Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 251714
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1214 PM CDT SAT JUN 25 2016

.SHORT TERM...(Today and tonight)
Issued at 341 AM CDT Sat Jun 25 2016

A myriad of weather threats will affect Minnesota and Wisconsin
today as a cold front and anomalously strong upper trough for June approach
from the west.

The first concern will be on the potential for heat impacts ahead
of the front as temperatures warm into the lower 90s and combine
with dew points in the lower 70s. The result will be a corridor of
forecast heat indices around 100 degrees across the heart of the
forecast area, generally extending from the MN river valley across
the Twin Cities Metro area. While we will see increasing cloud
cover and winds abating the threat for heat impacts somewhat,
still think a heat advisory is warranted for the aforementioned
area that will see about a 3-5 hour period of excessive heat this
afternoon. Looking at the top 15 CIPS analogs for today, around 60
percent had max heat indices over 100 degrees.

By 18z, CAMS show thunderstorms popping across west central
Minnesota. It is no secret that we will have plenty of instability
in play (with Mixed Layer CAPES forecast circa 3000 J/Kg). The
one quandary is the fact deep layer shear will be marginal.
However, that being said, 0-3km shear looks more than sufficient
for supercells during the infancy stage of the event. Eventually expect
discrete cells (capable of damaging wind, hail, and tornadoes) to
congeal into a line, with the primary threat transitioning to
damaging winds as the line crosses east central MN into west
central WI. For the CIPS analog fans, 17 June 2010 and 14 July
2010 remain in the top 4 for today, with 11 July 2008 now
appearing as well (which was the Willmar tornado). While no two
events are the same, the fact that several notable events for MN
are being pinged as analogs for today illustrate the potential for
an for a notable severe weather day.

In addition to the previously mentioned threats, the potential for
flooding also exists, given precipitable water values are over 2
inches. This threat looks the highest over Wisconsin once the line
forms.

By 09z Sunday, our area should be clear of showers and
thunderstorms. Drier dewpoints work in behind the front, and allow
lows to cool into the 50s across parts of central MN. Low to mid
60s will occur across south/east central MN and west central WI.

.LONG TERM...(Sunday through Friday)
Issued at 341 AM CDT Sat Jun 25 2016

After what looks to be a busy short term portion of the forecast
things will become fairly quiet for the bulk of the long term. The
upper trough responsible for today`s weather will move east of the
area by Sunday night as ridging builds over the western U.S. We
look to be in cooler and drier northwest upper flow for the
balance of the forecast period, with no precipitation expected
Sunday through Wednesday. Although we will see a cold front push
across the area this afternoon and evening, it will initially
serve mainly to just bring in drier air, with Sunday looking to
remain rather warm with highs in the 80s. But, cooler conditions
will arrive by Monday and remain in place through the week, with
80s probably not being seen again until perhaps Thursday or
Friday.

Although the GFS and ECMWF agree reasonably well on the large
scale upper flow, there are some differences in their sensible
weather fields over the latter half of the week. The GFS is a bit
more ambitious in allowing some moisture return into the area, and
manages to bring shower and thunderstorm chances back by Wednesday
night. Both of those solutions, along with the Canadian then show
some spotty precipitation chances for Thursday and Friday as we
see a few weak shortwaves embedded in the northwest flow work
through the area with some marginal instability in place by that
time. Included chance PoPs for much of the area from Wednesday
night into Friday given the reasonable consensus on periodic
chances for showers and thunderstorms, but hope subsequent
forecasts are better able to identify dry periods within that time
frame, since at this point that looks to be the primary weather
condition.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1215 PM CDT Sat Jun 25 2016

Timing of thunderstorm development remains the main challenge this
afternoon and early evening across MPX forecast area. Based on the
latest models and surface observations, thunderstorms will develop
in western Minnesota between 19-20z and move off to the east-
southeast, affecting KSTC/KRWF by 21z, KMSP by 22z, KRNH/KEAU
after 00z. The potential of severe wind gusts and torrential
rainfall will affect the airports which leads to temporary IFR
conditions. Conditions will improve rapidly behind the cold front
with VFR developing between the mid afternoon through midnight
from west to east. Gusty winds will likely redevelop Sunday
morning from the west-northwest.

KMSP...

Thunderstorms will a temporary period of IFR or lower are likely
by the late afternoon, early evening. Timing is the main challenge
with the best period of the worst conditions between 23-01z.
Thunderstorms may linger past 01z, but the main threat of severe
winds and lower ceilings will decrease.

/OUTLOOK FOR KMSP/

MON...VFR. Northwest wind 10 kts.
TUE...VFR. North wind 5-10 kts becoming west under 5 kts.
WED...VFR. Isolated TSRA late. Southwest wind 5 kts.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...Heat Advisory until 6 PM CDT this evening for MNZ059>063-066>070-
     074>077-082>084.

&&

$$

SHORT TERM...LS
LONG TERM...
AVIATION...JLT


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