Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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517 FXUS65 KGJT 251000 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 400 AM MDT Wed Sep 25 2024 .KEY MESSAGES... - Dry and unseasonably warm conditions are expected for the remainder of the week. Near-record highs are expected from Thursday through the weekend. && .SHORT TERM /THROUGH THURSDAY/... Issued at 359 AM MDT Wed Sep 25 2024 High pressure remains overhead today and tomorrow resulting in continued warm and dry conditions. Today`s temperatures are forecast to be a few degrees warmer than yesterday with abundant sunshine. The additional 2-3 degrees will lead to near-record temperatures in some locations. For example, today`s daily record high temperature is 89 at GJT and the forecast currently sits at 88. Seasonably warm conditions amplify again tomorrow with afternoon highs around 10 degrees above normal for late September. As a result, records will once again be on the line. Winds remain light and terrain driven through the short term forecast. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 359 AM MDT Wed Sep 25 2024 High pressure across the West, though flattened by the mid-level shortwave trough which moved across the northern Rockies on Thursday, will persist on Friday. However, a couple of subtle changes in the pattern are expected to bring some light shower/thunderstorm activity along the southern and central mountains along the Continental Divide Friday afternoon through early Friday evening. First, the passage of the trough causes the 700 mb high to recenter over the eastern Colorado Plains resulting in convergence along the Divide. Secondly, jet level heights take on a decided cyclonic curvature overhead as they tilt toward the deepening low over the east-central U.S. where remnant moisture from TS Helene merges with a quasi-stationary low already in place there. Since the 315 K isentropic surface didn`t indicate an advection of moisture into the area, and in fact showed moisture was already in place on Thursday (Thursday forecast is dry), it appears these factors, when combined with above normal warmth, will be the drivers of moist convection. Per the previous discussion, expect this activity will mainly occur on the eastern side of the Divide, but can`t rule out some development on the western Colorado side. NBM was a bit slow to pick up on these developments, but expect PoPs will rise with subsequent runs as all operational models generated QPF over the aforementioned area during this time frame. This activity is unlikely to pose much of a threat to the region as moisture depth appears insufficient for heavy rain and very little shear indicated to sustain organized convection. Therefore, expect the main threat will be gusty outflow winds as high as 45 mph. For the remainder of the forecast area on Friday, above normal warmth will be the big story with record or near record highs expected for some locations. The low with remnants of Helene will persist over the east-central states through the weekend essentially preventing the area of high pressure over the West from moving off. In fact the high retrogrades just a bit and as a result, temperatures will remain near record levels with little chance for precipitation. A trough moving over the northern tier states flattens the ridge and by Monday return flow towards the Divide from the east brings the potential for isolated showers and/or thunderstorms during the afternoon/early evening both Monday and Tuesday. Again, this activity isn`t likely to be impactful and NBM just hinting at moist convection at this time. Meanwhile, highs will continue to run well above normal with highs continuing to challenge records. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 1012 PM MDT Tue Sep 24 2024 High pressure will continue with VFR conditions at terminals through the TAF period. Light terrain driven winds and clear skies will continue. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...KAA LONG TERM...NL AVIATION...TGJT