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Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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060 FXUS63 KMPX 011133 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 633 AM 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 /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 633 AM CDT Mon Jul 1 2024 VFR for much of the day today before the next round of rain moves in later today. That does not mean there will be no aviation impact during the day as winds will increase this morning. Gusts will generally be in the 20 to 30 knot range and will remain gusty until after the showers and storms come to an end tonight/tomorrow morning. Rain and MVFR is very likely to occur at all terminals later today. What is still uncertain is the coverage of thunderstorms. There will likely be some areas of TSRA and IFR, but pin pointing the terminal that will get it is a challenge. Thunder is also more likely to occur over western Minnesota and less likely as it moves to the east. So went prevailing for the western terminals and TEMPO to the east. As we get closer confidence should be increasing to provide greater detail. After the rain comes to an end low stratus will likely hang around. KMSP... Winds will increase from a southeast to southerly direction today with gusts as high as around 30 knots. Cloud coverage will increase and ceilings will fall as we get later in the day. This evening will see the arrival of MVFR and possible TSRA. IFR conditions could also occur with TSRA. As mentioned in the main aviation discussion confidence in TS is currently higher to the west and future TAF issuances should be able to add more details. /OUTLOOK FOR KMSP/ TUE PM...MVFR. Chance IFR/TSRA. Wind W 10-15 kts. WED...VFR.Wind WSW 10-15G20 kts. THU...VFR. PM MVFR SHRA/TSRA.Wind SE 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...ETA AVIATION...NDC