Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 171143

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
543 AM CST Sun Feb 17 2019

Issued at 540 AM CST Sun Feb 17 2019

Updated to include 12z aviation discussion below.


.SHORT TERM...(Today through Monday)
Issued at 245 AM CST Sun Feb 17 2019

Surface analysis early this morning shows a fairly flat pressure
pattern across the region with high pressure nestled in central
Canada while a complex low pressure system rolls eastward through
the deep South. Aloft, the large western NOAM trough continues to
expand eastward, with a discernible axis from southern Alberta
province southeast into the central Plains. An upper low is
progged to develop over southern MN/northern IA as the day
progresses, helping to add enough lift even though the main
surface low will remain well to the south and southeast of the
area today. Surface models continue to show a meandering trough
remaining over MN/IA/MO today through tonight, aiding low level
convergence within a wide and deeply moist atmosphere. As such,
confidence remains high that accumulating snow will still be
realized for much of southern MN today through tonight. KMPX radar
is already showing a swath of snow shifting as far north as the
Minnesota River early this morning, and the snowfall will try to
shift as far north as I-94 later today but no snowfall is expected
north of I-94. With the trough remaining in place through
tonight, a fairly steady light snow is expected all day into this
evening before diminishing during the early morning hours Monday.
High pressure from western Canada will then make inroads to the
area and push the low pressure features off to the east by
daybreak Monday. As for the forecast details, little in the way
has changed with respect to QPF and snow ratios. Still looking for
ratios around 18:1 with QPF from around 0.10" just south of I-94
to around 0.30" near the Iowa border. The combination of all these
factors still looks to produce 3-6" snow accumulation over far
southwestern and southern MN through tonight. As such, no changes
were made to the timing, areas or amounts included in the Winter
Weather Advisory.

Temperatures will run a little closer to normal today, with highs
between the upper teens and lower 20s. As the system departs
tonight, another shot of cold air advection is expected. Lows
tonight will run from zero to 5 above zero, followed by highs on
Monday between 10F and 20F.

.LONG TERM...(Monday night through Saturday)
Issued at 245 AM CST Sun Feb 17 2019

Through the week, little change in expected with the overall flow
pattern across the region. Anomalous trough remains over the
western CONUS and will continue the cold and stormy trend across
the CWA.

Initially, we have a sprawling 1040mb high which will drift
slowly across the area into Tuesday. Provided we have enough
clearing, we should cool through the single digits below zero over
most of the area. Winds are expected to be light under the highs
influence so wind chills are not expected to be a problem into
Tuesday morning.

The deterministic models continue to indicate another accumulating
snow event moving in Tuesday night and lingering into Wednesday
evening. The ECMWF continues to be strongest with its trough
moving through. It has higher QPF versus the GFS as well. Blended
guidance gave us widespread 0.10 to 0.25 inch QPF for the event
with snow at least 2 to 4 inches. This will likely affect at least
the Wednesday morning commute.

Following this system, the models diverge some in handling the
western CONUS trough. The GFS eventually splits the upper flow
over the area with a northern stream trough with sheared trough
lifting some moisture out ahead of the eventual ejection of the
southwest trough energy. The ECMWF continues its trend of bringing
out most of the energy into next weekend. It develops strong
cyclogenesis over the nations midsection Saturday as it lifts
northeast toward the southern Great Lakes by Sunday. The 00z ECMWF
trended a bit farther south with its track but ample moisture was
lifted out ahead of the system and would generate widespread snow
for the CWA for the weekend. The GFS remained split and took the
system south of the area. We will continue to use the blended
guidance PoPs for now affecting the area Friday through the
weekend. Surely another system to watch during the week.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 540 AM CST Sun Feb 17 2019

-SN will steadily shift north thru the day today, reaching as far
 north as I-94 later this morning. Southern sites will likely run
 IFR-or-worse with the -SN, mainly due to visibilities, while
 ceilings remain as MVFR. -SN will gradually diminish this
 evening, with VFR conditions likely restored by late evening if
 not the overnight hours. Not expecting any BLSN problems with
 wind speeds at or below 10 knots.

KMSP...-SN looks to hold off until about 14z but ceilings may
bounce between VFR and MVFR prior to -SN arrival. Ceilings will
then continue to drop while visibilities bounce between MVFR and
IFR. Not looking for 1"/hr rates but the -SN will likely be
prolonged and steady through the day, resulting in a couple inches
of accumulation. -SN will diminish this evening with VFR likely

Mon...Mainly VFR. MVFR ceilings possible. Wind N 5-10 kts.
Tue...Mainly VFR. Chance p.m. -SN/MVFR. Wind SW 5 kts becoming SE.
Wed...MVFR-IFR likely with -SN. Wind 5 kts, shifting from E to S
to W.


MN...Winter Weather Advisory until midnight CST tonight for MNZ054-



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