Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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099 FXUS65 KCYS 042045 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 245 PM MDT Tue Jun 4 2024 .KEY MESSAGES... - High Wind Warnings remain in effect for a large part of southeast Wyoming until Wednesday afternoon. Wind gusts 60-65 MPH are expected, especially overnight into early Wednesday morning. - A significant warming trend is expected through mid to late week, with widespread highs in the 80s and lower 90s on Thursday and Friday. - Increasing chances for showers and thunderstorms late in the week through the weekend. Strong to severe storms cannot be ruled out. && .SHORT TERM /THROUGH WEDNESDAY NIGHT/... Issued at 219 PM MDT Tue Jun 4 2024 Strong winds are expected to persist across much of southeast WY through at least mid-day Wednesday. Occasional wind gusts around 55 to 60 MPH have been observed over the past several hours over areas mainly along/west of the Laramie Range, but have generally seen a lull in the strongest wind speeds given the weakening low level gradients in the wake of the first fropa. 700 millibar CAG to CPR gradients are expected to quickly ramp up to 60-70 meters by 03-06z tonight, in response to strong pressure falls ahead of the next frontal passage. H7-H8 flow peaks near 60-65 knots over the southeast Wyoming wind corridors (also spilling into central and eastern Laramie County) at 12z Wednesday. Forecast soundings for Cheyenne suggest a very steep near-surface lapse rates along with a sharp, well-pronounced mountain top inversion which would suggest strong potential for mountain waves overnight into early Wednesday morning, especially closer to sunrise. Have gone ahead and upgraded the High Wind Watch to a Warning for Cheyenne. High Wind Warnings for remaining zones are in excellent shape through Wednesday. Winds should begin to slowly diminish after Noon Wed. && .LONG TERM /THURSDAY THROUGH MONDAY/... Issued at 219 PM MDT Tue Jun 4 2024 Thursday and Friday will be the warmest days of the extended forecast, with afternoon high temperatures being in the 80s and 90s for the lower terrain and high plains. This is approximately 10-15 degrees above normal for the first week of June. 700mb temperatures on Thursday and Friday for portions of southeast WY will be approximately +15C to +18C. With dry conditions being favored for the weather forecast both days combined with surface high pressure, KLAR and KRWL could approach record high temperatures of the upper 80s. The mountain elevations of the Snowy and Sierra Madre should see 60s, which should be pleasant weather for those that are planning outdoor recreation. Northwest flow at H5/H3 will be the persistent upper level steering flow pattern, due to the upper level ridge axis being firmly entrenched across the Great Basin area. Isolated showers and a possible thunderstorms are expected to pop up by late Friday afternoon east of the Laramie Range and the Nebraska Panhandle. Not much has changed regarding the forecast for the weekend. We will continue to be under the influence of northwest flow aloft. Although, our cwa will be near the periphery of a passing shortwave trough, and subsequent cold front. Daytime highs are likely to be approximately 10 degrees cooler for most of the cwa on Saturday and Sunday, but the warmer temperatures aloft may mix down for portions of Carbon County, keeping those areas in the upper 70s to lower 80s. This is in response to 700mb temperatures hovering near +10C for most locations in the region, which is approximately +4C to +8C cooler than the previous couple of days. We will have much more moisture being present for the weekend however. Bulk shear, modest lapse rates, PWATs being near or above 0.75-1.0 inches, surface convergence should all play their part for afternoon diurnal convection. This could be the first of several days of thunderstorm activity in a row, which would bring some much appreciated moisture to drought stricken areas of the cwa. Model guidance has the upper level ridge become flattened by Sunday as a progressive longwave trough intensifies further upstream across the Pacific NW. Strong to potentially even severe thunderstorms may be favored on Sunday afternoon and evening if model guidance remains consistent in the coming days. The only change for early next week is that deterministic model guidance is favoring a much cooler solution for daytime highs on Monday. The GFS is the most aggressive, with keeping daytime highs in the 40s and 50s behind a strong cold front and pesky cloud cover sticking around. The Euro and Canadian model are not as aggressive, but still on the cooler side of daytime highs as 50s and 60s are favored. Ensemble members are not showing as much of a daytime high shift between Sunday and Monday, so have gone with a conservative approach to temperature changes. The showers and thunderstorm potential continues for weather impacts on Monday into Tuesday, before we begin to warm back up by the middle of next week. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1113 AM MDT Tue Jun 4 2024 VFR is anticipated at all terminals through the forecast period. Strong, gusty winds are expected for the southeast WY terminals up to 40-50 knots this afternoon. LLWS is also anticipated for KCYS and KLAR early Wednesday morning by 12z. The Nebraska Panhandle terminals will experience wind gusts of 20-35 knots this afternoon before tapering off overnight. They will once again pick up shortly after sunrise for wind gusts of 20-30 knots through 18z Wednesday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until noon MDT Wednesday for WYZ104. High Wind Warning until 6 PM MDT Wednesday for WYZ106-109-110- 115>117. High Wind Warning from midnight tonight to noon MDT Wednesday for WYZ118. NE...None. && $$ SHORT TERM...CLH LONG TERM...SF AVIATION...BW