Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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204 FXUS63 KFGF 121748 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1248 PM CDT Wed Jun 12 2024 .KEY MESSAGES... - Scattered severe thunderstorms this afternoon in northwest Minnesota. All hazards possible with up to 2" hail, wind to 70mph, and isolated tornadoes. && .UPDATE... Issued at 1248 PM CDT Wed Jun 12 2024 Temperatures have been very toasty across the central and southern portions of the Red River Valley this afternoon, with many spots already above 80 degrees. Raised highs a bit. Dew points have not been coming up as fast as temperatures, but a few elevated showers/storms have started to develop over northwestern MN. Still thinking there could be some surface based convection later on this afternoon, mainly in western MN as the surface low moves east. Will continue to monitor. UPDATE Issued at 958 AM CDT Wed Jun 12 2024 A few lingering elevated showers and isolated thunderstorms near Lake of the Woods, but looks like the main show will still be later on this afternoon as the boundary later destabilizes and the weak surface low currently over eastern ND pushes east. Adjusted POPs for current radar trends and latest CAMs. Highest probabilities severe have shifted slightly east and are more over DLH`s area, but still a 2 out of 5 risk for severe storms later this afternoon in western MN. UPDATE Issued at 627 AM CDT Wed Jun 12 2024 Thunderstorms forced by elevated instabilty on the nose of a LLJ will continue to work east through the morning clearing the area by 9 to 10am. Thunderstorm forecast remains on track for the afternoon with a notable outflow boundary laid down along HWY 2 from northern convection overnight and will be key to see how this evolves through the day or if it remains by initiation this afternoon. && .DISCUSSION... Issued at 324 AM CDT Wed Jun 12 2024 ...Synopsis... Currently noting two clusters of storms with one straddling the Canadian border in our north and another along the ND/SD border in central SD. Northern area will continue to translate east with the 850-700 mb flow and isolated thunder. Southern cluster approaching Aberdeen being aided by strengthening low level jet with very steep mid level lapse rates atop a sfc inversion. Elevated convection may pose a wind risk through the AM as any stronger updrafts collapse with negative buoyancy translating these stronger LLJ winds through the inversion to the sfc. Max wind speed above the inversion looks to be around 40 mph so compressional heating could push gusts into sps territory though low confidence in this scenario. Main thing to watch with any of this overnight convection will be if any outflow boundaries are produced which would heavily dictate the mesoscale environment for initiation later in the day with the regards to the afternoon severe threat. Lastly while not meeting any heat criteria, today will likely be the warmest day of the year thus far with 925 mb temps in the low to mid 20s C translating to highs well into the 80s for most except the far north where max temps will only reach 80 as the effective warm front remains just south of the intl border. ...Severe Today... Current picture is messy to say the least with a ceiling of hail near 2", winds to 70 mph and a few tornadoes. Floor of isolated hail as boundary parallel shear leads to a messier convective mode with less discrete convection and upscale growth. A 500mb jet streak of 50-60 kt will overspread the area ahead of a weak shortwave in southern Manitoba this afternoon. In combination with an incoming EML and steep mid level lapse rates over 8 C/km the environment will be primed for strong to severe convection this afternoon. A sfc trough will continue to shift east into northern MN this aftn with an effective warm front extending east along the MN/Canada border. Tds in the warm sector in the low 60s and temps in the mid 80s will contribute to MLCAPE of 2500-3000 J/kg near the sfc low in NW MN. All this and the ingredients for scattered to numerous severe storms across northern MN exist today. Any tornado threat will likely be tied closely to storms along boundaries toady (cold front, warm front, residual outflow from morning convection) as low level shear is not particularly favorable for tornadoes and thus remains a conditional threat. Low level stretching will however be maximized with 0-3 km CAPE at least locally exceeding 100 J/kg near the low. When looking at the hail threat best chance for sig hail (> 2") would be from storms forming off the cold front and racing E/ESE as minimized CAPE below the 0C would maximize time for hail embryos in the HGZ. Eventual upscale growth is still possible this evening with wind becoming the main threat though this aspect remains slightly more uncertain. ... Thursday and Beyond... Upper flow towards late week shifts northwesterly as an intensifying ridge sets in keeping us quiet at least through Friday until southwesterly flow becomes prominent and gives us increased chances for widespread rainfall. How much rain falls is dependent on intensity and track of the wave. At this point in time, NAEFS percentiles do have an enhanced corridor of PW in the 97.5th percentile across the northern plains from South Dakota into North Dakota and west central Minnesota. This gives us solid confidence in a more widespread rain event but also the potential for more focused moisture advection across the northern plains. After this system, ensemble guidance diverges and predictability for impacts next week is low. There is a strong signal for another wave to move through early next week, although the potential range of outcomes is very wide and predictability needs to increase to ascertain potential impacts. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1248 PM CDT Wed Jun 12 2024 VFR conditions now and throughout the period. Some convection possible mainly at the MN airports, probability has diminished quite a bit some removed any mention further west. Winds will shift to the northwest behind a surface low currently over the central Red River Valley, with some gusts around 20 kts this evening. Winds will come down a bit overnight, then pick up again during the mid to late morning tomorrow. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR/TT DISCUSSION...TT AVIATION...TT