Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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343 FXUS65 KCYS 021039 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 439 AM MDT Tue Jul 2 2024 .KEY MESSAGES... - A few showers and perhaps a rumble of thunder will remain possible across the region through mid-day. Gusty winds can be expected mainly along and west of the Laramie Range today w/ gusts up to 45 MPH. - Thunderstorms are possible on Wednesday afternoon, especially across east central Wyoming & the western Nebraska Panhandle. Any storms which develop will have the potential to become severe with all hazards possible. - A cool and pleasant Independence Day is expected in the wake of a strong cold front set to sweep across the area on Wednesday night. && .SHORT TERM /THROUGH THURSDAY/... Issued at 413 AM MDT Tue Jul 2 2024 Scattered showers are expected to persist across southeast Wyo & the western Neb Panhandle through mid-day as the axis of the mid level short wave traverses the central Rockies. Gusty winds near 55 MPH may occur beneath some of this activity. Otherwise, gusty winds are expected for areas along/west of the Laramie Range for today as 700-mb CAG to CPR gradients climb to near 35 meters. We should see a brief warm up on Wednesday w/ short wave ridging in advance of the next sharp trough. Substantial WAA at 700-mb will contribute to some questions w/ the eastward extent of the EML & thus the impact of capping on overall coverage of storms in some portions of the CWA, but the primary focus for Wednesday will be northern & eastern zones along the edge of the thermal ridge for potential thunderstorm development. SSE near-surface flow should support dew points in in the mid/upper 50s by 18-21z assuming we do not see the dryline mix eastward too quickly. Very steep mid- level lapse rates combined w/ the moist boundary layer will help to support MLCAPEs of 1500-2000 J/kg while increasing flow at H5 supports 35-45 knots of effective bulk shear. As such, organized supercell structures will be possible with all hazards possible, including very large hail & damaging winds. Notable veering wind profiles in the low levels suggests a few tornadoes will also be possible if storms can remain at least quasi discrete. Expect to see a strong cold frontal passage late Wednesday night w/ 700-mb temperatures plunging to +5 C or less by 15z Thursday. While the overall thermal profiles should rebound nicely by afternoon, the net result should be a cool and pleasant Independence Day w/ day time highs only in the 70s for many. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Issued at 413 AM MDT Tue Jul 2 2024 Looking at a relatively quiet long term as the region makes the gradual transition from broad troughiness to strong ridge. With an upper-level low ejecting into the Great Lakes Region Friday afternoon, expect a warm-up in temperatures as the CWA sits just downstream of a ridge building over the west coast. This will usher in both warmer, and drier 700 mb air into the region, contributing to about a 5 degree warm up from Thursday`s comfortable highs. Overall, looking at dry weather on Friday with gradual 500 mb height rises, despite the weak vort maxes passing aloft. Heading into Saturday, both the deterministic GFS and ECMWF show a distinct cold front dropping down from the north as a strong shortwave moves into Montana and the Dakotas. GFS and ECMWF are roughly in agreement time wise, with the GFS bringing that front through a tad faster than the ECMWF. Based on frontal timing, still expecting a warming trend through the day Saturday, with another 5 degree jump in high temperatures compared to the previous day. Frontal passage appears to be Saturday evening or night, either of which leads to a cooler day on Sunday. 700 mb temperatures drop into the +4C to +10C range, likely leading to below average highs. Did bump temperatures below NBM guidance as they seemed too warm for this magnitude of cold front. Highs on Sunday could be in the 70s to low 80s. Cannot rule out some light precipitation with the front, as well as behind the front since mid-level moisture does increase in the presence of forcing. So, did increase PoPs Saturday night and into the day Sunday, but went with slight chance wording. With a strengthening ridge building over western CONUS, expect warming temperatures and dry conditions through the beginning of the work week. Increasing 700 mb temperatures will likely lead to the return of 90 degree temperatures by Tuesday of next week. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1020 PM MDT Mon Jul 1 2024 Westerly flow aloft will continue. Wyoming TAFS...Scattered clouds from 8000 to 12000 feet will prevail. Winds will gust from 25 to 32 knots from 15Z to 00Z. Nebraska TAFS...Scattered to broken clouds from 8000 to 10000 feet will prevail. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...SF AVIATION...RUBIN