Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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734 FXUS63 KBIS 210800 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 300 AM CDT Sat Sep 21 2024 .KEY MESSAGES... - Low to medium chances (20 to 60 percent) for rain showers will continue through the early morning hours, mainly across the north. A few rumbles of thunder will remain possible near the International border. - Northwest winds will continue to increase through the morning and into the afternoon. Sustained winds to 25 mph and gusts to 40 mph will be possible. - Expect cooler temperatures through the weekend and into early next week, with forecast highs today and Sunday mainly in the 60s. Some frost is possible Sunday morning across portions of the west. && .DISCUSSION... Issued at 300 AM CDT Sat Sep 21 2024 An upper level trough and surface cold front continue to move east across the region early this morning. Forcing from these two features will maintain low to medium chances (20 to 60 percent) for showers across much of western and central North Dakota, with the best chances along and north of the Highway 2 corridor. A few rumbles of thunder will also remain possible along the International border across the north central. While instability is limited, SPC mesoanalysis does suggest some pockets of 250 J/kg MUCAPE, likely driven by steep midlevel lapse rates. After the trough moves through early today, high pressure will start to move in later this afternoon and tonight. Showers should pretty much move out of the area to the northeast by 15z or so. Clouds will also start to erode from west to east through the day as high pressure moves in. Behind the front, northwest winds will also be on the increase through the morning and into the early afternoon. Most guidance has strong pressure rises and strong cold air advection sweeping across the state through the mid to late morning. Very steep low level lapse rates are then forecast to develop across all of western and central North Dakota by the afternoon hours. This will mean increasing northwest winds through the morning and maintaining them into the afternoon. Sustained values up to 25 mph and gusts to 40 mph will be possible. As of now, it appears that the strongest winds will generally be south and east in the mid morning through mid afternoon. It will be much cooler today with highs in the lower 60s north to the mid to upper 60s south. Combined with the windy conditions, it should feel quite blustery, but there should be plenty of sunshine. Winds will relax by this evening as high pressure continues to slide in. A clear sky and generally light winds will lead to a fairly cold Saturday night/Sunday morning, especially across portions of the west. The latest NBM shows widespread lows in the mid to upper 30s across the western third of the state. This will be a tricky forecast as even the NBM 50th percentile suggests we will see several more sites in the mid 30s and some in the lower 30s. If we trend more towards the NBM 25th percentile, we could see widespread lows in the lower 30s (maybe even a few upper 20s). As the NBM has warmed slightly over the last few runs, some uncertainty remains about how low we will go Sunday morning across the usual cold spots over the southwest. Pattern recognition would say that we should trend towards the lower side of guidance but we will continue to roll with straight NBM for now given the uncertainty. Frost headlines will likely be needed across the southwest and possibly the entire west should we, in fact, do trend colder. There was some discussion of issuing a Frost Advisory on this shift, but we decided to hold off until the next shift in coordination with our neighboring offices. Highs will mainly be in the 60s again on Sunday but it will be a touch warmer (maybe a few lower 70s returning to the southwest). Winds will be much lighter was well, so it will likely feel warmer than it actually is when compared to Saturday. Northwest flow aloft will dampen through the day on Sunday, becoming nearly zonal before the next shortwave trough approaches on Monday. For now, it appears that most of the synoptic forcing with this next wave will remain north of the International border. That being said, it wouldn`t be a surprise if we eventually see some lower rain shower chances introduced late Monday afternoon or evening. Ridging starts to move in again by mid to late week, leading to at least a modest warmup. Highs on Monday are forecast to range from the mid to upper 60 north to the low to mid 70s south and then maybe just a touch warmer on Tuesday. By Wednesday through Friday, the NBM has some low to mid 80s returning to the forecast as ridging moves across the state and we transition back into southwest flow aloft. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1206 AM CDT Sat Sep 21 2024 Isolated to scattered showers will continue over the next few hours across much of western and central North Dakota. A few rumbles of thunder and gusty winds will be possible with the showers across portions of the northwest and north central, potentially impacting KMOT with wind gusts up to 50 mph in the next hour or two. Precipitation will continue to diminish from west to east through the morning. Winds will increase out of the northwest through the morning, with breezy conditions hanging around through much of the afternoon. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...ZH AVIATION...ZH