Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 190355
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1055 PM CDT MON JUL 18 2016

.UPDATE...For 06z Aviation discussion below

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 331 PM CDT Mon Jul 18 2016

High pressure is overhead today, which is resulting in a post card
perfect summer day for the upper MS River Valley. To the south,
there is a wavy stationary front from KS/NEB over to the southern
Great Lakes. Tonight, as h5 heights build across the Plains, The
front will begin to get better organized and begin lifting north as
a warm front, which looks to move northeast into MN during the day
on Tuesday.

For tonight into Tuesday morning, did reduce PoPs quite a bit and
it`s looking like we may even be dry during this period. The warm
front is coming north a bit slower than initially forecast, keeping
possible convection farther southwest. Beside that, llj and
associated isentropic lift is rather disorganized tonight and there
really is no short wave to help focus activity. The CAMS have a lot
of spread as to if/where storms will be ahead of the warm front, but
even for those that have convection, they do not have anything
moving into our southwest counties until after 12z Tue. In fact our
precip chances do not really look to pick up until Tuesday
afternoon, as a wave of SW monsoon origin rides around the ridge and
into MN, though that wave does not really look to become active
until Tuesday night as the LLJ intensifies, but there`s more on that
in the long term section.

For highs Tuesday, did boost forecast highs as both the MAV and MET
have MSP hitting 89 tomorrow, which is similar to what the bias
corrected raw model guidance has. In addition, as the warm front
lifts north, we will see dewpoints in the low/mid 70s coming into
MN. These dewpoints combined with highs up near 90 will already be
pushing afternoon heat indices to near 100 in west central MN.
However, much warmer conditions are one the horizon and will let the
worst of the heat expected for Wednesday through Friday drive any
heat related headlines.

.LONG TERM...(Tuesday night through Monday)
Issued at 331 PM CDT Mon Jul 18 2016

Heavy rain and flash flooding is possible Tuesday night into
Friday as a warm front lifts through the region. Hot and humid
conditions remain on tap in the wake of the warm front for
Wednesday, Thursday, and Friday. Expanded the Extreme Heat Watch
to include western Wisconsin, since this will certainly be the
warmest airmass of the year and it comes at a climatological peak
for heat.

The heavy rain threat seems to be coming together for Tuesday
night into Wednesday. PWAT values near 2 inches surge northward
along the warm front. Meanwhile a subtle shortwave is forecast to
ride the H500 ridge and move across MN/WI which should provide
forcing for ascent. Forecast soundings show a tropical airmass
with MUCAPE along the front that should lead to convection along
the warm front. Mean layer winds are westerly around 20kts, while
the low level jet is from the southwest at around 35kts. This
results in Meso Beta Elements that will actually move southwest
setting up a training thunderstorms scenario. These storms with
the warm layer cloud depth of 12 to 14 kft will be capable of 2 to
3 inch/hr rainfall rates. If thunderstorms train over the same
location for multiple hours could have significant rainfall totals
and flash flooding. As of now, the area most at risk is along the
MN/WI border, and WPC has highlighted this area with a slight risk
for excessive rainfall.

As for the heat, the previous forecast was right on track so did
not make any significant changes. Overnight lows continue to look
like upper 70s to near 80, and daytime highs will be in the 70s.
The mid 70 dewpoints and abundant sunshine will lead to
significant health risks for active people outdoors if precautions
are not taken, so have expanded the heat watch to include western
WI. Looking ahead, a cold front is forecast to move through the
region this weekend and provide a reprieve from the the heat, as
well as a chance for showers and thunderstorms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1055 PM CDT Mon Jul 18 2016

VFR conditions are expected overnight, with Tuesday bringing an
increase in broken mid level clouds as a warm front lifts toward
the area. Showers and thunderstorms associated with the warm front
may hold together enough to reach KRWF around or shortly after 12z
Tues before waning, but the activity is expected to stay south of
the rest of the TAF sites. Winds will be nearly calm to southeast
under 5 kts for the overnight hours, and then increase to 10-15
kts from the southeast by Tuesday afternoon (with gusts to between
20 and 25 kts) at western sites (KAXN-KRWF and KSTC).

KMSP...
Mostly clear skies overnight with nearly calm winds. Mid level
clouds will be on the increase by Tuesday afternoon and southeast
winds increase to 12kts as well.

/OUTLOOK FOR KMSP/
Wed...VFR. Chc -TSRA. Wind S at 10g20kt.
Thu...VFR. Wind SSW at 5-10kts.
Fri...VFR Chc -TSRA late. Wind SE 5 kt.

&&

.MPX Watches/Warnings/Advisories...
WI...Excessive Heat Watch from Thursday morning through Friday
     evening for WIZ014>016-023>028.

MN...Excessive Heat Watch from Wednesday morning through Friday
     evening for MNZ041>045-047>070-073>078-082>085-091>093.

&&

$$


SHORT TERM...MPG
LONG TERM...JRB
AVIATION...LS


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