433 FXUS65 KBOU 161123 AAB AFDBOUArea Forecast Discussion...UPDATED National Weather Service Denver/Boulder CO 523 AM MDT Tue Sep 16 2025
.KEY MESSAGES...
- More active today, with scattered afternoon thunderstorms or most areas. A few may be strong to severe in the plains.
- Shower/t-storm potential will linger into Wednesday, with cooler conditions through Thursday.
- Drier weather Thursday onward, with warmer temperatures beginning Friday.
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.DISCUSSION /Through Monday/... Issued at 150 PM MDT Mon Sep 15 2025
Water vapor satellite imagery showing a large upper level trough over the northwest part of the country with drier air and weak ridging over Colorado. Other than a couple high based showers, dry conditions are expected through tonight. Satellite imagery is also showing a strong shortwave trough spinning near the Idaho/Wyoming border within the large upper level trough. There is also a second weaker shortwave trough near the Washington/Oregon border. This second one will track southeast bringing scattered showers and thunderstorms Tuesday afternoon and evening. A weak cold associated with this system will bring cooler temperatures Tuesday. The cold front stalls over far eastern Colorado Tuesday. Along and east of this CAPE reaches 2000 J/kg, which may lead to a few strong to severe thunderstorms. On Wednesday, this trough closes off somewhere over northeast Colorado to western Nebraska and becomes part of the larger upper level trough over the central part of the country. For Wednesday, temperatures cool more with showers likely. SBCAPE is reaches up to 500 J/kg, so we should see isolated to scattered storms during the afternoon and early evening.
Come Thursday we will see a broad upper level low over the Northern and Central Plains and ridging to the west. Across Colorado, a north to northwest flow aloft will prevail. Cool temperatures will persist again with highs in the 60s across northeast Colorado. Scattered showers will be possible Thursday, but rainfall amounts should be light.
The ridging off to the west slides eastward Friday and should be centered over Colorado late in the day. Expect dry conditions to return to the area with temperatures warming into the 70s over northeast Colorado.
For the weekend models trend towards a zonal flow, but differ on the placement on the shortwave troughs and ridges. Chances for precipitation look low under this pattern, so will keep the forecast mostly dry. Temperatures will be near to slightly above normal with highs in the upper 70s to mid 80s over northeast Colorado. For early next week, models indicate ridging builds over the southwest part of the country and could extend eastward into the Rockies. Expect dry conditions and above normal temperatures under this pattern.
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.AVIATION /06Z TAFS through 06Z Wednesday/... Issued at 1128 PM MDT Mon Sep 15 2025
VFR conditions will prevail for all terminals through at least 06Z Wed. A frontal passage 16-17Z will bring reinforcing N/NE winds, with peak gusts 20-25 kts possible with and immediately behind the front.
Near 20Z, +/- 1 hr, -SHRA and -TSRA will develop over the Denver metro and push east. Coverage looks marginally sufficient to support TEMPO group for the terminals, favoring 21-01Z. More isolated convective showers may linger beyond that through the late evening hours. Gusty outflows to ~30 kts will be possible in the vicinity of any -TSRA.
Winds should become considerably lighter overnight, generally retaining a NW component but with some directional variability likely at times. Some lower stratus may fill in early Wed AM, mainly due north of Denver, but spatial extent is questionable. Latest guidance has reduced the low CIG potential, but will retain SCT decks ~020-030 in TAFs for now to message this potential.
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.BOU WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION...Meier AVIATION...Rodriguez
NWS BOU Office Area Forecast Discussion