Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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198 FXUS63 KBIS 220930 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 430 AM CDT Sat Jun 22 2024 .KEY MESSAGES... - Cloudy this morning with areas of fog and scattered morning showers. An isolated thunderstorm is possible west and south. - There is a 20 percent (south) to 50 percent (north) chance of thunderstorms. A few could be strong to severe. Quarter sized hail and 60 mph winds are the primary hazards. - After a dry day on Sunday, thunderstorm chances return late Sunday night into Monday over northwest into north central North Dakota and again Monday afternoon into early Monday evening over eastern portions of central North Dakota. - Temperatures increase through the weekend, topping out in the 80s north to lower 90s south on Monday, then cool slightly to the upper 70s to upper 80s through next week. - Mostly dry Tuesday and Wednesday with thunderstorm chances returning Thursday and Friday. && .DISCUSSION... Issued at 154 AM CDT Sat Jun 22 2024 Widespread low clouds and some fog early this morning, across the southern half of the CWA. Currently the fog is pretty much limited to the southwest and south central. Light rain/drizzle continues over the south central into the James River Valley in what looks like an area of weak low level warm advection and moisture convergence. In eastern Montana convection is located around Miles City and continues to move east southeast towards far southwest ND. There is and area of around 1000 J/KG of CAPE and 30-35 knots of effective shear situated over southwest ND, thus there is the potential for this activity to reach the state. On the negative side, the mid level lapse rates look to be flattening and CIN looks to be increasing. Most CAMS have a handle on this convection show it weakening as it moves into ND, although some keep convection bubbling as it moves into ND. Will continue to monitor. For today, an upper level circulation will track across southern Canada. At the surface there is little indication of any frontal boundary, other than a wind shift. However, it does look like as clouds break up and temperatures warm this afternoon, there should be a broad area of weak to moderate instability across the forecast area. Forecast soundings indicate that if we reach our forecast highs, there would be a window of opportunity for a few thunderstorms this afternoon/early evening. If we would see thunderstorms there is anywhere from around 30 to 50 knots of 0-6km bulk shear. From the forecast soundings there is little if any directional shear but there is some decent speed shear. There is a nice jet dropping south around the Canadian circulation into the north central as well. There are some limiting factors. In fact, they probably outweigh the favorable severe factors. Surface heating is a question, and thus overall instability. Although speed shear is favorable, I`d like to see it more unidirectional. At times we see winds backing with height. We also see surface pressure rises moving into the west by late afternoon. CAMS are not real consistent and are not in agreement. You could pretty much pick an area and at least one CAM would have convection there. If we had to pick and area most favored, it would be the north central, closer to the upper circulation and the upper jet dropping down. Second would probably be pretty much anywhere except the southern James River Valley. But if convection would hold together it very well could reach the JRV this evening. As far as threats and coverage, we think the severe threat would be isolated, but as mentioned it`s hard to pinpoint any one particularly favored area. And as far as hazards are concerned, there could be a bit more of a wind threat north central, but overall we think a mention of 60 mph winds and quarter sized hail could be justified pretty much anywhere and it would be hard, at this time to go any higher with the threats. We will message isolated to scattered thunderstorms possible this afternoon and early evening, and a few could be severe with 60 mph winds and quarter sized hail. Later shifts can adjust if needed. Once convection, if it develops, ends this evening we should be warm and dry through the day Sunday with highs from the mid 70s Turtle Mountains to the upper 80s southwest. Sunday night into Monday would be the next chance for thunderstorms as a shortwave flattens the upper level ridge that moves over the are Sunday. Currently SPC has a marginal risk for severe storms over a good portions of west central through north central. At this time we will message 60 mph winds and quarter sized hail. Monday will be interesting in that as we rise into the 80s and 90s, we become quite unstable over central into eastern North Dakota. However we are also quite capped. Currently SPC has a slight risk for severe storms over Much of Minnesota with a marginal risk back into central North Dakota. This is a conditional severe threat in that if the cap would break, severe storms would certainly be a good bet, but currently the cap looks to be quite strong. Will certainly need to monitor this as well as we go forward. After Monday, temperatures cool down a bit and it looks like we may see a break in convection mid-week until another upper wave moves from the Pacific Northwest and into the northern Plains, bringing increasing thunderstorm chances Thursday and into Friday. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1245 AM CDT Sat Jun 22 2024 Widespread MVFR-IFR ceilings across southern portions of the forecast area, including KDIK-KBIS-KJMS. IFR visibilities have also developed at KDIK and MVFR-IFR visibilities can not be ruled out at KBIS and KJMS also through mid morning. Also areas of drizzle around KBIS and KJMS. Northern portions of the forecast areas have mainly MVFR to low VFR ceilings and this is anticipated to continue, although some lower ceilings can not be ruled out. Expect MVFR-IFR ceilings to slowly improve from west to east during the day Saturday as winds also shift from easterly to westerly. Isolated convection is possible early this morning mainly over the southwest, and again most anywhere Saturday afternoon. At this time only added a mention of a VCTS at KMOT. Otherwise too much uncertainty and will update as needed. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...TWH AVIATION...TWH