Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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273 FXUS63 KMPX 131730 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN Issued by National Weather Service La Crosse WI 1230 PM CDT Thu Jun 13 2024 .KEY MESSAGES... - Showers across southern Minnesota this morning, then drying out until early Saturday. - More widespread showers and thunderstorms likely Saturday with locally heavy rainfall possible. - An intense heat wave will build across the eastern third of the country next week with the Upper Midwest on its western periphery. This will mean periods of hot and humid conditions and multiple rounds of thunderstorms with heavy rainfall. && .DISCUSSION... Issued at 335 AM CDT Thu Jun 13 2024 Storms have finally exited to the southeast early this morning. A front is trying to make its way eastward across central and southwestern MN, but surface winds have become light or calm and for now it has stalled. West of the front dew points have dropped into the upper 40s to mid 50s while remaining in the 60s east. Areas of fog are developing along the front and some locally dense fog is possible, especially where heavy rain fell last evening. Mid level clouds across SD will spread east early this morning and a band of showers will likely develop across western and southern MN just after sunrise. The development of these showers is almost certain, but CAMs are inconsistent with the spatial details so for now kept 50-60 PoPs for this area. Once development occurs, PoPs will likely need to be increased further for some areas. Showers will exit to the southeast early this afternoon and clearing will follow for the rest of the day. Despite early day rain, highs in the low 80s are expected area wide. Dry conditions will prevail through most of Friday night, but a shortwave will eject northeast from the Four Corners region and could begin spreading showers to southern MN by early Saturday. A 40 kt LLJ and pwats as high as 1.75 inches are likely to accompany the shortwave across the area Saturday/Saturday night. While lapse rates will remain poor and instability limited, relatively strong moisture flux should allow for a moderate to heavy round of showers and isolated storms to bring more healthy rainfall totals. The track of the center of the disturbance across IA will place southern/eastern MN and WI in the heaviest swath of rain, where 1-2 inches may fall. There is a Slight Risk of excessive rainfall for those areas. The disturbance will exit early Sunday and upper ridging will quickly follow. A surface cold front will approach from the northwest Sunday afternoon. Thermal ridging will work up the front and 925 mb temps of +25 to +27C suggest highs in the lower 90s. Dew points around 70 will send heat indices into the mid to upper 90s, leading to the first elevated heat concern of the season. The front should reach at least central MN by Sunday evening. An EML with mid level lapse rates greater than 8 C/km should cap the atmosphere and prevent convective development, but if forcing along the front can overcome the cap, there will be a conditional risk of severe weather through Sunday evening. How far south the front sags Monday before returning northward will depend on the strength of the synoptic system well to the north in Canada and the building ridge across the east. By late Monday or Tuesday, a trough over the Rockies should lift it back north and allow it to become a southwest-northeast oriented quasi-stationary boundary through at least midweek. Intense heat and humidity will overspread the Great Lakes and Ohio Valley throughout this time, and depending on the surface frontal position and related convective activity, may occasionally make an appearance this far west. The ensemble spread for temperature is quite large next week due to spatial differences with the front. One thing is near certain, there will be a tremendous amount of moisture over the Gulf, marked by pwats greater than 2.75 inches. The strength of the ridge across the east and a 50 kt LLJ across the Plains will funnel some of this moisture up the front and into the Upper Midwest. Rounds of thunderstorms, potentially severe, and very heavy rainfall are possible throughout next week. Flooding may become an increasing concern over the next several days. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1230 PM CDT Thu Jun 13 2024 VFR conditions are expected for the TAF period with elevated showers over south-central Minnesota departing by 21Z today. Northwest winds of 10-15G20kts this afternoon--strongest in central/western MN--decrease after sunset to around 5kts or less. Winds will be light and variable for Friday with a SCT CU deck for the afternoon. KMSP...VFR conditions expected for the TAF period with northwest winds around 10kts this afternoon decreasing to 5kts or less overnight. CU develop by midday tomorrow with VFR bases. /OUTLOOK FOR KMSP/ FRI...VFR. Wind N at 5 kts. SAT...RA/TSRA/MVFR likely, IFR possible. Wind SE 10-15G25kts. SUN...Mainly VFR. Slight chc TSRA/MVFR. Wind S 10-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Borghoff AVIATION...Skow/ARX