Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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537 FXUS65 KGJT 051035 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 435 AM MDT Sun May 5 2024 .KEY MESSAGES... - Very strong winds for much of eastern Utah and western Colorado today, with gusts up to 65 mph for the valleys and 80 mph for the mountains. - A strong spring storm will bring widespread precipitation tonight and Monday with significant mountain snow expected across the northern Colorado ranges. Light snow accumulations are possible for the higher valleys by sunrise Monday. - Much cooler and unsettled weather will be the rule for the rest of the week ahead as several disturbances keep mountain showers in the forecast most afternoons. && .SHORT TERM /THROUGH MONDAY/... Issued at 435 AM MDT Sun May 5 2024 The deep mid-level closed low which has been the prime topic in previous discussions was centered over the Oregon-Nevada-Idaho triple point at 09Z. Ahead of the system the height gradient had begun to strengthen. Models continued to show anomalously strong southwest winds of 40 to 50 kts at the 700 mb level shifting over eastern Utah by sunrise as the low tracks eastward. The strong winds aloft will spread into western Colorado during the day as the low moves to extreme northwest Utah by early evening. Deep mixing will help transfer stronger winds aloft to the surface resulting in very windy conditions. As pointed out in the previous discussion, today`s winds stand out climatologically as occurring only once every ten years or more, so it doesn`t appear this will be your garden variety windy day. Wind Warnings and Advisories issued by the day shift appeared to be on track and made no adjustments. Precipitation ahead of the cold front will be limited to mainly virga except for over the eastern Uinta Mountains where showers become likely during the afternoon. Showers become widespread tonight as the base of the low tracks across northern Utah driving the cold front eastward across the forecast area and onto the high plains by sunrise Monday. Lift from the surface to jet level will be maximized during this period and as a result, mountain snow becomes heavy with rates exceeding an inch an hour for the northern ranges. As the colder air filters in, snow levels lower below mountain bases and light snow accumulations are expected in the higher valleys by Monday morning. Meanwhile, winds shift to the west behind the front and weaken, but remain brisk. The low lifts to the northeast over the northern High Plains on Monday, though lingering moisture, instability and orographics is expected to keep snowfall going over the northern and central Colorado Mountains late into the day. QPF values came up with the latest model runs which seemed reasonable given the strength of this system. Amounts across the northern Colorado mountains were solidly in the 5 to 10 inch range with local amounts up to 18 inches indicated over the higher ridges. Meanwhile, though amounts came up for the central and southern mountains, higher amounts seemed to be limited to only the highest areas which limits impacts. Consequently, issued a Winter Weather Advisory for the Elkhead Mountains, Park Range and Flat Tops from 00Z/Mon to 00Z/Tues but held off elsewhere. The day shift is encouraged to consider whether advisories need to be expanded. Since the area remains in the warm sector of the storm today, afternoon highs will remain mild, though increased clouds are expected to shave a couple of degrees off Saturdays max temperatures. The arrival of colder air tonight will drive temperatures down across the region with lows Monday morning expected to run close to 10 degrees below normal while afternoon highs fall somewhere between 10 to 15 degrees below normal. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 435 AM MDT Sun May 5 2024 Lingering troughing and favorable orographics will continue to act on residual moisture and keep the snow showers going across the northern Colorado mountains Monday night. Any additional accumulations are expected to be light. Another wave embedded in the broad westerly to northwesterly flow will dig across the northern Four Corners states and bring another round of snow showers across parts of northeast Utah, northwest Colorado, and the northern and central Colorado mountains on Tuesday. Additional minor accumulations are a good bet, particularly across the Flat Tops, Elkheads, and Park Range mountains. Given the time of day and year, impacts should be low. Most snow showers will come to an end by late Tuesday evening, but some may linger across the northern mountains through Tuesday night. Elsewhere, mainly dry weather will prevail under partly cloudy skies. The wave will also drag a strong cold front through much of eastern Utah and western Colorado, ushering in a much colder air mass in its wake. Latest 00Z model guidance is advertising 700mb temperatures falling to between -8C and -12C by Wednesday morning, which is quite cold for this time of year. The unseasonably cold air mass will make for very chilly overnight lows Tuesday night into Wednesday morning, with widespread temperatures nearing or dropping below freezing. Even some lower elevations like the Grand Valley and Uncompahgre Basin may near 32 degrees, which could be an issue for budding vegetation. For historical context, the record low temperature at the Grand Junction Regional Airport for Wednesday morning (May 8th) is 33F, set back in 1979. With near record cold temperatures possible, those with agricultural interests will want to pay close attention to the forecast over the next few days as freeze headlines may be necessary. For Wednesday and beyond, the bottom line is that cool and unsettled weather is likely to persist across the northern tier of eastern Utah and western Colorado as well as the Continental Divide mountains... with mainly dry weather and a slow warm up likely elsewhere. Ensembles are still showing a fairly complicated synoptic pattern developing later next week with a possible Rex block featuring a ridge over top a cut-off low setting up over the Western CONUS. As it stands, it looks like high elevation and mountain showers are possible almost daily through the end of the long term period, with the exact position of the Rex block determining how widespread those showers may become (particularly Thursday and Friday). For now, will heavily lean on the blended guidance until we get closer and details become more clear. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1140 PM MDT Sat May 4 2024 Mid and high level clouds will continue to increase overnight and through the day on Sunday out ahead of an approaching cold front. Ahead of the front, very strong winds will develop out of the south and southwest by mid-morning and continue through the afternoon and evening. Sustained winds of 25 to 35 kts with gusts of 40 to 50 kts will occur. A few showers may develop across the higher terrain ahead of the front as well, but the heaviest and most widespread precipitation will push through along the front mainly after 00Z Sunday evening. As a result, reductions in ceilings and visibility are likely Sunday night. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...High Wind Warning from 8 AM this morning to midnight MDT tonight for COZ001-006-011-020. Wind Advisory from 8 AM this morning to midnight MDT tonight for COZ002-007-008-021-022. High Wind Warning from 6 AM this morning to midnight MDT tonight for COZ003-017. Winter Weather Advisory from 6 PM this evening to 6 PM MDT Monday for COZ004-013. UT...High Wind Warning from 8 AM this morning to midnight MDT tonight for UTZ022-024-027-029. High Wind Warning from 6 AM this morning to midnight MDT tonight for UTZ025-028. Wind Advisory from 6 AM this morning to midnight MDT tonight for UTZ023. && $$ SHORT TERM...NL LONG TERM...MDM AVIATION...TGJT