Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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504 FXUS63 KMPX 101809 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 109 PM CDT Mon Jun 10 2024 .KEY MESSAGES... - Showers and a few thunderstorms expected tonight into Tuesday morning. Redevelopment of a few strong thunderstorms possible in eastern MN/WI Tuesday afternoon. - Warm and muggy Wednesday with strong to severe thunderstorms possible in the afternoon and evening. - Seasonable temperatures to end the week with precip chances returning next weekend. && .DISCUSSION... Issued at 316 AM CDT Mon Jun 10 2024 Apart from slower winds compared to yesterday, another beautiful day will be in store for Monday. Sunny skies, light/variable winds, and highs in the low to mid 70s will provide no excuse to not be outside for at least some of the day. Clouds will build in from the west this evening as an incoming shortwave brings our next good chance of rain tonight into Tuesday. Showers and thunderstorms will develop over the Dakotas along a cold front and travel east, likely reaching western MN just after midnight, the MN/WI border by around 7 AM, and then exiting our WI counties by early Tuesday afternoon. While the original precip from the Dakotas will be decaying once it reaches western MN, CAMs do suggest some redevelopment is likely along the front over south-central MN with the strengthening of the LLJ. Guidance mostly favors a widespread 0.1-0.2" of QPF from this activity, with a few localized streaks of up to 0.5" possible. CAMs also suggest that a 2nd round of isolated to scattered thunderstorms may form over eastern MN later in the afternoon. This convection would then travel east into WI by Tuesday evening. If cloud cover in the wake of the morning precip can break apart enough to allow some daytime heating, the environment should have 500-1000 J/kg of CAPE amid 30-40 knots of bulk shear. For this reason, SPC has given eastern MN/western WI a Marginal risk for damaging winds and large hail Tuesday afternoon. The main uncertainty being if enough heating can occur to offset the expected nearly moist adiabatic lapse rates. A dry, seasonable Tuesday night is expected afterwards. Wednesday is when the forecast turns even more interesting. A strong, low-level thermal ridge will advance into the Northern Plains ahead of a zonal jetstreak along the US/Canadian border. Highs Wednesday afternoon will be the warmest we`ve seen in awhile. 80s are expected across the area, with southwestern MN making a run at 90. Meanwhile, guidance forecasts ample low-level moisture being advected north by the low-level southerly ageostrophic flow in the exit region of the upper-level jet. Mid to upper 60s dewpoints seem likely for most of MN by Wednesday afternoon, with guidance suggesting lower 70s in western MN! With moderately steep lapse rates in place, 2000-3000 J/kg of MLCAPE should result across the much of our area. This along with bulk shear values of 40-50 knots would allow for an environment supportive of strong to severe thunderstorms. SPC has put nearly the entire MPX CWA in a Slight risk for Wednesday. Current thinking is that large (to potentially very large) hail will be the initial concern as supercells form from western to central MN along the frontal boundary. These storms would then travel east/southeast growing upscale into a mesoscale convective system, transitioning the main severe threat to damaging winds. However, there is one factor casting uncertainty on this event: Does elevated morning convection develop across the risk area due to the strong moisture advection? Forecast soundings in southwest MN do show elevated instability growing during Wednesday morning with strong convergence occurring at the nose of an LLJ. If this precip does occur, it will be crucial to see how much it affects the afternoon environment. Heavy rain will also be likely with any thunderstorms as PWATs will be 1.5-1.8". While significant flash flooding doesn`t appear likely due to strong steering winds, small stream and urban flooding could occur if an area experiences repeated storms. The convection should exit to the southeast by Thursday morning, giving most of the area a break in precip to end the work week. However, a few showers and storms may develop in southern MN Thursday afternoon ahead of a trailing cold front. This front will also finally push southeast of our area by Thursday night. Seasonable temperatures should follow into next weekend, but precipitation chances look to return Saturday into Sunday. A short- lived "ring of fire" setup on the periphery of a thermal ridge is favored by guidance Saturday, followed by an incoming shortwave during the Sunday timeframe. Thus, if you have outdoor plans for next weekend, you may want to already consider bringing an umbrella. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1232 PM CDT Mon Jun 10 2024 VFR to start for all TAF sites with generally light/variable winds. Winds will eventually become SE later this afternoon with speeds close to 10kts. Winds will continue to steadily veer to S overnight then to SW during the day Tuesday with speeds increasing to near 15G20kts. Clouds will increase late this afternoon, with upper level ceilings developing this evening that will lower to the mid-levels overnight. Rain will develop over western MN overnight and press eastward over eastern MN around or shortly after daybreak then spread into western WI. Very little in the way of CB/TS expected overnight into tomorrow thus have kept its mention out of this TAF set. Once the morning rain ends, additional scattered convection looks to develop Tuesday afternoon so some isolated/scattered CB/TS is possible then. At this point, have only gone the "chance" route with MSP. With the rain tonight into tomorrow, MVFR conditions are likely during and shortly after until partial afternoon clearing. KMSP...Light/variable winds will persist into late afternoon, then winds pick up from the SE this evening through tonight in the 5-10kts range. Winds then continue veering to SW during the day tomorrow with speeds nudging up to 10-15kts. Showers move into the area prior to daybreak, with best timing of rain at MSP right around sunrise and continuing through late morning. Some heavier batches of rain look to bring visibility into MVFR range late morning. After this morning rain diminishes, scattered SHRA/TSRA will develop in the afternoon, which could impact MSP later on Tuesday. Uncertainty as to the timing/placement forces just a PROB30 mention at this point so this will be adjusted in later TAFs. /OUTLOOK FOR KMSP/ WED...Mainly VFR. MVFR/-TSRA likely late. Wind SW 10 kts. THU...Mainly VFR. Slight chance MVFR/-SHRA. Wind NW 5-10 kts. FRI...VFR. Wind N 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ DISCUSSION...CTG AVIATION...JPC