449
FXUS63 KMPX 081727
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1127 AM CST Wed Jan 8 2025

.KEY MESSAGES...

- Thursday afternoon and evening, slick roads and slow travel
  possible from light snow. Most locations will see less than in
  inch.

- Saturday night through Sunday, confidence continues to
  increase another round of snow (most likely less than 2
  inches), but some uncertainty on timing.

&&

.DISCUSSION...
Issued at 243 AM CST Wed Jan 8 2025

Today through Friday Night...Early morning satellite imagery with
500mb heights and surface obs showed a breaking ridge across the
region, with clear skies and surface high pressure beneath it. Winds
were light, and temperatures were generally in the low single
digits. For today expect mostly sunny skies to start out, with some
high clouds moving in this afternoon. Highs will be near 20 degrees,
with light southerly winds around 5 to 10 mph developing.

These southerly winds will continue overnight into Thursday ahead of
the next weather system, which is a open wave and surface pressure
trough. This is a rather weak system, but forecast soundings do show
a few hours of lift as it passes through, which should produce some
light snow. Did increase precipitation chances above the blended
guidance (50 to 60%), and expect this trend to continue if the
system remains on track. One thing of note is upstream there is
another breaking ridge, so that subsidence should be the limiting
factor and keep snowfall amounts to less than an inch for most
locations, with higher amounts across western MN, and lower amounts
in western WI. Northwest winds will increase as the system exits the
region, with gusts of 20 to 25 mph possible Thursday night. Another
area of surface high pressure will build in behind the system, which
will lead to decreasing winds throughout the day.

Saturday through Wednesday...Forecast models continue to indicate a
more compact upper level wave moving across the Upper Midwest this
weekend. While the moisture isn`t great, this wave will act on a
northwest to southeast temperature gradient, so expect widespread
lift tied to an area of isentropic ascent, with some embedded areas
of enhanced lift in regions of frontogenesis. Although the forecast
has lower pops due to timing uncertainty, we do expect light snow
overall with this system, just not sure when 6hr forecast block it
will fall into from Saturday night through Sunday. If you expand the
window out to 24 hours, all but 3 (out of 50) of the EC ensemble
have measurable precipitation at MSP, which would equate to 94%.
The GFS is similar with only 2 out of 25 members dry, while the
Canadian ensemble is drier. In other words, plan on snow sometime
between Saturday nigh and Sunday, but amounts will be light,
generally less than 2 inches.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1121 AM CST Wed Jan 8 2025

The trend for the 18z TAF period will be slowly increasing
clouds with eventual lowering as our next wave of light snow
arrives late in the period. VFR with FEW/SCT high clouds to
begin, followed by more clouds arriving generally after 06-08z
before eventual -SN from west to east. Timing for incoming snow
was following the quicker CAM guidance with the HRRR/RAP showing
a start time roughly 4-5 hours earlier than current global
guidance. MVFR CIGS/VIS are possible once snow starts with BKN
CIGS lowering gradually in the 3-4 hours before arrival. Winds
remain below 10kts with no significant gusts.

KMSP...Snow arrival time within current guidance is around
17-18z, and this may wobble an hour or two over the next couple
of TAF issuances based on the latest guidance. Accumulation
potential right now is expected to remain an inch or lower with
the best chance for impacts from roughly 18-21z, give or take an
hour or two based on when it arrives. Rates should generally
remain less than 1/4 inch per hour.

/OUTLOOK FOR KMSP/
FRI...MVFR/-SNSH early, then VFR. Wind NW 5-10kts.
SAT...VFR. Wind W to S 5-10kts.
SUN...VFR, sl chc -SNSH/MVFR. Wind NW 5-10kts.

&&

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

&&

$$

DISCUSSION...JRB
AVIATION...TDH