560 FXUS65 KBOU 081110 AFDBOUArea Forecast Discussion National Weather Service Denver/Boulder CO 510 AM MDT Mon Sep 8 2025
.KEY MESSAGES...
- Isolated, high based showers/storms today. Very little to no rainfall, but gusty winds of 40-50 mph possible.
- Better chances for showers/storms (and rainfall) mid to late next week.
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.DISCUSSION /Through Sunday/... Issued at 207 PM MDT Sun Sep 7 2025
Scattered showers and thunderstorms will continue to track eastward across the area. Brief moderate to heavy rain and winds to 40 mph will be possible with most of this activity. Across far eastern Colorado, better moisture and instability will reside east of a surface trough and may lead to a couple strong to briefly severe thunderstorms through the early evening hours.
Upper level ridging slides east over Colorado for Monday. This will bring warmer and slightly drier air with it. Models in good agreement showing very little rainfall, but the hi-res models show high-based showers and a few weak storms Monday afternoon. So we likely see isolated showers/storms with very little to no rainfall and gusty outflow winds of 40-50 mph. Temperatures trend warmer as well with highs in the mid to upper 80s over northeast Colorado.
The ridge slowly slides east of the state Tuesday with southwest flow aloft prevailing behind through Thursday and beyond. This will keep temperatures above normal with highs in the mid to upper 80s over northeast Colorado. Would not be surprised if we end up seeing a few low 90s as well. Precipitable water values are slightly above normal ranging from 0.75 (in) to one inch over the plains. Enough moisture for isolated/scattered showers and thunderstorms. There is an uptick in moisture for Thursday along with a shortwave trough. This is expected to lead to better chances for showers and thunderstorms.
For Friday and next weekend, the upper level ridge off to the east amplifies and stretches into the Great Lakes and possibly into Canada. This will start to block the flow aloft to the west across western North America. Models generally show some sort of an upper level longwave trough or closed low over western Canada and the northwest part of the country. A lot of uncertainty what the main pattern will look like. Colorado should be at the base of whatever trough/low that forms off to the northwest. This is expected to keep temperatures at or above normal. Precipitation chances will depend on the amount of moisture that is able make it into the region. Southwest flow aloft could transport desert air into the area, so will generally keep PoPs in the 10-30 percent range at this time.
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.AVIATION /12Z TAFS through 12Z Tuesday/... Issued at 510 AM MDT Mon Sep 8 2025
VFR conditions will persist, but main concern will be gusty and variable outflow winds late this afternoon into early evening. For this morning, we still expect a transition from SW-W-NW 12Z-17Z and then more northerly 17Z-01Z. While the airmass will be drier, there will likely be just enough moisture and strong daytime heating for isolated high based showers/sprinkles with gusty outflow winds. The threat of thunder is less than 15%. Thus, we`ll go with PROB30 for light showers and gusty winds to 35 kts in the most likely time frame of 21/22Z-02Z.
After 02Z, skies will clear again with winds transitioning to normal diurnal south/southwest through 06Z. Those winds will then persist through at least 12Z Tuesday morning with speeds generally 8-12 kts or less.
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.BOU WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION...Meier AVIATION...Barjenbruch
NWS BOU Office Area Forecast Discussion