Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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064 FXUS65 KBOU 020611 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1211 AM MDT Sun Jun 2 2024 .KEY MESSAGES... - A chance (20-30%) of one or two severe storms Sunday over the northeast corner of the state - Summer heat through most of next week, with a few 90 degree readings over the plains. && .UPDATE... Issued at 749 PM MDT Sat Jun 1 2024 Latest radar and GOES-16 satellite imagery shows the strongest convection has nearly exited the northeast corner o f Colorado. Storm intensity has weakened significantly over the past couple hours such that the severe weather threat is less than 5% now. Thus, we have cancelled the severe thunderstorm watch for the counties in our CWA. The PoP forecast was updated to reflect the latest trends, which hold onto 10-15% through midnight for the northern mountains. PoPs across the far NE corner and Lincoln County drop below 10% after 9 PM this evening. Should be a quiet night across the area, with skies becoming mostly clear. Temperatures were left alone as they appear to be on track, with lows from the upper 40s in the cool valley spots to mid 50s in the urban corridor, and 30s in the mountain valleys. && .SHORT TERM /Through Sunday/... Issued at 222 PM MDT Sat Jun 1 2024 Dry line is currently a little west of a line from Sterling to Limon. The dry line will progress eastward through the rest of the afternoon and be east of the area by early evening. ML CAPE is expected to reach 2000 J/kg. This combined with 0-6km Bulk Shear of 35-40 knots should produce a few supercell thunderstorms. Large hail up to tennis ball size and damaging winds will be possible with these thunderstorms. To the west of the dry line, ML CAPE only reaches 500 J/kg. Dew points are falling into the 20s and 30s which will result in high-based showers and thunderstorms. Gusty outflow winds to 50 mph will be the main threat with these thunderstorms. The showers and storms come to an end this evening as the airmass stabilizes. For Sunday, a wave embedded in the westerly flow aloft will track across the region. At the surface, lee side trough will extend from far eastern Colorado north-northeast into South Dakota. Best lift from the passing wave will be over northern Colorado into Wyoming. Isolated high-based showers are expected to form over far northern Colorado. Eventually an organized outflow from the storms in Wyoming dives south and increases low level moisture which will bring a better chance for rainfall. Over the far northeast corner of Colorado where it will be more unstable, a severe storm or two will be possible. Airmass continues to warm Sunday, with highs across northeast Colorado expected to reach the mid to upper 80s. && .LONG TERM /Sunday night through Saturday/... Issued at 255 PM MDT Sat Jun 1 2024 Zonal flow is expected across the CWA Sunday night well into Monday, then a weak upper trough moves across Monday night into Tuesday. There is neutral synoptic scale energy over the CWA Sunday night with weak upward motion Monday through most of Monday night. Downward vertical velocity is progged on Tuesday. Looking at moisture, precipitable water values are progged in the 0.30 to 0.80 inch range Sunday night, then they increase into the 0.50 to 1.10 inch range Monday afternoon and night, then they decrease again Tuesday. For CAPE, models show values under 1,000 J/kg over the far northeast corner Sunday night. On Monday afternoon and evening there is limited CAPE, under 600 J/kg, over much of the CWA with slightly higher values over the far northeast corner. There is no CAPE progged on Tuesday. So for pops, will go with 10-30%s over the far northeast corner Sunday evening, then 10-20%s for the northern half of the CWA Monday afternoon and evening. That`s it. Temperatures stay above seasonal normals through the periods, with both Monday`s and Tuesday`s highs very closed to Sunday`s readings. The plains will see mid 80s to lower 90s both days for highs. For that later days, Wednesday through Saturday, models have upper ridging to dominate the weather for the forecast area into Friday. The center of an upper ridge is over southern Utah Wednesday, then central New Mexico on Thursday. By Friday, the upper ridge axis is pushed west and northwest of Colorado due to a strong upper low over the Great Lakes. By Saturday, the upper ridge axis moves back east towards and into Colorado. Moisture is sparse Wednesday, Thursday and Saturday, with a bit more progged on Friday. Overall, it will be dry and pretty warm with the only decent chance of showers and thunderstorms to be on Friday. && .AVIATION /06Z TAFS through 06Z Monday/... Issued at 1137 PM MDT Sat Jun 1 2024 VFR through the TAF period. Winds are transitioning to the expected drainage (SSW) direction. Currently, a few storms are passing to the NW of BJC that could bring a brief northerly wind shift if outflows develop. Probabilities are low of this happening, but there is a low chance for this to happen in the first hour or two of the TAF period. For Sunday, winds from the west will begin increasing with 20-25 kt gusts around 18Z-19Z. Models are in agreement that winds will have a northerly shift around 1Z with winds winding down by 3Z. With passing virga and DCAPE values around 1400 J/kg, there is a chance that rapidly shifting winds could temporarily develop in the afternoon hours. With high based virga and dry lower levels, the chance for any precipitation to reach the ground is low (~10%). && .HYDROLOGY... Issued at 255 PM MDT Sat Jun 1 2024 Alpine snowmelt will increase runoff the next few days. Hydrologic forecasts from the River Forecast Centers show a few streams getting to action stage by Monday or Tuesday, which means flows will be high and fast but flooding threat appears limited. Please use caution and respect these fast moving and cold flows in the high country. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Schlatter SHORT TERM...Meier LONG TERM....RJK AVIATION...Bonner HYDROLOGY....RJK/Barjenbruch