Area Forecast Discussion
Issued by NWS Twin Cities, MN

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767
FXUS63 KMPX 241737
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1237 PM CDT Thu May 24 2018

.updated for 18z taf discussion below...

.SHORT TERM...(Today and tonight)
Issued at 359 AM CDT Thu May 24 2018

Early morning convection was developing, and moving off to the east
across east central Minnesota, and north of the Twin Cities. This
area of thunderstorms was developing along a rich theta-e
environment with the support of a strong low level jet.

The main upper level storm system remains across Montana early this
morning, with several embedded short waves riding north/northeast
from the southern Rockies, and into the Plains. Today`s forecast
hinges on the initiation of convection along the leading edge of
this wave across Montana moving east/northeast across North Dakota,
and eventually northern Minnesota tonight.

Morning convection will likely fester across far western Minnesota,
and west central Wisconsin where the combination of a moisture
atmosphere, and outflow boundaries remain. The mid levels of the
atmosphere across southern Minnesota remains dry initially which
will inhibit any substantial updrafts from the outflow boundaries.
Slowly this afternoon, the atmosphere will begin to moisten across
western Minnesota in advance of the wave in Montana. Thus, and with
a stronger mid-level impulse, convection should develop across far
western Minnesota in the afternoon. Although confidence is quite low
anyway east of this area in Minnesota, and western Wisconsin, I
can`t rule out an isolated storm just because of the amount of
instability present. The best chance of thunderstorms across
central/southern Minnesota will occur by the late afternoon, and
evening hours. West central Wisconsin may need to wait until after
dark for most of the activity to enter it`s area.

As for severe weather potential, as with previous discussions, deep
layer wind shear is weak and less than 25 kts. However, some
enhancement of the mid-level wave across North Dakota this afternoon
could manage to increase these parameters to produce isolated severe
storms. The main hazard will be large hail and gusty winds. Further
to the south across southern Minnesota, the amount of wind shear
weakens, and with most of the activity not until after max heating,
severe weather is not anticipated. See the latest SPC convective
outlooks for more details. Thunderstorms will likely decrease in
western Minnesota in the evening, with eastern Minnesota, western
Wisconsin having a continued chance overnight.

.LONG TERM...(Friday through Wednesday)
Issued at 359 AM CDT Thu May 24 2018

The long term forecast concerns start out with a risk for a few
severe storms on Friday, and then transition to primarily heat
over the weekend.

Friday morning we could have some lingering convection and cloud
cover from nocturnal activity that develops Thursday night atop
the ridge. This could hold temps down a couple degrees from
Thursday`s highs, but the westerly wind component and building
ridge should easily translate to highs in the mid 80s to lower
90s. Friday afternoon during peak heating the front will be
situated near the I-35 corridor. Storms will be possible
along/east of this axis. Lack of convergence/shear will again
likely limit severe weather potential, but a few storms could tap
in to enough instability to produce hail/wind in east central MN
or western WI.

Few changes were made to the forecast for the holiday weekend,
with highs in the 85 to 95 degree range being common with the mid
level ridge nosing into the Upper Midwest. These days will feel
even muggier given dewpoints will be in the 60s and winds will be
fairly light. Still cannot entirely rule out a few stray showers
and thunderstorms given the GFS insists on a few weak waves
topping the ridge. Meanwhile the ECMWF maintains a mostly dry
forecast, and is the preferred solution.

What is more probable, however, is for us to see shower and
thunderstorm chances return Tuesday as the deep trough over the
southwest lifts into the Plains. Have inserted high chance POPs
for this potential Tuesday/Wednesday. Temperatures will retreat
back toward more seasonal values mid to late next week as the
ridge is suppressed by the aforementioned trough.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu May 24 2018

Still retain lower end confidence forecast for timing and overall
coverage of convective potential this period. Does appear the
latest avbl HIRES solution pick up development over central MN
and moving east into the evening. This likely in connection with
any remaining weak trough for the southwest combined with greater
instability, Expect at least scattered convection mainly east of
KSTC-KMKT this afternoon evening. Could see some convection move
in from the eastern Dakotas early but believe this will be more
isolated. A mixture of VCTS and some tempos introduced at
locations with forecast greater areal coverage. Surface winds
mixing S-SW and gusty into the afternoon ahead of the front with
fropa into western areas Friday morning.

KMSP...
Confidence increasing of at least scattered coverage in the VCNTY
during the evening. This should wane later tonight and shift east
per latest HIRES trends. Gusty S-SW winds ahead of the front
becoming more west Friday afternoon with fropa. Could see
redevelopment Friday morning in the vcnty but timing still
difficult to ascertain at the moment.

/OUTLOOK FOR KMSP/

FRI night...VFR. Wind W 5-10 kts.
SAT...VFR. Wind WSW 5-10 kts.
SUN...VFR. Wind W 5 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

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



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