Area Forecast Discussion

KEY MESSAGES

1. Continued dry and warm conditions through the week *Heat Advisory in effect*

2. Isolated to scattered thunderstorms Wednesday and Thursday *Red Flag Warning Wednesday For Abundant Lightning*

3. Hot, dry and windy conditions return Friday

DISCUSSION

Current radar is showing a few echos across the central portion of the region. Satellite shows some mid level cloud cover over the same area as the mid level moisture begins to build into the region. So far no ground observations are showing any precipitation with the cells that are moving across. Enough of the smoke has cleared that temperatures were able to climb this afternoon with the current temperatures around the region being in the low to mid 90s with high 70s and 80s along the ridgelines.

Models show the upper level ridge to remain overhead through Thursday keeping the region under dry and warm conditions. Temperatures will steadily increase and there is 80% chance of seeing major HeatRisk Tuesday through Thursday with highest probabilities being Wednesday. If the smoke lifts, NBM shows temperatures to reach between 100-105 in the Columbia Basin and the Gorge with isolated areas along the foothills seeing upper 90s to 100 degrees. That coupled with the high overnight temperatures in the upper 60s to low 70s will cause heat related impacts to occur. Confidence in the HeatRisk is high (80-90%).

By Wednesday, models are in firm agreement and show a slight pattern shift with the upper level ridge shifting towards the Four Corners and advecting some monsoonal moisture up into the region. NBM raw ensembles show Wednesday to have 40% chance of thunderstorms through Deschutes and Grant counties after 2 PM. Looking at soundings show CAPE values over 800 J/kg, lapse rates 9-10 C/km, effective bulk shear of 30 kts and LIs of -4 and PWATs of 0.05-1.0 inches. Cannot rule out isolated dry thunderstorms mixed with wet thunderstorms and with the fuels as ready as they are, not a lot is needed to ignite a fire, especially if there are strikes outside of the wet core. Thursday the NBM raw ensembles shows a 30% chance of thunderstorms creeping up along the WA Cascades as well as out over the eastern mountains. Forecast soundings show CAPE values in the 500 J/kg range with -3 LI, 7 C/km lapse rates, we could see some shallow thunderstorms ignite. Again, fuels in these areas are very receptive.

Thursday models show a dry upper level low beginning to push into the region shifting the upper level high of to the east. In house calculations show the pressure gradients along the Cascades tightening which will bring elevated winds to the Cascade Gaps as well as portions of the southern Blues and central OR. NBM raw ensembles shows the region with the highest probabilities for 20 mph sustained winds is through the Gorge and foothills of the southern Blues at 70-90%. 15 mph sustained winds expected through the Kittitas Valley and through portions of central OR with 60-80% probabilities. With the continued dry and warm conditions, relative humidities will remain low and coupled with the winds elevated fire weather concerns for Friday and Saturday.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Smoke from surrounding wildfires continue to impact local TAF sites in the Columbia Basin through Central Oregon. Visibilities are reduced to 1-3 miles in the most impacted areas. For RDM, smoke is expected to inhibit visibility during a general wind from the north direction and from the west in ALW/PSC. Winds in generally will be light, which will make forecasting smoke impacts difficult as it "swishes" around the region.

FIRE WEATHER

Isolated to scattered thunderstorms expected Wednesday through central OR and the southern Blue mountains with 20-40%. There will be a mix of wet and dry thunderstorms and any strikes outside of a wet storm core still has the potential to ignite a fire. These storms are also high based in nature and plenty of virga will be visible and the potential for gusty outflow winds of 25-35 mph is likely.

Preliminary Point Temps/PoPs

PDT 65 98 67 96 / 0 0 0 10 ALW 70 100 71 99 / 0 0 0 10 PSC 68 102 70 101 / 0 0 0 0 YKM 70 102 72 100 / 0 0 20 10 HRI 69 102 71 99 / 0 0 0 10 ELN 68 100 70 96 / 0 10 20 10 RDM 63 96 59 93 / 10 40 50 0 LGD 65 98 66 99 / 0 0 10 40 GCD 63 97 62 98 / 20 10 20 20 DLS 73 103 71 91 / 0 0 20 10

PDT WATCHES / WARNINGS / ADVISORIES

WA...Heat Advisory until 9 PM PDT Thursday for WAZ024-027>029. Air Quality Alert until 9 AM PDT Wednesday for WAZ028>030. OR...Heat Advisory until 9 PM PDT Thursday for ORZ041-044-507. Air Quality Alert until 4 PM PDT Wednesday for ORZ044-049-050- 502-503-505>509-511. Red Flag Warning from 11 AM to 11 PM PDT Wednesday for ORZ698- 700-705.