Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 191042

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

.updated for 21z aviation discussion below...

.SHORT TERM...(Today and tonight)
Issued at 356 AM CDT Mon Mar 19 2018

The short term concern remains the timing of incoming trough and
attendant snow and amounts.

Clouds have been persistent but there have been sporadic holes in
the lower clouds, especially to the east. This trend may continue
into the morning mainly to the east as the easterly lower level
flow tries to draw in some drier air from the Canadian high. This
will influence overall movement of the western trough into the
area and should limit any significant precipitation over the
eastern cwa. Temperatures are expected to warm into the lower 40s
to the east today, with mainly the mid/upper 30s to the west.

We presently increase the snow chances into far west central MN by
00z Tue. This precipitation area will move into western cwa during
the evening with categorical PoPs indicated as the upper
trough/surface inverted trough move in. Forcing remains rather
weak with the trough and will slowly work into eastern MN by 12z
Tue. Currently we have around 2 inches accumulating over west
central MN by 12z Tue with less than an inch toward the west

.LONG TERM...(Tuesday through Sunday)
Issued at 356 AM CDT Mon Mar 19 2018

Tuesday through Thursday...While the aforementioned low pressure
system through the short term portion of the forecast shifts to
the southeastern CONUS, a lingering surface trough from this
system extending into the Upper Mississippi River Valley will be
responsible for continued light snow (with possibly some light
rain mixed in at times) for much of the day on Tuesday and mainly
for the MN portion of the WFO MPX coverage area. The snow looks to
wind down late Tuesday through Tuesday evening, resulting in
potentially up to an additional inch of snow accumulation, most of
which will be seen in western MN. High pressure oriented nearly
N-S over the central portion of the CONUS will then prevail across
MN/WI for Wednesday-Thursday. In conjunction with the surface high
pressure, an upper level ridge which had been building over the
western CONUS over the early portion of this week will shift into
the central states. The combination of the surface high with
increasing heights aloft will produce mainly clear skies and mild
temperatures. While highs only remain in the lower 30s on Tuesday,
highs will jump to the mid 40s by Thursday.

Friday through Sunday...This portion of the forecast still remains
rather murky due to poor model agreement and fairly wide swings in
temperatures throughout the duration of what looks to be a
prolonged rain/snow event. A potent upper level low will move into
the Pacific Northwest during the day on Friday with its trough
opening up over the Rockies during the day on Saturday. A smaller
piece of energy out of this trough will eject into the Central
Plains Friday night, helping kick a compact low pressure center
from western KS into the Ohio Valley Friday night through Saturday
afternoon. A mixture of Pacific and Gulf moisture in advance of
this system will be quickly tapped to produce 0.50"-1.0-" of QPF
across the WFO MPX coverage area. The bulk of this QPF looks to
come as rain Friday into Friday evening then change over to snow
as the system shifts slides off to the east Friday night into
Saturday morning. After a break in the action Saturday night, the
remainder of the western trough will shift into the central CONUS
in a weakened state and produce additional rain/snow showers
Sunday into Monday. This portion of the event looks to be more
disorganized than the Friday portion, so while PoPs are in the
likely to categorical ranges for Friday, PoPs are capped in the
chance ranges for Sunday. Because temperatures will range from the
lower 20s to lower 40s throughout this portion of the forecast,
confidence is low on any kind of snowfall amount at this point.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 535 AM CDT Mon Mar 19 2018

Cigs continue to improve most areas. Drier easterly low level flow
continues to lift cigs and generate large breaks. Expect this
trend to continue much of the day with VFR over all but KAXN/KRWF
perhaps early and again later this afternoon with the approach of
the trough. Expect IFR conditions to move into these areas first
at KAXN and then KRWF 03z-06z and continue the rest of the night.
We expect -sn to move into the KMSP area by 12z. It should remain
light most of Tuesday morning however, providing MVFR cigs/vsbys.
We expect VFR trends over west central WI through the forecast.
NE-E winds 5-10kts into tonight becoming more E into tonight.

KMSP...Still looks like VFR trends into tonight. We dropped to
MVFR after 10z and perhaps some flurries around 10z and light
snow by 14z Tues.

TUE night...MVFR cigs likely. Flurries psbl early. Wind NE 5 kts.
WED... MVFR cigs possible. Wind E 5 kts becoming NW.
THU...VFR. Wind SE 5 kts.




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