Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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851 FXUS65 KCYS 171751 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1151 AM MDT Fri May 17 2024 .KEY MESSAGES... - Warm & dry conditions prevail through Saturday. Daytime highs today may reach the lower to middle 80s for areas along and east of I-25. - Windy today as a strong disturbance tracks across the northern high plains. Wind gusts 45-55 MPH are expected for Arlington and Bordeaux. A couple brief gusts in excess of 60 MPH cannot be ruled out. && .SHORT TERM /THROUGH SUNDAY/... Issued at 438 AM MDT Fri May 17 2024 A very warm (and breezy) day ahead for much of southeast Wyoming & the western Nebraska Panhandle as the thermal ridge axis moves overhead in advance of a vigorous mid and upper-level short wave tracking across the intermountain west & northern high plains in the next 6-12 hours. 700-mb temperatures soaring to +10 to +12 C along w/ a strong west-to-east oriented MSLP gradient supporting strong westerly downslope flow along/E of the Laramie Range will likely support highs in the 80s for many along/east of I-25 this afternoon. H7/H85 CAG-CPR gradients of 40-50 meters will support potential for occasional 55-58 MPH gusts across the southeast WY wind corridors. A few rogue gusts to 60 MPH are possible, but do not believe a warning is necessary at this time w/ in-house high wind probabilities favoring sub-warning gusts. Moisture profiles look to be quite modest today, but high-res guidance suggests we may have enough to generate isolated high-based showers and weak thunderstorms by mid/late afternoon. If they develop, a very dry sub-cloud layer would certainly support convective wind gusts in excess of 60 MPH. Finally, expect elevated to near-critical fire weather conditions today with RHs falling into the lower teens & widespread 30+ MPH wind gusts. Fuels only remain critical across the western Nebraska Panhandle zones, where winds should be much less than areas further west. Even so, we will need to watch the area closely for possible fire weather headlines. Warm & dry for Saturday before a deepening trough over the north western US leads to increasing southwesterly flow aloft over the central Rockies. As such, the general theme of unsettled weather continues with increasing chances for showers & storms likely on Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Issued at 438 AM MDT Fri May 17 2024 An active pattern expected for much of the long term forecast. Several upper-level disturbances will pass overhead, leading to afternoon shower chances nearly every day. Sunday night into Monday a longwave, upper-level trough is progged to drag across much of the western CONUS, with a tighter trough depicted in the GFS and a broader trough in the ECMWF. As this upper-level trough pushes towards the area, an attendant cold front will move across the region. This cold front with concentrate the lift near the surface on Monday and lead to decent precipitation chances area wide, around 40-60%. Winds are expected to increase behind the front. Temperatures on Monday will be several degrees colder than Sunday, with highs int he mid-50s to low-70s across the region. On Tuesday, the upper-level trough will continue to swing through the area, though the GFS is notably a few hours behind the ECMWF on the propagation of the trough. Forcing will once again be present ahead of the trough as reinforcing cool air remains overhead. Temperatures are expected to be in the mid-50s to low-60s with the reinforcing cold air aloft. Afternoon showers will be possible as the trough slowly swings overhead and forcing out ahead of the trough favors the development of showers. Zonal flow will move overhead once the upper-level trough finally advects out of the reason by early Wednesday. Riding at 700mb and 700mb temperatures increasing to 0-2C will promote high temperatures on Wednesday in the low-60s to mid- 70s across the region. Minimal precipitation chances will exist during the day Wednesday, but cannot rule out a few isolated showers as weak forcing from cyclonic vorticity advection at 500mb favors subtle lift across the region. Any showers that develop will likely not be strong or long-lived. For the remaining long term, a secondary upper-level is progged to swing around the upper-level trough and impact the region Thursday and Friday. There is significant disagreement between the GFS and the ECMWF on the exact placement, speed, and timing of this secondary low. The GFS places the low over northern Idaho Thursday afternoon and over Montana and Wyoming by Friday morning. The ECMWF on the other hand is about a day behind, with the upper-level low still off the coast of the Pacific Northwest Friday morning and does not approach the region until late in the weekend. Instead, the ECMWF favors zonal flow across the region for Thursday and Friday. Decided to drop temperatures just a little for Friday, as long range model suggest 700mb temperatures just above 0C for Friday. Kept precipitation chances low, around 20-30% for both days to account for the uncertainty in the upper-level evolution. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1149 AM MDT Fri May 17 2024 VFR conditions expected to prevail across southeast Wyoming and western Nebraska through the 18Z TAF period. Gusty west to west-northwest winds 25 to 35+ knots through this afternoon, turning northwest and remaining elevated with a dry frontal passage this evening and overnight. An isolated shower is possible, but confidence is low in any direct impacts to terminals. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...AM AVIATION...LEG