National Weather Service Forecast Discussion |
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006 FXUS65 KBOU 091820 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1220 PM MDT Thu Jul 9 2026 .KEY MESSAGES... - Scattered to numerous thunderstorms through early evening, with a few severe storms possible over the northeast plains. - Prolonged period of very to hot temperatures arrive Saturday, lasting through most of next week. && .DISCUSSION /Through Thursday/... Issued at 1209 PM MDT Thu Jul 9 2026 Airmass has dried slightly over the past 24 hours with precipitable water ~0.60 (in). This is about a tenth inch decrease from yesterday at this time on the Denver ACARS sounding. Water vapor satellite imagery also shows this drier air.One can also pick out a shortwave trough centered roughly over southwest Wyoming. We`ll see a slight increase in moisture and lift this afternoon as this wave advances eastward. MLCAPE has trended lower as well with 400-1000J/kg expected this afternoon across northeast Colorado. The far northeast plains may end up more unstable, up to 1500J/kg. Gusty outflow winds up to 70, brief heavy rain, and small hail are expected to be the main threats today with the highest threat over the far northeast plains. The upper level ridge off to the southwest begins to build northward Friday, causing flow aloft to turn northwesterly. Precipitable water values will be similar to today`s, with slightly less instability. Most of the storms Friday are expected to form over the higher terrain and the Palmer Divide due to a lack of large scale lift tomorrow afternoon. The number of storms is expected to decrease because of this. Northwest flow aloft will push the storms southeastward, potentially leaving the far northeast plains free of storms. The ridge intensifies and will be centered over Utah and Colorado on Saturday. Mid level temperatures will warm, and the airmass will dry. Can`t rule out a stray shower/weak storm over the Palmer Divide and Front Range Mountains/Foothills, but chances are low (less than 20%). Elsewhere, dry conditions will prevail. Surface temperatures warm as well, with highs reaching the 90s across northeast Colorado. For Sunday and next week, the ridge continues to intensify as it tracks northeastward. The 500mb heights are expected to top 600 (DAM) which is impressive, especially since the high will park itself over Wyoming and South Dakota. East to southeast flow around the high will help hold in some low level moisture over eastern Colorado. This low level moisture and the weak upslope easterly winds will likely keep areas along the Front Range and across the eastern plains from breaking records. As for areas west of the Continental Divide, this easterly flow will be a downslope component and help dry the airmass, For Summit and Grand Counties, record highs will be likely and all time records could be reached. Chances for showers and thunderstorms Sunday through Thursday are very low over the higher terrain, and almost nil across the Front Range and eastern plains. && .AVIATION /18Z TAFS through 18Z Friday/... Issued at 1055 AM MDT Thu Jul 9 2026 VFR conditions expected through the TAF period. Winds are currently northeast at all terminals and should continue for the afternoon. Scattered showers and thunderstorms will then develop over the foothills in the next few hours and then trek east throughout the afternoon. Have kept the TEMPO groups as is for all TAF sites, with gusty VRB outflow winds of 35-40 kts possible. Expect convection to end by 00Z, with outflow boundaries mainly keeping winds from the east this evening. Tonight, a bit more westerly wind is possible within the drainage flow. For tomorrow, light northeasterly winds are expected again. Despite a decrease in moisture, another round of isolated showers are possible later in the afternoon. Have introduced a PROB30 for this reason, with gusts of 25 kts. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...12 AVIATION...MAI