981
FXUS63 KMPX 201746
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1246 PM CDT Mon May 20 2024

.KEY MESSAGES...

- Slight potential for strong to severe storms across southern
Minnesota this afternoon.

- Increasing likelihood of strong to severe thunderstorms Tuesday PM
across southern Minnesota and western Wisconsin. SPC day 2 SWO
brings an Enhanced Risk (3 out of 5) into SE MN.

- Heavy rainfall is likely and totals may exceed 3 inches through
mid-week. This will likely lead to rises on rivers and their
tributaries into the holiday weekend.

&&

.DISCUSSION...
Issued at 322 AM CDT Mon May 20 2024

Currently a mid-level low spins over the Dakotas and is forecast to
prog east over MN/WI today. Convection has already begun initiating
ahead of a warm front that extends from west-central MN over to Eau
Claire, WI. Severe weather is not expected with this initial band of
storms however, some of the stronger storms could produce pea size
hail and brief gusty winds. Broader forcing associated with a cold
front currently resides over Western MN where mainly showers and
embedded thunder exists. This band of precip will spread over
central and southern MN early this morning and begin to clear from
west to east just after sunrise. There will be a few hours and some
partial clearing to the skies later this morning into the early
afternoon with highs into the mid-70s. The aforementioned boundary
that brought the early morning precip, will become stationary as a
trough over the inter-mountain west begins to become negatively
tilted. This will force a potential MCS to develop over SE Nebraska,
and SW Iowa. Its expected that system will lose its support and
become disorganized. With that said however, another afternoon of
convection does look possible. Forecast soundings showing an
environment that features 0-6km shear nearing 30kts and elevated
1500 J/kg of MUCAPE thus allowing for the potential for gusty winds
and large hail which aligns with the SPC`s slight risk (level 2 of
5) across southern MN. Although given the questionable forcing
mechanisms, kept only slight mention of PoPs in the grids for now.
Rainfall amounts through today will range between a tenth to a half
inch, with locally higher amounts associated with stronger cells.

By Tuesday into Wednesday, the trough over the intermountain west
will eject a Colorado low towards the northern plains and
intensifies by the time it reaches MN/WI. Like with previous
discussions, the MSLP for this low pressure is forecast to reach
climatological minimums per the ensemble situational awareness table
and the return interval for a system of this caliber for late May
comes about once per decade. A defined gradient in temperatures will
exist from Duluth, MN down to Sioux Falls, SD. Areas north and west
of this gradient will struggle to reach 60 degrees whereas mid 60s
to low 70s to the south and east. As this low pressure progs
through, widespread rain and thunderstorms will occur. The
kinematics for convection do look favorable for more severe storms
Tuesday afternoon which is highlighted in the SPC Day 2 Outlook for
southeastern MN under an enhanced risk (level 3 of 5). A slight risk
for severe storms is forecasted north and west including the Twin
Cities as there are uncertainties with northward progress of the
system`s warm sector. Primary hazards will be a few tornadoes based
on forecasted hodographs, gusty winds, and large hail. NBM QPF
totals still holding high confidence that much MN and western WI
could see at least 1 to potentially 3 inches of rainfall through
Wednesday night. Wednesday also looks to be the coolest day of the
week with highs in the mid 60s and lows in the 40s.

Thursday features a lull in the precipitation as a brief ridge of
high pressure progresses overhead. Temperatures will return to the
70s and lows in the 50s. Some more rainfall tries to sneak back in
on Friday and again on late Sunday as another series of shortwaves
develop and make their way east across the Northern CONUS.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1224 PM CDT Mon May 20 2024

A busy stretch of weather is expected through this forecast
period. MVFR/IFR cigs have been slow to move out through early
this afternoon, despite guidance saying otherwise. Decided to
keep things on the pessimistic side because of this. MVFR/IFR
conditions are expected through the majority of the period once
showers and thunderstorms move through late this evening into
Tuesday afternoon and beyond. Timing still remains the tricky
part of the forecast with hi-res guidance all over the place for
a round of showers and storms before 06z for our southern sites.
Most agree that all will see rain with embedded storms from 12z
through the end of the period. Wind gusts may be underdone by
Tuesday morning, but will wait until later forecasts to adjust.

KMSP...The TAF is long and ugly to say the least. Based on ob
trends, kept MVFR cigs through mid afternoon. While we have
plenty of instability building this afternoon, we are lacking
any sort of lift to initiate thunderstorms until the LLJ kicks
in later tonight. Thinking there will be a break between the
first and second round of storms overnight with chances once
again increasing just before sunrise. A lot of uncertainty
surrounds the midday Tuesday timeframe, but yet another round of
storms is expected during the afternoon. These storms may be
strong to severe with heavy rain and possible LIFR conditions
into the evening. However, confidence is too low to include that
in the TAF at this point.

/OUTLOOK FOR KMSP/
WED...MVFR bcmg VFR. Chc -SHRA. Wind W 15G25kts.
THU...VFR. Wind W 10 kts.
FRI...VFR/MVFR chc -SHRA. Wind SE 10-15kts.

&&

.HYDROLOGY...
Issued at 655 AM CDT Sun May 19 2024

A heavy rain event remains on track for Tuesday, with a large
footprint of 1 to 3 inches of rain, with some locations pushing
4 inches. The greatest rainfall totals are expected across
southwest, west central, and central MN. Exactly where and how
much rainfall we see will determine where a threat for river
flooding will exist going into Memorial Day weekend, but given
current rainfall forecasts, flooding during the holiday weekend
may be possible in the Cottonwood, Redwood, Minnesota (upstream
of Mankato), and Crow river basins.

&&

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

&&

$$

DISCUSSION...Dunleavy
AVIATION...Dye
HYDROLOGY...MPG