Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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454 FXUS63 KFGF 021750 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 1250 PM CDT Sun Jun 2 2024 .KEY MESSAGES... - There is a level 2 out of 5 risk for severe storms this afternoon and evening for the entire FA. Hazards include hail up to golf ball size, wind gusts up to 60 mph, and a few tornadoes possible. - Widespread showers and thunderstorms are expected late Monday night into Tuesday. Severe storms are unlikely. && .UPDATE... Issued at 1250 PM CDT Sun Jun 2 2024 Showers and thunderstorms continue to develop near the I-94 corridor, slightly stronger than earlier this morning, but still not severe. The better surface based CAPE and effective bulk shear are setting up over south central ND to our west, so will have to keep an eye on that area and see if severe cells can develop there and move into our western counties later this afternoon. At this point do not see any reasons to make changes to our overall messaging, but will continue to monitor. UPDATE Issued at 955 AM CDT Sun Jun 2 2024 Scattered areas of showers and some thunderstorms continue to push into the forecast area with warm air advection and a weak lead shortwave in the southwesterly flow. Some stronger cells have developed just southwest of our counties in the James River Valley, but seem to be elevated and do not think they will maintain strength very far as they push eastward into southeastern ND. Still a lot of question marks as far as how things will develop later this afternoon. With clouds and precipitation affecting destabilization in the Red River Valley, the best bet for severe may be storms developing in central ND and pushing eastward into our area, which is what some of the CAMs show at this point. Will continue to see how things develop as the morning progresses. UPDATE Issued at 627 AM CDT Sun Jun 2 2024 POP grids where tweaked to reflect the ongoing radar signatures moving across our forecast area this morning. Weak thunderstorms moved over the Fargo metro area this morning as well as the Devils Lake Basin. CAMs are still in disagreement about the initiation time but have general consensus of transitioning to a linear mode after 21z. Otherwise the severe potential still looks to be in the afternoon and persist during the evening. && .DISCUSSION... Issued at 304 AM CDT Sun Jun 2 2024 ...Synopsis... As the CAMs were starting to show at this time yesterday, scattered showers have begun to show up along the Interstate 94 corridor early this morning. There haven`t been any lightning strikes yet, but the HREF 1-hour thunder probability does show this potential developing in the next hour or two. This is elevated convection, tied more so to 700mb warm advection and a developing 25-35 knot low level jet. These parameters lift northward, so by sunrise into mid Sunday morning most of this activity should lift into the highway 2 corridor and northward. After seeing this consistency from yesterday, have pretty good confidence with it. However, this will have implications on heating and instability for later, as the clouds and any precipitation will hold down the temperature rise along and north of highway 2 today. The NBM has caught on to this with cooler highs in these areas today. ...Severe potential this afternoon and evening... After having pretty good confidence on how convection may occur early this morning, the confidence for how things may unfold this afternoon is much lower. So why is that? First, the surface features look very weak today, versus what was there at this time yesterday (a surface low near Jamestown at 00z Monday with a trailing cold front, and a warm front extending eastward along Interstate 94). As of now, not sure there will be much of any surface low or boundaries, or it will just be a weak trough. Surface winds do look pretty gusty from the south today, but behind the so called cold front/trough they are pretty light. So there is no strong push behind this weak boundary in the 21z Sunday to 03z Monday period. Second, as mentioned in the synopsis section, morning clouds and precipitation will likely limit the convective potential across the north. CAMs yesterday had showed a nice line of storms forming over central North Dakota 21z Sunday-00z Monday, then moving into eastern North Dakota and weakening during the evening. CAMs now show an earlier and more southern track to the best severe potential this afternoon and evening. And again, this could change. To start, SPC kept the entire FA in a slight risk for severe weather. Some of the main parameters remain the same, starting with good moisture return. However, SPC did note that surface dewpoints by afternoon in the 60s might be a little too optimistic. The upper support is not ideal, but enough. The HREF is indicating maybe 1500-2000J/kg of MLCAPE across southeast North Dakota by 21-23Z Sunday, with about 35 knots of 0-6km effective shear. The better mid level lapse rates hold along the Dakotas border down into eastern South Dakota. Meanwhile, the low level jet cranks up pretty good from 21z Sunday to 00z Monday (around 50 knots), so much stronger than it is right now. However, its best focus may be into Minnesota lifting into southern Canada in the evening. CAMs seem to be latching on to one cluster of storms across northwest Minnesota during the late afternoon and early evening, feeding off the low level jet, while another cluster tries to get going from Jamestown to Oakes. As the storms from Jamestown to Oakes push east during the late afternoon and early evening, they turn linear and sag southeastward toward the better CAPE. These would be more wind producers. The HREF shows the best UH tracks developing around Barnes County about 22z Sunday, and continuing across southeast North Dakota and adjacent areas of west central Minnesota until about 03z Monday. Will maintain the inherited hazard wording for hail (although will go golfball size to match Bismarck, wind (60 mph), and a few tornadoes possible, although it may be trending more toward wind and maybe hail. ...Next event Monday night into Tuesday... The next good shortwave is still on track to move through the FA Monday night into Tuesday. This is a little faster than what was seen yesterday, so that most of the precipitation moves through during non-peak heating hours. This means there is not very much CAPE to work with. The track of the wave may favor the northern half of the FA with slightly heavier precipitation amounts now. Quarter inch amounts look pretty favorable for all areas, ranging from a 90 percent probability along the Canadian border to 60 percent along the Dakotas border. Probs for amounts greater than 1 inch range from 40 percent along the Canadian border to 10 percent along the Dakotas border. Uncertainty then comes into play for the later periods, with the potential for an upper low to linger over the Northern Plains for a few days, or slowly shift east. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1250 PM CDT Sun Jun 2 2024 Scattered showers and a few thunderstorms will continue to impact area airports through this afternoon and evening, and cannot rule out some severe convection although unknown at this point if the strongest cells will impact the TAF sites. The best chances for convection will be during the 21Z to 03Z time frame, ending from west to east later tonight. Mostly VFR ceilings but could see some brief drops to MVFR vis with heavier rain. More widespread MVFR to IFR conditions later tonight into tomorrow morning as stratus moves in behind the departing thunderstorms, but some improvement by the end of the period. Winds will shift from the south to southeast with gusts to around 25 kts around to the southwest then northwest by Monday morning. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...MM/JR DISCUSSION...Godon AVIATION...JR