Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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460 FXUS65 KBOU 061141 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 541 AM MDT Thu Jun 6 2024 .KEY MESSAGES... - Slight cooling today, back to 90F+ across the plains and I-25 Corridor Friday - Minor snowmelt impacts from rising streams, mainly in Grand County - Increasing chances for showers and thunderstorms this weekend into early next week, along with cooler temperatures. A couple storms could be strong. - Gradual trend towards warmer/drier weather towards the middle of next week. && .SHORT TERM /Through tonight/... Issued at 344 AM MDT Thu Jun 6 2024 Water vapor imagery shows the forecast area under a dominating and dry upper level ridge. We did have a weak frontal push in the late night hours, which will help us start off a little cooler, and likely stay a couple degrees cooler than yesterday. In fact, the latest guidance is pointing at mid to upper 80s for highs across the plains and I-25 Corridor due to the slight low level cooling and upslope flow that we`ll experience today. With regard to precip chances, the only real chance of any showers or storms will be in the Park County area late this afternoon, perhaps spilling east onto the crest of the Palmer Divide this evening. That`s the easiest place to get enough influence of the low level moisture advection combined with the weakest cap. But even then, don`t expect anything more than isolated coverage of generally weak convection. && .LONG TERM /Friday through Wednesday/... Issued at 344 AM MDT Thu Jun 6 2024 Ensemble guidance is in good agreement for the return of moisture to the region by the weekend, bringing increased shower/storm chances through early next week. Friday, the upper ridge shifts further east over Colorado accompanied by a mid-level thermal ridge. Warming 700mb temperatures and downslope flow to support highs in the upper 80s to low 90s for plains/urban corridor. A plume of moisture will also begin to round the ridge, nudging into Colorado. Model soundings show moisture more- so in the mid-levels. A weak shortwave trough also moves through the NW flow aloft by the evening. This will bring back instability with MLCAPE values around 500-1000 J/kg across the plains. Scattered showers and thunderstorms return to the forecast by Friday afternoon. The eastern plains may see a few stronger to severe storms with hail and winds are the primary hazards. By the weekend, anomalous moisture reaches the forecast area as ensemble mean precipitable water values increase to 150-180% of normal. Model soundings also show a deeper moisture profile with increased lower level moisture. Details still remain a little fuzzy on the exact timing and strength of a shortwave or two that moves through in the Sat-Mon timeframe. There should again be sufficient instability around (500-1000 J/kg MLCAPE) on Saturday, with better instability shifting more west into the urban corridor. We`ll have to see if a stronger consensus arises on the timing of the waves which would support a more organized push of showers/storms. Models are starting to hint at Sunday being more stable in between the waves which would keep precipitation chances slightly lower and the higher chances more south. The unsettled pattern continues through Monday with scattered showers and storms. It will also be cooler over the weekend into early next week as well with highs in the mid 70s to near 80 across the urban corridor and plains. By mid-week next week, the upper pattern favors a warming and drying trend as another ridge builds in from the west. && .AVIATION /12Z TAFS through 12Z Friday/... Issued at 541 AM MDT Thu Jun 6 2024 VFR will persist through the TAF period. Light and variable winds will prevail through about 15Z. Then there will be a transition to normal diurnal easterly flow around 10 kts which will hold 17Z-01Z. Winds will then begin their normal return to south/southwest flow during the overnight at KDEN and KAPA, but speeds will average close to 15 knots for the 05Z-12Z period. && .HYDROLOGY... Issued at 344 AM MDT Thu Jun 6 2024 Mountain snowmelt and runoff accelerated yesterday as seen by a spike in river/stream gauges in the high country. The main focus is up in the headwaters of the Colorado River including the Fraser River where minor flooding (minimal impacts) of a few low lying areas anticipated. Many other streams, including those in the Front Range, are seeing quick rises as well but remain well below Action Stage. That said, flows along Clear Creek, Boulder Creek, and the Cache La Poudre to name a few are on the rise. Continue to respect the fast moving and cold flows. In addition, there is a limited threat of burn area flash flooding this weekend into early next week, as an anomalously moist airmass advects into the region. Scattered showers and thunderstorms are forecast most afternoons, which would be capable of brief heavy downpours. However, mean cloud-layer flow should be strong enough (15-25kt) to keep the overall chances of heavy rain/flash flooding low. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Barjenbruch LONG TERM...Mensch AVIATION...Barjenbruch HYDROLOGY...Barjenbruch