FXUS63 KMPX 131140 AAA
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
640 AM CDT Mon Jul 13 2020
.SHORT TERM...(Today through Tuesday)
Issued at 409 AM CDT Mon Jul 13 2020
Thunderstorms are ongoing across North Dakota early this morning
and a cirrus shield is spreading east over the northern half of
Minnesota. This complex will weaken during the next few hours and
abundant sunshine is expected for much of the day. Highs could get
quite warm today in the absence of any convection. 925 mb temps
increase to +28C across western MN late this afternoon, and could
rise to +25C farther east. It's possible highs reach the mid 90s
across far western Minnesota, while the rest of the area climbs
into the upper 80s.
Moisture will be increasing throughout the day. The atmosphere
should remain capped until late afternoon when supercell
development is possible as the cap begins to break in spots. All
severe hazards are possible with this initial development. The
best forcing will be across the northern half of Minnesota, while
the most robust instability will be south. CAMs seem to favor the
forcing more than the higher instability and the most widespread
convection is advertised to the north. However, the best
possibility of discrete convection will be over west central MN
and thus better potential for higher end severe. A secondary area
of convective development could occur along the surface warm
front over central and eastern Minnesota very late this afternoon
or early evening. Some guidance indicates this possibility for a
short time before either fading or shifting to the northeast.
Convection will continue for much of the night, growing upscale
into complexes this evening and tracking east or southeast.
Damaging winds will eventually become the main threat before
storms weaken late tonight.
Another disturbance will slide east northeast along the cold front
across southern Minnesota Tuesday morning. Additional convection
is expected to form and could train along the front, bringing the
risk of heavy rainfall in a swath across east central MN into
northern WI. Farther south, instability will recover during the
afternoon and a few stronger storms could develop. The best severe
potential will be southeast of the area. Activity will shift south
and east in the afternoon and will be exiting by Tuesday evening.
Highs were reduced a bit due to the clouds and showers/storms.
.LONG TERM...(Tuesday night through Sunday)
Issued at 409 AM CDT Mon Jul 13 2020
Tuesday evening will have residual moisture along the frontal
boundary which could keep occasional showers/storms in south
central Minnesota, and west central Wisconsin. However, the
progressive nature of this system will quickly dry things out by
Wednesday morning. Wednesday and Thursday will be the driest and
most comfortable as a modified Pacific/Canadian air mass moves
Both the EC/GFS have similar 50H with a deep upper trough
centered across central Canada later this week. The northern tier
of the nature will remain in a progressive west to east flow aloft
with strong westerlies expected. Thus, once return flow develops
and the air mass becomes more tropical in nature next weekend,
several short waves will ride along the northern edge of the
strengthening ridge in the central part of the country. Timing of
these short waves, and the subtle boundaries from residual
thunderstorm outflow, will dictate the chances of precipitation
later this week, and into the weekend. I wouldn't be surprised to
see a strengthening cap especially early in the weekend as mid-
level temperatures rise significantly, and limit updrafts. Still,
based on the amount of instability expected as dew points rise
back into the 70s, and the stronger westerlies, severe weather
potential is possible if and when the cap breaks.
Based on dew points rising into the 70s Saturday, the actual
temperatures around 90 to 95 degrees, heat indices will likely
surpass 100 degrees. WBGT numbers rise to around 83 degrees which
is a more effective means of assessing heat risk to person
involved in physical activity. Once the WBGT rise above 85
degrees, conditions worsen.
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 640 AM CDT Mon Jul 13 2020
VFR through most of the period. CU developing later this morning,
then TSRA expected around or after 00Z over western MN, spreading
east overnight. IFR and strong winds are possible in some storms.
After a break early Tuesday morning, another wave will bring a
round of TSRA Tuesday.
KMSP...A few storms could develop early this evening over eastern
MN, but the better chance will be overnight (after 04Z).
Otherwise, no concerns today.
/OUTLOOK FOR KMSP/
Tue...TSRA/MVFR likely, mainly before 21Z. Wind NW 5-10 kts.
Wed...VFR. Wind NW 5 kts.
Thu...VFR. Wind SW 5-10 kts.
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