Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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409 FXUS65 KCYS 291742 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 1142 AM MDT Sat Jun 29 2024 .KEY MESSAGES... - Possible severe thunderstorms Sunday afternoon and evening. - Cooler week ahead before strong ridge and toasty temperatures return for the weekend. && .SHORT TERM /THROUGH MONDAY/... Issued at 220 AM MDT Sat Jun 29 2024 Surface cold front currently lays across northern Colorado this morning. A 1029mb surface high located over central Montana behind this front. Radar echo free and satellite showing mostly clear skies over the CWA. A pretty nice day expected across southeast Wyoming and Nebraska Panhandle today. Single digit 700mb temperatures across the Panhandle to +16C over Carbon County to the west. Afternoon temperatures in the upper 70s to near 80 for our eastern forecast zones...while Carbon County will be the warm spot with mid 80s expected. May see a few showers/storms over our western mountains this afternoon as advertised in HRRR/RAP simulated radar. Most other locations expected to be dry. Begin to see southeasterly winds returning to the Panhandle this afternoon with increasing low level moisture late tonight into Sunday morning. GFS advertising 850mb humidity near 90 percent in the Panhandle by 12Z Sunday. May be dealing with low clouds Sunday persisting across the Panhandle. Looking at mid 50s to near 60 dewpoints by Sunday afternoon. Upper levels showing a shortwave moving through overhead Sunday afternoon. This will be our next best chance for thunderstorms...depending on low cloud dissipation. SPC has a Marginal Risk area identified for the Panhandle and southeast Wyoming east of the Laramie Range. Low level moisture stays in the area east of the Laramie Range Sunday night into Monday. So another night of low clouds and fog is possible. Upper shortwave moves through Monday morning that looks to force the low level moisture east into central Nebraska through the late morning hours. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Issued at 220 AM MDT Sat Jun 29 2024 Long range models remain in good agreement on the overall weather pattern expected this coming week, with better agreement seen for later in the work week. Upper-level troughing is expected to dominate the region Tuesday and Wednesday as two troughs pass overhead bringing northwest flow to the region. Northwest flow is a favorable regime for southeast Wyoming and western Nebraska in July, so attention turns to the potential severe threat posed by this flow pattern. Moisture looks to be the main limiting factor for Tuesday, as surface dewpoints struggle to increase with limited southerly flow Tuesday and dry, westerly flow Wednesday. Forecast soundings are not overly impressive with average PW values, very dry atmospheric moisture profiles, and weak CAPE for Tuesday. Wednesday looks to be much better, with MLCAPE values above 1500 J/kg in the Panhandle, PW values approaching 1 inch, and decent shear across the region. While this is still several days out, Wednesday will be a day to watch for the potential of severe weather with northwesterly flow aloft. Cool, northwesterly flow will continue for Independence Day, with seasonable temperatures expected across the region. Friday looks to be the transition day as the upper-level trough continues its eastward progression and an strong, upper-level ridge builds over the western CONUS. This ridge will mostly end the best chances for precipitation as strong subsidence moves over head. 700mb temperatures will increase into the 15-17C range, per the GFS. The ECMWF is a little slower with ejecting out the upper-level trough, leading to the warmest 700mb temperatures lagging behind the GFS by a day or so. Both models suggest a strong ridge remaining overhead for most the weekend into the following week at this time. Expecting temperatures to return to the roasty level by the weekend. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1140 AM MDT Sat Jun 29 2024 Fairly quiet weather expected today with a modest southerly breeze at KLAR and KCYS, and a few showers or very weak thunderstorms developing near Wyoming terminals. Can`t rule out brief light to moderate rain and some gusty winds, but this activity will be pretty isolated. A strong low-level jet will develop tonight, with gusts of 30 to 40 knots possible at most terminals between this evening and Sunday morning. There is a slight chance for some low clouds Sunday morning, mainly near KCYS, KSNY, and KAIA, but the probability is too low to add to the TAF at this time. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...GCC LONG TERM...AM AVIATION...MN