Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 312049
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
349 PM CDT TUE MAY 31 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 347 PM CDT Tue May 31 2016

Cold front at 3pm extended from Des Moines up to Rochester to around
Turtle Lake, where there is a triple point with an occluded front
that extends back to the northwest corner of MN and eventually to a
1002 mb surface low near Rugby, ND. There is about 1000 j/kg of
sbCAPE in the warm sector, with a line of thunderstorms now along
the front from central IA into western WI. Beside CAPE being
marginal, bulk shear ranges from 20-30 kts, so not seeing a big
severe threat with these storms. Biggest severe threat will come
with gusty winds, though that threat is largely east of the MPX CWA
where over 8 deg C/KM low level lapse rates are currently being
analyzed over the southeast tip of MN. What we have seen is some
pretty efficient rainfall production with these cells as storm
motion has been slow, with the bulk shear vectors lined up
parallel to the front, favorable for more of a heavy rain threat.

This front has been moving east at a pretty good clip during the day
and there is good agreement in the CAMs with this activity largely
being east of the MPX cwa by 00z, so sped up the departure of PoPs
quite a bit tonight. Otherwise, behind the front, we are seeing
dewpoints drop into the 40s across western MN, so we will cool down
nicely tonight, with lows in the lower 50s looking like a safe bet
out in western MN.

Wednesday, the surface low will continue to fill as it moves along
the international border. Made a couple of changes to the forecast
for tomorrow as well. First cu rule supports the development of a
broken to overcast cu field, so boosted sky cover through the
afternoon. With more clouds, also backed off on highs a couple of
degrees. Finally, reduced PoPs as well and limited how far south
a mention comes. The cold pool at h5 will be heading for NW Ontario,
with the associated steep mid-level lapse rates heading to northern
MN. In addition, forecast soundings are showing an inversion between
750 and 700 mb at all of the MPX bufkit locations that looks to keep
a lid on how deep our convection can get and really limit our shower
potential. Only reason we left PoPs where we did is for the strong
spoke of PV the NAM/GFS show moving across central MN during the
afternoon. Other than that, it`s hard to find much support for
seeing any precip in the MPX CWA Wednesday.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 347 PM CDT Tue May 31 2016

Cooler weather is expected in the extended period of the
forecast. The best chance for thunderstorms is Friday, with
lingering showers through the weekend.

Cool and cloudy conditions will be in place Wednesday evening with
brisk westerly winds making it feel more like early April than early
June. High pressure will slowly build in on Thursday with western MN
seeing more sun, while western WI hangs on to clouds for most of the
day.

Friday will be the most active weather day across the region as an
upper level low embedded in the northwest flow will bring a
favorable shear profile across the Upper Midwest in term of both
directional and speed shear. The lingering uncertainty is whether or
not there will be enough instability for deep updrafts and organized
convection. At this point the threat for severe weather hinges on
that variable. Forecast sounds show deep saturation, and no elevated
mixed layer across the northern part of the forecast area, but
soundings across southwest Minnesota are less cloudy, and generate
2000 to 2500 j/kg of CAPE by late Friday evening. This wave is
deepening with time, and despite the northwest orientation is taking
on a negative tilt. The combination of these factors should produce
severe storms across the Midwest. When it get to June, often times
the thermodynamic environment will over-achieve if the dynamic
environment is in place, so will continue to watch

Looking ahead, the upper level wave driving Fridays storms will slow
down as it becomes more amplified, and as a result should lead to
lingering chances for showers and thunderstorms Saturday into
Sunday. Early next week an upper level ridge will build out west
with warming temperatures by Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 115 PM CDT Tue May 31 2016

At 1730z, the cold front extended from about Waseca to St. Paul,
with thunderstorms rapidly developing along it from central IA
into wrn WI. The field that looks to have the best shot at
getting a TSRA is EAU, and here, with the HopWRF and HRRR showing
a line of storms working through EAU around 22z, felt confident
enough to go with a prevailing TSRA between 2130z and 2230z. For
RNH/MSP any activity looks to be more scattered in nature at these
locations, so maintained nothing more than VCTS. LAMP winds have
not had enough of a west component to them behind the front, so
followed the HRRR forecast with winds. Wednesday, sfc low over
north central ND will continue to fill as it moves across the
Canadian border. CU rule supports a BKN-OVC cu/sc field developing
area wide Wednesday morning. As for chances that cloud field will
be MVFR or VFR, MVFR is likely for AXN, possible for STC, and
unlikely for everyone else.

KMSP...The HRRR had been supporting storm development over the
western Twin Cities, but with front already east of MSP, TSRA
chances will be better east of the field. Still, expect some TSRA
nearby for the first hour or two, so left the VCTS in. The HRRR
has had a better handle on wind direction than the LAMP, so
followed it for the wind forecast. Expect the cu field to rapidly
develop after 13z Wednesday. Likely starting out near 3k ft, but
quickly working toward 5k ft for the afternoon.

/OUTLOOK FOR KMSP/
THU...VFR. Winds WNW 5-10 kts.
FRI...VFR. TSRA likely with chc MVFR. Winds S 5-10 kts.
SAT...MVFR likely. Chc -shra. Winds NW 10-15 kts.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

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



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