Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 251052

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
552 AM CDT Tue Jul 25 2017

.Updated for 12Z Aviation Discussion...
Issued at 545 AM CDT Tue Jul 25 2017


.SHORT TERM...(Today and tonight)
Issued at 358 AM CDT Tue Jul 25 2017

Today will be interesting. The majority of the time was spend on
temperatures and dewpoint for today, followed by thunderstorms with
heavy rain and severe weather potential later this evening and

A decaying MCS is slowly moving across Minnesota into Wisconsin.
Skies are clear on the back side of this so should see temperatures
warm quickly today across western Minnesota. Went above guidance for
dewpoints in this region given the overnight rainfall across west
central Minnesota, climatological peak of evapotranspiration, as
well as the expected pooling of dewpoints along the warm front.
Forecast dewpoints later today in the mid to upper 70s, together
with air temps near 90 yield heat indices of 100 to 105 for a few
hours during the late afternoon, so have a small heat advisory for
parts of west central Minnesota.

This hot, unstable air beneath a stout inversion should lead to late
afternoon MLCAPE values around 3000 to 4000 J/kg. Surface
convergence along the boundary should eventually break through the
CAP by early evening in eastern SD and western MN. Storms will
develop quickly and should become severe shortly after convective
initiation. Deep layer shear is only marginal for severe weather,
but an increasing jet aloft should help compensate for the
relatively weak mid-level flow. Hodographs along the warm front
would be favorable for a tornado or two, and SPC has a 5% contour in
this region if surface-based storms are able to develop by early

Widespread convection is expected closer to sunset when the low
level jet decouples from the boundary layer. These storms will pose
a flooding risk with rainfall rates easily in the 2 to 3 inch per
hour range. Fortunately there is not a strong surface low developing
upstream which would keep the low level jet anchored in one
location, so should see it gradually veer and become southwesterly
overnight, but there is still a small window of time in the late
evening where a legitimate training thunderstorm threat exists. Any
locations that does have an hour or two of training storms could
easily see 3-4 inches of rain or more. Eventually the cold pool
should develop and work in concert with the waning forcing for
ascent to drive the boundary southward and make for a more
progressive movement of the storms.

.LONG TERM...(Wednesday through Monday)
Issued at 358 AM CDT Tue Jul 25 2017

Thunderstorms will be ongoing early Wednesday morning ahead of the
cold front pushing into southern and eastern MN. Models are in
pretty good agreement in organizing an MCS over southwest MN and
driving it southeast into Iowa by afternoon. That will likely be
the main feature nearby for Wednesday. Forcing along the front to
the northeast of this area, particularly from west central WI
northeastward, will weaken overnight tonight, the core of the LLJ
will be shifting to the east, and the decaying upper jet will
leave little to support widespread convection into Wednesday
across Wisconsin. Kept 50-60 PoPs in place for now, but this may
be reduced further in future updates.

Surface high pressure builds in late week and into the weekend.
Mostly clear skies and near or slightly below normal temperatures
can be expected.

A front embedded in the northwest flow will push through Sunday.
It appears moisture will be limited with the expansive high
shutting off the Gulf, so not expecting widespread convective


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 545 AM CDT Tue Jul 25 2017

Expect VFR conditions this morning, but scattered showers could
move across the TAF sites. There is a few thunderstorms as well,
but storms are trending down and that should continue. Southerly
winds will continue today. Later this evening expect widespread
thunderstorms to develop across the region and slowly move
southeast. These storms will likely produce heavy rain and reduced

Could have some thunder move across MSP this morning, so continued
with VCTS in the TAF through 15Z. VFR conditions will prevail
until after sunset when storms should be ongoing west of MSP.
These storms should eventually bring MVFR/IFR conditions across
MSP overnight.

Wed...VFR with TSRA possible early. Wind NW at 5 kts
Thu...VFR. Wind NE at 5-10 kts.
Fri...VFR. Wind E at 5kt.


MN...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening
     for MNZ054>057-064-065-073.



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