Area Forecast Discussion
Issued by NWS Twin Cities, MN

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488
FXUS63 KMPX 201812
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
112 PM CDT SAT AUG 20 2016

.UPDATED for 18Z Aviation Discussion...
Issued at 105 PM CDT Sat Aug 20 2016

&&

.SHORT TERM...(Today and tonight)
Issued at 403 AM CDT Sat Aug 20 2016

Early morning water vapor imagery shows sharp upper trough axis
through the Dakotas and advancing eastward with time.  At the
surface, the low pressure center was analyzed near southwestern
WI. This system is going to deepen significantly today as the
surface pressure falls to near 992mb by this evening over
southeastern Lake Superior. Aloft, the main trough will dig and
broaden out across the upper midwest with the PV maxima swinging
through our region during the day today. This combination of a
rapidly deepening surface low and upper trough axis and associated
PV feature moving through will make for plenty of showery activity
with isolated thunder possible this afternoon, in addition to
widespread low clouds throughout the day, especially in eastern MN
and western WI closer to the surface low center.

Another consideration for a nearby deepening surface low is the
wind speed potential. The strongest winds will remain off to our
east this afternoon, closer to the actual surface low as the high
pressure to our west at the surface is not particularly strong.
Even so, went ahead and pushed the wind up a few MPH across the
forecast area today given increasing confidence in the low
strength and placement as it deepens throughout the day. Expecting
NW winds of 15-20MPH with gusts up to 25MPH.

Daytime high temperatures will be much cooler than anything we`ve
experienced in months with the trough coming overhead, decent low
level CAA, and the combination of clouds and precip overspreading
much of the area. Knocked the temps back a few degrees in western
WI where it will likely by precipitating all day. Highs in the low
to mid 60s there, with upper 60s and a few spots hitting 70 in
western MN. Clouds will start scattering out in far western MN
this evening, and that clearing will slowly work its way through
eastern MN and western WI through the night.

.LONG TERM...(Sunday through Friday)
Issued at 403 AM CDT Sat Aug 20 2016

Sunday and Monday...Sunday will start out with the base of a longwave
trough axis having moved into the Great Lakes region while a
ridge builds over the Rockies. This will put the region within
dry northwest flow aloft along with surface high pressure aligned
over the northern and central Plains. The coolest air in some
time will be felt early Sunday morning with morning lows into the
upper 40s to lower 50s. Temperatures will start to rebound on
Sunday and even more so on Monday as the surface high shifts
away, resulting in a warmer southerly flow, and upper level
riding arrives to raise H5 heights. While dry weather continues,
highs will increase to the 70 to 75 degree range on Sunday
followed by highs in the upper 70s to mid 80s on Monday.

Tuesday through Friday...A more unsettled pattern is
expected starting Tuesday as the ridge axis shifts off to the
east while an upper level low which moved onshore southern
British Columbia province on Sunday rotates eastward just north
of the international border. This upper low and its associated
trough axis sweeping over the Rockies Tuesday will help develop a
low pressure system and push it from KS/CO Tuesday morning to
southern Manitoba province by Wednesday morning. A cold front
will trail the surface low, expected to cross the area Tuesday
night through the first half of Wednesday. This timeframe,
Tuesday night into Wednesday night, will be the best chance of
precipitation throughout the extended portion of the forecast.
Timing of the front won`t be optimal for taking advantage of
instability so any possibility of strong storms would be relegated
to the need of stronger dynamics which, depending on the model,
may or may not occur so am not impressed with severe potential at
this point. Behind the front, more zonal flow aloft looks to
develop while surface high pressure returns. Still, temperatures
will rise into the 80s once again ahead of the front then fall
back into the 60s and 70s for the latter portion of the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 105 PM CDT Sat Aug 20 2016

Showers and a few isolated thunderstorms will continue across the
region today. The chance for thunder is too low to include mention
in the TAFs. MVFR ceilings will gradually lift later tonight,
with VFR conditions expected on Sunday.

KMSP...
The steady rain has ended at KMSP, but a few scattered showers an
even an isolated thunderstorm are possible this afternoon. The
MVFR Cigs are starting to take shape, so may need to include them
back in the TAF at KMSP through the evening hours. VFR conditions
are expected for Sunday.

/OUTLOOK FOR KMSP/
Mon...VFR. Winds SSW at 20G25 kts.
Tue...VFR. Winds SSW at 15G25 kts.
Wed...VFR with -TSRA possible. Wind S at 10G15 kts.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

SHORT TERM...SPD
LONG TERM...JPC
AVIATION...JRB



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