956 FXUS65 KCYS 052332 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 532 PM MDT Sun Jul 5 2020 .SHORT TERM...(This evening through Tuesday Night) Issued at 215 PM MDT Sun Jul 5 2020 Storms beginning to pop this afternoon off the Laramie Range and to the west. Some storms have already produced wind gusts to 50 mph with a very dry surface layer in place to the west of the Laramie Range, where a Special Weather Statement is in place to cover this threat. East of the Laramie Range, the front associated with the shortwave passing to our north is now in the process of dropping south over Niobrara and Converse Counties, picking up the dryline that was located just east of the Laramie Range and dragging it east with storms developing along the lines and ahead of them. As both boundaries move south and east this afternoon and evening, expect to see continued storm development. PWATS are much higher as we pass to the north of the North Platte River Basin, and with increased shear associated with the cold front, looking for strong to severe weather possibilities across northern Nio, Converse, Sioux and Dawes Counties. Here, hail, and strong winds are the expected threats. To the south, across the northern Front Range, moisture is available, but shear is lacking, so slow moving storms with little organization are expected, much like what we saw yesterday with a steering flow around 20 mph expected - this means locally heavy rainfall is a possibility. To the west of the Laramie Range, diurnal heating and a sliver of moisture will allow storms to develop and build, but with a lack of mositure available as a zonal mean flow has ushered in a dry airmass from the west, dry lightning and gusty winds will be a true concern. All that said, isolated to widely scattered storms are still expected across the region today; storms will transition over the WY/NE border by 5 PM. Storms will pass east of the Panhandle by 9 PM. Quiet overnight, with the possibility of fog development where any heavy rain showers occur, but have left fog out of the forecast for now pending shower development this afternoon and evening. Monday will bring another chance for afternoon showers and thunderstorms, under decreasing surface moisture availability, so will see decreasing extent to the development. Gusty winds will be the primary threat; however, as a shortwave passes through southeast Wyoming and the western Nebraska Panhandle will see 0-6 km shear will increase substantially, though CAPE will also decrease yet again as dry air and midlevel subsidence deepens as an upper level ridge strengthens over the Front Range, pushing further east and kicking the moisture plume further east as well. Tuesday will see storms of a more isolated nature as the warming and drying trend kicks off for the duration of the week. Highs will top off in the 90s, even reaching 100 in the North Platte River Basin. Fire weather conditions will be elevated to critical each day, especially beginning Tuesday. See the Fire Weather Discussion below for further details. .LONG TERM...(Wednesday morning through Sunday) Issued at 215 PM MDT Sun Jul 5 2020 Dominant high pressure and upper level ridge will stay firmly entrenched over the 4 corners region of the southwest CONUS. This will keep temperatures hot and dry conditions can be expected as well. A few ripples along the 500mb level flow aloft are shown on the GFS, EURO, and Canadian models. The minor shortwaves may help with creating a few showers over the CWA for the extended period on Thursday evening and then again on Saturday evening. Medium range model guidance really showing an overall dry pattern for the coverage area, which will create some very dry conditions to enhance current drought outlook per U.S. Drought Monitor guidance for WY. Wouldn't be surprised to see abnormally dry and moderate drought conditions move south toward the WY state line this week. Further support during the atmospheric ridging can be seen by looking at the 700mb temps. Continued surges of warm air advection show afternoon readings of 18-22 degrees C, especially the Friday-Sunday timeframe. This will create temperatures in the mid 90s to low 100s east of the Laramie Range and the high plains of western Nebraska for the extended period, with areas that include RWL and LAR near the 90 degree mark also. Our break from the heat and dry conditions could come as early as next Tuesday, July 14th. Between Wednesday morning and Tuesday of the next week, expect summer temperatures with very little precipitation to stick around the area. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 528 PM MDT Sun Jul 5 2020 Wyoming TAFS...VFR at Rawlins and Laramie with thunderstorms in the vicinity until 02Z. Wind gusts to 25 knots until 02Z, then to 25 knots after 15Z Monday. VFR at Cheyenne, with occasional MVFR and gusts to 35 knots in thunderstorms until 02Z. Nebraska TAFS...VFR, with occasional MVFR and gusts to 40 knots in thunderstorms until 03Z. Wind gusts to 20 knots at Chadron, Alliance and Sidney after 15Z Monday. && .FIRE WEATHER... Issued at 215 PM MDT Sun Jul 5 2020 ...FIRE WEATHER WATCH IN EFFECT FROM TUESDAY MORNING THROUGH TUESDAY EVENING FOR FWZS 310 AND 311... Elevated to critical fire weather conditions as a deep, dry air mass transitions east. The ridge of high pressure, located west of the Laramie Range, will become increasingly dry as it strengthens under increasing subsidence. Daily afternoon dry storms are possible with some residual surface moisture in place. Scattered storms today; decreasing chances daily. Deteriorating conditions with Haines 5/6 expected starting Tues and very low min RHs, in the teens and single digits at times, with recoveries in the 30s west of the Laramie Range beginning Wednesday morning. Winds will be gusty at times, especially Tuesday and Thursday. A fire weather watch is in effect for FWZs 310/311 Tuesday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Fire Weather Watch from Tuesday morning through Tuesday evening for WYZ310. NE...Fire Weather Watch from Tuesday morning through Tuesday evening for NEZ311. && $$ SHORT TERM...AB LONG TERM...BW AVIATION...RUBIN FIRE WEATHER...AB