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Area Forecast Discussion
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
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428 FXUS63 KBIS 132040 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 340 PM CDT Sat Jul 13 2024 .KEY MESSAGES... - Very warm temperatures are expected through the weekend, with a Heat Advisory in effect over Dickey and LaMoure counties from 1 PM to 8 PM today. - Isolated to numerous severe storms are possible this evening and into the night. Hail to the size of tennis balls and damaging winds up to 70 mph will be the main hazards, mainly southwest. - Scattered severe storms will be possible once again late Sunday afternoon and into the evening. Hail to the size of golf balls and damaging winds up to 70 mph will be the main hazards. && .DISCUSSION... Issued at 340 PM CDT Sat Jul 13 2024 Currently a cold front is moving southeast through the northwest part of the state. Besides cooling temperatures, the front is also drying dew points to the mid 50s. A thin band of cumulus clouds is seen across the front from Roulette County down through the big lake and over through Watford City. There is a possibility that this front could kick some convection in the James River Valley where the pressure is lower, however confidence is low as only one or two CAMs have this solution. So we will keep a close eye on it. There is also a surface low pressure on the border of the Dakotas near Ashley. Aloft there is a very slight shortwave over eastern Montana, creating some diffluence over North Dakota. We still have the Heat Advisory for Dickey and LaMoure counties for heat indexes around 103 expiring at 8pm CT. *Severe Threat Tonight* The new SPC outlook has an enhanced in the southwest, a slight in the west and south central and a thin marginal followed by a general thunder in the north central. We just released a special timed weather balloon to measured the atmosphere here in Bismarck. There is still a cap here, and unfortunately we cant measure the real atmosphere where the main show will be (southwest ND). The upper level shortwave will move into western North Dakota, creating more lift as time goes on. The complex of storms is currently north of the International border in eastern Montana, moving south. MUCAPE values after 00z (when storm will be near ND) is around 1400 J/kg on the Montana border, to 2500 J/kg near Bismarck. The 0-6km shear is off the chart at 60kts. The 0-3km shear (most useful for severe wind) is around 32kts. This amount of low level shear is very favorable for severe winds over 70mph. DCAPE is another good indicator of severe wind potential and it is well over 1000 J/kg. The special sounding we launch has the drier lower level "inverted V" look. So like yesterday, when storms are alone hail will be the threat. When they form into a line at least 70mph winds are possible. The main area for that is western ND and southwestern ND. Basically where the enhanced is. Timing looks to be 8 and 9pm MT for storms coming across the Montana. The challenge is timing with CAMs all very different, plus some have the storms missing ND to the south. *Sunday`s Threat* Sunday we have very high MUCAPE over most of the CWA. Shear both 0-6km and 0-3km is still very high. Currently we are in a slight risk. CAMs have storms popping in the north central pretty much all day and then so more scattered storms in the west. Then into the evening, scattered supercells pop all over. With how the CAMs have been all over the place the last two days, not sure there is high confidence in this solution. Aloft little waves look to move through all day kicking off storms. *Rest of the week* Starting Monday the flow aloft turns northwest, bringing slightly cooler temperatures (in the 80s) while a ridge sets up over the Western CONUS. There are on and off chances of showers and thunderstorms as little embedded waves move through. By Thursday that ridge moves in. Highs will warm back to near 90 to end the week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 130 PM CDT Sat Jul 13 2024 VFR except maybe MVFR in thunderstorms overnight. This afternoon will be mostly clear skies with winds up to 15kts from the north in western ND, and from the southeast in eastern ND. Overnight there will be scattered severe thunderstorms in the west and south central, maybe the central, through about 10z. Winds will be gusty in thunderstorms. Sunday should start with mostly clear skies and winds from the east. && .BIS WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for NDZ048-051. && $$ DISCUSSION...Smith AVIATION...Smith