663
FXUS63 KMPX 142015
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
315 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.&&

.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 /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 112 PM CDT Fri Jun 14 2024

Aviation...VFR with rainfall arriving by tomorrow morning.
Other than the diurnal cu field this afternoon, cigs will
becoming BKN to OVC tonight as our next system arrives from SW
to NE across all sites. Rainfall is most likely to pester RWF
and MKT early tomorrow morning before becoming more widespread
tomorrow afternoon. Rainfall could be heavy at times, especially
for our southern sites thus impacts to flight categories are
possible. Winds will begin NW`ly then shift to SE`ly by this
evening. Winds will increase in speed tomorrow morning once the
system arrives with gusts reaching 20-25kts.

KMSP...Not much chance in the near term for regarding the TAF. Still
expecting the NW`ly winds to shift SE`ly by 00z. Aside from few
afternoon 050 clouds, the more prevalent cloud cover develops
overnight but should remain in VFR. Rain chances increase
through the morning hence the introduction of PROB30. Rainfall
will becoming likely after 21z. Rainfall could be heavy at times
and may require MVFR vsby but was reluctant to include this
period due to heaviest rainfall timing. Winds tomorrow will
remain a SE/SSE component and becoming breezy with gusts between
20-25 kts by the afternoon.

/OUTLOOK FOR KMSP/
SUN...Mainly VFR. Slight chc TSRA/MVFR. Wind S 10-15 kts.
MON...MVFR with MVFR/TSRA possible. Wind S at 05-10G15-20 kts.
TUE...MVFR with MVFR/TSRA possible. Wind S at 10-15G25-30 kts.

&&

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

.Hydrology

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.

&&

$$

DISCUSSION...Dunleavy
AVIATION...Dunleavy
HYDROLOGY...CCS