Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 122323
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
623 PM CDT Thu Oct 12 2017

.UPDATE...For 00Z Aviation discussion below

&&

.SHORT TERM...(This evening through Friday)
Issued at 138 PM CDT Thu Oct 12 2017

Surface analysis this afternoon shows a cold front extending south
from central Manitoba province through the central Dakotas to
along the CO/WY border. In advance of this front is extensive NE-
SW high pressure from central Quebec province through the Great
Lakes into the mid-Mississippi River Valley. Aloft, pronounced SW
flow is entrenched over the area between a subtropical ridge over
the Gulf Coast states and a longwave trough over the western
CONUS. While the southeastern ridge will generally hold its place
through tomorrow morning, a chunk of the trough aloft will break
off and shift east, moving into central Canada, helping nudge the
cold front across Minnesota tonight and across Wisconsin tomorrow.
Very little upper level support will accompany the front while
deepest moisture is generally south of the WFO MPX coverage area.
Therefore, aside from an increase in cloud cover for the bulk of
the coverage area, the only precip potential lies in far southern
and far eastern parts of the coverage area tonight and tomorrow
morning, mainly in the form of sprinkles/drizzle. High pressure
will fill in behind the front, bringing in cooler air for the
area. Whereas highs ranged from the upper 50s to the upper 60s
from east to west this afternoon, highs will only range from the
mid 50s in central MN/WI to the lower 60s in southern MN/WI.

.LONG TERM...(Friday night through Thursday)
Issued at 412 PM CDT Thu Oct 12 2017

Main concern for the long term is the storm moving in Saturday
morning. It`s certainly a harbinger of winter, but temperatures
will be too warm to be concerned with that now. It is possible,
however, that rain may become mixed with a little bit of snow
early Sunday morning in central MN as the cold air arrives. Once
the system moves through this weekend, the pattern will generally
be somewhat zonal over this area for at least a couple days. Thus
dry conditions and temperatures a little above normal are in the
offing next week.

After a weak short wave moves through tomorrow morning, upper
ridging will briefly take place, keeping MN/WI in quiet weather
tomorrow night, and temps should be a little above normal as
surface winds shift from north to east in advance of the main
system.

Models seem to be in decent agreement with the sharp trough
moving through Saturday night. Core of jet max around 150 knots
will have moved over the area, and there does seem to be a double
structure to it, with some energy coming from the Pacific Northwest
while most arrives from the southwest. Surface low strengthens
significantly as it moves northeast toward the Great Lakes. Main
low level jet Saturday will be to our south and southeast, so
heavier rainfall is not as much of a concern here. But there are
hints of a dry punch arriving midday Saturday, and a couple models
do indicate some modest elevated instability, so will not be
surprised if there is a bit of thunder.

Surface low really deepens as it tracks from south to east of our
area, and northwest winds rev up for a time Saturday night. Some
gusts may exceed 40 mph in favorable areas of southwest and south
central MN. Rain should taper off Saturday night.

After this, a fast moving pattern will bring the next front
through here Monday evening and possibly another Wednesday
afternoon. But that is when some major differences begin showing
up, so a consensus of the models is best for next Wednesday and
Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 523 PM CDT Thu Oct 12 2017

A cold front will move across the area overnight, and bring back
in low stratus clouds, primarily across west central WI. Expect
ceilings to lower back down to MVFR at KRNH/KEAU, possibly
reducing to IFR overnight. Have decreasing expectations for MVFR
to develop at MN sites, including KMSP, per model trends. Have
therefore only kept the bkn-ovc MVFR mention to the east at WI
sites. In the wake of the front, skies clear out by late morning
(with except possibly at KEAU) and VFR conditions will prevail.
Winds shift to southwest and then northwest as the front passes,
eventually becoming north/northeast by the end of the period.
Speeds will be the strongest this eve, then generally 6-12 knots
overnight and Friday.

KMSP...
It appears less likely that an MVFR deck will develop with the
frontal passage, with the threat greater to the east over WI. Have
included a SCT020 mention and will monitor evening trends.

/OUTLOOK FOR KMSP/
Sat...Mainly VFR. MVFR late with p.m. SHRA likely. Wind ENE 5-10
kts.
Sun...VFR. Wind NW 5-10 kts.
Mon...VFR. Wind SW 5-10 kts

&&

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

$$

SHORT TERM...JPC
LONG TERM...TDK
AVIATION...LS



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