Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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946 FXUS63 KMPX 031717 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1217 PM CDT Wed Jul 3 2024 .KEY MESSAGES... - Thunderstorms and locally heavy rainfall likely for Thursday and Thursday night. - Chances for showers and a few thunderstorms will linger into next week with temperatures remaining below normal. && .DISCUSSION... Issued at 358 AM CDT Wed Jul 3 2024 Aside from some low stratus lingering in parts of western WI, skies are clear across the Upper Midwest this morning. Water vapor imagery shows several weak disturbances across the northern Plains. These will continue eastward today and could spark a few showers or storms across the northern half of MN, but rising mid level heights and a dry atmosphere should limit coverage of these to less than 20 percent. The rest of the area could have some fair wx CU this afternoon with highs in the low to mid 80s. The trough over the northern Rockies will dig southeast tonight and begin to reach the Upper Mississippi Valley late tonight and early Thursday. Showers and a few storms will overspread western MN after midnight and begin reaching eastern MN/WI by midday Thursday. As the upper low continues across the northern Plains and reaches MN late Thursday, it will continue digging and become neutrally tilted. Forcing will become more focused and a broad surface low will develop and track across southern MN. Scattered to numerous thunderstorms are expected by afternoon, which will continue Thursday night along and north of the low track. Mid level lapse rates will remain poor and the prospects of significant surface heating appear limited given the extensive cloud cover, so instability will be lacking. However, there is some potential for a few stronger storms with several hundred joules of CAPE given moist surface conditions. Some non-supercell tornadoes can`t be ruled out near the surface low. This system is beginning to reach the window of the CAMs and many of the members seem too sparse with precipitation - possibly as a result of low instability. From a synoptic standpoint, one would expect more widespread activity than the CAMs would currently indicate. Nevertheless, even the less bullish CAM output does generate some impressive totals locally due to a combination of the location of the deformation zone across central MN and WI and slow storm motions. Some localized totals could exceed 2 or 3 inches, with some model output indicating the potential for even higher values than that. Kept PoPs in the 70s to 80s, but it doesn`t appear rain will be continuous for many hours at a time in any given location. Problem for Thursday evening will be determining where and when specific locations will be impacted as activity could remain more scattered than with other events recently. The showers will linger into Friday across eastern MN/WI, but some activity could redevelop farther west in the afternoon with breaks in the clouds and some instability developing within the cyclonic flow. Multiple waves within a broad north central U.S. trough will keep precip chances going for much of the remainder of the period. Nothing looks particularly widespread or heavy, but it will continue the gloomy and un-Julylike weather for the region. Temperatures will remain below normal until if/when the western Ridge builds east. Some of the extended guidance is hinting at that possibility toward mid-July. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1153 AM CDT Wed Jul 3 2024 VFR conditions expected through tonight, but broken to overcast skies and lowering cigs will move in from west to east during Thursday morning. RWF looks to have a good chance to falling to MVFR cigs towards the end of the period. Rain chances will also increase from west to east during Wednesday morning as our next system arrives with a band of thunderstorms possible across western and southern MN. Due to this potential, have kept or added PROB30s for -TSRA at most of our MN terminals with visibilities dropping to MVFR within the heavier cores. Outside of any storms, general conditions will be either scattered light showers or overcast skies. Steady westerly winds will slow to calm/variable overnight before becoming more south- southeasterly near 5 knots Thursday morning. KMSP...Have added a PROB30 from 15-18Z Thursday for the possibility of some rain showers. Scattered showers and thunderstorms become more likely heading thru Thursday afternoon with the best timing for storms and MVFR after 22Z. Westerly winds of 10-15 knots will gust to near 20 knots this afternoon. Light southwesterly winds tonight will become easterly at 5-10 knots by 18Z Thursday. /OUTLOOK FOR KMSP/ THU PM...MVFR/IFR SHRA & TSRA. Wind E 5-10 kts. FRI...MVFR SHRA/TSRA likely. Wind N 10G20 kts. SAT...Chance PM MVFR SHRA/TSRA. Wind SW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Borghoff AVIATION...CTG