Area Forecast Discussion
Issued by NWS Twin Cities, MN

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862
FXUS63 KMPX 172006
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
Issued by National Weather Service LA CROSSE WI
306 PM CDT Tue Apr 17 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 305 CDT Tue Apr 17 2018

Latest water vapor satellite imagery shows upper low over the
northeast United States...shortwave ridging over the central United
States and upper level trough over the Rocky Mountains. Latest 19z
surface analysis indicates high pressure over southern Minnesota
providing mostly sunny skies across the forecast area.

Main focus tonight through Wednesday night is upper level
trough/closed upper level tracking into the Great Lakes region. The
17.12z deterministic GFS/NAM/ECMWF have shifted track of surface low
slightly further south than previous runs. This will have impacts on
location of where the deformation band of heavy snow sets up. As of
right now...heavy snow band location appears to be mainly along and
south of the Minnesota/Iowa border and impact the far southern
forecast area. At this time...confidence is high snow will fall
across much of the forecast area. However...confidence in snowfall
amounts is lower...based on slightly further track of system.
Expect snow to move into the forecast area after 06z Wednesday.
The deterministic models continue to indicate about elevated
CAPE in the mid levels of the atmosphere. Left mention of a slight
chance of thunder across the far southern forecast area Wednesday
morning. This will also potentially produce snowfall rates of 1
to 2 inches per hour mainly along and south of Interstate 90.
Total snowfall amounts are expected to be 4 to 6 inches along and
south of Interstate 90 with lesser amounts north. At this
time...no changes to headlines with the Winter Storm Warnings and
Advisories.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 CDT Tue Apr 17 2018

Thursday into Friday...Surface ridge over the eastern Dakotas and
central Minnesota becomes the dominant weather feature across the
forecast area and provides dry weather and slightly warmer
temperatures. High temperatures should climb into the 40s across the
forecast area both days.

Main forecast concerns Friday night into Tuesday are temperatures
Saturday into Monday...then precipitation chances Monday night into
Tuesday. The deterministic 17.12z GFS/ECMWF/GEM are in good
agreement with building upper level ridge into the Northern Plains
and Upper Great Lakes Region Saturday into Monday...then upper level
ridge breaks down and upper level trough moves into the Northern
Plains States Monday night into Tuesday. The deterministic models
are suggesting 925mb temperatures warming to plus 5 to plus 10
degrees celsius Saturday into Monday. This will allow temperatures
to warm into the middle 40s to middle to upper 50s across the
forecast area. With subsidence underneath upper level
ridge...expect dry weather Saturday into Monday. Upper level
trough and associated cold front moves across the forecast area
Monday night and into Tuesday. With moisture convergence and lift
along the cold front/upper level trough...this will provide
chances of rain across the forecast area.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1223 CDT Tue Apr 17 2018

VFR conditions will persist this afternoon. Increasing clouds are
expected this evening into Wednesday, with ceilings trending
towards MVFR late tonight and Wednesday. Snow will increase late
tonight, especially at KRWF to KMKT, continuing on Wednesday with
IFR visibilities at times. The snow will spread northward through
the morning, although have not introduced any snow yet into
central MN and west-central WI TAF sites.

KMSP...VFR conditions through this evening with lowering ceilings
this through tonight becoming MVFR around sunrise Wednesday.
Chances for snow increase late in the morning with IFR
ceilings/visibilities possible.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind N at 5 to 10 kts
Fri... VFR. Wind light/vrb
Sat... VFR. Wind bec S at 5 kts


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Warning from 7 AM Wednesday to 1 AM CDT Thursday
     for MNZ084-085-092-093.

     Winter Weather Advisory from 7 AM Wednesday to 1 AM CDT Thursday
     for MNZ065-067-075>078-083.

     Winter Storm Warning from 4 AM to 7 PM CDT Wednesday for MNZ091.

     Winter Weather Advisory from 4 AM to 7 PM CDT Wednesday for
     MNZ054-064-073-074-082.

&&

$$

SHORT TERM...DTJ
LONG TERM...DTJ
AVIATION...JM



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