Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222333
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
533 PM CST Sun Jan 22 2017

.SHORT TERM...(This evening through Monday)
Issued at 253 PM CST Sun Jan 22 2017

Quite the uneventful next 24 hours over this region as there`s
deep upper level troughs over each CONUS coast with weak ridging
over the central states along with weak high pressure moving in
from the west. With very weak advection both at the surface and
aloft, the deeply moist atmosphere will be slow to exit the
region. Thus, low stratus and fog will again be the prevailing
weather features overnight into tomorrow but not at the extent
seen last night with such prevalent dense fog. Visibilities will
commonly drop to between 1-4sm so, at this point, a Dense Fog
Advisory is not expected. After daybreak Monday, the rate of
clearing will improve as drier air will be advected in from the
west, aiding in visibility first then scouring out the low clouds.
Temperatures will run very similar to today with highs again in
the mid-upper 30s. With some clearing and drier air in western MN,
lows will be a bit cooler, dropping to the mid 20s to lower 30s.
The lack of drizzle and dense fog should prevent icing issues
tonight.

.LONG TERM...(Monday night through Sunday)
Issued at 253 PM CST Sun Jan 22 2017

A Winter Storm Watch has been issued for about the southern third
of Minnesota for the potential of 6"+ snow from Tuesday through
Wednesday, with the heaviest falling Tuesday night. In addition
there will be some patchy blowing and drifting snow on Wednesday.

While there is still plenty of model spread when looking at the
GEM and NAM solutions, the GFS and ECMWF continue to advertise
the potential of several inches of snowfall from the Tuesday-
Wednesday storm. The GEFS ensemble has increased probabilities for
two consecutive runs for QPF>0.50" liquid equivalent. Snow ratios
may not be all that impressive as the lower atmosphere is not
very cold. With that said, plenty of moisture will be available
with this system. We felt more confidence siding with the
GFS/ECMWF and GEFS members with a track north of the GEM and NAM.
Now, this track could still shift but we still felt confident
enough to hoist a Winter Storm Watch for southern MN. The forcing
is coming together with a decently strong jet streak nosing into
the midwest placing us in a very favorable divergence zone, along
with an impressive PV anomaly pushing through, and plenty of
theta-e advection to provide low level lift and moisture.

While the best threat area of 6"+ is in the watch, farther north
will also see accumulating snow including the Twin Cities. At this
time 2-4" with some pockets of 5" looks reasonable from across
south central MN including the metro, through much of western WI
including Menominee and Eau Claire. Shifts in the storm track
either north or south would either increase or decrease amounts
across the forecast area. Please stay tuned for the latest
forecast details as we gain more confidence with this storm.

After the storm goes through, wrap around snow showers could be
seen for a couple days to round out the week and temperatures
will be seasonable, below freezing every day and near the average
max T with highs in the 20s generally expected. We do not expect
any bitter cold through the next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 533 PM CST Sun Jan 22 2017

Ceilings and visibilities are already starting to slip lower late
this afternoon as low level moisture remains in abundance due to
several days of snowmelt. There is a little bit of a pressure
gradient across MN and WI with low pressure over the central Great
Lakes and high pressure over ND/SD. Short term guidance would
suggest visibilities improving some in western MN this evening
while deteriorating across eastern MN and western WI. Not buying
the improvement in the west and feel lower cigs/vsbys are in store
for the Twin Cities as well as KRNH and KEAU almost out the gate
if not by 03z and persisting into Monday morning. A little bit of
low level drying is expected on Monday as the high to our west
settles overhead. Continued the trend of driving vsbys to VFR
along with ceilings in the 012-022 range. Light WNW winds through
the period.

KMSP...Expect ceilings below 010 by the start of the TAF along
with MVFR visibilities in BR. This will likely persist through
Monday morning. Ceilings improving to 020 by late Monday afternoon
along with VFR visibilities.

/OUTLOOK FOR KMSP/
Tue...MVFR with IFR possible. Chance -SN in the mrng with SN in
      the aftn. Winds E less than 10 kts becoming NE 10-15 kts.
Tue night...IFR with SN. Winds NE 10-20 kts becoming NW.
Wed...MVFR with IFR possible. -SN likely early. Winds NW 15-25 kts.
Wed night and Thu...MVFR possible. Chance -SN. Winds NW 10-20 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Winter Storm Watch from Tuesday afternoon through Wednesday
     afternoon for MNZ073>078-082>085-091>093.

&&

$$

SHORT TERM...SPD
LONG TERM...JPC
AVIATION...RAH


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