FXUS63 KBIS 260611 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 111 AM CDT Fri Apr 26 2024 .KEY MESSAGES... - Showers are likely (60-90%) tonight through Friday, with the highest probabilities across central and eastern North Dakota. - Isolated thunderstorms may be found tonight through Friday. Severe weather is not expected at this time. - Cooler temperatures on Saturday and Sunday, with low to medium chances of rain showers across southern and central North Dakota. - Temperatures warm up back to above normal next work week, with low chances for showers most days. && .UPDATE... Issued at 1259 AM CDT Fri Apr 26 2024 The forecast for tonight remains on track. Modified POPs and the aerial coverage of precipitation to better match current radar imagery and trends. While not seeing much lightning about, will keep in the forecast for now and revisit in a bit. Did add some fog in the southwest, with both the HRRR and RAP indicating this, along with a few obs there already reporting some reductions in visibility. UPDATE Issued at 1050 PM CDT Thu Apr 25 2024 Minor updates late this evening mainly for current radar trends. Showers look to linger across much of central North Dakota tonight, spreading slowly eastward. Thunderstorms have diminished in coverage, and overall are now expected to be isolated in coverage through the night. Limited thunder mention to slight chance as a result. More widespread showers are then expected for much of Friday, with perhaps some isolated thunderstorms across southern and eastern portions. Gusty winds in the east have come down some. They may remain elevated through the night although below advisory criteria. Gusty northeast winds could then be found across the west tomorrow. UPDATE Issued at 705 PM CDT Thu Apr 25 2024 Limited updates needed so far this evening. In the east near to isolated advisory winds are being reported. Coverage was more isolated to scattered thus held off on an advisory at this time. These winds could gust 45 to 50 MPH this evening, diminishing around sunset. Meanwhile in the west and south central, continue to monitor thunderstorm development. Pockets of MUCAPE near 1000 J/KG remain, although shear values of 20 to 25 knots are proving to be not enough to sustain severe thunderstorms in ND at this time. That being said, still cannot rule out an isolated strong storm through the evening. Hail and perhaps gusty winds would be the main threat, although still expecting storms to be sub severe. Brief heavy rain could also be possible as precipitable water values are currently above normal for this time of year. Overall will continue to monitor winds and thunderstorms with little updates needed at this time. && .DISCUSSION... Issued at 304 PM CDT Thu Apr 25 2024 Currently, mostly mid to high level clouds are present across the area, with widespread temperatures in the low to mid 70s. There is still the potential for some areas out west to reach 80 within the next few hours, however the intrusion of thicker clouds from Montana and western South Dakota may limit those chances. Some cumulus has begun to form across the border in eastern Montana as well. Winds across the area are out of the south southwest, with some places in the James River Valley reaching sustained wind speeds in the 20 to 30 mph range, with occasional gusts nearing 35 mph. These winds are expected to decrease near sunset, when mixing weakens. We are still on track to receive our first real chance at some convection and the development of thunderstorms. Recent deterministic guidance indicates a corridor of 1000 - 2000 J/kg of MUCAPE, along with modest lapse rates, supporting the potential for the development of thunderstorms. However, shear continues to be the main limiting factor, with 0-6 km shear maxing out at 15 to 20 kts across the region with highest instability. Should any storms develop, small hail and gusty winds will likely be the main concerns, as these storms will not be able to sustain themselves without the shear. Gusty winds from these storms may continue as the storm collapses as well. Initially, these storms will begin to develop across the southwest during the late afternoon and early evening hours, before spreading across the rest of the area after sunset. CSU machine learning continues to advertise a low chance for severe hail during this period, mostly across western portions of the state. Our area is still only in a general thunder risk from the SPC, but the Marginal Risk (level 1 of 5) has been expanded up to our southern border. Following this round of thunderstorms, a warm season Colorado Low is forecast to move to the south of the area through Friday, bringing much of the area a period of showers. Wrap around moisture long the northern periphery of the surface low will make its way into the southern half of the state late tonight, expanding northward through the day Friday. Chances for precipitation at its peak will range from 20 to 30% across the far northwest, to 80 to 95% for nearly the entirety of central North Dakota and the James River Valley. Precipitable water values are forecast to be near 1.00", which approaches the 90th percentile of the precipitable water climatology. Parts of south central and the southern James River Valley currently have a 45 to 75% chance of exceeding 0.50" of rain, while the chances for exceeding 1.00" remain rather low, at around 10 to 20% for the same area. Most of the area is expected to see at least some rain through the day Friday, with chances tapering off overnight and into Saturday as the surface low pushes out into the Great Lakes region. A cold front is forecast to drop down across the area from the north this weekend, with high temperatures on Saturday and Sunday forecast to be a bit cooler than what we have been seeing lately. Widespread highs are forecast to be in the upper 40s to the upper 50s, with overnight lows in the 30s to lower 40s. While some areas may see temperatures below freezing, precipitation is unlikely to occur in those areas, so any concerns for snowfall are minimal. As that cold front moves through, a secondary, weaker low pressure system is forecast to take a similar path to the previous Colorado low, just displaced a bit further south. Moisture associated with this system are expected to be reduced, with chances for precipitation mostly displaced further southeast. Chances for exceeding 0.50" will be rather low, only maxing out around 20 to 30% in the far southern James River Valley, with most locations remaining lower than 10%. After these systems move through, upper level flow is expected to be a bit more zonal, with an upper level ridge moving into the area from the west. Temperatures are forecast to increase Monday and through the rest of the week, increasing into the 60s to lower 70s. However, there is still some disagreement in the placement and strength of this ridge, which would affect how active the pattern becomes. Current WPC cluster analysis suggests two separate scenarios: 60% of members suggest a stronger ridge, leading to a warmer, less active, and therefore drier pattern, with only occasional daily chances for afternoon and evening showers. The other 40% of members suggest a more southward displaced ridge, leading to a more active and wet pattern, with the potential for greater chances for showers and thunderstorms. Either way, next work week is looking to be a bit warmer than the weekend that precedes it. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1259 AM CDT Fri Apr 26 2024 Periods of showers and a few thunderstorms will bring MVFR to IFR conditions at times through the forecast period. Early this morning, showers were mainly over central and southeastern North Dakota, moving north, with KJMS, KBIS, and KMOT having the better chances of seeing precipitation. In addition, a large area of MVFR-IFR ceilings will develop over all but KXWA this morning, and will likely persist through the 06Z period. Towards 12Z this morning and into the day Friday, showers and a few thunderstorms will increase in coverage south, central, and east, continuing into Friday night. Prevailing showers are in most TAF sites as a result, with the exception being in northwestern North Dakota including KXWA. Breezy southeast winds could linger across the east through Friday morning, with a breezy north/northeast wind developing across the west during the day Friday. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...NH DISCUSSION...Besson AVIATION...NH