Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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652 FXUS65 KGJT 151131 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 531 AM MDT Wed May 15 2024 .KEY MESSAGES... - Scattered to widespread showers and thunderstorms are expected again this afternoon, with gusty outflows, brief heavy rain, and small hail the main threats. - Drier and warmer conditions move in for tomorrow onward, with temperatures running around 5 degrees above normal. && .SHORT TERM /THROUGH THURSDAY/... Issued at 237 AM MDT Wed May 15 2024 The few light showers lingering over the Continental Divide and into southeast Utah will slowly dissipate as we head toward daybreak this morning as the shortwave driving this activity shifts to the east. Behind this wave, some drier air and weak subsidence are trying to push in, leading to clearing skies across northeast Utah and portions of northwest Colorado. The next wave will round the base of the trough around midday, providing some modest dynamic forcing, in addition to orographic lift and diurnal heating. The question is, will the drying this morning put a bit of a damper on storm coverage this afternoon? Models seem to think so, with forecast PoPs really keeping activity confined to the higher terrain along the Divide. Although, models do have a habit of drying things out far quicker than reality, leading to underdone precipitation. That may indeed be the case today, with activity winding up more widespread that current guidance would lead us to believe. The best coverage will likely still be along the Divide, where the best moisture and lift will be located. But other usual spots for storm genesis, such as along the Bookcliffs, will likely spawn a shower or two this afternoon. These showers and storms will be capable of producing gusty outflow winds, brief heavy rain, small hail, and lightning. As this trough is moving overhead, the cutoff low that has been lingering over SoCal will finally begin shifting east. Model guidance has this cutoff finally phasing with the northern stream low this evening, leading to a shift in storm focus to the southern mountains through about midnight tonight, after which activity will slowly begin to taper off. This now elongated trough of low pressure will finally shift east of the Divide tomorrow morning, with ridging and much drier air building in across the northern half of the area. Moisture will linger longest over the San Juans, although some may sneak up into the central mountains as well. Daytime heating will act on this moisture to produce some isolated to widely scattered showers and thunderstorms tomorrow afternoon, with the usual threats of gusty winds and brief heavy rain once again anticipated. Temperatures today will be near normal as some slightly cooler air is advected in, along with showers and clouds. Temperatures return to around 5 degrees above normal tomorrow under warm air advection and clearing skies, with the exception of the southern and central mountains, which will be a bit cooler. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 237 AM MDT Wed May 15 2024 The high latitudes will once again fold southward into the mid latitudes as we end out the week with a strong trough arriving to the N.Rockies by early Friday...shoving the ridge back into the Pacific. This is a trend that will continue well through this forecast period and beyond. The CPC outlooks reflect this with better probability of below normal temperatures across much of the West over the next 6 to 10 days. The bulk of the stronger QG forcing remains well to North initially with the cyclonically curved jet only dropping into central Wyoming. However moisture transport vectors show Pacific moisture being pulled inland on the fringe of the jet which arrives during peak heating Friday. There is a hint of a weak frontal boundary being pushed across the northern CWA for low level forcing and isolated storms will be the result. By Saturday the Southern stream arrives to the SW CONUS leading to a downstream confluence of the split flow over the central Rockies region. Moisture pooling near the above mentioned boundary and the arrival of the SubTrop jet to the 4 Corners looks to excite the atmosphere enough for an uptick in afternoon convection Saturday which will likely linger into the early morning hours on Sunday. As heights lower to the West and the split flow pattern merges Southwest flow increases downstream over our CWA after sunrise on Sunday. This looks to force in some drier air with the bulk of the thunderstorm chances lifting to or north of our CWA border with Wyoming. Above normal temperatures can be expected to persist through the weekend at least. Models then diverge quite a bit on how the Western trough absorbs and spits out the high latitude energy with some vast differences in timing attm. Either way cool and unsettled weather looks like it will take hold again as we head into next week. This is probably good news for runoff season with some snow coming off during the warmer days through the weekend then tapering off next week. Who knows...depending no how this western trough pattern plays out we may just add some back before it`s over. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 529 AM MDT Wed May 15 2024 The shower and thunderstorm activity has waned near sunrise and should hold off until mid-day when heating gets it going again. VFR should hold over the next 24 hours and with a lesser coverage of showers today limited mention in the TAF forecast attm. However gusty outflow winds will continue to be a threat and if a shower/storm moves over the airfield ILS and a low probability chance of MVFR is possible through sunset. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BGB LONG TERM...15 AVIATION...GJT