Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 241032

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

.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 12Z TAFS through 12Z Friday morning)
Issued at 530 AM CDT Thu May 24 2018

Very low confidence on timing of thunderstorms today. The best
scenario is to keep the continued PROB30 with better timing as
thunderstorms begin to develop this afternoon. Isolated storms are
possible in western Minnesota through 15z, and possibly affecting
KRWF/KAXN. I may introduce VCTS at KRWF for the activity moving
into far southwest Minnesota at this time. Otherwise, winds will
increase this morning and become gusty ahead of the front.


As mentioned above, confidence on thunderstorms moving into the
terminal area is very low, but due believe thunderstorms will
develop later this afternoon. Later TAFs will have a much better
idea once thunderstorms develop in western Minnesota. Winds will
remain from the south/southeast today and become gusty. The
frontal boundary will move across the area between 12-18z Friday.


FRI...Mainly VFR. Chc TSRA early. Wind SW Bcmg W 5-10 kts.
SAT...VFR. Wind WSW 5-10 kts.
SUN...VFR. Wind W 5 kts.




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