NWS Forecast Discussion

Below is the latest Area Forecast Discussion from the Twin Cities National Weather Service office in Chanhassen, MN. It gives insight into why the forecasters are making the predictions you read in your local forecast. The overall "big picture" of the atmospheric setup is well described, as well as the forecasters' interpretation of the various Computer Atmospheric Models (CAMs). Sometimes, very specific information is available here that is not available, or otherwise generalized, in the public forecast.

578
FXUS63 KMPX 210508
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1108 PM CST Wed Nov 20 2024

.KEY MESSAGES...

- Light snow continues through this evening. Slick travel is
  possible, especially with gusty winds.

- Strongest winds in western MN, gusts as high as 35mph.

- Dry weather returns tomorrow, with strongest winds shifting
  east into western WI.

&&

.UPDATE...
Issued at 835 PM CST Wed Nov 20 2024

After a few hours of moderate snow this evening, reports of
1-1.5" of accumulation are common from the Twin Cities metro
southward. Any heavier/accumulating snow will continue to wind
down across the region, but occasional flurries/freezing
drizzle will continue overnight. Travel remains treacherous
with very slick roads following this evening`s snow, which seems
to have largely melted before refreezing on roadways.
Temperatures will remain below freezing tonight, so expect
difficult travel to persist into tomorrow morning. Gusty
northwest winds continue across western Minnesota with gusts
near 40 MPH at times, further complicating travel in this area.

&&

.DISCUSSION...
Issued at 254 PM CST Wed Nov 20 2024

Snow totals have generally remained at or below an inch through our
first round of snow this morning, with the highest totals further
north and west where the Winter Weather Advisory is still in place.
It currently is in effect until 6PM, but that may need to be
extended depending on how quickly the second round of snow moves
southeast. Latest hi-res guidance keeps additional totals right
at or below 2 inches for those northwestern counties, and at or
below 1 inch for elsewhere. It is expected that well-traveled
roadways will largely avoid any accumulations (similar to this
morning), but slick conditions may still develop with
temperatures dipping below freezing for much of the region
already. The main driver of forcing associated with this second
push of snow is positive (cyclonic) vorticity advection as the
low moves east. These setups can result in sporadic bursts of
heavier rates, which is highlighted by the latest suite of
models, favoring portions of east-central and southern
Minnesota. These high rates combined with strong, gusty winds
could lead to reduced visibilities at times. This is important
to be aware of given the timing taking place during the evening
rush hour. Snow should begin to taper off from north to south
around 7 to 8 PM, completely moving out of the area overnight.

As the surface low and occlusion aloft weaken, the strongest forcing
and winds will move east. As a result, most locations will be
entirely dry tomorrow, outside of a few light rain/snow showers
across west-central Wisconsin. The main concern will be a return of
strong, gusty winds, primarily over western Wisconsin and eastern
Minnesota. The latest RAP and HRRR show potential for 35 to 40 mph
wind gusts to mix down from 925 hPa. These locations have seen the
lowest totals for snowfall so far, and are expected to have little
to no blowing snow concerns with these winds.

An area of ridging upstream of the upper low will help lead to
drier, and consistent conditions through the weekend. Long
range ensembles continue to highlight potential for multiple
systems moving across the central CONUS next week, however there
is quite a bit of spread in timing and location. Members of the
GFS ensemble have higher agreement of a low impact snow-maker
moving through as early Sunday night, while the EPS favor a more
impactful storm moving through towards the end of the week
without as much of a sign for an early week system. All that to
say, there is still a lot to decipher after our current system
departs east, but there is at least a notion that an active
pattern is likely across the region.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1049 PM CST Wed Nov 20 2024

Models have not done well with cigs/vis or wind this evening.
Winds are considerably lighter than guidance and ceilings are a
mix of higher or lower than guidance depending on the location.
Additionally, there are a handful of UP/BR reports, particularly
across western Minnesota. Suspect this is freezing drizzle that
should come to an end over the next 2-3 hours. Mainly MVFR cigs
are expected through the period. As mentioned in the previous
discussion, a few brief hours of VFR conditions are possible
through early this morning for our easternmost sites. Winds are
gusting in the 15-20kt range, but should come back up into the
25-30kt range for gusts by tomorrow morning through the late
afternoon.

KMSP...Very frustrating forecast as VFR conditions have
returned to start the TAF period. Kept VFR in there through 12z
based on satellite trends and upstream obs, but added a TEMPO
group for MVFR since I would not be surprised if it comes down
occasionally. MVFR should return after sunrise and stick around
through the end of the period. As mentioned above, winds will
increase by tomorrow morning into the 25-30kt range.

/OUTLOOK FOR KMSP/
FRI...Chc MVFR cigs. Wind NW 10-15kts.
SAT...Chc MVFR cigs. Wind NW 5-10 kts.
SUN...VFR. Wind SE 5-10 kts.

&&

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

&&

$$

UPDATE...Dye
DISCUSSION...BED
AVIATION...Dye

NWS MPX Office Area Forecast Discussion