Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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390 FXUS63 KBIS 161203 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 703 AM CDT Mon Sep 16 2024 .KEY MESSAGES... - Thunderstorm chances continue through tonight with a isolated to scattered severe thunderstorms possible, along with very heavy rain. - An active pattern continues through the week, with strong to severe storms again possible Tuesday night, along with a general cooling trend from mid to late week. && .UPDATE... Issued at 646 AM CDT Mon Sep 16 2024 Scattered to numerous showers and thunderstorms continue, mainly across north central and into northeast ND this morning. More stratiform rain extends back into southwest and south central North Dakota. For the morning update we trimmed back pops in the southwest and south central and bumped them up a bit north central. The risk for severe storms will be the big question today. With the late start to the convection last night, we`re setting under dense cirrus and atmosphere has been worked over quite a bit. Would not be surprised to see a lull in the activity, especially southwest and south central this morning and early afternoon, and then it`s a question as to whether or not convection can develop again. Farther to the north and east, closer to the slight risk area, we could see convection bubble through the day and also develop/intensify later this afternoon into tonight. Stay tuned. .DISCUSSION... Issued at 208 AM CDT Mon Sep 16 2024 Convection is developing over Mercer, Oliver and McLean counties of central North Dakota. This is near/ahead of an east to west band of 35-40kts of effective shear and on a gradient of strong MUCape (2000J/KG) to the south and weak (<500J/KG) to the north. This is also on the nose of a quite strong low level jet lifting north-northwest through central/western ND. This activity has the ingredients to produce severe hail up to ping pong ball size and possibly some locally gusty winds. The main question here is will everything line up, and for how long. Shear and instability is quite low just to the north, but everything is also propagating quickly north. Also wondering if the ingredients from the EMC RAP are keeping up with the rapid development and northward propagation of severe ingredients. Nonetheless we could see scattered strong to severe storms continue over central ND for a few hours yet early this morning. For today, ongoing convection over central ND will continue to drift to the north and east through the day. Severe ingredients will remain and SPC has introduced a slight chance for severe storms over south central into northeast North Dakota, with a marginal risk extending back southwest into far southwest ND. Besides the potential for severe storms we will also need to monitor for the potential for very heavy rain and areas of localized flooding, especially if we would see multiple round of storms or training of storms. The MCV mentioned from the central High Plains convection looks like it`s lifting north northeast, a bit farther to the west than was noted yesterday, which is likely the reason the marginal risk was pulled back more into southwest ND. This area will remain quite unstable today, actually pretty much everywhere south of the warm front that lifts north through the forecast areas, and multiple impulses will continue to lift northward through the upper level flow. However the greatest risk will likely exist within the slight risk area from the south central into northeast ND. Will also mention a possible tornado over the slight risk area. This area will be favored for strong low level helicity this afternoon with low lcl`s. Will mention golf ball sized hail and 60 mph winds across the the slight and marginal risk area, which covers all but the far northwest CWA. Tonight into Tuesday morning, the western upper level trough will close off as it tracks over the Rockies, promoting a transient upper level ridge that will help clear out any lingering showers and thunderstorm over the forecast area during the early morning hours. Late Tuesday afternoon and Tuesday evening, another cold front will be dragged through the northern Plains as the upper low an its associated surface low lifts north into Canada. Another round of showers and thunderstorms are anticipated to develop along and behind this front Tuesday evening, with some potential for severe weather shifting in out of eastern Montana and over the western Dakotas. SPC has placed much of western and portions of south central North Dakota into a Marginal (level 1 of 5) risk for severe thunderstorms on Tuesday, with a Slight (level 2 of 5) risk for severe storms over northeast Montana and skirting portions of far northwest ND. High temperatures will also peak ahead of the cold front on Tuesday, forecast from around 80 in the north central to the lower 90s in the southwest. As the the upper level low begins to shift northward into the Canadian Prairies Wednesday, the another upper level low will dig into the western CONUS and sustain the active weather pattern through at least the end of the workweek. The potential for, the timing of, and the strength of any showers and thunderstorms become increasingly uncertain this far out. However, the better moisture returns from the golf looks to be cut off late in the week. There remains better agreement for a cooling trend through the end of the week, as NBM forecast highs drop broadly into the 60s by the coming weekend. Low temperatures also drop with overnight lows mainly in the 40s but with 25th percentiles dropping into the mid and upper 30s over western ND late in the weekend and into early next week. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 646 AM CDT Mon Sep 16 2024 Chances for showers and thunderstorms will continue across central North Dakota through much of the day while slowly drifting eastward. MVFR/IFR visibility will be possible with any storm. Outside of thunderstorms, VFR conditions are likely to prevail, though some lower ceilings cannot be ruled out in and around areas of showers and storms. Easterly winds around 5 to 10 kts will turn to the southeast and increase to 10 to 15 kts this afternoon, with some higher gusts possible, before diminishing by early evening. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...TWH DISCUSSION...TWH AVIATION...TWH