Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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563 FXUS66 KPDT 082327 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 427 PM PDT Mon Jul 8 2024 .Updated for Aviation... && .PREV DISCUSSION... /issued 252 PM PDT Mon Jul 8 2024/ SHORT TERM...Tonight through Wednesday night...Although no precipitation is in the forecast through Wednesday night, there are multiple weather concerns--the heat and fire weather. Starting with the heat, nearly all of the forecast area are under Excessive Heat Warnings or Heat Advisories. Widespread temperatures are in the 90s to around 105 at this time, and it will be even hotter tomorrow. The inverted surface thermal trough will be directly over us and the 850mb temps will climb from around 26-30C today to 27-32C tomorrow. There will be locations pushing 110-113F tomorrow in the Lower Columbia Basin, eastern CR Gorge, and the John Day Basin. Wednesday will be cooler, particularly in our western zones, but a 5-10 degree drop in temperatures still means triple digits with no relief in cooling. Areas under the Excessive Heat Warning will only cool down into the 60s to lower 70s at night. The position of the thermal trough is a key player in the instability, especially as the upper ridge shifts to the east. The axis of the surface thermal trough will be along the Cascades tonight and Tuesday where Red Flag Warnings have been posted. Fire Weather Watches were issued earlier for the Blue Mountains, Wallowas, and the John Day-Ochoco Highlands in effect for Tuesday afternoon through Wednesday. Confidence is about 60-80% for the atmosphere to become more unstable in these areas. Last night`s HREF showed several members with isolated returns on the simulated reflectivity over southeast Oregon late Tuesday. The forecast soundings also showed high based inverted V. The same CAMs in the most recent runs were less "impressive" on the reflectivity. Another tool often used for elevated instability (DIV Q aloft and theta-e decreasing with height between H7-H5) had little indication. Due to low confidence in thunderstorms on Tuesday (<15%), Tuesday will remain as dry throughout the CWA. The ridge will flatten on Wednesday, increasing the westerly flow at the surface and aloft. A Fire Weather Watch was issued earlier for the Kittitas Valley and the WA/OR Basin zones, and confidence is around 70% for these zones to meet red flag criteria. Based on the wind forecast for areas along the Columbia Deschutes Plateau, fire weather highlights may need to be extended down to central Oregon. Confidence in central Oregon meeting red flag for wind and RH on Wednesday is currently around 50%. Wister/85 LONG TERM...Thursday through Monday... Starting Thursday, the long-lasting ridge will finally lose its potency as the synoptic pattern becomes zonal through Saturday. This will support relatively hot conditions along with elevated fire weather concerns via breezy winds through the Cascade Gaps, possibly extending into the Basin. Ensembles are in good agreement through Saturday as the ridge flattens into a more zonal pattern, which typically supports gap flows. NBM probabilistic guidance shows high chances (>70%) of wind gusts at 25-35 mph through our usual areas: the Columbia River Gorge, Kittitas Valley, Simcoe Highlands, and extending into the Columbia Basin. The dry hot environment will allow high temps to remain in the 90s for a majority of our lower elevation and valley zones. Around the Columbia Basin, temps will be in the lower 100s. Being said, RHs are most likely (70-80%) to remain at critical levels in the teens but around 20s and 30s along the Cascades, suggested by the NBM. Temps begin to cool Sunday through Monday with the incoming shortwave trough moving inland of PacNW. Small differences in the ensembles begin to show starting Sunday along with the models, as both GFS and Canadian try to bring in a shortwave trough through the region around Monday. However, it is still a little too far out to accurately determine how much moisture this system will bring. Given how dry the environment will be through the period, dry thunderstorms could also be a concern (<20% confidence). Feaster/97 AVIATION... 00Z TAFS...VFR conditions are expected through the TAF period. Winds will be 10 kts or less everywhere, except BDN and RDM late Tuesday afternoon where there could be some gusts to around 20 kts. && .PRELIMINARY POINT TEMPS/POPS... PDT 62 106 69 103 / 0 0 0 0 ALW 64 109 72 106 / 0 0 0 0 PSC 66 109 72 109 / 0 0 0 0 YKM 68 108 70 106 / 0 0 0 0 HRI 64 111 70 108 / 0 0 0 0 ELN 64 108 68 101 / 0 0 0 0 RDM 59 105 61 99 / 0 0 0 0 LGD 58 101 66 100 / 0 0 0 0 GCD 60 104 64 101 / 0 0 0 0 DLS 71 111 72 101 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning until 10 PM PDT Wednesday for ORZ041-044- 505-507-508-510-511. Red Flag Warning until 11 PM PDT Tuesday for ORZ610-611-639-640. Fire Weather Watch from Wednesday afternoon through Wednesday evening for ORZ641. Heat Advisory until 10 PM PDT Wednesday for ORZ049-050-502-503. Fire Weather Watch from Tuesday afternoon through Wednesday evening for ORZ642>645. Heat Advisory until 10 PM PDT Tuesday for ORZ509. WA...Excessive Heat Warning until 10 PM PDT Wednesday for WAZ024- 026>029-521-523. Red Flag Warning until 11 PM PDT Tuesday for WAZ694-695. Fire Weather Watch from Wednesday afternoon through Wednesday evening for WAZ690-691. Heat Advisory until 10 PM PDT Wednesday for WAZ030. Fire Weather Watch from Tuesday afternoon through Wednesday evening for WAZ692-693. Heat Advisory until 10 PM PDT Tuesday for WAZ522. && $$ SHORT TERM...85 LONG TERM....97 AVIATION...77