Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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948 FXUS65 KCYS 060143 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 743 PM MDT Fri Jul 5 2024 .KEY MESSAGES... - Near critical to critical fire weather conditions expected on Saturday for parts of Carbon and Albany County. A Fire Weather Watch remains in effect for those areas due to gusty winds and low humidity during the afternoon and early evening. - Occasional chances for showers and thunderstorms will exist over the next several days as a series of weak disturbances impact the region. The potential for measurable precipitation will remain quite low. - A few storms may produce small hail and gusty winds on Saturday afternoon with a brief surge of pacific moisture, but the overall potential for severe storms will remain very low. - Gradual warming trend expected through next week with limited precipitation chances. && .UPDATE... Issued at 740 PM MDT Fri Jul 5 2024 In a recent update...went ahead and upgraded Fire Weather Watches for the Laramie Valley and the Upper North Platte River Valley to Red Flag Warnings. Looks pretty clear cut that these two fire weather zones are going to hit Saturday afternoon. As for the other 3 fire weather zones in the watch...decided to continue just in case there is any last minute updates in fuels in those zones overnight or Saturday morning. Updates sent. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 230 PM MDT Fri Jul 5 2024 A pleasant day remains firmly in place across the region this afternoon. Surface temperatures in the 70s to the lower 80s for the high plains, and the higher terrain remain in the 60s in our mountain forecast zones. Breezy winds are also present across the area, with 20-30mph wind gusts being prevalent in our cwa. Water vapor satellite imagery shows very dry air being present in the lower levels, but diurnal heating this afternoon has create an evident swath of fair weather cumulus and cirrocumulus while taking a look at the current GOES-16 visible satellite imagery. Wouldn`t be surprised if a sprinkle or two falls in a few spots before the afternoon is set and done, which could create an elevated wind gust or two higher than 40mph. Mostly clear skies are expected tonight along the I-80 corridor, especially west of the Laramie Range. A passing shortwave disturbance to our north across eastern MT and the Dakotas will create an isolated opportunity for a rumble of thunder and a brief shower overnight into early Saturday morning mainly north of the North Platte River Valley into the NE Panhandle. This will allow for pesky clouds to build and stick around, keeping temperatures elevated overnight in western NE. The shortwave disturbance will propagate to the east across the Northern Plains on Saturday. Weak upper level energy from the Pacific Northwest will combine with moisture, marginal instability, and modest lapse rates by late Saturday afternoon and evening. Chances for isolated showers and thunderstorms late in the day and overnight Saturday will be possible for areas along and east of the Laramie Range. Before this, daytime highs will be warm as several areas see upper 70s to middle 80s. Slightly cooler temperatures will be present for the Snowy/Sierra Madre mountain ranges for those that are planning outdoor extracurricular activities. Very dry air will propagate into our western forecast zones, especially Carbon and Albany County on Saturday. Fire weather concerns will ramp up as breezy to gusty winds of 20-30+ mph are favored. A Fire Weather Watch has been issued to reflect this. Some areas could dip into the single digits for relative humidity, which will cause flashy fuels to burn easily and potentially spread quickly thanks in part to the wind gusts. The main shortwave trough axis will swing through the cwa by Sunday, and bring another cold front to the area. This will cause pleasant conditions as surface High pressure builds into the area behind the cold FROPA by late Sunday. Daytime highs by late Sunday afternoon will struggle to eclipse the 70 degree mark in southeast Wyoming. Lower elevations in western Nebraska will creep into the lower to middle 70s. Scattered rain showers and isolated thunderstorms will remain possible through the evening hours. Unfortunately, a wetting rainfall in excess of 0.10 inches is not favored for many areas where the scattered rain showers occur across our cwa. Sunday night will see mostly clear skies. Despite it being the first week of July, we could see some areas in the low to middle 30s for the highest elevations in the Snowy and Sierra Madre Mtns by daybreak Monday. The remaining areas will see 40s to low 50s for morning lows as we begin the new full week of July. && .LONG TERM /MONDAY THROUGH FRIDAY/... Issued at 230 PM MDT Fri Jul 5 2024 A gradual warming trend and fairly dry conditions will be the overall theme for next week`s weather. The main synoptic driver will be the persistent ridge that is currently building near the West Coast. Ensembles are in reasonably good agreement on this feature very slowly drifting eastward over the course of the week. Monday still look several degrees cooler than average for this time of year in the wake of the last more significant shortwave trough rotating around the central US. Tuesday should warm back to near or slightly below average as the ridge slowly expands eastward. For Wednesday, several ensemble members (mostly ECMWF) have a slower expansion of the ridge, which would allow the next shortwave riding around the longwave trough to bring its cold front through the area and briefly stall the warming trend. Other members (mostly GEFS) build the ridge in faster, which would shunt this next front off to the east. Precipitation will be hard to come by in this period with fairly dry air in the lower atmosphere. Monday might be nearly completely dry, but precipitable water values should climb closer to climatological norms for Tuesday and Wednesday. This should allow for some isolated afternoon convection, mainly over and near the higher terrain. We`ll have to watch the plains in the ECMWF slower warm-up scenario, as this would also allow the vort-max aloft to kick off some activity on Tuesday/Wednesday in the Nebraska panhandle. The GFS and GEFS generally keep this more towards central and eastern Nebraska. By Thursday, ensembles are in good agreement that our area will be firmly under the influence of the ridge. Thus, expect above average temperatures to return to the forecast, bringing widespread upper 80s to 90s to the area. While essentially all ensemble members are on board with hot weather returning by Thursday, the GEFS/GFS solution is a bit more aggressive than the ECMWF and its ensemble. NAEFS mean 500-mb heights and 700-mb temperatures are already approaching the 90th percentile of climatology by Friday, more so for northern and western portions of the forecast area. While it certainly looks hot, probabilities of record highs are fairly low at this time, mainly because this is the climatological hottest time of the year. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 520 PM MDT Fri Jul 5 2024 Northwest flow aloft will continue. Clear skies will prevail, with occasional scattered to broken clouds from 10000 to 12000 feet. Showers will be in the vicinity at Chadron and Alliance from 08Z to 14Z. Winds will gust to 27 knots at the Wyoming terminals and Sidney until 02Z, and to 25 knots at all terminals after 14Z Saturday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Fire Weather Watch from Saturday afternoon through Saturday evening for WYZ422-423-427. Red Flag Warning from noon to 8 PM MDT Saturday for WYZ425-428. NE...None. && $$ UPDATE...GCC SHORT TERM...BW LONG TERM...MN AVIATION...RUBIN