Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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118 FXUS63 KBIS 070946 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 446 AM CDT Fri Jun 7 2024 .KEY MESSAGES... - Scattered showers will move into the northwest (Williston area) this morning and advance east and south. This afternoon, along and east of a line from Hettinger to Garrison to Rugby, thunderstorms will be possible (as high as a 45 percent chance). Storms are expected to be below severe limits. - Isolated showers (20 percent chance for rain) are forecast for Saturday, mainly north and east of Minot, and then on Sunday (20 percent) over central and eastern North Dakota. - With high confidence it is expected to be cooler Sunday and Monday, the question is how much cooler, and then warmer for the middle of next week with high temperatures into the 80s. && .DISCUSSION... Issued at 430 AM CDT Fri Jun 7 2024 The surface analysis as of 4 AM showed weak high pressure centered near Bismarck with a clear sky and winds that were light, under 10 mph, and variable in direction. An inverted trough extended north through eastern Montana. Low pressure aloft was drifting south through central Saskatchewan with pockets of energy (short waves) passing through the cyclonic flow and heading toward the international border. Clouds in association with the waves were both moving through southern Saskatchewan and developing there. Radars showed an increase in reflectivity north of Glasgow, Montana, with movement to the east and south. For today that first wave, and the cyclonic flow, will bring increasing weak ascent of air parcels into the forecast area. Guidance shows an abundance of 0-6km shear forecast to be over the area but little in the way of CAPE, at least until later this afternoon, and mostly along and south of Interstate 94. Because of this CAMS bring showers into the northwest this morning and intensify them as they move south and east, but only slightly (the intensification). By intensification we mean going from showers to thunderstorms. Looking at the HRRR fields, a pocket of higher MUCAPE, on the order of 300 J/kg, is forecast to move from southwest of Bismarck to south of Jamestown during the late afternoon and into the evening. That would be the highest chance and most likely location for a stronger storm. In discussion with my shift partner we are concerned on one hand of a storm there being able to produce some small hail, but on the other hand, with strong shear, concern goes to the updrafts not being able to gain much altitude before being sheared off. We`ll have to watch to see how convective parameters change through the short term to have more confidence in the risk of small hail. Another wave brushes the northeast on Saturday with chances for showers, maybe a storm, mainly east and north of Minot. Then on Sunday, the upper low advances into the state with cooler air and shower chances in the cyclonic flow, over the central and east. Sunday should be the coolest day over the next seven with that upper low over the state, followed by warming then through at least Wednesday. The NBM 1D Viewer shows a wide range in possible high temperature outcomes on Sunday, but all lower than 70. The question then becomes, cool Sunday, but just how cool, especially north. 60s at this point would be a high expectation, but lower, mid or upper 60s will need to be determined. The Viewer then shows narrower ranges (higher confidence) for high temperatures for the middle of the week, basically 80 to 85. It does look like the 80s could be accompanied by unsettled weather as the mean H5 ridge is broken down every 24 hours or so by short wave troughs passing through it, and bringing chances for rain. By Thursday the ridge could be replaced by cyclonic flow troughing (cooler and more unsettled). && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 430 AM CDT Fri Jun 7 2024 Surface high pressure near KBIS at 07/09Z will drift east and allow an inverted trough to push in from Montana. Light and variable winds to start the TAF valid period will shift northwest and increase with the trough passage. Expect scattered -SHRA at KXWA through 07/18Z to move east and south and grow into isolated -TSRA around KBIS after 07/18Z and around KJMS after 07/20Z. If a stronger storm is able to form it would be south of Interstate 94. Showers and any storms will end at KBIS by 08/02Z and at KJMS by 08/06Z. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...JPM AVIATION...JPM