Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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802 FXUS63 KBIS 180320 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1020 PM CDT Fri May 17 2024 .KEY MESSAGES... - Scattered severe thunderstorms are possible this evening. The expected hazards will be damaging winds up to 70 mph and hail up to quarter size. - Windy and cooler on Saturday with highs mostly in the 60s. - Daily chances (40%) for showers and thunderstorms continue through the weekend and into early next week. && .UPDATE... Issued at 1020 PM CDT Fri May 17 2024 Cancelled the Severe Thunderstorm Watch for Foster, Stutsman, and Logan counties. The remaining counties in the Severe Thunderstorm Watch (LaMoure, Dickey, and McIntosh) could still see a strong wind gust up to 70 MPH through the late evening hours. Thus the Severe Thunderstorm Watch remains in these areas. UPDATE Issued at 930 PM CDT Fri May 17 2024 The Severe Thunderstorm Watch in Sioux, Emmons, and Kidder county have been allowed to expire. Just southeastern portions of the CWA remain in a Severe Thunderstorm Watch until midnight central time. Overall the remnant line of thunderstorms in the remaining watch areas are running into an increasingly capped environment. There is a decent gradient of DCAPE though in this area and high amounts of 0 to 3 KM shear. If a stronger storm can make use of these strong wind ingredients, then perhaps some strong wind gusts up to 70 mph are still possible. Will continue to monitor for this potential. Behind this line could be another round of mainly showers with a few thunderstorms moving from west to east tonight. Severe weather is not expected with these, although perhaps some gusty winds are possible with any more developed shower or thunderstorm. UPDATE Issued at 725 PM CDT Fri May 17 2024 Increasing CIN across the west and north has brought enough confidence to drop portions of the Severe Thunderstorm Watch to these areas. Severe Thunderstorm Watch still remains in southern and eastern portions for this evening. These areas could still see 70 MPH wind gusts and hail up to the size of quarters. UPDATE Issued at 700 PM CDT Fri May 17 2024 Severe weather operations continue. The main severe weather threat has now transitioned to southern, central, and eastern portions of the state. Severe Thunderstorm Watch remains in these areas until 9 PM CDT, and has been expanded eastward until midnight. The Severe Thunderstorm Watch in the northwest has been dropped. Western North Dakota still has a Severe Thunderstorm Watch. There are some thunderstorms that have redeveloped in eastern Montana that have reported some gusty winds. If these can hold together perhaps another round of storms with strong winds are possible. However these storms are moving into an environment that has already had thunderstorm activity and is becoming increasingly capped. Will continue to monitor for any watch adjustments. Otherwise continue to keep an eye on the latest watches and warnings as the stronger storms can still produce winds up to 70 MPH, with perhaps hail up to an inch in diameter. UPDATE Issued at 557 PM CDT Fri May 17 2024 ** MESOSCALE UPDATE** The primary severe-storm risk the next few hours will be in the form of damaging winds of 60-70 mph from the Hettinger area toward Fort Yates, Linton, and toward Ashley/Wishek and into Stutsman, LaMoure, and Dickey Counties. The northern edge of the more sustained damaging wind risk will likely be limited by the sagging, though gradually-decelerating outflow boundary/radar fine-line extending from Carrington to Steele and now to the south of Bismarck/Mandan. The storms near Hettinger are on the leading edge of stronger forcing aloft and increasing low- and deep-layer wind fields, including 0-3-km bulk shear increasing to at least 25 kt. The area ahead of that convection and south of the outflow boundary will have sufficient bouyancy to present an organized damaging wind risk, assuming it does not outrun the increasing winds aloft to the west, or that the outflow boundary does not progress to the south too quickly. Otherwise, the boundary layer to the north and west has cooled and the severe-storm risk is diminishing in west central and north central ND. The storms immediately north of the outflow boundary, e.g., near the Bismarck/Mandan area toward Carson and Elgin, are likely elevated and pose a more marginal severe risk given the cooler boundary layer in that zone. UPDATE Issued at 241 PM CDT Fri May 17 2024 Quick update that there is now a Severe Thunderstorms watch for most of western and central ND until 02z. Hazards are still 70mph winds and quarter sized hail. It may need to be expanded into the far southeast, but we will see how the storms go. && .DISCUSSION... Issued at 200 PM CDT Fri May 17 2024 The upper level wave has started to move into the state, as seen in satellite with agitated mid level clouds at 18z. Near the Montana/North Dakota border near Glendive, MT, south to Bowman, ND and over to Glen Ullin, ND cumulus has started. We should be warmer than our convective temperature now, so more and more cumulus should start to pop in the next hour, especially with the diffluence over head from the upper level wave. The latest SPC update at 1630z expanded the slight risk through the whole CWA. Some CAMs have isolated storms forming now before the main cold front moves through and forms a line. The main threat is still 70mph winds because of a lack in CAPE, and the storm mode. The storm mode is a line because the shear vector will be parallel to the cold front, continuously allowing new convection to form in the line. DCAPE look very favorable with values around 1000 J/kg, and model soundings have an inverted V with steep lapse rate. This allows the wind to mix down very easily. So the isolated storms that form now, will then combine into a line as the cold front moves in. Timing on the line forming looks to sometime around 21-23z. The CAMs are all a little different on the which storm mode they start as. The line will move west to east, leaving our area around 03z. Most CAMs are confident on that. Then on the back side of the front, more showers and possibly thunderstorms will form again in the west, lasting through the night. Saturday will be breezy on the backside of this front with cold air advection and a tight pressure gradient. Westerly winds will gust to 40mph, with sustained winds at 30mph. We will most likely need a Wind Advisory from Saturday morning, until around 00z. Since we have active storms today, we will wait until the overnight period to issue that. Highs on Saturday will be much cooler in the 60s, this cooler trend will continue through the weekend. Flow aloft this weekend will remain southwest with another low and wave moving through Sunday and Monday. Chances for showers and thunderstorms will continue through the forecast period with the highest chances ending Monday when the southwest flow relaxes some. Mid next week the flow is weak in a quasi-zonal flow. Another big low pressure possibly forms in the Pacific Northwest Wednesday. This could bring another round of storms with diffluence flow aloft and southerly flow at the surface Thursday and Friday. Temperatures look to stay slightly below average in the low to mid 60s through Friday. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 700 PM CDT Fri May 17 2024 Showers and thunderstorms, some possibly strong to severe, will be possible across most TAF sites this evening with an additional round possible tonight. MVFR conditions are possible in the stronger storms or heavy rain. Breezy northwest winds will also develop behind a cold front tonight. Lingering showers will push out of the area Saturday morning. The rest of the day should see FEW to SCT VFR clouds with breezy to windy northwest winds. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Anglin DISCUSSION...Smith AVIATION...Anglin