953 FXUS65 KBOU 180525 AFDBOUArea Forecast Discussion National Weather Service Denver/Boulder CO 1125 PM MDT Wed Sep 17 2025
.KEY MESSAGES...
- Fewer and less intense showers and storms through this evening, decreasing overnight.
- Drier weather Thursday onward, with warmer temperatures beginning Friday.
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.UPDATE... Issued at 801 PM MDT Wed Sep 17 2025
The forecast remains largely on track this evening, with only minor adjustments made to the PoPs. Have trimmed them slightly across parts of the plains, particularly south of the Cheyenne Ridge, where persistent northerly winds are expected to limit precipitation potential.
Despite the upper-level low remaining over the region, we are already observing increasing atmospheric stability, which should further suppress convective development overnight.
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.DISCUSSION /Through Wednesday/... Issued at 259 PM MDT Wed Sep 17 2025
The upper low over southeast Wyoming will be drifting southeast overnight. There`s a pocket of cooler air aloft and a bit of QG lift that will come along with it. We had been favoring the southern part of our area for better instability and higher PoPs overnight, but the situation is more complicated than that. The surface will likely wind up warmer in the south, and showers that form over the relatively warm Front Range and central mountains will drift that way. But the cooling aloft will be better in the north along with the moisture and lift. So we`re bumping up PoPs a bit in the north and dropping them a bit in the south. CAPEs are lower today, around 400-600 J/kg so enough for some thunder but we shouldn`t have anything strong. Weak lift persists much of the night, so we may just see a gradual fade in the shower activity.
Thursday morning drier and warmer air aloft will be moving over, but there will still be some cool moist air at low levels. There will likely still be some stratus over the plains that will take a while to break up. It`s not clear if Denver will still have cloud cover or if it will be drifting east by morning, but we`ll likely have plenty of sun in the city much of the day. There may still be enough moisture for some weak mountain convection in the afternoon, but the drying will be continuing.
The models are trending less amplified with the upstream ridge over the weekend, bring a vigorous shortwave that may have a closed low embedded in it down into the plains early next week. While there`s an upward trend in the dynamic strength of this system and it may be near to us, it`s in a relatively dry and stable environment. The NBM hasn`t really responded to this trend yet, keeping PoPs low with only a little cooling in the Monday/Tuesday time frame. We`ll have to keep an eye on the possible need for a greater impact, but given the surroundings it still probably won`t be much. It still looks like there will be a high amplitude ridge west of us by the middle of next week, so we`ll likely continue to have dry weather and seasonal temperatures.
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.AVIATION /06Z TAFS through 06Z Friday/... Issued at 1123 PM MDT Wed Sep 17 2025
SCT-BKN clouds with bases 040-070 are expected to persist for the next 3-5 hours for Denver area terminals before dissipating early morning. Light southwesterly drainage flow will become progressively more established through the overnight hours, before a period of light and variable winds in the morning prior to transition to NE flow near 18-19Z as daytime mixing increases.
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.BOU WATCHES/WARNINGS/ADVISORIES... None.
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UPDATE...Bonner DISCUSSION...Gimmestad AVIATION...Rodriguez
NWS BOU Office Area Forecast Discussion