Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 141150

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
550 AM CST Sun Jan 14 2018

.UPDATE...For 12z Aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 403 AM CST Sun Jan 14 2018

Main concerns in the short term period are associated with a
clipper system arriving today followed by a blast of arctic air.

There is good agreement on the timing of snow for today, with
accumulating snow arriving in the northwest by 18Z, peaking in
areal coverage during the afternoon, then shifting out of
Minnesota (but lingering in Wisconsin) by 03z. 12-18 hour
accumulations look to range from 1-3 inches in MN, to 3-4 inches
in west central Wisconsin. In the wake of the snow, winds increase
from the northwest. Areas of blowing snow are expected, primarily
from west into south central MN. All in all, this even looks to
be a typical (healthy) clipper system, not quite worthy of a
winter weather advisory.

What is worthy of headlines, however, is the cold that follows
tonight. Given the aforementioned brisk northwest winds, combined
with temps lowering into the -10 to -15 degree range, wind chills
look to dip into the mid 30s below zero across west central MN
(from Alexandria to near St Cloud), with -25 to -35 sneaking to
just west of the Twin Cities and south to southern Minnesota.

.LONG TERM...(Monday through Saturday)
Issued at 403 AM CST Sun Jan 14 2018

Main concerns in the extended are the impacts from wind chills
through Tuesday in the current arctic outbreak, how mild we get by
the end of the week as Pacific air returns, with things getting
rounded out by the potential for more active weather next weekend.

Monday, an anomalously strong ridge up across central Canada
combined with a positively tilted trough extending from the central
Plains to an H5 low over the Great Lakes will promote strong
subsidence over the Dakotas. In this subsidence region you will find
a 1052mb high drop down into western ND. Core of the coldest 925mb
air will be located to the east of the high, or across the
eastern Dakotas into western MN. In WI though, that Great
Lakes h5 low will keep cloud cover and "warmer" air in place across
WI. Net result, is we should see a pretty good gradient in highs
Monday from west to east, with highs out by the SD border struggling
to get above -10F, while temps warm into the teens above zero out in
Rusk/Chip/Eau Claire counties in WI. Monday night, as the high moves
toward central Nebraska, we`ll see our coldest morning area wide,
though we will maintain a breeze all night, so not ideal radiational
cooling conditions to see crazy temperature drop offs like we are
seeing tonight in western WI.

One change needed to the forecast was a significant increase in PoPs
for western WI Monday. GFS/NAM soundings out at Eau Claire and
Ladysmith show weak lift within a deep moist layer through the day
Monday. Model QPF also spits out low QPF through the day Monday. Net
result is there will likely be light snow through the day on Monday
in WI. However, it only works out to 0.5-1" of snow over about an 18
hour period. So yes storm totals out toward Eau Claire and Ladysmith
may push 5", they will get there because it will be lightly
snowing for nearly 30 hours, hence not going with any headlines
for snow.

For wind chills, given the cold highs out west, little improvement
in wind chills is expected during the day Monday, so the
warning/advisory we have for tonight, we will just continue through
the day Monday. Monday night will bring some of the coldest wind
chills of the season and current predicted wind chills have changed
little over the last couple of days, so Monday night, we extend the
warning down to the IA border in western MN, while expanding the
advisory into the first row of counties western WI. Confidence
remains high that the Twin Cities metro will be staying out of wind
chill warning criteria (-35F or colder) Monday night/Tuesday morning.

After Tuesday, a deep trough currently over the northern Pac will
continue to send energy into western NOAM, breaking down the ridge
to our west, allowing it and its Pacific airmass to quickly build in
across the northern Plains. Still looks likely most of our area will
see highs into the 30s Thursday and Friday.

For the weekend, the longwave pattern becomes more conducive for a
more active pattern across the western/central CONUS as a western
trough becomes established, sending shortwave energy out into the
Plains. With the 14.00 runs, we are certainly seeing that.  However,
there is tons of spread in both the deterministic models and
ensembles, so at this point all you can really do is acknowledge the
fact that the large scale pattern is conducive to being more active
by next weekend and watch how things play out over the next few days.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 550 AM CST Sun Jan 14 2018

MVFR conditions will become prevalent this morning, with IFR/LIFR
becoming possible this afternoon/eve attendant with the snowfall.
Sites look to have around a 4-6 hour window for 1/2SM to 1SM
visibilities in snow, with scattered flurries behind the main
area out of the low cloud deck. Winds shift to the northwest
behind the front (and behind the main area of snow), so
west/northwest sites will be vulnerable to prolonged minor
visibility restrictions due to blowing snow.

KMSP...VFR until light snow begins mid morning. The heavier snow
will arrive early afternoon (around 21z), becoming light around

Mon night...VFR with MVFR possible. Wind NW 10G20 kts.
Tue...VFR. Wind NW at 5-10 kts.
Wed...VFR. Wind SW at 5-10 kts.
Thu...VFR. Wind SW at 5-10 kts.


WI...Wind Chill Advisory from 6 PM Monday to noon CST Tuesday for

MN...Wind Chill Advisory from 3 AM Monday to noon CST Tuesday for

     Wind Chill Warning from midnight tonight to noon CST Tuesday for

     Wind Chill Advisory from midnight tonight to noon CST Tuesday
     for MNZ043-044-050-058-066.

     Wind Chill Advisory from 6 PM Monday to noon CST Tuesday for

     Wind Chill Warning from 6 PM Monday to noon CST Tuesday for

     Wind Chill Advisory from midnight tonight to 6 PM CST Monday for



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