Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190319

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1019 PM CDT Sun Mar 18 2018

.SHORT TERM...(This evening through Monday)
Issued at 242 PM CDT Sun Mar 18 2018

A still and cloudy day across the region beneath high pressure. The
lack of sunshine or mechanical mixing kept high temperatures about
10 degrees cooler than yesterday.

Over the next 24 hours a weak upper level short wave will move
across the region and lead to broad ascent across the region. Clouds
should prevail, and deeper saturation should lead to some
precipitation developing across western Minnesota Wednesday
afternoon. Thermal profiles show a mix of rain/snow. Should have
enough ice crystals to limit any potential for freezing rain, so
have continued along the lines of the previous forecasts and removed
it from the forecast. This system will gradually weaken as it heads
toward eastern Minnesota and western Wisconsin Monday night into
Tuesday. Total accumulations will be around 2 inches in western
Minnesota, only a trace in eastern Minnesota and western WI.

.LONG TERM...(Monday night through Sunday)
Issued at 242 PM CDT Sun Mar 18 2018

Aside from the aforementioned light rain/snow on Monday night and
Tuesday, the upper level wave will also push a reinforcing cool
airmass across the Upper Midwest. Meanwhile height rises and warm
air advection over the Rockies will lead to a tight temperature
gradient oriented along the Missouri River Valley.

This temperature gradient will become active Thursday night into
Friday as an upper level wave move onshore the west coast. A
shortwave trough will take on a negative tilt as it moves across the
High Plains. Despite a pronounced deepening surface low pressure
system, there will be very strong frontogenesis which will lead to a
band of heavy precipitation Friday/night into Saturday.

Thermal profiles off the ECMWF are much cooler than the GFS and show
a significant snow storm over the forecast area. Meanwhile the GFS
is warmer, but still produces enough QPF for several inches of snow
to accumulate. Given the high-impact potential for this event, did
increase the temperature spread to have snow mentioned on Saturday.
Details will probably be difficult to pin down with this set up, so
don`t get too hung up on any one model forecast.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1019 PM CDT Sun Mar 18 2018

Cigs will bounce around tonight through Monday between 2500 and
4000 feet, so we will be in and out of MVFR cigs. RAP still shows
considerable low level drying occurring through Monday as
northeast winds becomes established, helping to raise the cigs.
For precip, followed timing of the NAM, which is much slower than
the GFS. With the dry northeast winds, slower is better when it
comes to timing for snow moving in. AXN will likely see by the end
of it`s TAF, with RWF, STC, and MSP having precip on their
doorsteps by the end of each TAF period.

KMSP...RAP and NAM say MSP will see more VFR cigs than MVFR.
Played cigs to prevail VFR, but left the idea of periods of MVFR
cigs happening with the SCT025 cloud grouping seen throughout.
Snow will likely be close to MSP by 12z Tuesday, but snow chances
look better after 12z, so kept snow out of the 06z MSP TAF.

TUE...MVFR cigs likely. Chc IFR with -SN. Wind E 5 kts.
WED... MVFR cigs possible. Wind E 5 kts.
THU...VFR. Wind SE 5 kts.




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