Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 131720
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1120 AM CST Mon Nov 13 2017

.updated for 18z taf discussion below...

.SHORT TERM...(Today and tonight)
Issued at 336 AM CST Mon Nov 13 2017

Increasing thin cirrus has only had minor effects on the freezing
mist/fog this morning across central MN and WI. Visibilities
aren`t being significantly reduced, but even at MSP where
visibility is unrestricted the ASOS reported a trace of icing
(heavy frost). Therefore, there could be some slick spots on the
roads this morning, especially where visibilities are reduced to
less than a mile.

Today will be dry with increasing clouds. Southerly flow will pick
up this morning and bring a milder airmass in with highs in the
upper 30s in northwest WI to near 50 in southwest MN.

Low level moisture arriving this evening will bring extensive
stratus. Negative omega through this moist and shallow layer will
likely be enough to produce some drizzle in areas. Temperatures
will be above freezing, except early evening toward Rice Lake and
Ladysmith where a brief period of freezing drizzle is possible. No
icing is expected with temps rising above freezing relatively
quickly following the onset.

.LONG TERM...(Tuesday through Sunday)
Issued at 336 AM CST Mon Nov 13 2017

Two forecast concerns over the next week as whether the faster and
more progressive GFS model becomes the better forecast for late in
the week weather system, plus how much colder will the pattern
remain past next weekend.

The GEM/EC have been slower for the late week system, and has
allowed for much warmer air to move northward. The GFS, which is
more progressive, remains mild ahead of this system, but takes the
bulk of the precipitation out of the forecast by Friday afternoon,
compared to the EC/GEM which lingers longer. The differences in the
models seem to correspond to the upper ridge build off the east
coast and eastern North America. Although the GFS does show this
ridge building, it is not as amplified allowing for the more
progressive nature of the late week system. Due to the uncertainties
in the models, a blend is preferred, but not necessary the best way
to advertise the forecast. It does seem that most of the
precipitation will be liquid as the warmer air will likely be in
place before precipitation develops sometime Friday. Depending upon
the speed and the amplification of this system, will depend if the
precipitation changes over to snow as this system begins to tap in
much colder air Friday/Friday night.

Even though models have a different scenario for the late week
system, all weather models forecast a much colder air mass replacing
the mild conditions this week by late Saturday/Sunday.

Beyond the 7 day forecast remains questionable as to whether a
colder regime holds for most of the Upper Midwest, or does some
modification develop as a large scale upper ridge begins to develop
over the Rockies next week. Based on the 5-day ensemble mean of the
500 MB level, an upper ridge begins to build across the Rockies,
especially the central and southern Rockies, and spills out into the
Plains. There is a well established long wave trough across the east
coast which leads to a somewhat west/northwest flow aloft for our
region. Therefore, the coldest air will be concentrated in the Great
Lakes region, and the Northern Plains will likely be milder. In
between, will be questionable and highly variable with either mild
air, or cold Canadian air.

In the short term, a fast moving short wave will move across the
Rockies, and into the Plains, Upper Midwest by Tuesday afternoon,
evening. Large scale lift ahead of this short wave will lead to some
precipitation, but likely very brief and light due to the fast
nature of this system. Otherwise, the advertised milder air will
continue with readings slightly above normal for Wednesday/Thursday
and Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1120 AM CST Mon Nov 13 2017

Timing of the developing/advecting stratus from Iowa in the
southerly low level flow is the main concern. Looks like it
should be moving into most taf sites 00z- 03z period. Expect
lowering vsbys...especially over central mn into western wi
overnight with -dz. Could see a period of -fzdz over parts of
WI...it appears KEAU will be on the fringe of that possibility
with remaining drier sfc dewpts initially. Done expect much
improvement in the IFS/LIFR into Tuesday morning.

KMSP...VFR conditions becoming at least MVFR by 00z and IFR
developing through 03z with -dz br. Little improvement into Tue
morning with perhaps rising to mvfr through 17z.

/OUTLOOK FOR KMSP/
Tue night...MVFR cigs. Chc -DZ. Wind SW 5-10 kts becoming NW.
Wed...Chc MVFR. Wind NW 15G20 kts.
Thu...VFR with MVFR/-RASN possible late. Wind SE 10 kts.

&&

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

$$

SHORT TERM...BORGHOFF
LONG TERM...JLT
AVIATION...DWE



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