Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000 FXUS65 KCYS 211137 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 537 AM MDT Sat Oct 21 2017 .SHORT TERM...(Today through Sunday) Issued at 300 AM MDT Sat Oct 21 2017 Currently, very windy conditions continue along the I-25 corridor as a stout cold front has tracked across the region. Winds have briefly gusted as high as 60 mph at Whitaker and Bordeaux over night but have not been consistently gusting that high and thus have continued with the SPS highlighting strong wind gusts early this morning. Most short range guidance indicates that these winds will relax a bit after sunrise as the front pushes further east. A few showers also continue along the 700mb frontogenesis axis this morning over the Panhandle and these showers will quickly exit to the east after 12z. Any break in the winds will be short-lived today however as a strong 150kt upper jet impinges on the NW US and extends into the Northern Rockies tonight. Classic high wind scenario will unfold with SE Wyoming on the anticyclonic and subsident side of the jet. Lee troughing develops rapidly after 03z tonight and low level gradients tighten dramatically. CAG-CPR gradient peak near 78 meters by Sunday morning. 700-750 mb flow increases to around 60kt by the same time frame. Went ahead an upgraded the high wind watches to warnings as this seems pretty clear cut for the wind prone areas such as Arlington, Bordeaux, and the South Laramie Range. Winds will likely gust between 60 and 70 mph by Sunday morning. The question is how far east will the high winds extend? GFS soundings for Cheyenne between 12 and 18Z Sunday are pretty impressive with 50+ kt flow just off the surface. Local wind model is not producing very high probability for high wind criteria in Cheyenne currently, likely due to lack of flow above 700 mb and weaker lapse rates. Too many question marks now to issue any headlines but later shifts will need to monitor as any increase in lapse rates or mixing potential will likely bring high wind potential into Cheyenne Sunday morning. It will be mostly sunny with much cooler temperatures today with highs ranging from the low 40s west to around 60 over the Panhandle. Went slightly above MOS guidance for tonight where the winds are strongest as downslope warming and mixing should keep over night lows a bit higher. .LONG TERM...(Sunday night through Friday) Issued at 300 AM MDT Sat Oct 21 2017 Elevated winds Sunday night before a backdoor cold front moves into the area from the northeast. 700mb temperatures drop to -7C across the northern Panhandle, but cold temperature short lived as westerly winds return Monday afternoon. Warming temperatures and windy conditions Tuesday and Wednesday as 700mb temperatures climb back to +10C. GFS 700mb winds close to 50kts, so wind prone areas probably seeing warning level winds. Stronger system set to move into the area Thursday with fairly widespread rain and snow mix, turning to snow once the colder temperatures arrive Thursday night. && .AVIATION...
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(For the 12Z TAFS through 12Z Sunday morning) Issued at 536 AM MDT Sat Oct 21 2017 Mainly VFR through next 24 hours with increasing winds. Skies to scatter out behind a cold front that pushed through the area overnight.
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&& .FIRE WEATHER... Issued at 224 AM MDT Sat Oct 21 2017 Min RH values will drop to between 15 and 20 percent east of the Laramie Range this afternoon. Some elevated conditions are possible as it will also be breezy to windy but overall, cooler temperatures will prevent critical fire conditions from developing. Dewpoints creep up a bit for Sunday into Monday so in spite of the dry conditions, the fire weather threat after today will be low. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning from 7 PM this evening to 6 PM MDT Sunday for WYZ106-110-116-117. NE...None. && $$ SHORT TERM...DEL LONG TERM...GCC AVIATION...GCC FIRE WEATHER...DEL

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