Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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167 FXUS65 KGJT 172023 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 223 PM MDT Fri May 17 2024 .KEY MESSAGES... - Warm and breezy conditions are expected through the weekend. Temperatures will remain at least 5 to 10 degrees above normal. - A series of systems will bring daily showers and thunderstorms Saturday and Sunday afternoon. Gusty outflows and small hail will be the main concerns. - Cooler, unsettled weather will prevail early next week before drier and warmer conditions return by midweek. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 223 PM MDT Fri May 17 2024 A weak shortwave will track across the north along a weak frontal boundary that will be draped across the northern Colorado and Wyoming border. We are already seeing increasing cumulus development and the hi-res CAMs are indicating some isolated showers and storms developing late this afternoon across the north, favoring higher terrain. This boundary is also resulting in a tightened surface pressure gradient which is lending itself to breezier winds with gusts up to 35 mph observed at sites mainly north of I-70. Gusts 25 to 30 mph are being observed elsewhere. Any shower and storm activity as said earlier looks to remain isolated with gusty outflow winds from any virga enhancing the already breezy surface gusts as low levels remain dry. Temperatures today continue to warm with highs at least 5 to 10 degrees above normal, and a few degrees warmer than yesterday. On Saturday, our CWA will be caught in between a split flow pattern with the polar jet remaining to our north across the Intermountain West into Wyoming, while the subtropical jet remains south of the Four Corners across SoCal through Arizona and New Mexico. The flow shifts to southwesterly ahead of a shortwave trough that will move through the area Saturday afternoon and evening. We can expect an increase in shower and thunderstorm coverage with scattered showers and storms, favoring high terrain initially with some drifting into adjacent lower valleys late in the day. Hi-res CAMs tend to favor development along the central portions of the area initially with the focus shifting towards the northern portions of the area by Saturday evening. The presence of embedded shortwaves within the flow may trigger storms to last into Saturday night, especially across the north. Moisture levels take a bump up to 140 to 160 percent of normal PWAT on average, equating to a value of around 0.5 to 0.7 inches. Gusty winds remain a threat but wetting rain chances also increase, although the QPF output looks fairly minimal, which makes sense as the atmosphere usually takes some time for the low levels to saturate with the initial influx of moisture. Higher terrain remains favored for activity but enough motion exists for storms to deviate and drift off terrain into adjacent valleys. Temperatures remain warm on Saturday as WAA continues in the southwest flow with highs about 4 to 8 degrees above normal, so slightly cooler than today given increasing clouds and shower potential. Western Colorado remains in the left exit region of a 90 kt jet streak that arrives with the shortwave trough, south of the Four Corners, associated with the subtropical jet. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 223 PM MDT Fri May 17 2024 On Sunday, a plume of moisture will stretch over northern portions of the forecast area. A weak front may also be draped across the same area due to a shortwave way up in the Northern Plains. The front and moisture looks to support showers and storms mainly during the afternoon and evening. These features may stall on Monday as the trough deepens to our west. Therefore, the chance for showers and storms lingers for the northern half of the area. On Monday night into Tuesday, the western trough comprised of several waves becomes elongated and pushes eastward through our region later in the day. Rain chances expand southward as the system moves through the region. Although, the model consensus of QPF reveals that a majority of the precip falls along and north of I-70 as the main trough passes overhead. Snow levels appear to stay around 10-11 kft, which should keep impacts fairly limited. Conditions dry out Tuesday night as the trough axis swings east of the Divide. Quasi-zonal flow aloft develops in the wake of the trough. This should keep the weather fairly quiet into midweek. Late next week, the main takeaway is that the pattern stays active in the Pacific Northwest keeping our sensible weather on repeat. It should also result in near to below normal temperatures. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1223 PM MDT Fri May 17 2024 VFR conditions under mainly clear skies can be expected the next 24 hours...with a few afternoon gusts over 25 mph possible. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MDA LONG TERM...KJS AVIATION...TGJT