Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 281833

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
133 PM CDT Wed Jun 28 2017

.SHORT TERM...(Today and tonight)
Issued at 400 AM CDT Wed Jun 28 2017

Fairly widespread showers and thunderstorms are ongoing early this
morning across southern and portions of central Minnesota along a
tight 850 mb moisture gradient. One nearly stationary band
stretching from Long Prairie and Alexandria southward to Redwood
Falls and New Ulm is evidence the LLJ has strengthened to at least
the mean wind. Some building of convection to the east is expected
with the jet veering around sunrise, before the best moisture
convergence shifts to the east of the CWA and support for the rain
and thunder diminishes for the rest of the morning.

Infrared satellite imagery shows cloud tops warming across eastern
South Dakota with cigs greater than 12kft per observing stations.
This is a good sign we`re going to clear out later this morning with
atmospheric recovery expected by afternoon. Increased high
temperatures into the lower 80s across southern MN. Dew points will
also be climbing in the warm sector to the upper 60s, beneath a
pocket of mid level lapse rates as steep as 7.5-8.0 C/km. This will
contribute to 2500-3000 J/kg SBCAPE by mid afternoon across eastern
MN and west central WI while a mid level vort passes overhead.
Scattered to numerous thunderstorms should develop in this area,
shifting southeast by evening. As previously discussed, wind shear
is a major limiting factor for severe thunderstorms with the mid
level jet down to the south across Iowa into southern Wisconsin. A
few could still become severe given the moderate to strongly
unstable airmass, however.

.LONG TERM...(Thursday through Tuesday)
Issued at 400 AM CDT Wed Jun 28 2017

Cool yet unstable weather persists through the weekend, and then a
pattern transition occurs at the end of the long-term forecast
period which brings a return to warm and humid air late next week.

The daytime period on Thursday looks to be dry as brief ridging
sets in over the area. This break in precipitation is short-lived,
as the next shortwave trough arrives Thursday evening and
amplifies over the area on Friday, bringing another round of
showers and thunderstorms. Cyclonic flow looks to persist over the
area on Saturday, and bring scattered showers and thunderstorms
primarily along/east of I-35.

It will be another cool weekend as high temps on Saturday and
Sunday top out in the 70s.

Monday and Tuesday bring mid level ridging into the central CONUS
which is expected to translate to dry weather and moderating
temperatures. Highs for Fourth of July holiday look to be right
around normal in the 80-85 degree range.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 133 PM CDT Wed Jun 28 2017

Two concerns this period are thunderstorm potential this afternoon
and threat for IFR or lower cigs to drop out of central/northern
MN tonight. For storms, clearing south of I-94 and west of I-35
has resulted in instability growing in this region, with a warm
front extending from Albert Lea up toward Long Prairie and the
cold front sitting from Alexandria down to Marshall. Like the
idea of the HRRR with a broken line of storms developing along the
boundary at about 21z. Just think the HRRR is too far west with
its development based on where the front is now. This puts MSP
and especially RNH/EAU at risk for another round of storms.
Tonight, as the surface low currently north of Alexandria shifts
into northern WI, the NAM/RAP/HRRR show IFR and lower CIGS
dropping south out of northern MN. Expect these clouds down to
about I-94, with MSP likely being near the southern edge of these
clouds. The HRRR looks to provide a general idea of how these
clouds will evolve overnight, though is likely a bit too far south
with where the low clouds are by 10z tonight.

KMSP...Based on where the front is now, MSP looks to be very near
where afternoon initialization occurs, so storms will either
go up overhead or just east of MSP. 22z to 00z will be our prime
time for any storm activity. For clouds tonight, the RAP would
slam the low clouds in after 9z, but the NAM keeps this enhanced
low level moisture to the north and the SREF probs for MVFR or
less cigs are confined to central MN, so kept MSP VFR for now.

Fri...VFR. Chance MVFR with likely TSRA. Winds variable 5 kts.
Sat...VFR. Winds WNW 5-10 kts.
Sun...VFR. Chance of TSRA/SHRA. Winds light and variable.




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