Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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620 FXUS63 KFGF 211943 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 243 PM CDT Fri Jun 21 2024 .KEY MESSAGES... - Isolated strong to severe storms are possible in the northern Red River Valley and Devils Lake region late Saturday afternoon into the evening. - Potentially strong to severe storms again Monday afternoon and evening. && .DISCUSSION... Issued at 243 PM CDT Fri Jun 21 2024 ...Synopsis... The southwest flow at 500mb over the Northern Plains finally turns more zonal tonight into Saturday. After a low point yesterday, surface dewpoints have risen into the mid to upper 50s over most of the FA, with even some greater than 60F values across the far south. Precipitable water values have nosed back above 1 inch over most of the FA, although the values closer to 1.8 inches are still down across southeast South Dakota into far southern Minnesota. Extensive cloud cover today has helped to moderate the temperature rise somewhat. There is another shortwave west of the Bismarck that has been pushing another batch of precipitation slowly east-northeast today. Not expecting much low level jet support for the above mentioned shortwave tonight, so the activity to the west may decay or slowly die as it progresses into this FA. Dewpoints and precipitable water values will continue to rise on Saturday. The next 700mb wave will drop into north central North Dakota by 00z Sunday, then slowly into Minnesota Saturday night into Sunday morning. A brief period of ridging follows, before a ridge rider scenario develops late Monday afternoon into Monday evening. After that the pattern shifts to northwest flow aloft and less confidence on the timing of any potential waves. ...Late Saturday afternoon and evening... The HREF shows building CAPE across the FA on Saturday, with values possibly reaching 1000-1500 J/kg over central and possibly southeast North Dakota by late afternoon. Overall, the surface flow is very weak, so don`t expect much forcing there. Another caveat is how much cloud cover may linger across the FA during the day, limiting instability. The NBM keeps it pretty cloudy through the morning, but shows the clouds thinning by afternoon, especially across central North Dakota. The arrival of the shortwave should help initiate some convection, although there is not a good consistent signal on that either. The strongest portion of the wave may stay north of the border (in Canada) or it could be a little slower reaching this FA. So the exact timing is still uncertain as well. UH tracks on the HREF show a better potential north of the border, although a few CAMs have some weaker UH tracks potentially reaching the Langdon to Cooperstown corridor. There is no low level jet support Saturday night, so would expect any strong to severe storms to weaken after dark. ...Monday afternoon and evening... Monday still looks like the warmest day of the 7 day period, as brief ridging moves in. Similar to yesterday at this time, 700mb temperatures appear to hit about +10C as far north as Winnipeg, with near +15C across the southern FA. Surface dewpoints should rise into the 60s with precipitable water values reaching about 1.5 inches, so again there will be plenty of CAPE. The main uncertainties with this event are how much of a surface boundary there may be and how strong it is. Same story for the wave, its timing and strength (the stronger portion may again lift into southern Canada). How much capping holds. So although strong to severe storms are again possible, there are a lot of question marks yet, so stay tuned. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1231 PM CDT Fri Jun 21 2024 VFR conditions are expected through this evening. There is a streaky layer of low level clouds across the TAF sites that general sits between 3000 and 4000. These clouds are expected to remain thin enough to be scattered but at times may be become dense enough to be broken. The most uncertainty is the development of showers late this afternoon and evening. The environment conducive to produce showers seems very conditional however if showers do develop they would most likely start around 03-04z for KDVL, KFAR, and KGFK. MVFR and IFR may develop tonight after 00z as the models depict clouds below 2000 but not quite sure how feasible that is. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...Godon AVIATION...MM