Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210946

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
446 AM CDT TUE JUN 21 2016

.SHORT TERM...(Today and tonight)
Issued at 445 AM CDT Tue Jun 21 2016

It`s a quiet and cool morning across Minnesota and Wisconsin
underneath a surface high. The closest showers and storms are in
eastern Nebraska and southwest Iowa this morning ahead of warm
front that is gradually moving north. This feature will be the
focus for thunder across MN/WI tonight and tomorrow morning. A
dry boundary layer and sunshine should allow temperatures to get
into the lower 80s across much of southern MN and portions of
western WI today. After sunset, a surface low and warm front will
approach MN from the W-SW. This wave will bring a surge of
moisture into the Upper Mississippi River Valley. By midnight
tonight, a band of thunderstorms along this surging warm front
should be entering or developing over southern MN somewhere near
the I-90 corridor. There is a Slight Risk for severe weather
across southern MN tonight because of the threat for nickel to
golf ball hail with this elevated convection. The main area of
thunderstorms will be on the nose of the strongest 925-850 flow,
which will quickly dive into Iowa and southern WI as we head
toward sunrise Wednesday morning. There is still a decent shot at
weaker storms in St. Cloud, Twin Cities and Eau Claire because of
the widespread warm advection and isentropic lift that moves in
between 12am and 6am. Sometimes storms with warm advection happen
faster than what the models depict, so it is probably better to
hedge toward late evening and early tonight for storm initiation,
with much of the activity moving out of the forecast area by 6am

.LONG TERM...(Wednesday through Monday)
Issued at 445 AM CDT Tue Jun 21 2016

The long term will start off Wednesday morning with thunderstorms
likely ongoing from what forms to the north of the warm front
tonight.  Though what we see Wednesday morning may get folks excited
about seeing some healthy rainfall totals Wednesday, that does not
look to be the case as the MPX area looks to largely get split
between primary forcing mechanisms. The LLJ coming up out of
Nebraska toward SW MN tonight will be veering quickly Wednesday
morning over toward Milwaukee/Chicago. This will quickly shift the
focus of thunderstorms over south central MN tonight off to the
southeast of the MPX area Wednesday morning. The other area of
forcing largely missing the MPX area is the main upper wave itself.
During the day Wednesday it will go from near the ND/Sask/Man border
to western Lake Superior, with strong PV advection associated with
it going across northern MN. For us, it`s broad isentropic lift and
that-e advection as moist air gets pulled north toward the main
shortwave. This looks to result in a scattered to broken area of
showers and thunderstorms working across MN and into WI during the
day on Wednesday, which is why mainly chance PoPs we had were not
changed much. PoPs will linger in western WI Wednesday night as the
main short wave passes across northern WI with an inverted surface
trough hanging back into the region as well. Precip will have
cleared the area by Thursday, with high pressure leading to dry
weather and pleasant conditions with temperatures right near normal.

Thursday night, ridging will be building across the Plains in
response to an h5 low moving onshore and into the Pac NW. We will
see return flow set in on Friday, with the heat and humidity making
a return. However...the nose of the LLJ and thickness ridge Friday
and Friday night are up across the international border, with
thunderstorm chances during these periods remaining largely north of
our area. What we will see arrive Friday night is a significant
capping inversion associated with a southwest US EML move in as h7
temps increase to between 12c and 14c.

Our best shot at precip over the weekend continues to be with the
strong cold front passing across the area Saturday. H5 wave
associated with this front will have a negative tilt as it works
across ND, with the best forcing and upper divergence associated
with the wave remaining north of the MPX CWA. Still, a significant
surge in low level moisture is expected ahead of the cold front,
with dewpoints increasing into the lower 70s. The question then
becomes when does the cap break. This may take a while given the h7
temps, but as the upper wave moves across ND, we will see cooler h7
temps work across the area, weakening the cap. Right now, it looks
like storms will most likely initiate somewhere in the eastern half
of the area, with best thunderstorm chances Saturday afternoon and
evening across eastern MN and western WI. Severe thunderstorms will
certainly be possible given that we should see 2k-3k j/kg of MLCAPE
ahead of the front, but best shear will be lagging behind the front,
so we are currently not anticipating a significant severe episode
with this front.

The upper low driving the front on Saturday will slowly track across
southern Canada through Monday. Being south of the upper low, we
will be on the dry side of the low, with cooler temperatures not
expected to work in until Monday, resulting in highs into the 80s on
Sunday falling back into the 70s on Monday. After that, the ECMWF
and GFS show the upper MS Valley finishing off the month of June on
a dry note.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1057 PM CDT Mon Jun 20 2016

VFR conditions throughout. Winds will become light generally from
the SW but potentially variable overnight before picking up from
the NW again tomorrow mainly in the 5-10 kt range, although a
little higher at KEAU. Winds will then remain around 5 kt after
00z tomorrow evening but have varying directions. Skies will go
clear overnight then have high cirrus clouds filter in from the W.
Southern and western MN will see multiple layers of clouds
moving into the area approaching midnight, with a few showers
developing near KRWF although choices do increase closer to 12z.

KMSP...No significant weather impacts expected.

WED...VFR. Chc MVFR/-TSRA. Winds E 5-10 kts.
THU...VFR. Winds N 5 kts.
FRI...VFR. Winds SE 5-10 kts.


.MPX Watches/Warnings/Advisories...


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