Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190444

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1044 PM CST Mon Feb 18 2019

.UPDATE...For 06Z Aviation discussion below


.SHORT TERM...(This evening through Tuesday night)
Issued at 400 PM CST Mon Feb 18 2019

After a cold night tonight, the main concern in the short term period
continues to be the potential for accumulating snowfall late
Tuesday night through Wednesday evening.

A 1040 mb high pressure centers over the region tonight and lingers
into tomorrow, with dry weather expected. A cold night in some areas
is possible tonight with calm winds and the high overhead, but just
how high we get will depend on the amount of high to mid cloud cover
present. It appears that we will have just enough cloud cover during
the overnight to keep temperatures from really plummeting over the
deepest snowpack in central and western Minnesota. Currently have
lows down to around -10 across central Minnesota but will have to
monitor satellite trends overnight as there is the potential for
temperatures to drop much lower.

High pressure slides off to the east Tuesday evening, with a
deepening area of low pressure approaching the area from the central
Plains Tuesday night. With fast 150+ kt flow aloft, confidence is
still high in expecting a relatively quick 10-12 hour burst of
snowfall during the day on Wednesday. However, models continue to
show slightly different solution in the deepening of the 500 mb
trough and associated track/intensity of the surface low. The
GFS/FV3 pass a quicker open wave over the region, with lower QPF
amounts of 0.25-0.4" primarily across southeastern MN into central
WI. Meanwhile, the NAM has a closed-off 500 mb low and a stronger
surface low with a swath of 0.5-0.6" QPF further north from
southwest MN through central MN. The ECMWF/CMC split the difference
between these two solutions with QPF amounts of 0.4-0.5" from
southern Minnesota through northwest Wisconsin. Believe the NAM
solution to be an outlier so have trended towards a blend of the
Euro/CMC/GFS, which puts widespread amounts of 2-5" across the
entire area, with a swath of 5-7" from south-central Minnesota
through west-central Wisconsin. Have issued a Winter Storm Watch for
these areas where confidence is highest in seeing the heaviest snow,
with a high-end advisory/borderline warning event looking most
likely. Confidence is still moderate in the exact location of where
this heaviest band of snow will set-up, so it is certainly possible
that additional counties are added to the watch or upgraded to
advisories/warnings if more a consensus is reached tonight and
tomorrow. The greatest impacts look to be with Wednesday morning`s
commute,as the heaviest snowfall is expected between 4 AM to Noon.
Snow will taper off from west to east across Minnesota Wednesday
afternoon, and linger into Wednesday evening across west-central
Wisconsin. Some travel impacts during the Wednesday evening commute
across far-eastern Minnesota and west-central Wisconsin also look to
be a possibility.

.LONG TERM...(Wednesday through Monday)
Issued at 400 PM CST Mon Feb 18 2019

The calm before the active winter weather will be Thursday as
surface high pressure will keep conditions dry. Meanwhile in the
Western CONUS, the mid to upper level trough will become more
amplified, allowing for the jet stream to become more
meridional- oriented across the Central CONUS. Strong warm air
advection in combination with upper level divergence from the
right entrance region of a jet streak will cause enough lift for
snow by Friday afternoon. Cyclogenesis lee of the Rockies will
occur as the trough continues shifting eastward. The trough will
become negatively tilted as a surface low deepens as it lifts from
the Oklahoma/Texas Panhandle region into the Central Plains on

There are still some model discrepancies with this panhandle hook
system that will affect how much precipitation MN/Central WI will
receive Saturday evening through Sunday. The 18.12 ECMWF solution
brings more precipitation to the Central MN as it lifts the low
through Central IA to Northeastern WI by late Sunday morning.
This solution also presents the possibility for mixed
precipitation with warmer low-level air. The 18.12 GFS solution
has the system further southward with the low reaching into
Northern IL late Sunday morning. This would likely bring less snow
to Central MN, but a lower chance for mixed precipitation. Both
solutions indicate that light snow will linger through Sunday
night with the trough axis still over the Upper Midwest. Overall,
there is medium confidence in the impacts we will see from this
system given model guidance differences and that we are still
several days out from the event. Otherwise, Monday is looking to
be mostly dry and much cooler


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1044 PM CST Mon Feb 18 2019

Clouds will lower and thicken through the period as the next
storm system approaches. By 00Z Wednesday expect low-end VFR
ceilings, with reduction to MVFR ceilings occurring overnight
Tuesday night into Wednesday morning as snow begins. Light and
variable winds overnight tonight become south/southwest at 6-8
knots on Tuesday, and then back to southeasterly on Tuesday

KMSP...Snow is expected to begin by the start of the Wednesday
morning push, with ceilings/visibilities lowering to MVFR/IFR.

Wed...IFR with -SN. Wind E 5-10 kts.
Thu...MVFR cigs possible. Wind WSW 5 kts.
Fri...MVFR cigs. -SN/IFR possible late. Wind SE 5-10 kts.


WI...Winter Storm Watch from late Tuesday night through Wednesday
     afternoon for WIZ023>026.

MN...Winter Storm Watch from late Tuesday night through Wednesday
     afternoon for MNZ063-070-078.

     Winter Storm Watch from late Tuesday night through Wednesday
     afternoon for MNZ076-077-082>085-091>093.



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