000 FXUS63 KBIS 170257 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 957 PM CDT Thu May 16 2024 .KEY MESSAGES... - Scattered showers and thunderstorms are expected this evening into the late overnight hours. A few stronger storms are possible this evening, with small hail and locally gusty winds. - Isolated severe thunderstorms are possible Friday afternoon and evening. The expected hazards will be damaging winds up to 60 mph and hail up to quarter size. - Warmer on Friday (lower to mid 80s south, central, and east), followed by a cooldown with windy conditions Saturday. - Daily low to medium chances for showers and thunderstorms continue through the weekend and into early next week. && .UPDATE... Issued at 955 PM CDT Thu May 16 2024 Aside from a mini-supercell in eastern North Dakota, the intensity of convection has steadily diminished over the past couple hours. The predominant line of showers and storms, now moving through the James River Valley, is still capable of producing gusts as high as 45 mph, as was observed at the Jamestown Airport shortly after 9 PM. These storms will soon be exiting our forecast area. The main area of focus for showers and storms over the next few hours will be from northwest to north central North Dakota, with elevated convection still developing upstream in northeast Montana. However, the threat for a stronger storm has greatly diminished with the loss of diurnal heating. UPDATE Issued at 725 PM CDT Thu May 16 2024 At 7 PM CDT, a line of showers and thunderstorms from near Minot to east of Bismarck to Fort Yates was tracking east at around 30 mph. Several wind gust reports around 40 to 50 were received for the portion of the line between Lake Sakakawea and Interstate 94 as it approached Highway 83. Both radar and surface observations show a decreasing trend in the strongest convection, but SPC mesoanalysis maintains a similar CAPE/shear space downstream. Back to the northwest, a couple of stronger storms have developed in northeast Montana, moving southeast. While buoyancy is more questionable there, with MLCIN likely to increase soon, effective bulk shear is much stronger, on the order of 50 kts. The stronger shear is forecast to spread into northwest North Dakota this evening, so it is possible the intensity of the ongoing convection could be maintained across the border. All measures of buoyancy are forecast to decrease after sunset though. && .DISCUSSION... Issued at 245 PM CDT Thu May 16 2024 Currently diurnal cumulus is growing strong in the west and southwest along the western side of the surface trough with a few of them producing rain. The effective shear is up to 35 knots in the south central but mixed level CAPE is only around 500 J/kg. So there is enough shear to organized storms but we need a little more energy to do it. All the CAMs have scattered showers this late this afternoon in the west and east, then an organized line moving west to east at 21z. Flow aloft this afternoon is turning more and more zonal as a upper level low in Canada moves closer. This will add some diffluence aiding in more storm development through this evening. Storms today should stay sub-severe, strong winds are possible and maybe small hail. These showers and thunderstorms should continue all night, moving west to east, clearing out by sunrise. Friday looks like a higher risk of severe weather happening. Flow aloft is southwest with good diffluence over the state. A very warm thermal ridge also moves in, providing us with the warmest day of the week with temperatures in the 80s. So as long as parcels can gather enough energy from the surface to break through this warm nose, storms can be expected. The SPC has us currently in a marginal risk for Friday, mainly just a wind threat and maybe a quarter sized hail stone or two. DCAPE looks high enough to produce severe winds. Most of the CAPE is east of the river in the afternoon on the lifting side of the surface trough, showers and thunderstorms are possible through the whole state however. This weekend colder air aloft wraps around the low, bringing surface temperatures down to the 60s. The combination of this cold air advection and a pressure gradient off the low, will create breezy winds CWA wide. Wind advisory level winds are possible in the southwest. We will keep an eye on this to potentially need a Wind Advisory Saturday. The chances of showers and thunderstorms continue through the weekend. Saturday the main chances will be along and north of HWY 2. Sunday it will be east of HWY 83 and south of HWY 2. Sunday another upper level low swings down from Canada through Montana, keeping us in southwest flow through Monday. No severe weather is expected for now. Sunday through monday the chances are more widespread. Temperatures through the weekend will be mainly in the upper 60s through the end of the forecast. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 955 PM CDT Thu May 16 2024 Scattered showers and isolated thunderstorms remain possible across most of western and central North Dakota tonight. If a storm moves over a terminal, erratic gusty winds up to around 40 kts and brief visibility reductions to MVFR/IFR levels can be expected. VFR conditions and light southerly winds are otherwise expected through tonight. Winds will turn southwesterly and eventually westerly on Friday as a cold front approaches. Showers and thunderstorms are expected to develop over western North Dakota mid to late Friday afternoon, with higher TS chances farther south. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hollan DISCUSSION...Smith AVIATION...Hollan