Sunrise 5:35 AM   Sunset 8:42 PM Moonrise 5:00 PM   Moonset 3:03 AM

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FXUS63 KMPX 201207 AFDMPX

Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 707 AM 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 /12Z TAFS THROUGH 12Z TUESDAY/
Issued at 658 AM CDT Mon May 20 2024

The first round of rain will end at EAU by 15z. MVFR cigs in the wake of the rain were non-existent all night, so greatly improved the cigs through the morning, though there is still a chance we'll see mvfr cigs as the cu field develops after a little heating this morning. Moisture and instability will remain in place through the day, but we lack a forcing mechanism, with increasing southeast winds at 850mb tonight looking to finally provide some forcing for precip development.
It's a lower confidence forecast on when the next round of shra/tsra will get going this evening, but chances will be increasing toward the end of this period.

KMSP...Looks like things will be going downhill pretty quick as traffic starts to tick up Tuesday morning. Before then, there is a 30% chance of seeing a cig down to 015 between 14z and 17z this morning. Also looks like we could see storms start to bubble along/behind the front that will be to our south shortly after 00z.

/OUTLOOK FOR KMSP/ TUE...MVFR or IFR. TSRA likely. Wind SE 10-15G25kts.
WED...MVFR bcmg VFR. Chc -SHRA. Wind W 15G25kts.
THU...VFR. Wind W 10 kts.

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.

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