Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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362 FXUS65 KGJT 181745 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1145 AM MDT Sat May 18 2024 .KEY MESSAGES... - Warm and breezy this weekend with temperatures remaining at least 5 to 10 degrees above normal. - Isolated to scattered showers are storms are expected today and Sunday. The higher terrain along the Divide will be favored with gusty outflow winds and small hail being the primary concerns from storms. - A larger system moves through early next week resulting in cooler and wetter conditions. Drier weather looks to return by midweek. && .SHORT TERM /THROUGH SUNDAY/... Issued at 218 AM MDT Sat May 18 2024 This morning`s synoptic pattern features a prominent trough of low pressure extending south from the Yukon with several waves of energy wrapping around this parent system. The first, which was responsible for yesterday`s breezy conditions and light showers up north, has lifted into the Northern Great Plains. Upstream, the next trough is just shy of the Washington border, while the Polar jet remains firmly settled over the remainder of the northwest CONUS. Flow aloft across western Colorado and eastern Utah will remain zonal as we start the day, gradually shifting to the southwest by this evening. The reason for this will be two-fold; it will not only be in response to the trough dropping into the Pacific Northwest, but also the progression of a separate shortwave inland across the Desert Southwest. We will finally begin to see some better moisture advection during this transition with PWATs beginning to increase from southwest to northeast throughout the day. The Four Corners will see PWATs that are 130 to 150 percent of normal by midday before this spreads into the central zones (and even climbs to almost 180 percent of normal) this evening. The northern third of the forecast area will rebound from their slightly below normal PWATs early this morning to around 150 percent of normal tonight. Ahead of the shortwave orographics will be the primary lifting mechanism but, with daytime heating and the uptick in available moisture, we can still expect to see scattered showers and thunderstorms throughout the day. Even though the higher terrain will be favored, weak lift provided by some embedded ripples in the flow will allow for some drift into the adjacent valleys, most notably in southwest and west-central Colorado. Strong outflow winds will be possible with storms with gusts of 40 to 50 mph likely. Outside of convection today, we can expect mostly to partly sunny skies with occasional breezy conditions as 700mb winds remain in the 20 to 25 kt range. The shortwave will begin to push through before stalling later tonight, resulting in nocturnal showers north of I-70 with continued partly to mostly cloudy skies elsewhere. Upper level troughing becomes more pronounced across the entirety of the western CONUS on Sunday, but the boundary will remain stalled up north. As a result, look for another round of afternoon showers and storms up north with generally dry weather elsewhere. The entirety of the area will experience breezy conditions as the gradient tightens overhead with gusts of 25 to 35 mph expected throughout the day. Temperatures will continue to be unseasonably warm both today and tomorrow. We were close to hitting the 90 degree mark for some of the lower desert valleys yesterday and, looking at the potential to exceed 90 degrees this weekend, we should still be able to hold off. The probability is less than 5 percent for the southwest and west-central Colorado valleys with a 10 to 20 percent chance of exceeding 90 degrees in southeast and east- central Utah. Some localized pockets of 30 to 50 percent are there but, overall, nothing too impressive. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 218 AM MDT Sat May 18 2024 A deepening trough to our northwest will act upon residual moisture and a stalled frontal boundary to keep showers going across portions of northeast Utah and northwest Colorado Sunday night into Monday. Elsewhere, mainly dry, but breezy weather will be the rule, particularly during the afternoon hours on Monday. This is in response to the tight pressure gradient and a 110kt 250mb jet draped overhead in between the trough to our northwest and a ridge to our southeast. Gusts up to 45 mph will be common. Monday night into Tuesday, the trough to our northwest digs across the region with a strong cold front and brings more widespread precipitation to the CWA, especially in the higher terrain. The exceptions to that may be across extreme southeast Utah and southwest Colorado where the trough has less influence and it`s more likely to stay dry. Despite the cooler air associated with the trough, snow levels are progged to stay mostly above 10,000 feet. Even at and above those elevations, snow accumulations are likely to be minor with minimal to no impacts. The storm system exits to the east Tuesday night into Wednesday, taking most of the precipitation with it. Showers may linger the longest across the northern Colorado mountains given unstable northwesterly orographics, but even these should dissipate by early Wednesday afternoon. Any break in the action is not expected to last long as another couple of shortwaves are forecast to skirt across the north through the end of the long term period. This should lead to more showers across northeast Utah, northwest Colorado, and the high terrain along the Continental Divide Thursday and Friday. Temperatures through next week are expected to start off near to a few degrees above normal on Monday before falling well below normal for Tuesday and Wednesday. Temperatures moderate some for Thursday and Friday, but are still expected to stay near to below normal for this time of year. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1145 AM MDT Sat May 18 2024 Skies will be partly cloudy south of I-70 with scattered showers and isolated thunderstorms moving across the central and southern areas, favoring high terrain. Some drift of showers into lower valleys is possible after 21Z. The area of scattered showers and storms will shift northward this evening with activity continuing overnight across northern areas. Gusty outflow winds will be the primary concern with any shower activity today with CIGS remaining above ILS breakpoints and no significant reductions to VSBY or CIGS expected. Outside of shower activity, winds remain breezy this afternoon with gusts to 30 kts possible. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...MDM AVIATION...MDA