Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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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