textproduct: Pendleton

KEY MESSAGES

1. Isolated to scattered thunderstorms with abundant lightning and gusty outflow winds *Red Flag Warning In Effect*

2. Sunday continued southwest flow will bring chances of thunderstorms and showers through Monday.

3. Increased Gap winds Tuesday

DISCUSSION

Current nighttime satellite shows some mid level clouds lingering over the region. Radar shows a few returns along the eastern slopes of the Cascades but no thunderstorms within the cells. Overnight temperatures will be in mostly in the 50s with isolated areas in the Basin seeing low 60s.

Southwest flow aloft will continue over the region with a trough just off the coast. Models show a shortwave will make its way into the region bringing with it increased moisture form the southwest. T his will lead to increased chances of thunderstorms and showers over the Cascades as well as the eastern mountains again today. Looking at forecasted NAM soundings, there are MUCAPE values between 250-750 J/kg with isolated pockets of near 1000 J/kg, LIs of -3 to -4, lapse rates between 1-10 C/km and effective bulk shear of 18-22 kts. HREF lightning density paintball shows much of the lightning forming along the crest and east slopes of the Cascades as well as across the eastern mountains beginning with highest density being after 1 PM. NBM raw ensembles show 30-40% chances of thunderstorms occurring in those same region. Even with the increased chances of showers accompanying these storms, there is moderate confidence (60-70%) of elevated fire weather conditions developing due to lightning potential outside of rain cores and gusty outflow winds. Therefore a Red Flag Warning has been issued for these areas through 9 PM tonight.

Sunday through Monday models show an upper level low off the coast moving towards the south and deepening the southwest flow across the region. Models do show some moisture being swept up into the region leaving slight chances (10-20%) of showers and thunderstorms occurring Sunday afternoon, especially along the Wallowa Mountains. There are also chances (10-15%) of thunderstorms in central OR as well as the WA Cascades. Monday also shows slight chances (10-15%) of thunderstorms along the same areas.

Tuesday models show a bit of split flow across the region as an upper level shortwave moves south out of B.C. bringing northwest flow aloft across the northern portion of the CWA while the trough remains just off shore and is pushing southwest flow into the southern portion of the CWA. The northwest flow aloft will allow for breezy gap winds to form Tuesday with NBM raw ensembles showing sustained winds speeds between 15-20 mph with 50-70% of the ensembles in agreement.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

VFR conditions to prevail through a majority of the period, with MVFR conditions possible through the remainder of the morning into the early afternoon. An upper weather system moving through the area early this morning continues to produce showers/thunderstorms that are impacting sites PDT/ALW/PSC. These storms should clear out from PDT around 18Z, then clear ALW/PSC between 19Z-20Z. Thunderstorms will continue to be possible along the WA Cascade east slopes and the Blue mountains through the afternoon and evening. There is a low chance (~15%) of shower/thunderstorm impacts at sites PDT/ALW between 21Z-00Z.

Winds will increase to 12-20kts with gusts 20-30kts at site DLS this afternoon, becoming light around or after 05Z. Breezy winds will develop at sites RDM/BDN with gusts up to 20kts this afternoon, becoming light late in the evening hours. Winds will otherwise remain light through the period at all other sites. Lawhorn/82

FIRE WEATHER

Continued monsoonal moisture will bring thunderstorm chances across the region again today with 30-40% chances for the Blues Mountains and Wallow Mountains. Eastern slopes of the WA Cascades will see 10-15% chances for thunderstorms today as well. Sunday and Monday will also continue to see 10-15% chances of thunderstorms for the eastern mountains s well as the WA Cascades. A slight pattern shift Monday night into Tuesday will bring breezy gap winds of 15-20 mph sustained.

Preliminary Point Temps/PoPs

PDT 87 56 88 58 / 20 0 0 0 ALW 90 62 90 64 / 30 10 0 0 PSC 92 57 93 59 / 20 0 0 0 YKM 89 60 91 61 / 20 10 0 0 HRI 90 60 91 62 / 20 0 0 0 ELN 85 58 86 59 / 20 10 0 0 RDM 85 49 86 52 / 20 10 0 0 LGD 86 54 89 57 / 70 20 10 0 GCD 88 54 91 56 / 40 0 0 0 DLS 90 63 89 62 / 20 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until noon PDT Monday for WAZ026-522-523. Red Flag Warning until 9 PM PDT this evening for WAZ692-693. Air Quality Alert until noon PDT today for WAZ027-521. OR...Air Quality Alert until noon PDT Monday for ORZ041-503-505-506- 508>511. Red Flag Warning until 9 PM PDT this evening for ORZ692>695- 699.