Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KMPX 201023
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
423 AM CST Sat Jan 20 2018

.SHORT TERM...(Today and tonight)
Issued at 421 AM CST Sat Jan 20 2018

The short term period will start out quiet, but a warm advection
band of snow could setup across central MN by later tonight in
advance of the winter storm set to impact the region tomorrow night
through Monday night.

The upper level trough that will eventually generate a surface
cyclone to the east of the Rockies is currently just reaching the
coast of California as of early this morning.  For today, another
warm day will continue melting the snow currently on the ground
while we stay south of the upper level jet.  Daytime highs should
have no trouble reaching the upper 30s to lower 40s.  Meanwhile, the
upper trough will continue its eastward progression through the day.
By 12Z tomorrow morning, a deepening closed 500mb low will be
located over the four corners region.

There is a chance we could see a band of light snow develop this
evening across central MN into northwestern WI as a west-east
oriented band of f-gen begins to saturate the column.  If snow does
develop, expect minimal accumulation of less than half an inch.

.LONG TERM...(Sunday through Friday)
Issued at 421 AM CST Sat Jan 20 2018

The winter storm potential for Sunday night-Monday night remains on
track.  Did not make significant changes to the going forecast.  We
still expect a swath of 6-10" of snow with localized amounts
reaching 12" in the heart of the winter storm watch area. Confidence
continues to increase that the placement of the heaviest snow will
be from the southwest corner of the state, through the Mankato area
and toward the Menomonie, WI area.  This track keeps the heaviest
totals just south/east of the Twin Cities.

The main update from the latest guidance is that we have a
convergent trend among the 00Z solutions.  The GFS has held pretty
consistently north of the ECMWF solution, and the 00Z ECMWF shifted
the system a little bit northward from it`s previous solution.  The
NAM continues to be rather inconsistent from run to run, so do not
have much trust in its solution at this time.  The CMC agreed fairly
well with a blend of the EC and GFS.  Looking at the GEFS 21-member
ensemble, it shows really good agreement with the operational ECMWF
forecast and the CMC as well (the operational GFS is on the
northern side of the GEFS ensemble). This increases our confidence
that the heart of the winter storm watch area has the best chance
of getting 6-10" totals. Elected to continue the watch as the
main event really won`t get underway until tomorrow evening in
western MN, and not until after midnight Sunday night in eastern
MN and western WI.

The actual QPF output from the guidance is impressive, with much of
the precip falling during the day Monday.  The NAM and the CMC have
close 1.75"-2.2" of QPF with this system, while the EC, GFS, and
GEFS show a more reasonable 1.0"-1.3" storm total QPF.  We went on
the conservative side with storm total snow given the system is just
now reaching the California coast and there is still
uncertainty/differences in the solutions.

In terms of precip type, the only p-type concern for our area at
this time is along the Iowa border and over toward Eau Claire, where
a period of freezing rain is possible.  Icing amounts still look to
be rather minor and snow still looks to be the primary p-type.  If
the southern track of the ECMWF works out, this would likely keep p-
type issues to our south.  The GFS on the other hand wraps warmer
air farther north.  For now, continued a blended approach of the
guidance for p-type.

Winds still look to increase to the 25-35 MPH range during the snow
Monday which will undoubtedly lead to difficult and dangerous travel
conditions within the heavy snow band.  Whiteout conditions at times
will be possible in open areas, mainly across the western and far
southern portion of MN.

Dry for the remainder of next week, temperatures will run near
normal through midweek, before warming returns late next week.


&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1045 PM CST Fri Jan 19 2018

The main concern for this TAF period is the chance for fog
overnight thru Saturday morning. High ceilings will prevail
overnight though there may be spotty SCT patches. Warmer air over
near-surface moisture, mainly due to melting snow, and winds
under 5 kts overnight will likely result in patchy fog. Thus, MVFR
conditions are possible between 10z-15z over much of Central MN
and northwestern WI. Winds in West Central WI are expected to
shift to the W/WNW tonight and then winds across the forecast area
will remain light and predominately out of the W/WNW through
Saturday afternoon.

KMSP...Patchy fog is possible from 10Z-15Z Saturday. VFR
conditions are forecast but a downgrade to MVFR may be needed
should future guidance indicate lower visibilities.

/OUTLOOK FOR KMSP/
Sun... VFR early, MVFR or lower with -SN or wintry mix likely
Sunday afternoon. IFR or lower with snow late Sunday night. Wind
NE 5-15 kts.
Mon...IFR or lower most of the day with SN/BLSN. Wind N 15-25 kts
gusting to 30 kts.
Tue...VFR with MVFR possible. Wind NW at 10-15 kts.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from late Sunday night through Monday evening
     for WIZ014>016-023>028.

MN...Winter Storm Watch from late Sunday night through Monday evening
     for MNZ053-059>063-066-068>070-077-078.

     Winter Storm Watch from Sunday evening through Monday evening
     for MNZ064-065-067-073>076-082>085-091>093.

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.