Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 181204

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
604 AM CST Wed Jan 18 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM CST Wed Jan 18 2017

Main concern overnight has been the excruciatingly slow departure of
stratus to the east. As usual this time of year, the stratus has
hung around longer than guidance would indicate, but do believe that
by mid morning most of our area will be clear of it, as depicted by
the HRRR. This makes sense as well as this morning we will briefly
get more of a westerly component to our low level winds, which will
bring in air from Neb/SD/western MN, which is cloud free. The lack
of clouds and ample sunshine will be key to our high forecast
working out as well, especially in western WI. However, we have a
fairly mild start to the day out there, so favored forecast highs
heavily toward the warmer guidance (bias corrected Euro MOS

Tonight the question is how much do we see the stratus return. By
this afternoon, our winds will turn back to the south. These winds
will be transporting moisture north across the Plains today, with
the extensive stratus currently across central Texas into Eastern
New Mexico heading this direction tonight. There are indications
that this stratus could extend from SW MN into NW WI by the end of
the night. Went with a tempered sky grid overnight, with most
coverage in the SW CWA. Not too concerned about fog tonight either
and it`s because of the south winds expected to remain up through the
night. As we have see tonight, once you get away from the stratus
deck, visibilities are pretty good and there`s little fog, so expect
something similar. Though the increasing dewpoints will likely
signal the return of haze as what could be a 7-10 day long period of
murk begins.

.LONG TERM...(Thursday through Tuesday)
Issued at 400 AM CST Wed Jan 18 2017

As alluded to in the short term, we expect a very moist boundary
layer through the entire long term period. This will lead to
periods of light rain/drizzle, a lot of low cloud cover, and
fog/mist as well. The time/height cross sections off the latest
numerical guidance are impressive with saturation below 5000ft
for nearly the entire 7-day period from Thursday to next Wednesday
in MN/WI. This also coincides with temperatures that should be
approximately 20 degrees above normal. The cloud cover may be the
only reason we don`t set any daily high temperature records over
the next several days. The best chance for light rain looks to
come with a couple weak surface lows that move through the area
early Friday and then again on Saturday. There is a chance some
locations will have a surface temperature right at 32 degrees when
the rain falls late this week, and thus there is a chance for
light freezing rain or drizzle, but temperatures will more likely
be in the 34 to 40 degree range with no icing impacts. The
stronger upper jet and storm track will be across the west coast
and southern CONUS through the weekend, and that`s where the
heavier precipitation is expected.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 604 AM CST Wed Jan 18 2017

Stratus is almost clear of the area this morning and we have a
beautiful day in store. Confidence low in forecast tonight, but
low levels of atmosphere will be very moist. Think winds will send
us toward more the stratus than the fog scenario, but at the very
least, feel GFSlamp is underplaying the fog/stratus threat, though
on the flip side, the NAM is too moist. For now brought in
br/stratus to most sites, but there`s low confidence on that
aspect of the TAFs.

KMSP...high confidence in TAF today. Low confidence on stratus
potential tonight, but SREF probs for CIGS under 1000ft and vis
under 1sm are both near 100% 12z Thu, so should be a very gloomy
end to the TAF period, just a question of when does the gloom

THU...IFR/MVFR. Winds SSE 5-10 kts.
FRI...IFR/MVFR. Chc -SHRA. Winds SE 5-10 kts.
SAT...IFR/MVFR. Chc -SHRA. Winds SE 5-10 kts.




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