textproduct: Pendleton

KEY MESSAGES

- Chances of thunderstorms for Central Oregon Wednesday with more widespread coverage on Thursday. Hail and gusty winds are possible embedded in these storms.

- Minor heat risk for today and Thursday, with greater risk on Thursday before thunderstorm development.

- Breezy to windy conditions develop on Friday.

DISCUSSION

Overhead ridging will bring dry conditions in the short term, with the cut-off low pressure system situated over Nevada and California bringing enough lift to initiate isolated thunderstorms in Central Oregon through Wednesday. Sufficient daytime heating through Thursday will build minor heat risk across the region with values of "1" on Wednesday, with more widespread pockets of "2" on Thursday (70-90% chance). High temperatures will climb into the high 80s to low 90s by Thursday. Consequently, this will enable thunderstorm development with abundant atmospheric energy in the later afternoon hours Thursday, increasing our chances of thunderstorms across the region to 30-40%.

GFS deterministic advertises high CAPE values of up to 1200 J/kg and dew point values in the mid to high 50s, with the highest values situated across the Foothills of the Blues and going up into the Northern Blue Mountains. ECMWF backs up higher than usual CAPE values Thursdays with relative forecasts of 0.7 to 0.91 and a shift of tails of 0 to 1. Widespread low-level lapse rates of 8.8 to 9.2 degrees is present with mid-level rates between 8.2 to 8.7 degrees. Looking at soundings, there's an apparent cap at around 800 mb that is preventing the storms from tapping into the full available energy. Depending on whether storms can overcome the cap will determine if storms will be stronger than anticipated. Per SPC, the entire CWA is fully in a marginal risk Thursday with 5% chances of severe wind and/or hail embedded with these storms. Regardless, gusty outflows is likely from any strong developing storms, bringing erratic 40-60 mph gusts.

For Friday, a cold front passes through the region that will develop tight pressure gradients and bring along breezy to gusty winds across the region. Thunderstorm formation will be limited to the eastern part of the CWA near the Wallowas and parts of the Foothills of the WA Blues (15 to 25% chance) as the low moves off to the east. Conditions quickly become more dry over the weekend as the pattern becomes more zonal/slightly ridged over the PacNW and a warming trend continues.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

VFR conditions currently across all sites, which will stay the course through the period. Breezy 20-30kt wind gusts are occurring for KRDM/KBDN and persist through the afternoon and evening, subsiding later this evening. These terminals will experience rain showers later today, and the potential for isolated thunderstorms through the afternoon. Any thunderstorms that develop will include breezy and erratic winds, brief hail, and periods of heavy rainfall. All remaining terminals will stay dry with winds of 10kts or less. 75

Preliminary Point Temps/PoPs

PDT 79 50 85 51 / 0 10 10 50 ALW 81 56 86 58 / 0 0 20 50 PSC 85 53 92 55 / 0 0 0 50 YKM 87 56 93 56 / 0 0 10 70 HRI 82 52 88 54 / 0 0 0 60 ELN 82 54 89 53 / 0 0 10 70 RDM 78 44 80 42 / 0 30 80 90 LGD 79 48 85 49 / 10 30 30 60 GCD 79 43 81 44 / 10 40 60 50 DLS 86 59 90 56 / 0 0 10 90

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.