Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190223

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
923 PM CDT Sat Mar 18 2017

Issued at 923 PM CDT Sat Mar 18 2017

Updated to include 06Z aviation discussion below.


.SHORT TERM...(This evening through Sunday)
Issued at 351 PM CDT Sat Mar 18 2017

Short term concern remains remaining low level clouds tonight and
the chance of showers/isolated thunder developing east Sunday

Low clouds were tough to break but it does appears most will have
dissipated with perhaps the exception of parts of west central
Wisconsin and southeast MN. There is some threat of this lower level
cloud cover to stall and then lift back to the northwest late
tonight as the southerly flow develops/increases ahead of the next
cold front. The HRRR has been pretty adamant on this occurring...
with most other deterministic models ushering drier lower level
humidity overnight. Will carry some of the mid level clouds east
tonight as some of this higher level moisture rides over the western

The next front moves into central MN by 18z Sunday. Models develop
some instability ahead of the front...and the do saturate the lower
levels by early afternoon into central MN. The GFS builds MUCAPEs to
500 J/kg and best LI`s to minus 3 ahead of the front across the
eastern half.  This could be enough to generate at least some
isolated showers. Will include a slight chance pops for the
afternoon...and move it east after 21z. Otherwise...other issue will
be the temperatures. With at least some cloud cover expected...we
may limit temperatures some...especially to the east...were
dewpoints remain in the 30s.

.LONG TERM...(Sunday night through Saturday)
Issued at 351 PM CDT Sat Mar 18 2017

A couple dry cold fronts, one Sunday night, and another Monday
night will keep the area in a northerly flow at the surface
through early next week. High pressure near Lake Superior early
Wednesday will slide to New England by Wednesday night which will
begin a return flow over the Midwest. A warm front may bring some
light snow Wednesday night, but accumulations would likely be
rather minimal.

Attention then turns to the large and slow moving cyclone late
week. The GFS is faster and further north than all guidance and
several ensemble members and thus was not considered. The GEM and
ECMWF along with several of the GFS ensemble members are in better
agreement with temporal and spatial details of the low center. As
the Gulf opens and moisture begins increasing northward, a
precipitation shield will develop from the central Plains to the
Upper Midwest Thursday afternoon. With the system only making slow
progress eastward across the central Plains and mid Mississippi
Valley through Saturday, there will likely be several periods with
precipitation and PoPs remain high later Thursday through Friday
night. GEM and ECMWF have trended a bit tighter with the deformation
band north of the system, favoring more Nebraska to southern
Minnesota and central Wisconsin. Both models are advertising 2 to
3 inches of QPF during the two day event from northwest Iowa,
across southeastern Minnesota into central Wisconsin, tapering to
about a 1/4 inch near Alexandria, MN. The good news is a high
probability of very warm air aloft with 850 mb temps of +5 to +10C
will keep p-type liquid in the heavy precip swath. P-type may be
a bit more questionable to the north where drier air may work in,
and it could be more of sleet or freezing rain scenario depending
on boundary layer temps. The system is still a ways off and things
are likely to change, but did take out snow from the grids except
near the onset and tail end of the precip.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 923 PM CDT Sat Mar 18 2017

Made no substantive changes to earlier forecast. Reasoning remains
similar, with high pressure drifting east overnight we`ll see
light winds. But, the winds will pick up from the southeast and
eventually south on Sunday as a frontal boundary approaches from
the west. Chances for showers still look best from near I-35 east
during mid to late afternoon. A thunderstorm is possible, but best
chance for that looks to be south of the forecast sites. Still
don`t have enough confidence in coverage of activity to try and
time in anything specific, so kept a mention of VCSH for now. Any
ceilings still look to be VFR.

KMSP...Primary uncertainty is with chances for showers Sunday
afternoon, but not yet sold on there being enough coverage to go
with more than VC at this point.

Monday...VFR. North wind 5 to 10 kt.
Monday night...VFR. Variable wind 5 kt or less.
Tuesday...VFR. North wind 5 to 15 kt.
Tuesday night...VFR. Northeast wind around 5 kt.
Wednesday...VFR. Southeast wind 5 to 10 kt.




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