Area Forecast Discussion
Issued by NWS Twin Cities, MN

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094
FXUS63 KMPX 271148
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
548 AM CST Mon Feb 27 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM CST Mon Feb 27 2017

Frontal boundary that sagged into the area yesterday started lifting
back north as a warm front overnight. Upglide over the boundary has
resulted in cloud cover and light snow developing north of the
boundary, but this snow will quickly lift into northeast MN early
this morning as the warm front continues to lift north. By the
afternoon, this front is progged to get near an Aberdeen, SD to
Hibbing line, which would place the entire MPX area in southerly
winds and the warm sector. As we have seen this February, south
winds plus bare ground results in high temperatures that often come
in at the high end of guidance. As a result have highs today pushing
well into the 40s north of the snowpack, with some 50s not out of
the question out around Madison. The one limiter for temperatures
today is the potential for ample mid/upper level cloud cover.
However, current forecast is near where majority of bias corrected
grids are going, so feel pretty confident in the warmer highs
projected in the snow free areas.

For tonight, things start getting a little murky. As moisture
advection increases ahead of the frontal boundary, which tonight
will become stationary near the northwest end of the MPX area. At
the same time, a significant surge of theta-e rich air will be
building north out of the mid/lower Missouri River valley within a
coupled upper jet structure. The best forcing with the coupled upper
jet and a 50kt LLJ both look to go across Iowa toward southern WI.
This puts much of the MPX area between main sources of forcing to
the northwest with the surface front and southeast with the upper
forcing and LLJ. This sets us within a zone of mid-level dry air,
which means drizzle. In addition, high dewpoint air moving over the
snowpack will result in a threat for fog over the snow, though the
boundary layer looks to remain mixed, which may keep us more 1-3
mile vis with 200-500 foot ceilings as opposed to dense fog.

With the front looking to remain mostly NW of the MPX area, we did
boost lows quite a bit for tonight, with lows currently progged to
remain above freezing tonight for all but the northwest CWA. This
helped to keep p-types pretty simple as well, with snow where temps
are forecast to go below freezing in the northwest with drizzle/rain
everywhere else.

.LONG TERM...(Tuesday through Sunday)
Issued at 400 AM CST Mon Feb 27 2017

The longer term concerns remain initial snow event for
Tuesday/Tuesday night and the overall warming trend into the
weekend.

The 00z deterministic runs continued to show a potential snow
band across portions of our western cwa. The 00z GEFS
probabilities of greater than 2 inches in 12hrs was also pointing
in that direction. We will mention an inch or two accumulation for
now mainly west of a line from near Willmar to Mora. The surface
low track is forecast to move from Colorado this evening...to
near Omaha by 12z Tuesday...and to southwest Wisconsin by Tuesday
evening. Normally...this would be a more favorable snow track a
little farther to the south of the current forecast. Models
guidance suggests better forcing to remain across the west and
northeast into the day Tuesday. Expect light rain/drizzle to be
the main weather p-type over the southeast portion of the area as
warm air remains in place. As the trough pushes east...we should
see mainly snow to the northwest...transitioning to
drizzle/freezing drizzle or light snow before it ends over most
the region through Tuesday night.

Cooler air drops over the area with the northern plains/western
Great Lakes near the baroclinic zone. The northwest flow does
bring down a weak clipper type system in the Wednesday
night/Thursday time frame. The GFS drops a couple inches of snow
with this feature across parts of southern Minnesota. Models
diverge some on the strength of the system so we will keep with
the chance type pops for the event for now.

More zonal flow develops late in the week with an overall warming
trend expected. We will see readings warm back into at least some
lower 50s in the southwest by Saturday. We expect 40s to be
common across the region for the weekend.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1054 PM CST Sun Feb 26 2017

Extensive low VFR ceilings late this evening along and north of a
warm front that stretches from west central MN through the south
metro to near KEAU. A few spots of MVFR ceilings to the west of
KMSP are moving northeast and may clip KSTC in the first couple
hours of the TAF. In addition, some light snow has formed in west
central MN and will lift northeast across KAXN through 08z with
MVFR or lower conditions occurring. The warm front will lift
northeast on Monday with VFR conditions occurring along with
southerly winds increasing to 10 knots. Low level moisture will
increase across the TAF sites Monday night as a low pressure
system moves our way from Nebraska. MVFR/IFR ceilings are likely
near the end of the TAF period for KEAU and for the rest of the
TAF sites after 28/06z. Drizzle will likely be developing as well
across southern MN and west central WI.

KMSP...There is a small threat ceilings could lower to 030 for an
hour in the 06z-07z time frame. Ceilings will lift there after
with VFR through the day on Monday. MVFR ceilings/vsbys/drizzle
developing after 28/09z. Ceilings could become IFR by daybreak.

/OUTLOOK FOR KMSP/
Tuesday...MVFR expected, IFR possible. Chance of light rain.
Southeast wind 5 to 15 kts becoming west.
Tuesday night and Wednesday...MVFR possible. Chance of light
snow. Northwest wind 10 to 20 kts.
Wednesday night...MVFR possible. Chance of light snow. Northwest
wind 5 to 15 kts becoming northeast less than 10 kts.
Thursday...VFR. North wind 5 to 15 kts.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 548 AM CST Mon Feb 27 2017

Front currently draped from north of RWF/MSP through RNH will
lift north through all terminals as a warm front today, but will
sag back southeast as a cold front tonight. VFR conditions will
prevail today south of the boundary, but as it drifts back into
the area, persistent southeast winds and increasing moisture will
eventually result in the development of IFR/MVFR cigs, it`s just a
question of when. Followed close to a GFS/LAMP timing for now. In
addition, behind the front, it is looking likely that snow will
develop tonight. Best shot for seeing this snow will be at AXN,
with -dz about as good as any other terminal will get as forcing
for more widespread rain/precip goes to the southeast.

KMSP...High confidence in the TAF through midnight, but after
that, less confidence on when MVFR and lower CIGS arrive. Have
delayed arrival of the lower cigs to closer to when the front will
be in the vicinity. As the boundary moves through, very moist
boundary layer should promote IFR CIGS, which will persist through
Tuesday morning. Other than maybe some drizzle, precip chances
look minimal.

/OUTLOOK FOR KMSP/
TUE...IFR/MVFR. Chc -ra/-dz. Winds NE bcmg NW 10kts.
WED...MVFR. Winds NW 5-10kts.
THU...Chc MVFR/-SN. Winds NW 5-10 kts.

&&

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

$$

SHORT TERM...MPG
LONG TERM...DWE
AVIATION...MPG



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