Area Forecast Discussion
Issued by NWS Twin Cities, MN
FXUS63 KMPX 250039
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
739 PM CDT FRI JUN 24 2016
.SHORT TERM...(This evening through Saturday)
Issued at 342 pm CDT Fri Jun 24 2016
This is a perfect scenario of calm weather before the storm in the
next 24-36 hours.
Slight adjustments were made for tonight, and Saturday afternoon
timing of the thunderstorms, but overall stuck close to previous
First, a very strong and abnormally deep upper low for late June was
moving across the northern Rockies this afternoon. Models continued
a straight forward forecast with this upper low progged to move
along the Canadian border, from North Dakota, to southern Manitoba
by Saturday evening.
As with previous values of wind shear and instability, models
continued to depict a period that highlights both of these
parameters maximized between 19z Sat - 01z Sun across central
Minnesota early, and then moving southeast into east central
Minnesota, and west central Wisconsin by early evening. 0-6km wind
shear values initially are forecast to be around 25 kts, but are
expected to increase to 30-40 kts by early evening. MLCAPEs range
from 2000-3000 J/kg in west central and central Minnesota at 18z
Saturday, to 1500-2000 J/kg by 00z Sunday in east central Minnesota
and west central Wisconsin. Other severe weather parameters
including CWASP (Craven-Wiedenfeld Aggregate Severe Parameter on SPC
website) and Helicity also show the potential of organized severe
thunderstorms Saturday afternoon, into the early evening. Latest SPC
Day 2 outlook has portions of east central Minnesota and west
central Wisconsin in an elevated risk of severe thunderstorms.
Latest CIPS also support an outbreak with today`s run (12Z Friday)
leaning toward July 14, 2010 which was the Northfield, Lakeville,
Randolph tornado (EF-1). This tornado also affected west central
Wisconsin near Ellsworth that had an EF2 tornado.
In the short term, a few elevated instability showers or
thunderstorms are possible tonight, but latest CAMS do not show any
type of organization or consistency. Therefore, kept isolated or
scattered showers and thunderstorms in the forecast. The best chance
of more organized or scattered activity will occur in northern
Minnesota after midnight, and drift to the southeast into east
central Minnesota and west central Wisconsin toward sunrise. This
is also where some of the local RAP/HRRR convective elements show
some potential. However, if any storms do develop, the amount of
instability and shear is weak enough to limit severe potential.
.LONG TERM...(Saturday night through Friday)
Issued at 342 pm CDT Fri Jun 24 2016
Strong to severe thunderstorms will likely be in progress across
eastern MN and western WI at the start of the long term with ample
shear and instability in place. CWASP values are most favorable from
the Twin Cities on north and east. PWAT values at or above 2 inches
are indicated in various model solutions for these same areas.
This is above the daily max for the MPX sounding climatology,
leading to a flooding concern if the storms would begin to train.
The culprit is a strong low pressure system moving eastward across
south central Canada with a trailing cold front arching southward
across MN. The worst of the storms should east of our forecast
area by midnight Saturday night, if not a few hours earlier.
By Sunday, the low pressure system will be just north of MN with
the cold front well east and south of the local area. There will
be a breezy west wind on Sunday, especially across central MN,
but highs will still likely top out in the lower to middle 80s.
Thereafter, the flow aloft will become more northwest with high
pressure building in for Monday and Tuesday. Both days will be
quite pleasant with highs in the 70s along with dew points in the
45 to 55 degree range.
For the balance of the work week, Wednesday through Friday, we`ll
remain in a northwest flow but there will be a few short waves
moving through. Some instability showers and thunderstorms can not
be ruled out during this period. The day with the best chance for
a little precipitation is Thursday, when the strongest of the
waves moves through. High will slowly rise to around 80 by the
time we reach Friday afternoon.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 730 CDT Fri Jun 24 2016
Scattered very light showers South of Mankato will fizzle out
during the next few hours as daylight heating subsides. Mdt mainly
SE flow over TAF sites will continue tonight as surface pressure
gradient tightens ahead of approaching sfc low currently over
Western Dakotas. All short term model data indicating very little
chance of convective activity tonight after midnight over most
airport sites. However, with modest Theta-E advection and weak to
mdt divergence aloft, decided to include short burst of light
showers at all sites save RWF and EAU. VFR conditions will ensue
tonight all airport locations, with short term MVFR VSBYs
anticipated on Saturday all locales with convective activity.
Best chance for thunderstorms will be early afternoon Western TAF
sites, with mid to late afternoon remainder save EAU which will
encounter same early evening. Severe weather is still a possibility
with some of these storms. Winds will increase markedly after 15Z
ahead of cold front all locales and will remain S to SW until
frontal passage Saturday evening all MN airports, and after
midnight WI sites.
VFR CIGS and VSBYS will be the rule prior to 12Z...save a brief
low chance shower scenario late tonight. Best chance for VCTS for
next few days should be anticipated after 22Z. Scattered severe
weather more likely over Eastern MN 22Z-00Z. If same does develop
look for both MVFR Cigs and Vsbys this time period. SSE winds will
turn more S on Saturday morning, increasing noticeably with strong
SW flow anticipated by late afternoon. Frontal passage expected by
26/06Z time frame.
/OUTLOOK FOR KMSP/
SAT...MVFR Ceilings possible aftn-early eve. Southwest Wind 12-26
SUN...VFR. West wind 10-20 kts becoming northwest.
MON...VFR. Northwest wind 10-15 kts becoming east 5 kts or less.
TUE...VFR. North-Northeast wind 7-10kts becoming East 5-8 kts.