Area Forecast Discussion
Issued by NWS Bismarck, ND

Current Version |  Previous Version |  Graphics & Text |  Print | Product List |  Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
533 FXUS63 KBIS 160708 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 208 AM CDT Sun Jun 16 2024 .KEY MESSAGES... - Scattered severe thunderstorms are possible across western and central North Dakota tonight through early Sunday morning. Expected hazards include damaging winds up to 80 mph and hail up to golf ball size, with a tornado or two possible. - Isolated to scattered severe thunderstorms are possible across south central and southeast North Dakota Monday through Monday night. - Warm and humid today, followed by below normal temperatures through the first half of next week. Windy in the northwest on Sunday. && .UPDATE...
-- Changed Discussion --
Issued at 207 AM CDT Sun Jun 16 2024 Severe thunderstorm threat starting to become more isolated, and the tornado threat is even more diminished as the cold front continues to push from west to east. Thus let the Tornado Watch expire at 2 AM CDT. The Severe Thunderstorm Watch in northeastern North Dakota remains until 6 AM CDT. Wind gusts up to 70 mph will still be the main threat through the night. Hail up to 1 inch in diameter is also possible through tonight. UPDATE Issued at 1244 AM CDT Sun Jun 16 2024 A line of thunderstorms has now formed along a cold front from the Canadian border to the South Dakota border. Winds will be the main threat along this line, with some recent reports up to 75 MPH. As a result a down stream Severe Thunderstorm Watch has been issued, while much of the Tornado Watch remains. Areas behind the cold front have been dropped from the Tornado Watch. In northwestern North Dakota, strong winds in the wake of severe weather have been found. Thus issued a High Wind Warning to cover this threat. Perhaps this will need to be expanded eastward if this trend continues behind the northern line of severe storms. Will continue to monitor. UPDATE Issued at 1035 PM CDT Sat Jun 15 2024 The line of storms that had been impacting northeast Montana has arrived to northwest North Dakota and we`ve had a handful of reports in the 55 to 65 mph range and one report just north of Alexander of 83 mph. This line of storms should continue to move east northeast over the next few hours and the chance for more 70 to 80 mph wind gusts still looks reasonable given the environment in place and radar presentation. The southern end of the line may start to struggle with some capping as it moves further east. No major changes were needed for this update. UPDATE Issued at 829 PM CDT Sat Jun 15 2024 Quick update to issue a Tornado Watch for all of western and most of central North Dakota through 2 AM CDT / 1 AM MDT. UPDATE Issued at 631 PM CDT Sat Jun 15 2024 Minimal updates were needed for the gridded forecast early this evening. We did slightly adjust precipitation chances to better reflect the latest trends and observations and blended in the latest observations to the forecast. For more details regarding the latest on the severe threat, please see the mesoscale discussions below.
-- End Changed Discussion --
&& .DISCUSSION... Issued at 238 PM CDT Sat Jun 15 2024 Upstream troughing digging into the Pacific Northwest places the Northern Plains under southwest flow aloft this afternoon. At the surface, a lee trough is developing just west of the ND/MT border. The air mass downstream of the lee trough is capped, but low to mid 60s dewpoints coupled with strong diurnal heating has already resulted in 2000 J/kg SBCAPE. A gradual lowering of mid level heights combined with low level convergence could provide enough forcing for convective initiation to overcome the capping in western North Dakota late this afternoon, and there are already signs for a sustained storm on satellite imagery along the MT/ND border near Trotters. Bulk shear through all layers AGL is forecast to increase this afternoon and especially this evening. Any storms that develop along the lee trough later this afternoon are favored to remain discrete, with long hodographs supporting very large hail up to tennis ball size. With a weakening of the capping inversion and an increase in the low level jet with poleward moisture transport early this evening, convection should become more widespread across western North Dakota. The enhanced southerly return flow could introduce a brief tornado threat with any discrete storm, with 0-500 m SRH increasing to 100-200 m^2/s^2 and 0-1 km bulk shear increasing to 15-25 kts. This may be especially true for the northwest due to a deepening northeast Wyoming low augmenting the surface wind field to a predominant easterly direction. Later in the evening and into the early overnight hours, several CAMs bring severe storms that originate in central Montana into northwest and north central North Dakota as an intense bowing complex. Simultaneously, existing convection could grow upscale and merge into a forward-propagating linear complex. The kinematic environment over northwest and north central North Dakota looks favorable for a higher-end damaging wind threat, with 0-3 km shear exceeding 40 kts and near surface winds directly opposing storm motion. This is where the highest potential for significant severe winds of 75 to 80 mph exists. Later tonight, following the convection, a deepening low over southern Saskatchewan will drive a cold front across the state. This will result in a cooler, drier, and windier Sunday. The strongest winds are expected in the northwest, where afternoon gusts could approach 45 mph. Outside of the southern James River Valley which could approach 80 degrees, high temperatures will primarily be in the upper 60s to mid 70s on Sunday. Multiple rounds of showers and thunderstorms are expected over the north central CONUS Sunday night through Monday night as a longer wave trough translates across the Northern Rockies. For Sunday night into Monday morning, there are medium chances (40 to 70 percent) for showers and storms across the southern half of the state, including a lower probability risk for elevated strong to marginally severe storms posing a large hail threat along the South Dakota border and east of the Missouri River. This will be conditional on the northward advancement of elevated buoyancy into a a highly sheared environment. For Monday afternoon through Monday night, there are high chances (70 to 90 percent) for showers, with thunderstorm chances ranging from low northwest to high southeast. All convection over this time frame looks to be elevated, but MUCAPE around 1000- 2000 J/kg paired with effective bulk shear of at least 50 kts could support a severe threat with any storm whose elevated inflow layer contains no CIN. Buoyancy prognostics limit this threat spatially to south central and eastern North Dakota. Showers remain in the forecast for Tuesday as the base of the shortwave trough swings through, though thunderstorm chances will be much lower. A southwest flow aloft regime is favored to continue through the week, with low confidence in the timing of shower and storm chances. Temperatures are favored to remain below through at least the middle of next week before warming back closer to normal by next weekend. The coolest time period is expected to be Tuesday through Tuesday night, with highs mainly in the 60s and lows mainly in the 40s. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1244 AM CDT Sun Jun 16 2024 A line of strong to severe storms will continue to push eastward across the state. MVFR conditions could briefly be found along this line. In addition strong winds with gusts over 50 knots could be found along and behind this line. VFR conditions should return for Sunday, although breezy to windy westerly winds may be found through the day. These winds then diminish Sunday evening. && .BIS WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 3 AM CDT early this morning for NDZ001- 002-009-010. && $$ UPDATE...Anglin DISCUSSION...Hollan AVIATION...Anglin