Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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475 FXUS63 KMPX 011825 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 125 PM CDT Mon Jul 1 2024 .KEY MESSAGES... - Widespread showers and thunderstorms this evening through Tuesday. Locally heavy rainfall possible, primarily across southern Minnesota & western Wisconsin. - Thunderstorms and locally heavy rainfall likely for the 4th of July. && .DISCUSSION... Issued at 419 AM CDT Mon Jul 1 2024 The main forecast challenge today will be how early showers and thunderstorms develop across the area with a wide spread in timing still present among both high-resolution & synoptic-scale models. Everything is in agreement with the most widespread thunderstorms & heaviest rains occurring tonight & overnight, with the uncertainty being how much precipitation develops this afternoon on the nose of the strengthening low-level jet. Strong southerly flow ramps up Monday morning & advects Gulf moisture into the region, with precipitable water values potentially exceeding 2" by late Monday night. This morning, most guidance initiates a narrow band of sowers & thunderstorms along a weak upper-level boundary across the eastern Dakotas. Some solutions keep this convection going into western & central Minnesota through late morning & into the afternoon. More likely, however, is that this convection decays as it heads east, with perhaps some light precip across far-western Minnesota early this afternoon. More widespread showers & thunderstorms will hold off until this evening when WAA from the low-level jet is strongest & better forcing aloft arrives from an approaching jetstreak. Precipitation will overspread the area fro west to east through the night, with the most widespread thunderstorm coverage & best chance for locally heavy rainfall looking most likely from south-central Minnesota through western Wisconsin. In general, rainfall amounts up to 0.5" are expected across western & central Minnesota, with amounts in excess of 1-2" more likely across eastern Minnesota & western Wisconsin through Tuesday morning. Hi-res models do indicate some swaths of 3-4" where the heaviest thunderstorms from south-central Minnesota through western Wisconsin, so locally higher amounts are likely and could lead to some flash flooding concerns. Isolated hail and strong wind gusts can`t be ruled out with the strongest storms tonight, but the severe chances look higher across the Dakotas where the shear & instability are higher. A lull in the precipitation appears likely Tuesday morning with a second wave of showers and thunderstorms expected during eh afternoon & evening along the surface frontal boundary. Trends over the last 24 hours have progressed this front through the area quicker, with the best chances for thunderstorms shifting southeastwards into southeast MN/northeast IA/southwest WI. Some showers and thunderstorms still look likely from south-central Minnesota through west-central Wisconsin, but the heaviest rain and strongest thunderstorms does appear to stay south and east of our area Tuesday. Rainfall amounts only look to be on the order of a few tenths across our area, but will be over an inch wherever the main band of thunderstorms develops. Drier conditions develop midweek as the flow aloft weakens & becomes more zonal, but another round of showers & thunderstorms looks likely for the 4th of July & into Friday as a broad shortwave trough develops & moves over the Upper Midwest. It looks very likely that most of the are will see rain Thursday, with some uncertainty still present with how much rain & where the heaviest rain will occur. Ensemble guidance continues to show high probabilities for rainfall amounts >1". Our highest PoPs from the NBM ensemble continue to be centered on the evening of the 4th, with some indications that at least morning events could stay dry. A chance for showers and thunderstorms continues over the weekend, but with not nearly as strong a signal for heavy rain or strong thunderstorms. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 123 PM CDT Mon Jul 1 2024 VFR with MVFR/IFR SHRA/TSRA likely late this evening into tonight through tomorrow morning. Scattered to broken ceilings are beginning to make their way into western MN this afternoon out ahead of our next system that will provide SHRA/TSRA across all terminals tonight from west to east. Breezy SSE`ly winds will range between 20- 30kts this afternoon before weakening some to 15-25kts overnight. IFR stratus is likely along with trailing scattered -SHRA in wake of the passing system. Winds will shift to SW and not as strong between 10- 15kts tomorrow morning although cigs reluctant to budge out of IFR categories for the remainder of the TAF period. KMSP...VFR to start then transitioning to MVFR to IFR categories overnight as -SHRA/TSRA arrive. Current hi-res guidance looks to have SHRA encroach on MSP as early as 2z with storms likely between 4 to 8z. Scattered SHRA is possible in wake of the system passing until about 12z. Low MVFR/IFR cigs will remain in place through the rest of the period. SSE`ly winds remaining breezy this afternoon with gusts nearing 30kts but should begin to decrease after sunset to near 20kts. Winds shift and decrease between 10-15kts out of the SW late tomorrow morning. A slight chance for -TSRA was hinted in the guidance late afternoon hence the PROB30 from 22/24z. /OUTLOOK FOR KMSP/ WED...VFR.Wind WSW M10-15G20 kts. THU...VFR. PM MVFR SHRA/TSRA.Wind SE 5-10 kts FRI...MVFR SHRA/TSRA lkly. Wind NE 5-10 G15-20 && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...ETA AVIATION...Dunleavy