PM CDT Tuesday for MNZ044-045-052-
     053-063.

&&

$$

UPDATE...JPC
SHORT TERM...BORGHOFF
LONG TERM...BORGHOFF
AVIATION...JPC



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