291
FXUS63 KMPX 112355
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
655 PM CDT Thu Jul 11 2024

.KEY MESSAGES...

- Quiet and dry weather continues through Friday.

- Heat (Low 90s) and humidity build this weekend, which will
  fuel several conditional chances for strong to severe
  thunderstorms through early next week.

- "Cooler" (Upper 70s/low 80s) for the middle of next week.

&&

.DISCUSSION...
Issued at 221 PM CDT Thu Jul 11 2024

Nice and quiet weather wise this afternoon, with forecast highs on
track to reach the low to mid 80s. Unlike the past few days, the
diurnal cumulus field across the region will not feature the
potential for development into showers and storms thanks to
subsidence aloft. Similar weather is expected for Friday, with just
a slight increase in the southerly winds and highs a degree or two
warmer than today. The benign nature of the short term forecast
allows us to spend more time looking ahead to what will likely be a
hot, humid, and potentially stormy weekend.

HEAT: Upper air analysis captures an expansive ridge across the
western CONUS, which is progged to build east into the Upper Midwest
this weekend. We`re still waiting on the first 90+ observation at
MSP this Summer, but we`ll have a few chances to break into the low
90s over the coming days. The combination of afternoon highs in the
upper 80s/low 90s and dew points in the upper 60s/low 70s looks to
push heat index values into the mid, to perhaps upper 90s. We have
not issued any heat headlines just yet, however the current trends
remain supportive of achieving Heat Advisory criteria both Saturday
and Sunday across southwest MN and in the Twin Cities Metro. There
won`t be much relief from the heat overnight, as lows are forecast
to remain in the upper 60s/low 70s Saturday, Sunday, and Monday.
This type of heat scenario brings with it concerns for quick fatigue
and heat related illness, so we want to encourage folks to practice
heat safety when making weekend plans outdoors. Monday looks hot,
though indications are that temperature values will remain below
headline criteria. Cooler temperatures are set to follow for the
middle of next week.

STORMS: The expansion of the thermal ridge into the northern Plains
will bring the return of a more active period of weather. The upper
air pattern has some resemblance to the classic Summer "ring of
fire", where several MCS`s travel around the periphery of the heat
dome centered in the Great Plains. This setup is a little different
in that there will be some influence from large scale forcing,
particularly by late Sunday into Monday as a shortwave trough dips
southeast out of Canada. Nonetheless, the forecast looks potentially
active, with the development and persistence of organized, bowing
MCS type convective structures as the primary concern. The expected
heat and humidity will yield extreme instability Saturday and
Sunday, which will pair with ample shear to support strong to severe
thunderstorms. The SPC has recognized this potential with a Slight
Risk across the region Saturday, followed by a 15% outlook area
(which correlates to a Slight Risk) across southern Minnesota and
western Wisconsin Sunday and Monday. Working against widespread
convection will be notable capping due to mid-level warm air, as
700mb temperatures are forecast to climb near/above 12C over much of
south central MN and western Wisconsin.

The first window for convection will be very late Friday into
Saturday morning. Guidance suggests convection will develop on the
nose of the LLJ across southern Canada and then race south/southeast
along the instability axis into western MN into early Saturday
morning. Should these storms become organized, damaging winds would
likely serve as the main concern. The forecast becomes more
uncertain following this initial round, as continued advection of
the heat dome eastward will strengthen the cap during the day on
Saturday. Using the 12C gradient as the "tracks" for where
convection may develop and track, the greatest threat for severe
thunderstorms would be along and north of I-94 Saturday/Saturday
night into Sunday morning. That is "if" storms can develop in a
weakly forced, heat driven environment through the middle of the
weekend. A similar setup is expected for Sunday, prior to the
arrival of better forcing from the advance of shortwave trough set
to slide through southern Canada late Sunday into Monday. The
associated surface cold front will be a focus point for more
widespread precipition and potential thunderstorm development. The
southward advance of the shortwave aims to suppress the northward
extent of the warm mid-level temperatures, such that capping should
be less of an issue.

There are still many details to work out and the forecast will need
to be re-evaluated every 6-12 hours in this type of heat driven
regime, but the pattern supports the need to stay weather aware from
late Friday night through Monday. All hazards are possible, but if
any MCS can become organized, damaging winds would quickly become
the primary threat.

EXTENDED: Heat, humidity, and severe weather concerns will exit the
forecast Tuesday and look to remain out of the picture through the
end of next week. Troughing over the Great Lakes will bring cooler
temperatures (relative to the 90s this weekend), with highs forecast
to dip into the 70s by Wednesday. Large scale subsidence associated
with expansive surface high pressure will promote dry weather for
much of the extended forecast. Highs are forecast to climb back into
the mid 80s by the end of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 647 PM CDT Thu Jul 11 2024

It will be a quiet period with high pressure centered off to our
east providing us with southerly winds, which will become a
little gusty across MN on Friday, though with gusts in the low
20s, it won`t be anything crazy. Cu field Friday will be even
more sparse than what we had today.

KMSP...No additional concerns with high confidence in this TAF.

/OUTLOOK FOR KMSP/
SAT...VFR, slight chc -TSRA early. Wind S 5-10 kts.
SUN...VFR, chc -TSRA. Wind S 5-10 kts.
MON...VFR, slight chc -TSRA. Wind W 5-10 kts.

&&

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

&&

$$

DISCUSSION...Strus
AVIATION...MPG