Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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699 FXUS63 KBIS 170945 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 445 AM CDT Fri May 17 2024 .KEY MESSAGES... - Isolated to scattered severe thunderstorms are possible this afternoon and evening. The expected hazards will be damaging winds up to 70 mph and hail up to quarter size. - Warmer today with highs from the mid 70s northwest to the mid 80s south central. Windy and cooler on Saturday with highs mostly in the 60s. - Daily low to medium chances for showers and thunderstorms continue through the weekend and into early next week. && .DISCUSSION... Issued at 332 AM CDT Fri May 17 2024 Isolated to scattered showers were moving across western and central ND early this morning. Low pressure continues to spin over southwest Saskatchewan, with surface pressures also developing over central and eastern Montana, ahead of a strong shortwave tracking across central/eastern Washington and Oregon. As shower activity dissipates and or exits to the east, we should see a quiet and mostly dry morning with temperatures climbing well into the 70s most areas by midday. This afternoon as temperatures climb into the lower and mid 80s over southwest and central ND, we see steepening low and mid level lapse rates and increasing instability over the forecast area. Strong bulk shear will be present across the entire forecast area today. The aforementioned shortwave and attendant surface low pressure will catch up with the lingering frontal boundary from the Saskatchewan low pressure system and push quickly across the forecast area late this afternoon and this evening. This will bring a chance of strong to severe storms to most of the forecast area. When looking at the potential for sever weather, just compared to yesterday, the areal extent and the window of opportunity looks a bit smaller (far southwest and south central then lifting a little more north, east of the Missouri, into the JRV from around 21Z-04Z). However, with the strength of the shortwave, strong to possibly severe storms can`t be ruled out pretty much anywhere across western and central ND (perhaps not the far northwest which is currently in the general TSTM risk). As far as hazards, it seems like winds will be the main threat. After coordination with FGF/ABR we bumped up the wind threat to 70 mph. There is an area of strong DCAPE over south central ND this afternoon. However, it does begin to dissipate as convective potential increases. Also, just with the strength of the shortwave and the strong jet dynamics, a strong wind gust seems possible. Bufkit soundings show the potential for 40-50 knot winds mixing down to near the surface just behind the cold front. Any convection with the front would help to push this cold air to the surface, and the Inverted V type soundings are favorable for stronger winds mixing to the surface. The hail threat seems lower with 1 inch hail a good upper limit at this time. There is some instability ahead of the front this afternoon and if there is convection there would be enough instability for some marginally severe hail. This will be a conditional threat given the capping that will exist ahead of the cold front. If we do see convection develop ahead of the front this afternoon we could see some hail to 1 inch. One additional thought...Latest RAP guidance and NAM guidance is showing some larger hail potential along the Canadian border. This wasn`t the case earlier, so will continue to monitor. As mentioned earlier, environmental winds alone will be strong behind the cold front tonight and added convection could make for a windy overnight. There is another shortwave following late tonight into Saturday morning. Shower/thunderstorm activity with that wave could also mix down some stronger winds aloft. Saturday looks to be windy across the forecast area and a wind advisory may be needed for at least portions of the area on Saturday. Saturday will also be much cooler, with scattered showers mainly in the north. Sunday will bring a modest warm-up with highs climbing back into the 70s across most of the forecast area. A broad southwest flow with an approaching shortwave could bring some shower and thunderstorm activity once again. At this time it looks the southeast CWA would be favored for thunderstorms. Monday and through the remainder of the forecast period temperature look to remain seasonable with near daily chances for showers and thunderstorms. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1238 AM CDT Fri May 17 2024 Scattered showers and isolated thunderstorms will continue to track across northwest and central ND through 12 UTC. Started KXWA with rain showers and mentioned VCSH at KMOT and KJMS early in the period. Generally a light south to southeast wind overnight and through Friday morning. Friday afternoon and evening showers and thunderstorms are expected to move through the forecast area from west to east. At this time we included a TEMPO for Thunder at KBIS (23-02Z) and KJMS (01-04Z) with gusty winds to 40 knots and MVFR Vsbys. At the remaining TAF sites storms and timing are more uncertain so for now just included a VCTS. Of course gusty and erratic winds with MVFR vsbys can be expected in any storms that develop. In the afternoon and evening winds will shift southwest then west to northwest with the passage of a cold front. Scattered showers with VFR Vsbys and moderate west to northwest winds at all sites behind the cold front and through 06 UTC. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...TWH AVIATION...TWH