197
FXUS63 KMPX 040902
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
402 AM CDT Thu Jul 4 2024

.KEY MESSAGES...

- Thunderstorms and locally heavy rainfall likely today and
  tonight.

- Numerous chances for showers and a few thunderstorms will
  linger into next week with temperatures remaining below
  normal.

&&

.DISCUSSION...
Issued at 402 AM CDT Thu Jul 4 2024

Showers are beginning to advance into and develop across
southwestern MN early this morning. They should reach the Twin
Cities metro in the next few hours. This will be the first of
potentially many rounds during the next 24 hours.

The trough over the northern High Plains will continue digging
southeast this morning, reaching MN this afternoon as a
seasonally potent wave. Forcing will become more focused and a
broad surface low will develop and track across southern MN.
Scattered to numerous thunderstorms are expected by afternoon,
which will continue tonight north of the surface low track and
roughly along the 700 mb low track. This favored area is
expected to stretch from the Redwood Falls area to the Twin
Cities metro. 00Z HREF neighborhood probabilities of greater
than 2 inches within this corridor range from 60 to 80 percent,
and 30 to 60 percent for greater than 3 inches. That`s a strong
signal for heavy rainfall, but there are some limiting factors
to consider for flooding. Many of the CAMs and even the global
guidance indicate rain will not be continuous for several hours.
There should be breaks between rounds which will allow runoff
from becoming excessive. Pwats aren`t too anomalous for this
time of year and rain rates aren`t expected to be too extreme
either. Perhaps some 1-1.5 inch/hr rates will be possible with
the most robust convection, but 1 hr flash flood guidance values
are generally 1.5-2 inches and those rates shouldn`t last an
hour`s time. Areas that do see totals of 3 inches through Friday
morning may have some issues, but these pockets should be
fairly localized. For these reasons, decided against a Flood
Watch at this time but trends will continue to be monitored.

Mid level lapse rates will remain modest and the prospects of
significant surface heating still appear limited given the
extensive cloud cover, so instability will be lacking in most
locations. However, across southern MN there may be better
heating near and south of the low track. Here, there is some
potential for a few stronger storms where CAPE may exceed 1000
J/kg and deep layer shear is better. Some marginally severe
hail and a couple weak tornadoes are possible.

The showers will linger into Friday across eastern MN/WI, but
some scattered activity could redevelop farther west in the
afternoon with breaks in the clouds and some instability
developing within the cyclonic flow.

Multiple waves within a broad north central U.S. trough will
keep precip chances going for much of the remainder of the
period. Nothing looks particularly widespread or heavy, but it
will continue the gloomy and un-Julylike weather for the
region. Temperatures will remain below normal until if/when the
western Ridge builds east. Some of the extended guidance is
hinting at that possibility toward mid-July.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 632 PM CDT Wed Jul 3 2024

A very unsettled period is expected as we see a mid-level low
track across southern MN on Thursday. Looking at the path of
850mb & 700mb low, the HREF shows these features tracking from
roughly Montevideo to Wabasha, along/north of this track will be
a favorable zone of forcing for seeing multiple rounds of
precipitation and thats what`s expected for most of the MPX
terminals. A continuous rain is not expected, but it will be on
& off activity for a good 12-20 hours. TS potential looks
greatest from the afternoon into evening. Surface pressure
pattern will be very baggy through the day on Thursday, so wind
directions will be tough to pin down, but speeds will be under
10 kts. Finally, RAP soundings show low levels moistening up
enough late in the afternoon to start bringing in MVFR cigs for
locations that area expected to be north & west of the
developing surface low.

KMSP...Models are absolutely all over the place with when/where
clusters of SHRA/TSRA will be through the day on Thursday and
into Thursday night, hence why precip mentions in the TAF are
VCs or PROB30. Current thinking is that the band of showers
along the eastern Neb/SoDak border will send an initial round of
showers through the metro during the morning, with a brief lull
in activity during the afternoon, before thunderstorms quickly
redevelop. As mentioned above, winds could be coming from just
about any direction on Thursday, though speeds will be generally
5 kts or less.

/OUTLOOK FOR KMSP/
FRI...MVFR SHRA/TSRA likely. Wind N 10G20 kts.
SAT...Chance PM MVFR SHRA/TSRA. Wind SW 5-10 kts.
SUN...MVFR/SHRA/TSRA likely. Wind SW 10G20 kts.

&&

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

&&

$$

DISCUSSION...Borghoff
AVIATION...MPG