Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 180418

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1118 PM CDT MON OCT 17 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 325 PM CDT Mon Oct 17 2016

Tonight and Tuesday...Surface analysis this afternoon depicts a wavy
cold front extending SW from a surface low in the middle of Lake
Superior, draped over northern WI and SE MN into eastern Nebraska.
The front transitions to a warm front in the vicinity of the NE/IA
border, east of the surface low in that area. Aloft, a generalized
SW flow will persist but there are some noticeable features within
the broad flow. A potent jet streak over Rockies will shift into the
Great Lakes region by the overnight hours, essentially helping to
shunt the NE/IA surface low northeast along the draped front. Plenty
of low level moisture is resident over the area, to the tune of low-
mid 60s dewpoints over much of the central-southern MN into western
WI portions of the coverage area. KMPX radar already showing plenty
of echoes across the coverage area, with the strongest ones in the
vicinity of and south of the aforementioned front where convection
has been expected to break out this afternoon. Said convection is
expected to last through the evening hours for much of the coverage
area as MLCAPE values have climbed to around 1500 j/kg and shear
will continue to increase with the approach of the mid-to-upper
level jet streak. Should storms have enough growth near the front,
enough convergence could produce an isolated tornado. However, the
main hazards look to be damaging straight-line winds and large hail,
especially with freezing levels only in the mid-12 kft range. Storms
will persist for only a few hours, dissipating with loss of max
heating/instability, but precipitation will continue into the early
morning hours in conjunction with an upper level trough axis
trailing the surface front. Both the surface front and the upper
level trough will be east of the coverage area by daybreak Tuesday
morning, leading to a dry Tuesday but with clouds through at least
the first half of the day.

Mild temperatures will persist through tonight in advance of the
cold front, followed by noticeably cooler and drier conditions
tomorrow behind the front. Lows tonight will bottom out in the mid
40s to lower 50s while highs on Tuesday only climb to the upper 50s
to mid 60s.

.LONG TERM...(Tuesday night through Monday)
Issued at 325 PM CDT Mon Oct 17 2016

Very quiet weather Tuesday night through Monday as no precipitation
is expected during this time period. That makes for a short and
simple forecast discussion.

Early afternoon water vapor imagery identified a broad longwave
trough over the western Conus, with a few embedded shortwaves. The
first one was just crossing the High Plains and will cause a cyclone
to rapidly intensify over the Great Lakes into Quebec. A second one
was located off the coast of California, and the other was just south
of the Allucian Islands. On Tuesday the second and third shortwaves
will arrive and dig a trough over the Great Plains, with a surface
low developing over the Ohio River Valley. This should keep the
precipitation well to the south and east of MN/WI as high pressure
builds over the region. The 17.12 ECMWF has and area of rain across
southern MN Wednesday night, but for now kept the forecast dry.

Upper level ridging will continue through the end of the week, which
means more dry weather for the Upper Midwest. The 17.12 ECMWF has
some warm advection precipitation Friday night across the region,
but for now kept the forecast dry. Meanwhile the 17.12 GFS shows a
shortwave forecast to move along the International border Saturday
night, but as of now all the precipitation with this system will
fall north of the forecast area.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1106 PM CDT Mon Oct 17 2016

Showers and storms are gradually on the decrease late this
evening, but they may still may impact KRNH and KEAU before 2AM.
For the remainder of the TAF sites, scattered showers or light
rain can be expected until the early morning hours with a gradual
drying trend around sunrise. There are a few pocket of MVFR
ceilings in MN/WI, but overall conditions are VFR and aside for
some low clouds in WI, we think the cloud cover will remain high-
based through tomorrow at most sites. Fog should also be limited
by the arrival of drier air, the high clouds that are in place, and
the presence of at least some wind through the morning.


Fortunately, it looks like the last of the thunder is making its
way east of the airport at this hour. Scattered light showers will
be possible through most of the night (before sunrise), but the
showers will gradually diminish as we head toward sunrise with VFR
likely through the day tomorrow.

Wed...VFR. Wind NW 5-10 kts.
Thu...VFR. Wind NW 5-10 kts.
Fri...VFR. Wind SE 5 kts.


.MPX Watches/Warnings/Advisories...


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