Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200307

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1007 PM CDT Mon Mar 19 2018

.Updated for 06Z Aviation Discussion...
Issued at 1005 PM CDT Mon Mar 19 2018


.SHORT TERM...(This evening through Tuesday)
Issued at 255 PM CDT Mon Mar 19 2018

A weak short wave was evident in the afternoon water vapor imagery
across the Dakotas, and Nebraska. This short wave, and associated
area of lift, especially in the dendritic growth zone, will be
centered in west central/southwest Minnesota late this afternoon,
and through the overnight period. The surface reflection is weak
and only a weak convergence zone in far western Minnesota
overnight is expected with this system. Thus, this is where the
best lift, moisture and convergence zone will highlight the area
of the best snowfall potential overnight. One to three inches in
likely in west central/southwest Minnesota, but amounts will
lessen significantly to the east as a persistent dry easterly flow
will limit the moisture depth. Slowly by morning, moisture will
deepen in eastern Minnesota which will allow for light snow to
develop. However, forcing is weak and most of the energy with the
system drops south into Iowa and slowly fades away. Therefore,
snowfall amounts will be less than an inch across eastern
Minnesota, with only trace amounts at best in far west central
Wisconsin. Temperatures will reflect the cloud cover and snow, and
overnight lows will be slow to fall. Daytime highs will be
cooler, especially along the Iowa border where cloud cover is more

.LONG TERM...(Tuesday night through Monday)
Issued at 300 PM CDT Mon Mar 19 2018

The main concern in the extended period is the potential of
accumulating snowfall, especially Saturday.

Most of the snowfall Tuesday afternoon will have ended, with a few
flurries possible Tuesday evening. The mean upper flow in our
region becomes more northwest as a deepening trough forms across
the eastern CONUS this week. Weak subtle waves will ride
southeast along this northwest flow, and may allow for some light
rain/snow in far southwest Minnesota on Thursday, but the bulk of
the impacted weather will stay far south of Minnesota.

Slowly the mean upper flow will become more amplified as an upper
ridge builds across the Rockies, and into the Northern Plains,
Upper Midwest by late in the week. The surface flow will slowly
become southeast, and increase in speed by Friday/Saturday as a
storm system begins to develop in the Rockies. This storm has the
potential of producing a considerable amount of precipitation over
the weekend, especially considering the long fetch of moisture
and the deep trough developing across the western CONUS.
Currently, there is a lot of model spread and uncertainties exist.
The latest model trends have the surface low further south across
Missouri than a few runs ago. Plus, thermal profilers are cooler
and this makes for a messy forecast. This system needs to be
watched closely as weather impacts are becoming likely. The main
impacts are the amount of precipitation (QPF), and snowfall. The
ground in Minnesota and western Wisconsin remains frozen and any
precipitation in the form of liquid water will run off quickly.
Thus, the potential of localized flooding exists. Secondly, the
snowfall could be significant is the atmosphere remains cool
enough during the strongest part of the system moving across the
area over the weekend. Stay tuned for further updates.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1005 PM CDT Mon Mar 19 2018

Snow should be at KAXN and KRWF shortly. VFR conditions will give
way to MVFR and eventually IFR as an area of light snow moves in
from the west. This snow will gradually weaken as it approaches
eastern MN and western WI. E/NE winds will be light throughout,
which means clouds should persist and lower overnight. Continue to
think ceilings may go below 1000ft, and could stay there most of
the day Tuesday.


Continued to back off a little on the snowfall, but kept lower
ceilings longer into Tuesday. Snow should be tapering off as it
reaches MSP, and could switch over to rain Tuesday afternoon.
Meanwhile low level moisture remains so should see lower ceilings
through most of Tuesday and possibly into Tuesday night.

WED... MVFR early, then VFR evening. Wind E 5 kts becoming NW.
THU...VFR. Wind SE 5 kts.
FRI...VFR early becoming MFVR with -RA/-SN. Wind E 15G25 kts.




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