Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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611 FXUS65 KBOU 171802 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1202 PM MDT Mon Jun 17 2024 .KEY MESSAGES... - Hot and dry across most of the area today. - Critical fire weather conditions expected until this evening. - Cooler by Tuesday and Wednesday. - Impacts from snowmelt across the high country will continue to diminish through the week. && .UPDATE... Issued at 1039 AM MDT Mon Jun 17 2024 Day Cloud Phase Satellite imagery shows this morning`s low stratus gradually eroding out this morning. Still several thicker areas across the plains that will take another hour or two to see improvement. How quickly the stratus erodes out will hold a good amount of weight in today`s forecast and highlights. Overall, this morning`s stratus event across the plains/urban corridor took away some heating time. It likely won`t have a large impact to highs as we have plenty of daylight hours for surface heating this time of year. Made minor adjustments to today`s highs, cooling a degree or two in areas. Regardless, it still looks hot and dry this afternoon. Despite a delay in heating and mixing, the Red Flag Warning will be in effect after 11am. It is likely that not all areas in the Warning will be hitting criteria at that time. Conditions will warm and dry with gusty winds mixing down from south to north, so the more north areas might take a bit more time (mid-afternoon) to hit Red Flag criteria. There is a slight risk for severe thunderstorms in the far northeast corner this afternoon/evening with MLCAPE 500-1000 J/kg, low level moisture, and decent shear. However, this is a low chance (<20%). There is a higher chance that storms initiate east of Colorado. && .SHORT TERM /Through tonight/... Issued at 309 AM MDT Mon Jun 17 2024 An upper level trough remains over the west coast. Warm and dry conditions will occur once more today across northeastern Colorado. It is possible a weak front will arrive this morning increasing winds just before mid-day. It seems this front will only result in southerly flow at the surface for the plains. Given that a few models such as the GFS and NAM display warm air advection, decided to increase temperatures this morning and afternoon along the eastern plains. Expect afternoon highs a few degrees warmer than yesterday. Generally, 90s for the plains and urban corridor. Mountains and valleys increase between 65-77F. Not confident in widespread heat impacts today especially due to widespread wind gusts up to 25-35 mph where the warmest afternoon temperatures reside thus no Heat Advisory. Considering widespread wind gusts up to 35 mph, majority of the forecast region will drop to humidities as low as 10-16 percent excluding the northeastern corner. The combination of these winds and low humidities will bring critical fire weather conditions today for parts of the urban corridor, plains, Palmer Divide, South Park, and Grand/Summit counties. A Red Flag Warning is in effect starting 11 AM to 9 PM MDT this evening. Tonight, as the next upper level system sweeps north of us, northwesterly winds will increase near the Wyoming Colorado border. Those traveling across I-25 could experience wind gusts up to 40-45 mph overnight. && .LONG TERM /Tuesday through Sunday/... Issued at 309 AM MDT Mon Jun 17 2024 SW flow aloft will remain over the area on Tue. Overall, the airmass behind a frontal system will be drier and stable thru the aftn, across much of the area. Still can`t rule out a few higher based storms over the higher terrain where some instability will exist. As far as highs, readings will be in the mid 70s to lower 80`s across the plains. For Tue night, a secondary surge of cooler air will move across the plains. There is still quite a bit of uncertainty as to how much low moisture there will be across the plains. It still looks to me like the deeper low level moisture will be to the east and south of the area. If that`s the case then best chc of showers and storms overnight would stay to the east and south. As a result have kept pops in the chc category over most of the plains. On Wed, sfc high pres will be over the area behind the front. This would lead to a stable airmass across the plains as highs only reach the upper 60`s to mid 70`s. Over the higher terrain, there will be some limited MLCAPE so will keep in a chc of aftn tstms. Looking ahead to Wed night into Thu, sfc high pres will gradually shift to the east. This will allow for southeast low level flow to develop with a return of deeper low level moisture. In addition, will begin to see a warm air advection pattern develop, which may lead to some nocturnal shower and tstm development Wed night over the plains. Still don`t have high confidence in this scenario so will keep pops mainly in the chc category. By Thu aftn, should see better MLCAPE across much of the area so expect sct tstms. As for highs, readings will rise back to seasonal levels. For Fri, the flow aloft will continue from the SW. There still should be decent instability so will keep in sct tstms with the highest coverage over the higher terrain. Highs will rise back to above normal across nern CO. By next weekend, a flat upper level ridge will begin to build across the srn Rockies. This will allow for the flow aloft to become more westerly. At this time, there still should be enough moisture and instability around to keep in a chc of aftn storms both days. && .AVIATION /18Z TAFS through 18Z Tuesday/... Issued at 1202 PM MDT Mon Jun 17 2024 VFR conditions expected for the TAF period. SE winds transition to gusty SW winds early this afternoon at the terminals with gusts up to 25 kts. SW winds decrease in the 01-03Z timeframe. A weak front moves southward overnight in the 08-10Z timeframe. It should attempt to transition winds light northerly. BJC may tap into a weak mountain wave with enhanced westerlies after midnight then becoming light northerly early Tuesday morning. E/SE winds are likely Tuesday morning, increasing into the afternoon at 10-15 kts. && .FIRE WEATHER... Issued at 309 AM MDT Mon Jun 17 2024 Critical fire weather conditions are possible this afternoon mainly for parts of the urban corridor, plains, Palmer Divide, South Park, and Grand/Summit counties due to humidity as low as 10 percent. Southwest wind could produce wind gusts up to 35 mph. Fire conditions will improve from Tuesday into Wednesday as a couple of cold fronts bring cooler temperatures and higher humidity to much of the area. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 PM MDT this evening for COZ213-214-216- 239>241-244>247-249. && $$ UPDATE...Mensch SHORT TERM...AD LONG TERM...RPK AVIATION...Mensch FIRE WEATHER...AD/RPK