-- Discussion containing changed information from previous version are highlighted. --
682
FXUS63 KMPX 150142
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
842 PM CDT Fri Jun 14 2024

.KEY MESSAGES...

- More widespread showers and thunderstorms likely Saturday and
  Saturday night with locally heavy rainfall possible.

- An intense heat wave will build across the eastern third of
  the country next week with the Upper Midwest on its western
  periphery. This will mean periods of hot and humid conditions
  and multiple rounds of thunderstorms with the potential for
  severe weather and heavy rainfall.

&&

.UPDATE...
-- Changed Discussion --
Issued at 820 PM CDT Fri Jun 14 2024

No major changes made to the forecast this evening, as the
general theme remains on track. Regional water vapor imagery
captures a region of broad ascent across the central Great
Plains, east of shortwave trough. Showers and thunderstorms span
from the Dakotas south into portions of Texas. Initial bands of
showers lifting through SE South Dakota and NW Iowa may creep
into SW Minnesota over the coming hours, but will likely
struggle to hold together as they outrun upper-level support.
However, this will not be the case as we fast forward into
Saturday morning. Low-level moisture transport will increase
ahead of the eastward shifting shortwave trough which will
assist in saturating the notable low-level dry air sampled by
the 00z MPX RAOB. Hi-res models have started to account for a
slightly slower arrival of precipitation, which is not
surprising given the conditions sampled this evening. As the
morning rolls on, the expansive precipitation shield will lift
northeast through the area. We feel this is likely more of a
"soaking rain" event into Saturday afternoon, before the
potential increases for convection later in the day. Speaking
of which, CAMs have illustrated the potential for a brief lull
in the precipitation across southern Minnesota late Saturday
afternoon, prior to the redevelopment of scattered to widespread
storms. It`s this convective activity that will feature the
potential for an isolated instance of damaging winds or large
hail, along with enhanced rainfall rates owing to a strengthening
low-level jet and PWATs near 2". The QPF forecast remains on
track, with 1-2" of rainfall possible for locations across south
central Minnesota to western Wisconsin.
-- End Changed Discussion --

&&

.DISCUSSION...
Issued at 315 PM CDT Fri Jun 14 2024

Gorgeous afternoon continues across MN and western WI with
temepratures ranging in the mid to upper 70s and and light
winds. Satellite showing mainly widespread diurnal cu across
much of MN/WI although a few bands of cirrostratus are
beginning to make there way into southwestern MN. That area of
cloud cover is part of the shortwave that will eject from the
four corners region later tonight. As this shortwave approaches,
a 40kt LLJ will increase moisture transport across the area.
PWAT values are forecast to increase near 2.0" throughout
Saturday and Saturday night. Forecast soundings continue to
support an environment that is not conducive for strong
convection initially, but more so highlighting the threat of
moderate to heavy rainfall. Considering the track of this low
pressure system`s core is progged across IA, southern/eastern MN
and western WI have a favorable chance of seeing 1-2 inches of
precip. Therefore a slight chance of excessive rainfall has been
issued by the WPC for those areas. Behind the main more
widespread rain late Saturday night, elevated instability
alongside steeper lapse rates will increase. CAM guidance hint
at the development of thunderstorms capable of producing a
potential for hail. Another concern with these storms is the
heightened flood risk on top of the rainfall just received
earlier.

For Sunday, to simply put it, its going to be hot and humid. The
shortwave that provided all the rainfall will depart to the east and
upper-level ridging takes hold. Guidance now showing with
confidence that the thermal ridge off to our west will advect in
overhead during the daytime hours. The aforementioned LLJ will
not weaken and continue to bring only greater moisture transport
up well into the the northern plains. Currently h925 temps
showing a 25-27C increase which indicates surface highs will
range in the lower 90s. Dew points will reach the lower 70s and
force heat indices to 95-100 degrees. With each forecast run,
heat headlines across the TC Metro may be necessary for Sunday.
A frontal boundary will track across MN/WI sunday
afternoon/evening. Forecast soundings continue to show an EML
with steep lapse rates that should inhibit any convective
development. However, should the frontal boundary be able to
overtake the cap, we could see conditional risk of strong
thunderstorms Sunday afternoon. The front will stall Sunday
evening and the EML will begin to weaken at the same time the
cap erodes. So some thunder potential remains and aligns with
the SPC Convective Outlook Sunday evening. Flooding concerns
will continue Sunday night as the LLJ increases to 50 kts and
leading to training development along the frontal boundary.

Next week`s forecast continues to look very active with several
chances of rainfall and potentially severe weather. A trough over
the CO Rockies will begin to lift Monday or Tuesday. At this time,
numerous shortwaves will eject off of the broader trough providing
continued rain/storm chances throughout next week. To our east,
upper-level ridging will continue to deepen well into Quebec thus
allowing for intense heat and humidity to reach the Great Lakes and
the Ohio River Valley. Depending on the location of the western
periphery of the ridge, some of the intense heat may encroach west
into MN. Specific temperatures are still uncertain as confidence
between ensemble members deviates but what is known is continued
flooding concerns across the region given a strong LLJ and
noticeably high PWATs.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 638 PM CDT Fri Jun 14 2024

No significant concerns in the short term as light southeast
winds prevail overnight, along with an increase in clouds.
Latest hi-resolution model data depicts a shield of precipitation
moving into southern Minnesota after ~12z and pushing northeast
through the morning. Very dry low-levels will assist in
delaying the onset of precipitation at each terminal, but once
the rain starts it will be an aviation concern through the
remainder of the TAF period. Chances for thunder/lightning
appear lower with the initial precipitation shield. Winds
increase out of the southeast after daybreak and will generally
sustain between 10-15kts, gusting upwards of 20-25kts into the
afternoon. Additional showers and thunderstorms will be
possible towards the end/beyond the TAF period Saturday evening
into Sunday morning, when convectively driven rainfall rates may
result in lower visibility.


KMSP...Light southeast winds overnight. SE flow between 10-15
kts and gusts of 20-25kts will prevail through the TAF period.
Showers may begin to impact the terminal as early as 14z,
however the persistent rain will likely hold off until 16/17z.
Rain prevails through most of the afternoon, with increasing
confidence that there may be a brief lull in the activity late
afternoon/early evening. Scattered t-storms are expected to
develop after 00z, which will have the potential to produce
locally heavy rainfall and create significant reductions in
visibility.

/OUTLOOK FOR KMSP/
SUN...VFR. Slight chc TSRA/MVFR. Wind S 10-15 kts.
MON...VFR with MVFR/TSRA possible. Wind SE 10-15G20 kts.
TUE...VFR with MVFR/TSRA possible. Wind S 10-15G25 kts.

&&

.HYDROLOGY...
Issued at 315 PM CDT Fri Jun 14 2024

The extended period of heavy rainfall brings with it a potential
return to river flooding in the 5-10 day period, extending to the
end of the month on the mainstems. HEFS graphics show the potential
threat nicely, and also show the degree of uncertainty with large
ranges even within the blue "most likely" band by day 10.
Factors that will determine flood severity (minor vs. moderate or
worse) include how fast the rain falls...a number of 6-12 hour
periods with less than an inch adding up to 3-5 inches is better
than a couple of 2-3 inch events in a short period. We will also
need to be wary of a boundary setting up with training storms moving
from southwest to northeast over the same area.
In summary, this scenario bears watching closely over the next week,
with lots of uncertainty along the way.

&&

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

&&

$$

UPDATE...Strus
DISCUSSION...Dunleavy
AVIATION...Strus
HYDROLOGY...CCS