Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 181859

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
159 PM CDT Tue Apr 18 2017



.SHORT TERM...(Today and tonight)
Issued at 340 AM CDT Tue Apr 18 2017

The surface trough is on our doorstep this morning, while water
vapor satellite shows a well-defined shortwave trough over the
Dakotas. A look upstairs also reveals a coupled jet structure
which is facilitating rather impressive differential divergence
over western MN. These factors are combining to generate showers
from western into central MN, with embedded thunderstorms to the
west where negative best lifted indices are negative. As the
surface low central moves across central MN to Lake Superior today
the precipitation will shift eastward and winds will become gusty
from the west/northwest.

Hi-res models have trended a bit slower with the eastward exit of
the precipitation today, so have tweaked grids to reflect that. By
18z activity should be mostly over west of the Interstate 35
corridor, and out of the area by 00z Wed.

Temperatures will have the potential to warm into the 65-70 degree
range over south central MN where some sun is possible and breezy
southwest flow will yield decent mixing. For the remainder of the
area, lower 50s to lower 60s are expected. Lows tonight are not
expected to get quite down to freezing, with mid 30s to lower 40s

.LONG TERM...(Wednesday through Monday)
Issued at 340 AM CDT Tue Apr 18 2017

Slight differences in the models continue for Wednesday/Thursday
weather system, as two short waves moving out of the Rockies, begin
to interact with each other.

Although most of the sensible weather elements will remain the same
as rain is almost certain Wednesday/Wednesday night across the Upper
Midwest. The differences begin late Wednesday night/Thursday morning
as a secondary short wave moves across the Canadian Rockies, and
into the Northern Plains. The GFS/MPAS/GEM remain fixed on the
southern short wave that moves across the Plains, and into the
western Great Lakes by Thursday morning. The EC is similar, but has
more interaction with the short wave in the Northern Plains. This
creates a northern bias of the EC weather elements vs. the
GFS/MPAS/GEM. The interaction of the EC also holds onto the
precipitation longer across east central Mn and west central Wi into
Thursday afternoon/evening.

Although confidence remains high for a prolonged period of
precipitation developing Wednesday morning, and lasting through late
Wednesday night, uncertainties continue on when the precipitation
will end Thursday. Due to more consistency of the GFS over the past
several days, am leaning toward a faster solution of the
precipitation ending late Wednesday night/early Thursday morning. If
the EC is correct, the precipitation will hold on longer through
Thursday. This will also affect highs on Thursday where only the
lower 40s are forecast if the precipitation holds on longer. Even if
the GFS/GEM/MPAS is correct, highs will likely on rise to near 50
with a cool northerly wind.

As in previous discussions, frost/freezing conditions are likely in
east central Minnesota, and west central Wisconsin Friday morning as
temperatures fall into the upper 20s to lower 30s.

No changes for the upcoming weekend as a storm system dives
southeast across the Rockies, and into the Southern Plains, Lower
Mississippi River Valley by Sunday. Easterly flow from this system
to our south will keep conditions dry, but cool for late April.

The weather pattern will likely change early next week to a more
active period once again as a series of storm systems dive southeast
across an active upper trough forming along the east coast.
Therefore, the Upper Midwest will be slightly cooler than normal on
temperatures, but wetter than normal.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1244 PM CDT Tue Apr 18 2017

Surface low streaking east across central MN, with strong
southerly winds ahead of the trailing cool front, but will quickly
switch to a westerly direction this afternoon. Plenty of MVFR cigs
behind the front except far southern MN has seen some clearing.
The winds will diminish greatly tonight, and the main concern is
the model guidance slamming 1.5kft ceilings into the area all
night. Thinking that the guidance is overdoing moisture, a
tendency so far this spring in these situations, so we are
leaning toward an optimistic forecast with SCT skies at those

KMSP...The wind will switch to westerly quickly this afternoon,
perhaps by 20Z. Gusts will continue through the afternoon, but
diminish tonight.

Thu...MVFR Cigs possible early then VFR. Wind NE at 5-10kt.
Fri...VFR. Wind NE 5kts.
Sat...VFR. Wind light and variable.




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