Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 191118
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
618 AM CDT Thu Apr 19 2018

.UPDATE...
Issued at 618 AM CDT Thu Apr 19 2018

Updated to include 12Z aviation discussion below.

&&

.SHORT TERM...(Today and tonight)
Issued at 242 AM CDT Thu Apr 19 2018

Early morning water vapor imagery together with 500mb heights and
surface obs showed the compact upper level vorticity maxima over
Indiana. Surface high pressure was building in the wake of this
system across the Dakotas, and this will move over Minnesota and
Wisconsin over the next 24 hours.

This will set the stage for clear skies and light winds and keep the
region dry. The one area of concern, if you want to call it that, is
the potential for fog overnight. Boundary layer moisture will
increase as snow melts, and the lack of mechanical mixing should
keep this layer fairly shallow and yield favorable conditions for
radiation fog. Did add patchy fog into the forecast for tonight, and
increased today`s highs a bit above guidance given the full sun
expected throughout the day.

.LONG TERM...(Friday through Wednesday)
Issued at 242 AM CDT Thu Apr 19 2018

The extended forecast looks warm and fairly dry. The lone exception
is Monday night into Tuesday. There is increasing model agreement
that an upper level wave will drive a cold front across the region
with rain showers developing along it. As of now thermal profiles
look too warm for snow except perhaps north of I-94, but at most
expecting a rain/snow mix with no accumulation.

The main area of interest is a deep western trough that become cut
off across the 4-corners region Friday and Saturday. This upper
level vorticity slowly slides to the southeast, and this seems
reasonable since it does appear to be caught up in the subtropical
jet. Could see some light rain showers across southern Minnesota
with this wave, but the more likely solution is just mid/high clouds
overspreading the region for the weekend. These clouds could hold
back temperatures on Saturday, so kept highs right at the blended
guidance.

Next week looks warm. Most of the snow should be gone, and warm air
advection becomes more common place across the Upper Midwest for
Sunday and Monday. Aside from the warmer temperatures, this will
also bring in stronger winds to aid in mixing and heating. Continued
the trend of the previous forecast to raise high temperatures above
guidance for Sunday and Monday. Tuesday is tricky with the frontal
boundary approaching with clouds and precip, so continued with the
blend the rest of the forecast.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 618 AM CDT Thu Apr 19 2018

A quiet period is expected as high pressure currently centered
just west of the area drifts eastward. Light and generally
northwesterly winds today will become calm tonight with the
surface high overhead before becoming more southerly on Friday.
Given the expected snowmelt today, which will boost boundary layer
moisture, some fog and possibly a bit of stratus could occur
tonight (especially across the eastern half of the area). Hit
things hardest at KRNH and KEAU, but hinted at some BR and low
cloudiness at KMSP as well. Subsequent forecasts may need to be
more aggressive if conditions and guidance continue to hint at
things.

KMSP...Main item of uncertainty is the degree of fog and possible
stratus overnight tonight into early Friday. Was optimistic for
now, but it`s possible conditions could be worse with some of the
guidance hinting at a brief period of IFR visibilities.

/OUTLOOK FOR KMSP/
Friday afternoon...VFR. South wind less than 5 kt.
Friday night...VFR. Variable wind less than 5 kt.
Saturday...VFR. Variable wind 5 kt or less.
Saturday night...VFR. South wind 5 kt or less.
Sunday...VFR. Southwest wind 5 to 10 kt.
Sunday night...VFR. Southwest wind around 10 kt.
Monday...VFR. Southwest wind around 10 kt.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...
SHORT TERM...JRB
LONG TERM...JRB
AVIATION...


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