Area Forecast Discussion
Issued by NWS Twin Cities, MN

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064
FXUS63 KMPX 211752
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1152 AM CST Tue Nov 21 2017

.SHORT TERM...(This afternoon through Wednesday)
Issued at 1139 AM CST Tue Nov 21 2017

Wind speeds in the wake of the cold front have begun to diminish
faster than originally expected, so the Wind Advisory was dropped
at 11AM as no observations were reaching criteria any longer. The
trend for a gradual wind speed reduction will continue through the
rest of the day and especially tonight. While still breezy this
afternoon, the winds will not be as strong as they were early this
morning as the greatest pressure falls shifts east of our area.

Skies will continue clearing through the afternoon and have
already for much of the area. Expect the clear skies to stick
around through the day but don`t be fooled by into thinking its
warm outside. With persistent northwest flow, temperatures will
remain below freezing, seeing no daytime improvement and combined
with the breezy conditions, the apparent temperature will be
in the teens all afternoon.

Winds will significantly weaken tonight, with around 5 to 10 MPH
expected overnight. Tomorrow will be slightly warmer than today
with low to mid 30s expected area-wide. A weak shortwave will
slide east through northern MN tomorrow afternoon and may graze
central MN with some light snow or flurries. No accumulation is
expected.

.LONG TERM...(Wednesday through Monday)
Issued at 330 AM CST Tue Nov 21 2017

The extended still looks to be dominated by a relatively fast and
progressive flow with no significant winter systems and pretty
strong temperature swings centered around frontal passages. Model
agreement is still good through about 4 days, which gets us through
Friday, but diverge thereafter.  Only changes made to the
blended forecast were to increase winds Friday and Friday night in
the wake of what will be our next cold front.

Strong flow at the crest of of a ridge over the southern Canadian
Rockies looks to result in the development of a surface low over
southern Alberta tonight. That surface low will ride a baroclinic
zone southeast toward southern MN by Wednesday evening. Strong
isentropic ascent and warm frontal forcing looks to result in a
shield of light snow developing over northeast ND Wednesday morning
that will track east toward central and northern MN Wednesday
afternoon and northern WI Wednesday evening. Antecedent environment
ahead of this forcing still looks really dry and much of the time we
have forcing for precip will be spent moistening the atmosphere,
which should really limit precip potential. NAM shows a bit better
low level moistening down toward the Twin Cities, which is why it
drags precip farther south than the GFS and ECMWF. Sided toward the
GEFS/SREF probs for precip though, which keeps most of it north of
the MPX area. Even so, we are talking about a couple of hundredths
of an inch of QPF, so snow amounts, if we see any look minimal.

For Thanksgiving, it look ideal for this region, with light winds,
mostly sunny skies and highs around 40 as weak surface ridging moves
across the area.

The next system heading our direction will be moving out on to the
Canadian Prairies Thursday night, with a deepening sfc low going
across southern Canada during the day Friday. This will draw another
warm sector up toward us for Friday, though the peak of the warm
nose looks to move across the MPX area Friday morning. Still, model
spread is pretty strong that even in the Twin Cities, we`ll crack 50
for the first time this month. The SuperBlend has finally caught on
to these warmer temps, so no changes were needed to it. Like today
though, dense cloud cover could sink the Twin Cities attempt at 50.
During the afternoon, a strong westerly jet streak looks to come
across SD. GFS/ECMWF continue to generate an area of precip with the
lift on the nose of this jet streak, so increased pops into the high
chance/low likely category. Precip type will not be an issue with
this precip though as it will plenty warm enough to keep it all rain.

Friday night into Saturday, we get into another post frontal
environment similar to what we have tonight into this morning. Once
again, we should see borderline wind advisory winds behind the front
going into Saturday morning, with strong CAA resulting in falling
temperatures and highs Saturday that are about 20 degrees colder
than Friday.

Like we have been experiencing the last week, we will have two cold
days Saturday and Sunday, but we will head the other direction
by Monday with highs surging back into the 40s ahead of our next
system, which looks to be due in Monday night/Tuesday. This system
looks similar to what passed to our north last night and will pass
to our north Friday. The only difference is that this time around
the ECMWF/GFS have the low going across northern MN as opposed to
southern Canada. The impact of that is it would bring the heavier
precip closer to us. However, this pattern we have been in has only
shown much forecast reliability out about 4 days. So don`t bank on
this system being reliably forecast until we get to Friday or
Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1139 AM CST Tue Nov 21 2017

VFR through the period. Wind being the main concern and the
biggest change made was to reduce the wind speeds for this
afternoon as they are already weakening faster than previously
thought. Breezy northwest winds will weaken to under 7 knots
tonight and turn southerly tomorrow morning. A weak wave will
come in from the west and bring mostly mid and high clouds late
morning through tomorrow afternoon.

KMSP...no change from the main discussion.

/OUTLOOK FOR KMSP/
Thu...VFR. Winds NW 5 kts.
Fri...Mainly VFR. Chance MVFR/-SHRA late. Winds SW 10 kts turning
NW with PM FROPA and increasing to 15-20 knots
.Sat...VFR. Winds NW 10-15 kts.

&&

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

$$

SHORT TERM...SPD
LONG TERM...MPG
AVIATION...SPD



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