Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 121736

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1136 AM CST Fri Jan 12 2018

.Updated for 18Z Aviation Discussion...
Issued at 1131 AM CST Fri Jan 12 2018


.SHORT TERM...(Today and tonight)
Issued at 230 AM CST Fri Jan 12 2018

A 1033MB high is situated across the eastern Dakotas this morning.
A fairly packed pressure gradient ahead of this feature has kept
winds up in the 10-20 knot range overnight. These winds combined
with temperatures in the single digits to mid teens below zero are
yielding solid advisory-criteria wind chill readings in the
-25F to -35F range across the MN portion of the forecast area.

The area of high pressure will build more solidly into place
across the forecast area today, with single digit highs likely in
most areas (struggling to eclipse the zero degree mark over west
central MN near Alexandria).

Tonight we will see more of the same with regard to wind chills.
This time winds will be a tad lighter, but we will make up for it
with colder temps (by a few degrees). Lows will dip to between
-10 and -20, likely lowering wind chills into the -25 to -35
range. Wind chill headlines will most likely be needed.

.LONG TERM...(Saturday through Thursday)
Issued at 230 AM CST Fri Jan 12 2018

Two main stories in the long term are the cold and a clipper coming
down for Sunday afternoon.

Arctic high that starting coming in Thursday will remain with us
through Saturday. The clipper brings us the arctic interlude Sunday,
with another blast of arctic air (slightly cooler than the current
one) coming in to start next week. Given how cold these airmasses
are, wind chill headlines will likely be needed pretty much every
night through Tuesday night.  The period of greatest concern though
will be Sunday night/Monday morning and Monday night/Tuesday
morning. Both of these nights, we currently have wind chills dipping
down to around -40 out in western MN, so there will be the threat
for needing wind chill warnings these periods, mainly for the
western half of MN.

For Sunday, a potent clipper is still poised to drop across the
area, with the greatest impact coming Sunday afternoon/evening. 12
hour h5 height falls of around 100m along with a deepening surface
low suggest this will be a rather strong system as clippers go. Went
with a blend of the ECMWF/GFS for this system, which puts out about
0.15" of QPF centered on the MN/WI border. GEFS plumes at MSP for
this period show tight clustering around this value, so have pretty
high confidence in this forecast, with both the GFS and ECMWF fairly
stable in their solutions for Sunday afternoon the last couple of
days. Now 0.15" of QPF may not sound like much, but when you look at
forecast soundings you see our issue, a very deep DGZ. From both the
GFS/NAM, we are seeing just about every site showing the DGZ
extending from the surface up to 10k feet, which will support high
snow ratios. Primary blend used put out snow rations in the 20-25:1
range, which seems reasonable when looking at the forecast
soundings. These ratios with the QPF quickly puts snowfall totals up
around 3" for eastern MN/western WI. This will be a light fluffy,
easily blown around snow, but right now, it looks to fall east of
where are strongest winds are expected Sunday night into Monday, so
hopefully that will relegate the blowing snow issues Monday night
more into the nuisance category.

For the end of the next week, models continue to show a deep
Aleutian Low working toward western NOAM, which will start to break
down the western ridge. This will result in a pretty significant
pattern shift next weekend and beyond as we essentially see the
ridge and trough shift the sides of the continent they are on,
going for the current wester ridge/eastern trough to more of western
trough/eastern ridge pattern. This will mean two things for us, no
arctic air and the possibility for seeing more precipitation as we
head into the second half of January.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1131 AM CST Fri Jan 12 2018

VFR conditions throughout. Northerly winds will decrease overnight
and take on a more westerly direction by Saturday morning.

VFR conditions throughout. Northerly winds will decrease overnight
and take on a more westerly direction by Saturday morning.

Sun...MVFR with afternoon IFR/SN likely. Wind S 5-10 kts.
Mon...VFR with MVFR possible. Wind NW 15G20 kts.
Tue...VFR with MVFR possible. Wind NW at 10-15 kts.




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