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Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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197 FXUS63 KMPX 040902 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 402 AM CDT Thu Jul 4 2024 .KEY MESSAGES... - Thunderstorms and locally heavy rainfall likely today and tonight. - Numerous chances for showers and a few thunderstorms will linger into next week with temperatures remaining below normal. && .DISCUSSION... Issued at 402 AM CDT Thu Jul 4 2024 Showers are beginning to advance into and develop across southwestern MN early this morning. They should reach the Twin Cities metro in the next few hours. This will be the first of potentially many rounds during the next 24 hours. The trough over the northern High Plains will continue digging southeast this morning, reaching MN this afternoon as a seasonally potent wave. 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 tonight north of the surface low track and roughly along the 700 mb low track. This favored area is expected to stretch from the Redwood Falls area to the Twin Cities metro. 00Z HREF neighborhood probabilities of greater than 2 inches within this corridor range from 60 to 80 percent, and 30 to 60 percent for greater than 3 inches. That`s a strong signal for heavy rainfall, but there are some limiting factors to consider for flooding. Many of the CAMs and even the global guidance indicate rain will not be continuous for several hours. There should be breaks between rounds which will allow runoff from becoming excessive. Pwats aren`t too anomalous for this time of year and rain rates aren`t expected to be too extreme either. Perhaps some 1-1.5 inch/hr rates will be possible with the most robust convection, but 1 hr flash flood guidance values are generally 1.5-2 inches and those rates shouldn`t last an hour`s time. Areas that do see totals of 3 inches through Friday morning may have some issues, but these pockets should be fairly localized. For these reasons, decided against a Flood Watch at this time but trends will continue to be monitored. Mid level lapse rates will remain modest and the prospects of significant surface heating still appear limited given the extensive cloud cover, so instability will be lacking in most locations. However, across southern MN there may be better heating near and south of the low track. Here, there is some potential for a few stronger storms where CAPE may exceed 1000 J/kg and deep layer shear is better. Some marginally severe hail and a couple weak tornadoes are possible. The showers will linger into Friday across eastern MN/WI, but some scattered 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 /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 632 PM CDT Wed Jul 3 2024 A very unsettled period is expected as we see a mid-level low track across southern MN on Thursday. Looking at the path of 850mb & 700mb low, the HREF shows these features tracking from roughly Montevideo to Wabasha, along/north of this track will be a favorable zone of forcing for seeing multiple rounds of precipitation and thats what`s expected for most of the MPX terminals. A continuous rain is not expected, but it will be on & off activity for a good 12-20 hours. TS potential looks greatest from the afternoon into evening. Surface pressure pattern will be very baggy through the day on Thursday, so wind directions will be tough to pin down, but speeds will be under 10 kts. Finally, RAP soundings show low levels moistening up enough late in the afternoon to start bringing in MVFR cigs for locations that area expected to be north & west of the developing surface low. KMSP...Models are absolutely all over the place with when/where clusters of SHRA/TSRA will be through the day on Thursday and into Thursday night, hence why precip mentions in the TAF are VCs or PROB30. Current thinking is that the band of showers along the eastern Neb/SoDak border will send an initial round of showers through the metro during the morning, with a brief lull in activity during the afternoon, before thunderstorms quickly redevelop. As mentioned above, winds could be coming from just about any direction on Thursday, though speeds will be generally 5 kts or less. /OUTLOOK FOR KMSP/ FRI...MVFR SHRA/TSRA likely. Wind N 10G20 kts. SAT...Chance PM MVFR SHRA/TSRA. Wind SW 5-10 kts. SUN...MVFR/SHRA/TSRA likely. Wind SW 10G20 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...Borghoff AVIATION...MPG