NWS Forecast Discussion

338
FXUS63 KMPX 221719
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1219 PM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Excessive rain threat is diminishing this morning, but one
  more round of showers and thunderstorms is expected this
  afternoon. The threat for severe weather is low.

- There`s a Slight Risk (level 2 of 5) of severe storms Monday
  evening.

- More unsettled weather expected Thursday afternoon through
  Friday night.

&&

.DISCUSSION...
Issued at 432 AM CDT Sat Jun 22 2024

The worst of the heavy rain threat has shifted southeast of the MPX
area with the LLJ early this morning. We have let Flash Flood
Warnings expire overnight, but have replaced them with a couple of
Areal Flood Warnings that continue through tonight to cover ongoing
flooding seen along the Watonwan, Blue Earth, Le Sueur, Cannon, and
Straight rivers and their tributaries in south central MN. Though
the main heavy rain risk is shifting east of us, water vapor imagery
shows we have one more shortwave coming across SoDak that we`ll have
to contend. Most CAMs show this wave pushing another area of
scattered showers into western MN late this morning, with that
activity working across the rest of central and southern MN during
the afternoon. By then, the main cold front will be across eastern
Iowa into southern WI, so this activity will be elevated, with more
limited instability in turn keeping the severe risk for the MPX area
very low. This activity will also be progressive, so the heavy rain
threat will be low as well, but with how wet we`ve been, the bar is
set pretty low for seeing flash flood concerns across south central
Minnesota. However, with the primary warm front and eventual surface
low remaining across Iowa, we don`t look to have the redevelopment
of heavy rain like we`ve seen the past couple of days, so for now we
look to be transitioning to the river flood phase of this event.

Sunday looks to finally be a drier day and an opportunity to tackle
the jungle that has likely become your yard, but there is a threat
for some scattered afternoon showers/storms northeast of I-94 as a
shortwave in northwest flow tracks from northeast MN to northern
lower Michigan. Instability will be under 500 j/kg, so the severe
risk Sunday looks low as well.

Monday and Tuesday look to be the warmest days of the week as warm
air gets drawn north in response to a shortwave moving across
southern Canada. The cold front with this trough looks to come
through the MPX area Monday night, with that timing looking to help
hold highs both days in the 80s. The bigger issue is that front will
bring us our next chance of thunderstorms. This will be one of those
cases where forcing will be strongest north, but we`ll have the
better instability. Looking at the deterministic models, QPF from
them all show a pretty classic MCS signal for Monday evening as
storms develop in the Red River Valley and track southeast through
the evening into the better instability in southern MN. Given the
warmth on Monday, along with the moist airmass in place, we`re
seeing a favorable thermodynamic environment develop with mlCAPE
values possibly exceeding 3000 j/kg Monday afternoon ahead of what
would come down from the northwest. There`s still a good deal of
uncertainty with exactly when/where storms would develop and then
track through the evening, but the environment we`ll have in place
will definitely support a severe risk if we can drop some updrafts
into it.

Tuesday is trending dry, with the cold front looking to be far
enough south/east of the MPX area to have the next round of storms
fire south of our area, though it won`t take much of a slowing to
see storms again Tuesday afternoon in south central MN up into
western WI. After that, high pressure comes in and we get a breather
Wednesday and Wednesday night.

For Thursday afternoon through Friday night, it`s looking unsettled
once again as a shortwave moves across the international border from
the northern Rockies over to Lake Superior. These falling heights
back over Montana on Thursday will result in another resurgence in
the LLJ across the Dakotas. This LLJ right now looks to come across
the MPX area Thursday night, with our best chances for storms coming
Thursday night, then Friday afternoon over eastern MN and western WI
along the advancing cold front. This looks to be another system that
will support both the chance for severe weather and excessive
rainfall.

It`s then trending drier for the following weekend, but ensembles
are already showing the next active stretch of active weather
loading up for the start of July.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1157 AM CDT Sat Jun 22 2024

Current IFR/MVFR cigs should last at least into this evening.
Showers and thunderstorms currently over western MN will move
east through this afternoon. Visibilities will drop to IFR
within heaviest cells, though, a general downward trend in
intensity is expected as cells near our WI terminals. For most
of MN, conditions should improve MVFR/VFR during tonight as cigs
rise and skies break some. But, a reduction to MVFR is possible
Sunday morning with a chance for some patchy fog. For MKT, RNH,
and EAU, cigs should remain steady/drop into IFR overnight.
Conditions at all terminals should slowly improve during Sunday
morning. North-northeasterly winds will turn northwesterly and
slow to under 5 knots overnight before becoming west-
northwesterly at 5-10 knots Sunday morning.

KMSP...Added TEMPO from 22-00z today for periods of
thunderstorms where visibility could drop to IFR. IFR conditions
look more likely overnight with lack of cloud clearing.

/OUTLOOK FOR KMSP/
MON...VFR. Chc -TSRA/MVFR late. Wind SSE 10-15 kts.
TUE...VFR. Wind NW 10-20 kts.
WED...VFR. Wind NW 5-10 kts.

&&

.HYDROLOGY...
Issued at 303 PM CDT Fri Jun 21 2024

Despite a lack of confidence in the location of highest QPF for
tonight, we`ll see enough rain in areas already having issues from
last night`s and this morning`s rain to warrant an areal flood
warning in south central MN. This warning will need to be watched
for extension to the south depending on how the precip sets up along
I-90, could also go through the night. River forecasts are mainly on
track this afternoon, paying particular attention to the Cannon
where training has occurred today, along with the mid/lower
Minnesota where lots of inflow coming from the tribs south of
Mankato.

&&

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

&&

$$

DISCUSSION...MPG
AVIATION...CTG
HYDROLOGY...CCS

NWS MPX Office Area Forecast Discussion

Script by Ken True @Saratoga-Weather.org