Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230401
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1101 PM CDT Thu Oct 22 2020

.SHORT TERM...(This evening through Friday night)
Issued at 244 PM CDT Thu Oct 22 2020

While forcing for precipitation is on the decrease this afternoon,
faint shortwave energy aloft will continue to be sufficient to
generate light precipitation tonight. We will see another band of
moderate snow work into the Winter Storm Warning area during the
late afternoon and early evening, so the headline looks to be in
good shape for continuance through 03Z. Elsewhere, have included a
sprinkle/flurry mention, along with light freezing drizzle as we
lose saturation in the dendritic (ice crystal formation) layer.
The Winter Weather Advisory also continues until 03Z, which seems
reasonable given the potential for freezing drizzle.

Lingering cyclonic flow on Friday will bring stratocu clouds.
While an overall dry day is expected, we could see some scattered
rain/snow showers.

Cloud cover will keep temperatures from lowering much tonight,
with lows in the lower 20s to lower 30s. Highs Friday will
struggle to get much above freezing, with upper 20s to mid 30s in
most locations. Some of the coldest air of the season will arrive
Friday night as surface high pressure builds into the area. Single
digit lows are expected over the fresh snowpack of west central
MN, with teens elsewhere.

.LONG TERM...(Saturday through Thursday)
Issued at 244 PM CDT Thu Oct 22 2020

The main concern in the extended period relates to the amount of
precipitation, and associated QPF/PoPs for late Saturday and
Sunday.

A storm system off of the Pacific northwest this afternoon will be
the main player for this weekends precipitation event. Models have a
good consistency on the evolution of this system as it moves across
the Rockies, and into the Northern Plains/Upper Midwest. The
differences from previous model runs is the lower QPF amounts and
PoPs farther to the south as the system will likely be weaker, and
have less moisture to work with then today`s system. Therefore,
don`t expect any heavy snowfall amounts, with generally a few inches
at best, especially near the Iowa border as models have been
trending farther south with the main energy.

In terms of energy, lift and moisture... as previously said,
moisture content is lower which seems likely as today`s system will
likely dry the atmosphere out significantly by Friday. Return flow
is also weak with a consistent drier east/northeast flow during the
onset of this system late Saturday night. In terms of energy/lift,
despite a robust short wave and upper level support, low-mid levels
of the atmosphere are weak. So again, based on the weaker low-mid
levels of the atmosphere and the lack of any instability aloft, am
leaning toward the drier and less snowfall trend in the latest model
runs.

Past Sunday, the upper level pattern de-amplifies (less troughing
over Canada) but still remains active across the southern CONUS as a
cutoff low develops. Farther to the north, two weak disturbances by
midweek may increase cloud cover but precipitation is not expected
at this time. A gradual warming trend is also expected past Tuesday.
However, there remains a significant spread in the 850MB temperature
ensembles which equates to less confidence on any rapid warm up or
cool down.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1101 PM CDT Thu Oct 22 2020

Confidence is increasing in one last deformation band developing
late tonight in eastern MN, that will spend the morning tracking
across western WI. As a result, added snow mentions to
MSP/MKT/RNH/EAU. This doesn`t look heavy, though could see some
vis restriction down to around 2sm. Given the snow on the ground
and time of year, favored the much slower timing for cig
improvements seen in the LAV. Currently, any sort of clearing is
clear up in northeast NoDak, so not really buying into what the
CAMs have with skies clearing quickly in the morning.

KMSP...Confidence is increasing in some light snow developing
between about 10z and 16z. Does not look heavy, but some IFR vis
can`t be ruled out. Was pessimistic on cigs clearing out, but if
you want to believe the HRRR, we could see VFR conditions by 18z.
However, have favored a slower timing for cig improvements given
the weaker sun and snow on the ground.

/OUTLOOK FOR KMSP/
SAT...VFR. Wind NW 5 kts.
SUN...IFR or lower with SN likely. Wind N 5-10 kts.
MON...MVFR possible early, then VFR. Wind WNW 5-10 kts.

&&

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

$$

SHORT TERM...LS
LONG TERM...JLT
AVIATION...MPG



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