Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 141739
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1139 AM CST Tue Nov 14 2017

.updated for 18z taf discussion below...

.SHORT TERM...(Today and tonight)
Issued at 319 AM CST Tue Nov 14 2017

Areas of fog and drizzle are persisting across the region this
morning. The fog became dense in parts of west central MN
overnight which prompted a Dense Fog Advisory until 9 AM, but it
could be extended with guidance showing the fog continuing into
the afternoon. It may also be expanded eastward if near term
guidance is correct with visibilities dropping during the next few
hours. Radar indicates the best drizzle is currently occurring
from Mankato toward Eau Claire. This should taper off during the
predawn hours with patchy drizzle occurring through the day. The
better chance for drizzle or steadier rain will occur again this
evening ahead of the front when low level lift is maximized. Drier
air will follow the front tonight which should kick out the fog
and drizzle.

.LONG TERM...(Wednesday through Monday)
Issued at 319 AM CST Tue Nov 14 2017

As with the previous forecast, the extended period remains
uncertain in terms of timing, and how widespread the precipitation
develops Friday, and whether a much colder pattern develops next
week.

First, the upper air flow remains progressive and fast through
Friday. Differences remain in the GEM/EC/GFS on the speed of the
positive long wave trough moving across the Rockies and into the
Plains by Friday. The GFS continues to be the fastest with this
wave, and the GEM/EC have been the slowest. It is becoming apparent
that weather models have been difficult in determining the phasing
of the southern and northern jet streams entering the west coast
this week. Thus, the differences in each model run have play a
significant role in the timing and surface features later this week.
Several of the past model runs have tried phasing the jet streams,
but still have trouble, especially in terms of a split flow regime.
One item that is becoming apparent is the much warmer air flowing
northward before the main energy moves into the Plains. Therefore,
most of the precipitation will be in the form of rain. Only a brief
change over to snow is possible once this system departs to the east
sometime Friday night/Saturday morning. Due to the continued
problems with the models phasing the two jets, there is low
confidence on how widespread the precipitation becomes, and timing
could be a problem due to some of the energy further to the south.
The current forecast has decreased percentages to chance for most of
Minnesota, with western Wisconsin still having likely chances. I
would not be surprised to see these percentages decrease or even
increase once again as the system moves onshore and interacts with
the Rockies.

There is no doubt that once this system moves east of the Great
Lakes, a blast of Arctic air will move southward across the Upper
Midwest for the second half of the weekend.

Next week colder pattern remains questionable due to uncertainties
in the long wave pattern becoming established. Longer range
teleconnection of the NAO/PNA support a strong upper low forming in
southeast Canada, with an upper ridge building across the northern
Rockies, and the plains of central Canada. This support is do to the
a strong negative NAO developing, and allowing for a blocking type
of ridge over Greenland, and the North Atlantic. This would keep the
upper low in southeast Canada and the continued flow from the Arctic
region for most of the eastern 1/3 of the nation. Differences in the
deterministic models of the GEM/EC/GFS is where does the upper ridge
become established. Will the upper ridge be further to the east
allowing for more modified air across the Upper Midwest? or does the
upper ridge remain further to the west, supporting a much colder
pattern which is in line with the current GFS.

The current forecast is a blend of the models. Therefore, very low
confidence in the extended period past this weekend. Check back and
see how the forecast changes based on the mean flow developing.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1145 AM CST Tue Nov 14 2017

Little change from previous forecast. The LIFR/IFR conditions
will persist until a cold front passes through tonight. Some
improvement in visibilities across central MN is anticipated this
afternoon before deteriorating again this evening. Drizzle and
light rain will become more widespread this afternoon and evening
across WI and eastern MN. MVFR cigs developing Wed morning
becoming vfr from west to east into the afternoon. Southerly sfc
winds will become northwest and gusty into Wed.

KMSP...We will continue the IFR cigs and chc of vsbys The biggest
concern are cigs lowering to 500 ft in drizzle as it passes off
to the east early this afternoon. Some chance of cigs breaking out
briefly late tonight before filling back in with at least lower
end mvfr cigs for a time Wed morning. Then becoming vfr into the
afternoon.


/OUTLOOK FOR KMSP/
Wed night...Chc MVFR. Wind NW 5 to 8 kts.
Thu...VFR with MVFR/-RASN possible late. Wind SE 10 kts.
Fri...MVFR with Chance -RA. Wind W 7-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Dense Fog Advisory until noon CST today for MNZ041>045-048>050.

&&

$$

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



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