Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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619 FXUS65 KCYS 031026 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 426 AM MDT Mon Jun 3 2024 .KEY MESSAGES... - Scattered showers and a few thunderstorms are expected this evening with gusty winds possible. - Elevated to high winds are possible for the wind prone areas of southeast Wyoming late tonight through Wednesday. - Above normal temperatures likely Wednesday and Thursday as temperatures climb into the mid to upper 80s across much of the region, with 90F possible across the Nebraska Panhandle. && .SHORT TERM /THROUGH TUESDAY/... Issued at 425 AM MDT Mon Jun 3 2024 After another active day of convection on Sunday we will be seeing thunderstorm activity quiet down for a little bit. Today won`t be totally clear though as another more potent upper level trough is diving into the Pacific Northwest this morning. Abundant cloud cover is streaming out ahead of this low, with some high clouds already working into our western zones. WSW flow ahead of the trough will lead to strong warm air advection across the area today though temperatures may be held back by cloud cover west of the Laramie range. Further east, westerly downslope winds should lead to a warm to hot day with most of the area reaching the 80s. Some of the typical hotter spots like Torrington, Scottsbluff, and Chadron may have a chance at 90F. Isolated showers/storms are expected to kick off mid afternoon, but instability will be quite limited. Significant warming aloft is ongoing today, which will decrease lapse rates and instability. While some thunder is likely, severe weather is not expected today. The only concern is that dry microburst type events can`t be totally ruled out with inverted-v soundings and increasing wind speeds aloft. More widespread shower activity will work in from the west after about 5PM, but this looks more synoptically driven. Marginal instability will produce some embedded thunder, but the primary mechanism is the approaching upper level trough. The mountains may pick up a tenth or two of precipitation (which could fall as snow on the very highest peaks above about 11000 feet). The surface cold front will push through the area Tuesday morning, and a few showers or thunderstorms are possible along this in the US20 corridor through midday Tuesday. As the storm threat falls, the strong winds will return. Expect a breezy day today, but winds will be on the increase for Tuesday through Tuesday night. The approaching trough is much stronger than the previous troughs, and will increase the pressure gradient across the area. The strongest winds through this event are expected Tuesday morning just ahead of the surface cold front passage, when cross-barrier pressure gradients reach their maximum. While a breezy to windy period is all but guaranteed, there is some uncertainty still in if this will actually attain high wind criteria. The GFS and GEFS are very aggressive, showing widespread 700-mb wind speeds of 50 to 60 knots Tuesday morning and sharp MSLP gradients across the wind prone areas. GFS based in-house guidance shows probabilities of high wind around 60 to 80% for the Arlington/Elk Mountain area 40 to 50% for Bordeaux and the I-80 summit Tuesday morning. Probabilities for the latter two increase to the 60 to 80% range for Wednesday morning as the GFS shows a finger of even stronger 700-mb winds creeping over the area. However, all other global models and ensemble systems show considerably weaker winds. While the systems are closer together for Tuesday morning (median 700-mb wind at KCYS is 46 knots in the GEFS and 36 knots in the ECMWF ensemble), spread increases dramatically by 12z Wednesday. Then, the median 700-mb winds over KCYS is 57 knots in the GEFS and 33 knots in the ECMWF ensemble. There is higher confidence in elevated winds tonight through Tuesday morning, with a marginal threat for high winds. Tuesday night could be stronger event, but confidence is lower. For now, held off on High Wind headlines due to the lack in model consistency, but the next shift will have to take another look. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 425 AM MDT Mon Jun 3 2024 The long term forecast will feature a mixed bag of weather impacts for much of SE Wyoming and the Nebraska Panhandle. Elevated to potentially high winds will be ending across the Arlington wind prone and the south Laramie Range and Foothills Wednesday afternoon. This will giveaway to well above normal temperatures Wednesday and Thursday for much of the region. Could see widespread 90F across the Nebraska Panhandle with mid to upper 80s likely across much of SE Wyoming. Heading toward the end of the week and into next weekend, the pattern then shifts toward a more active pattern with daily chances of thunderstorms, some in which could become strong to severe, especially next Monday. Elevated to high wind gusts will be still ongoing across Arlington wind prone and area adjacent. Passing shortwave trough to the north and increasing heights to the south will keep a tight MSLP gradient across the region with localized areas of +65kt 700mb winds over those aforementioned areas. In-house guidance continues to show high probabilities (greater than 60%) for high wind gusts too occur and the long range GFS model continues to backup this notion. Still some uncertainty amongst the ensemble members and the ECMWF, so we will continue to monitor for potentially issuing some wind highlights. Nonetheless, it will be breezy through Wednesday afternoon before wind diminish as the shortwave passes to the east and the MSLP gradients begin to weaken. On the heels of this departing trough, a large ridge axis begins to develop across much of the Intermountain West and this will drive temperatures to well above normal for some locations Wednesday and again on Thursday. Moisture advecting into the region underneath this ridge may be enough to allow for some diurnal convection to develop by Friday afternoon and with the increase in both moisture and cloud cover, temperatures may be slightly "cooler" on Friday. Those daily chances for thunderstorms arrive Friday afternoon and could persist into the weekend as ripples in the flow will bring quick moving shortwaves through the area Saturday. We could see more scattered to widespread thunderstorms on Saturday as this ripple moves through and we stay rather warm and moist in the lower levels. Could see lesser chances for convection on Sunday as the ridge begins to shift eastward and parts overhead on Sunday as the next storm system begins to move into the Pacific northwest. That system is progged to move through on Monday and this could bring the best chance for some organized strong to severe thunderstorms to much of SE Wyoming and into the Nebraska Panhandle. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 535 PM MDT Sun Jun 2 2024 Upper level disturbance which brought severe thunderstorms to portions of the region Sunday afternoon will continue to track east tonight. A few remnant showers and thunderstorms are expected until 03z. HAZARDS/WEATHER TRENDS: VFR conditions expected to prevail this evening through tonight. Brief MVFR VIS possible near KCYS and KLAR as a fast moving line of thunderstorms move through those locations, otherwise...conditions will improve after 03z. There is a slight chance at some fog develop near KAIA and KBFF early Monday morning, but confidence is too low (less than 10%) to add to the TAF at this time. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ MESOSCALE...CLH UPDATE...AM SHORT TERM...MN LONG TERM...AW AVIATION...BW