Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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892 FXUS63 KBIS 040024 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 724 PM CDT Mon Jun 3 2024 .KEY MESSAGES... - Showers and thunderstorms tonight through Tuesday morning. A few storms could be severe this evening. - Strong northwest winds Tuesday through Thursday. - Seasonable temperatures expected through the week with slightly warmer temperatures possible late in the week. && .UPDATE... Issued at 704 PM CDT Mon Jun 3 2024 Line of convection has developed over southwest North Dakota right along the corridor of stronger CAPE values (~1000 J/Kg), though storms are now starting to push to the east of the higher values. Latest guidance tries to pull the core of elevated instability east, but appears that the storms may continue to push ahead of this. We did have one severe event (quarter size hail) over Adams County with our strongest storm, but that has since weakened, and the strongest storm in the area remains over Perkins County, SD. Would not be surprised to see a few more storms increase in intensity and become strong with gusts to 50 mph and small hail, but the severe risk remains low, though can`t be ruled out given the marginal shear in place. At this time, the Perkins County storm is the one to keep the closest eye on as it gradually makes its way northeast towards our area. Current area of storms will continue to move east, with additional showers/storms later tonight affiliated with a cold front now pushing through central into eastern Montana make their way east. && .DISCUSSION... Issued at 203 PM CDT Mon Jun 3 2024 A potent storm system will track from the Pacific North west this afternoon, across the Northern Rockies and close off into a closed upper low as it moves into the southern Canadian Prairie Provinces by Tuesday. Strong upper level divergence is expected to develop over western ND this afternoon, while increasing low level convergence develops along the Montana/North Dakota border. The latest satellite imagery shows an increasing cumulus field over southeast Montana and into the western Dakotas. As far as potential convection this afternoon and evening, not much has changed from this morning. Modest 500-1000 J/Kg MUCape with 30-40 knots of bulk shear will provide the potential for a few strong to severe storms. As for the storm mode, starting around 21 UTC the bulk shear is pretty much perpendicular to a thermal trough the looks to develop along the MT state line. A more stable airmass on satellite looks to be situated from around Beach northward, and also looks to be lifting to the north. Cumulus is building southwest and expected to continue building northward this afternoon. This could set the stage for a few discrete cells developing this afternoon. Current CIN is pretty high over southwest into south central ND, but you can see a min in the CIN poking into southeast MT that should lift northward late this afternoon. The SPC HRRR does show that CIN then increases quickly early this evening. By this time the shear backs to the southwest and trends to more parallel to the trough, but not completely, so you could have a mixed mode of convection with a trend towards a mixed or linear mode later in the evening and overnight as the forcing increases with the approaching. However, CIN also increased and elevated convection would be favored. Therefore the best bet for strong to severe storms looks to be late afternoon the southwest and possibly north into the west central, depending on how the more stable atmosphere in northwest ND erodes. All hazards would be possible here but the window appears small. A few NUCAPS soundings over the Mondak regions shows around 2000 J/KG cape in near Baker MT, but a nice bump of mid level warming providing a nice C cap. A Buffalo SD sounding showed a much more unstable atmosphere with MUCAPE above 3000 J/KG but also with a cap, albeit a not as strong. Both these soundings may be a bit warm for surface temperatures as well. A sounding north of Dickinson shows a more modest 1000 J/KG MUCape but was less capped than those soundings to the west. Not much vertical development of any CU at this time in southeast Montana, but possibly will develop more with heating and as cumulus meanders a bit farther east. Low level flow over ND is more south to southeast, ahead of the thermal trough, potentially yielding a longer residence time of any developing updrafts. Will certainly need to monitor. As for the threats, we mentioned all three, the tornado threat we think would be quite early on in the convective development with strong surface heating and some low level shear present. Large hail look to be a threat if we could get a rotating mesocyclone. Otherwise, CAPE in our local are seems less favorable for large hail compared to farther south into South Dakota. Thus quarter size seems reasonable. The wind threat would be more favored later on if we get some liner convection or bowing segments. But also here, the later we get into the evening, the more likely convection would be elevated. Thus 60 mph also seems reasonable. The strong shortwave will keep at least a small threat of strong winds as convection moves into the central part of the state, but overall, we think the severe potential would be quite a bit less later and farther east, especially after around 10 PM and east of the Highway 83 corridor. Overall we think the NBM probabilities of convection may be a bit high, especially this afternoon and early evening. However, showers and thunderstorms should become more widespread (but not severe hopefully) as we go through the late evening and overnight hours. Over central ND, ahead of the convection we could see some fog develop again from the James River Valley to the Turtle Mountains. However uncertainty in this is pretty high so we did not include fog at this time. Late tonight and into Tuesday we could also see some fog post convection but again, too uncertain for any one area. Showers and thunderstorms will exit the area on Tuesday with a strong westerly surface flow moving in from the west. Tuesday looks to be breezy over western North Dakota. Wednesday, however, looks to be the most likely day for wind highlights as a strong northwest surface flow develops beneath the Canadian upper level low. At this time it looks like a wind advisory will likely be needed for at least northern and western portions of the forecast area, and possibly all of western and central ND. The ECMWF continues to show a pretty good signal (80 percent probability) for significant winds and gusts over much of the forecast area, with the 90 percent probability approaching the northwest. With a strong upper jet in the area, a case could be made for possible HWW criteria winds given the strength of the winds aloft. There does seem to be quite a bit of low and mid level cloudiness around and some upward motion limiting the wind potential. Will need to monitor this as well. Wind potential shifts into eastern ND on Wednesday, but breezy to windy conditions could be felt over the central portion of the state. Beyond Wednesday we look to dry out with temperatures possibly showing a small warming trend as we head towards the weekend. Mid week will be more seasonable with 60s and 70s. Late in the weekend into next week the warming trend could continue but high NBM ensemble high temperature spreads increase so confidence in anything warmer is not high at this time. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 704 PM CDT Mon Jun 3 2024 Showers and thunderstorms over western North Dakota will continue to spread east this evening, with additional showers/storms passing through overnight. This will bring periods of MVFR/IFR visibility. In addition, small hail and gusty winds will be possible with the storms. The storms will exit from west to east late tonight into Tuesday morning, but westerly winds will be on the increase behind a cold front, possibly gusting to around 35 kts. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...JJS DISCUSSION...TWH AVIATION...JJS/TWH