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Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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570 FXUS66 KPDT 141700 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1000 AM PDT Wed Aug 14 2024 .MORNING UPDATE... Satellite imagery shows mostly clear skies across the forecast area this morning, with confined smoke aloft in central OR and Ochoco- John Day Highlands from local wildfires. For this morning, forecast updates consist of increasing winds and wind gusts at 15-25 mph through the Columbia Basin. This is due to increasing surface pressure gradients up to 3-4 mb. Temperatures will increase by a few degrees as daytime heating arrives. Otherwise, no changes to the POPs and thunderstorm forecast: chances are increasing up to 60% tonight around central OR mountains. Feaster/97 && .PREV DISCUSSION... /issued 228 AM PDT Wed Aug 14 2024/ SHORT TERM...Today through Friday...Overnight satellite imagery showing mostly clear skies over the forecast area as transitory ridging builds in overhead. Most of Wednesday will be quiet as a result, however our quiet weather will be short-lived as a series of low pressure systems will impact the PacNW starting overnight Wednesday into Thursday, keeping us in an active pattern through at least early next week. Not much to speak of weather-wise today, but models are in good agreement showing a closed upper-level low arriving from the WSW during the overnight hours heading into Thursday, bringing with it a band of showers and thunderstorms along a warm front leading the system. Fire Weather Watches are in effect as a result, however the main complicating factor with this system is just how cool we`ll be heading into Thursday, which will work toward cutting into instability needed for storm activity. Currently looking at overnight lows in the low 50s to even 40s for many of the zones under a Fire Weather Watch, which isn`t too cold for convection, but whether or not we`ll see "abundant lightning" remains to be seen. We`ll leave the decision whether to upgrade or drop the Watch to the day shift, but will say that as far as storm chances are concerned, the best chances do look to be concentrated around central Oregon. Shower and storm activity looks to spread northeastward up through the Blues and Wallowas during the day Thursday, but forecast models show a pretty saturated air mass with PWATs anywhere from 0.7 to 1 inches, certainly above average given the time of year. Storm chances are certainly there, but current thinking is that wetting rains may play enough of a factor to preclude issuing fire weather headlines for our eastern mountain zones. That being said, it is mid- August, and fuels are at their most vulnerable, but the forecast does look to be wet overall for the eastern mountains Thursday. A more robust low will begin to take shape on Friday, but with prolonged SW flow and moisture over the forecast area, cloud cover will work to severely inhibit instability, thus CAPE is expected to be very limited. What looked to be another day of storms now looks to be that of meager shower activity over the eastern mountains. High temps are expected to remain around seasonal averages. Evans/74 LONG TERM...Saturday through Wednesday...Ensemble models continue to show good agreement that the long term weather pattern will consist of an upper level closed low pressure off the coast of the Pacific Northwest but in various locations over time. This will place the forecast area under a south to southwest flow throughout the long term period. The initial deepening of this low occurs late Friday into Saturday which coincides with the best period of instability across the forecast. area. This will lead to showers and thunderstorms on Saturday. On Sunday the center of the low lifts a little further north allowing a dry slot to cover most of the forecast area while the better instability also shifts north and east of the forecast area. Monday through Wednesday the closed low will be located off the coast of Vancouver Island and a continuation of a dry slot across the forecast area being on the southeast side of the low. This keeps the better instability and moisture north and east of the forecast area with precipitation chances at 10% of less for the forecast area. Throughout it all, temperatures look to remain near seasonal norms with highs generally in the 80s in the lower elevations and 70s in the mountains. AVIATION...12Z TAFS...VFR conditions are expected through the 24 hour forecast period but do expect the development of some showers and possible thunderstorms in central Oregon after 00Z and overnight that could impact RDM and BDN. Otherwise, generally clear skies and winds of 5 to 15 kts expected. BDN/RDM and YKM may still be locally impacted from smoke/haze from nearby wildfires. && .PRELIMINARY POINT TEMPS/POPS... PDT 82 53 82 54 / 0 0 20 20 ALW 86 57 85 59 / 0 0 20 30 PSC 87 60 88 62 / 0 0 10 10 YKM 86 55 87 54 / 0 0 20 20 HRI 86 59 86 59 / 0 0 10 10 ELN 88 57 86 56 / 0 0 10 10 RDM 82 51 77 47 / 0 20 30 30 LGD 84 52 80 50 / 0 0 50 50 GCD 86 54 80 50 / 0 30 60 40 DLS 85 61 81 59 / 0 0 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from this evening through Thursday morning for ORZ611-640-642. WA...None. && $$ SHORT TERM...74 LONG TERM....91 AVIATION...91