Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/13/21

Area Forecast Discussion
National Weather Service Reno NV
136 PM PDT Mon Jul 12 2021 .SYNOPSIS... Excessive heat conditions continue for the region through Tuesday, with a cooling trend to near normal by midweek. Isolated thunderstorms mainly south of Highway 50 are expected to diminish into the evening. Smoke from the Beckwourth Complex fire will continue to impact portions of extreme eastern California and western Nevada with periods of degraded air quality and reduced visibility. && .SHORT TERM...Tonight through Thursday evening... * Still hot through Tuesday. * Isolated to scattered thunderstorms will continue this evening mainly south of Highway 50. Tomorrow will be much less active mainly over Mono/Mineral County. * Daily fire weather concerns persist. Limited periods of critical conditions are possible each afternoon through this forecast period. High pressure is expected to continue to dominate the weather pattern through mid week. Deterministic and CAMs still favor a general weakening of the overall high pressure pattern across the region as successive embedded short waves continue to sag further south and chip away at its western and northern edges each day. This will translate into cool temperatures region wide for the time being as the broader area of subsiding air finally gets pushed further south and east into southern NV and the desert southwest. Heat: As embedded waves continue to chip away at the omnipresent area of high pressure over the Great Basin, a slight cooling trend will follow, bringing temperatures into a more seasonal to slightly above average range through the remainder of the week. This includes overnight temperatures which should cool more efficiently as the influence of the upper ridge retreats further east and south from northern Nevada and northeastern California. With lower overnight temperatures, daytime highs tomorrow through Thursday should trend marginally cooler as well. Although temperatures cool a few degrees by Wednesday, afternoon highs will stay above seasonal averages with most western Nevada valleys still approaching highs into the low 100s. Not much cooling relatively speaking but its a good start. Thunderstorms: Fewer thunderstorms are expected tomorrow afternoon as less mid-level moisture and CAPE will be available and confined mostly to the Mono-Mineral County convergence zone. Therefore most storms will be isolated in nature and located mostly south of Highway 50 in those areas where sufficient moisture and instability remain. As with most storms this summer season, expect gusty outflows to 40 mph and occasional cloud-to- ground lightning. Drier air continues to move east and south into into the region through Thursday with afternoon storm chances dropping below 10%. Winds and Fire Concerns: With the dry fuel conditions, single digit RH, and breezy winds, higher fire weather concerns should continue into the evening. Marginal, more intermittent critical conditions will return tomorrow and Wednesday afternoons as the zephyr along with a slight tightening of the pressure gradient occurs with lower pressure moving into the Canadian Plains. Smoke and Haze: Smoke and haze will remain in the forecast for most of the region as long as fires remain active. Smoke was added to the Reno Metro this morning due to the proximity of the Garson Fire located just west of Reno. Air quality will likely be somewhat degraded during the early morning hours as winds decouple from the surface with low-level terrain driven flows dispersing more smoke into populated areas. Air quality issues will persist until mixing increases in the afternoon. Predictability remains lower since levels of air quality due to smoke depend directly on fire activity. Locations north of Intestate 80 are more certain since the Beckwourth Complex remains very active and will likely result in significant degradation of air quality for the next 24-48 hours across the region. -Chris/Amanda .LONG TERM...Friday through early next week... The long term period will start with somewhat cooler temperatures as compared to the most recent record breaking heat seen across the region. Ensemble simulations project by mid-week the anomalous higher pressure that marked the stronger upper high and accompanying ridging will recede more southeast into the Four-Corners region. Although it will continue to exert its influence over the southwest deserts, the ever present upper ridge will finally give way to the constant bombardment from upper short waves sagging further south and injecting cooler air into its western and northern quadrants. This will translate into cool temperatures region wide for the time being as the broader area of subsiding air finally gets pushed further south and east into southern NV and the desert southwest. A broad long wave trough pattern that has remained in reserve mostly offshore over the eastern PAC will also begin to edge slowly into the western US the latter half of the week. This increase a southwest upper flow over the western NV that lasts through the weekend. This will also ensure that the drier conditions continue, coupled with the afternoon Zephyr breezes will enable a continuation of elevated fire weather concerns into the weekend. Thunderstorm activity should ebb a bit into the weekend as the drier- stable southwest upper flow increases overhead. The southward receding monsoonal moisture plume will further decrease the risk of any storms but that may not stop an errant isolated storm from popping up over the southern area of the Sierra Front. Ensemble cluster guidance more or less carries along the above stated notion into this weekend. By early next week the strong upper high that has anchored itself over the Southwest Desert/Four-Corners region will once again strengthen and expand westward into Nevada. Uncertainty abounds as simulations show a resurgence of increasing temperatures. But the currently available simulations also show the return of the upper high increasing a southerly mid-level upper flow that could draw additional monsoonal moisture more west and north deeper into the western NV and the Great Basin region in general. Increased moisture over the region could also increases the risk of more hybrid thunderstorms and clouds which may also dampen the hottest temps. Successive model runs are needed in order to bring a more clearer image of upcoming weather going into next week. -Amanda && .AVIATION... * Hot near-record temperatures today and Tuesday will intensify density altitude values, which could be an impact for certain aircraft types during peak heating in the afternoons. * Breezy afternoon winds expected today and Tuesday for most airfields. Mainly W/SW with gusts ~25 knots or so. Plan for choppy rides as hot temps drive thermal development during the afternoons. Smoke plumes from ongoing fires will produce MVFR- IFR conditions east and northeast of the region. * A few t-storms are possible today for the Eastern Sierra (KMMH) and across parts of central NV (KHTH, KNFL). Probabilities are running about 20-30% with primary concerns from high-based storms being strong outflow winds above 40 knots and areas of MVFR-IFR blowing dust. -Chris/Edan && .FIRE WEATHER... Main concerns for today and tomorrow will be the near-critical fire weather conditions due to breezy winds, dry conditions, and high Haines (hot/unstable conditions). The next couple of days will be pretty close to `hitting` critical fire weather conditions, especially north of Interstate 80. For now, the winds don`t appear to span a large enough area and also won`t last for too long. The winds will likely be more of an enhanced zephyr wind the next couple of afternoons and evenings. Unfortunately, any breezes paired with the hot/unstable and dry conditions will promote fire growth and result in ongoing fires burning very actively through the evening. We will continue to headline these concerns unless the conditions warrant an update or the simulations start trending to stronger winds. These concerns are headlined in the FWF, the fire partner briefings, and spot weather forecasts. Winds will be more typical zephyr speeds with gusts around 30 mph for Wednesday. Later in the week and into the weekend, a trough sets up off the coast as high pressure strengthens across the 4-corners region. Plan for increasing SW flow aloft, which could allow for some enhanced winds again by later this week. The difference for the latter half of the week will be some extremely dry air across the Sierra and western Nevada. Mid slopes and ridges will experience extremely poor overnight recoveries from Wednesday through Thurdsay, due to this dry air slot. Extreme dry air along with a return of more breezy winds will bear watching for critical fire weather concerns. -Edan && .REV Watches/Warnings/Advisories... NV...Excessive Heat Warning until 9 PM PDT Tuesday NVZ001-003>005. CA...Excessive Heat Warning until 9 PM PDT Tuesday CAZ070-071. && $$ For more information from the National Weather Service visit...