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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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874 FXUS65 KGJT 120552 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1152 PM MDT Sun Aug 11 2024 .KEY MESSAGES... - Showers and thunderstorms continue each afternoon and evening until further notice with gusty outflow winds, small hail, and frequent lightning possible. - Heavy rain rates with storms will bring an enhanced threat of flash flooding and debris flows today through early next week. Saturated soils and steep terrain will be most susceptible to flooding. - Temperatures will remain near to several degrees below normal thanks to the abundance of clouds and showers. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 235 PM MDT Sun Aug 11 2024 Storms have been slow to re-develop this afternoon, but we`ve finally seen some cumulus popping and cells firing in the last hour or so. CAM guidance remains consistent in projecting another active day as a shortwave embedded in the westerly flow aloft tracks across eastern Utah and western Colorado through this evening. This system and the continued presence of a 60 to 70 kt jetstreak overhead will act on the abundance of deep moisture in place as precipitable water values remain in the 0.75 to 0.90 inch range across the western zones with 1 to 1.20 inches in the central and eastern zones. Scattered convection is expected through around 6 PM this evening before a line of showers and storms pushes into southeast and east-central Utah. This swath of precipitation will push through the Western Slope into the midnight hour before another cluster of showers moves into the Four Corners region later tonight. As has been the trend the last several days, storms will be capable of producing gusty outflow winds to around 45 mph, small hail, frequent lightning, and of course periods of moderate to heavy rain. Given the well saturated soils from the last several days of precipitation, flash flooding will be possible. Therefore, a Flood Watch remains in effect through 10 PM this evening. Isolated shower activity is expected to prevail into mid Monday morning before we see daytime heating kick off another round of scattered showers and thunderstorms Monday afternoon. While we`ll lose the jet tomorrow, yet another embedded wave will push through, leading to a couple of stronger storms. Opted to hold off on any additional flood highlights for now but, as always, be sure to stay tuned to the latest forecast for any updates. Nocturnal showers and some embedded storms once again look likely for Monday night as the wave exits to the east while yet another approaches from the west. Outside of any convection through the short term, look for dry weather and passing clouds. Temperatures will begin to drop back to below normal area-wide thanks to the abundance of clouds and showers. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 235 PM MDT Sun Aug 11 2024 The combo of low pressure driving into the PacNW and a monsoon plume will maintain a swath of anamolous moisture stretched along the spine of the Rockies on Tuesday. Widespread showers and storms are expected, once again, with nocturnal storms persisting through the night thanks to upper level support. The trough passage, though, will nudge high pressure into eastern Texas/Louisiana by Wednesday, which, in turn, shifts both sources of moisture east of the Divide. A new area of high pressure builds back in over the Desert Southwest in the wake of Tuesday`s wave. This hot and dry air mass will work its way into the CWA from the southwest, reducing storm coverage across the Four Corners and lower valleys on Wednesday. However, lingering moisture will still be sufficient for afternoon convection to flourish atop the high terrain. Ridge of high pressure shifting overhead on Thursday and Friday will continue to support dry air advection across the Western Slope, as such, we`ll see a downturn in terms of storm coverage and likely rainfall intensity for the end of the work week. Confidence in forecasting the evolution of the high decreases leading into next weekend. Half of the ensemble cluster analyses show above average moisture across the Western Slope by Days 6 and 7, which would allude to the monsoon redeveloping. However, subtle shifts in the high`s center may keep the monsoon plume to our west, and a dry air mass overhead. Temperatures during the long term start off approximately 3 to 8 degrees below normal, thanks to cloud cover and the abundance of moisture. We`ll see a rise mid week through Friday as the new area of high pressure builds overhead, with highs hovering right around normal as we end the work week. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1152 PM MDT Sun Aug 11 2024 Showers with embedded thunderstorms will continue through the early morning hours across southeast Utah and southwest Colorado but will decrease in coverage and intensity, coming to an end by 10Z for the most part. Scattered to broken skies will remain through the morning with storms redeveloping over the high terrain by 18Z Monday. Best potential for storms appears to be across eastern Utah and into northwest Colorado late Monday afternoon into the evening as a disturbance tracks across that area with less coverage across western Colorado with exception of some high terrain sites. && .HYDROLOGY... Issued at 1152 PM MDT Sun Aug 11 2024 Monsoonal moisture will keep showers and thunderstorms over the region through at least mid week with rainfall rates of 1 to 2 inches per hour possible with storms. Given how saturated soils have become over the recent days, there is increased potential for flash flooding and debris flows across much of the area. Stay weather aware over the coming days, especially if you live in terrain vulnerable to flooding, or are planning to recreate outdoors. Stay tuned to the latest forecast updates for any additional flood watches, warnings, and / or advisories over the coming days. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...ERW AVIATION...MDA HYDROLOGY...TGJT