Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222055
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
255 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 18Z TAFS through 18Z Monday afternoon)
Issued at 1120 AM CST Sun Jan 22 2017

IFR/LIFR ceilings still prevalent across the coverage area though
there are some pockets of lower level scattering with MVFR
ceilings. This is not expected to last beyond 3-4 hours after the
23/18z initialization with ceilings dropping back to IFR later
this afternoon and likely to LIFR overnight. Most sites have also
improved over 1/2sm and even to VFR visibility, so the fog is
slowly dissipating across the area during the day today. Fog will
fill back in overnight but dense fog is not expected to be nearly
as widespread. Visibilities will likely improve to VFR across the
board by late tomorrow morning but ceilings will still be stick in
IFR but improvement to MVFR is expected by tomorrow afternoon.

KMSP...Small pocket of improved conditions has drifted over the
Twin Cities metro, allowing for MVFR conditions at initialization.
This will last until around 21z-22z before IFR ceilings return.
Not expecting LIFR ceilings but cannot rule out the possibility.
Will also expect MVFR visibilities overnight but lower confidence
on IFR. Visibilities to hit 6sm by daybreak and remain there thru
the day tomorrow with gradually rising ceilings.

/OUTLOOK FOR KMSP/
Tue...MVFR expected, IFR possible. Chance -RA/-SN. Winds E less
than 10 kt becoming NE 10-15 kt.
Tue night...MVFR expected, IFR possible. -RA/-SN likely. Winds NE
10-20 kts becoming NW.
Wed...MVFR expected, 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...JPC


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