textproduct: Pendleton

KEY MESSAGES

1. Low chances of thunderstorms this afternoon with continued warm conditions

2. Widespread breezy to windy conditions tonight through Tuesday * Wind Advisory in effect*

3. Pattern shift brings uncertainty to the forecast beginning midweek

DISCUSSION

Current radar shows a few convective cells trying to form in the southern portion of Deschutes County. Guidance does show a 10-15% probability of thunderstorms forming across that area through the remainder of the afternoon into the evening. Latest CAMs are showing instability with MUCAPEs reaching 200-250 J/kg with shear only in the 15-25kts range. Gusty outflow winds will be the primary concern with the thunderstorms with models suggesting up to 50 mph outflows. DCAPE values of 300-500 J/kg support the outflow probabilities.

Temperatures today will be warm with temperatures 15-20 degrees above seasonal average. Could see some near record temperatures across the region today. NBM shows temperatures to be in the mid to upper 70s across the Basin, adjacent valleys, Gorge, foothills of the Blues, central and north central OR with 80-90% probabilities. There is also some isolated locations within the Basin (Hanford area) that could see temperatures reach at or near 80 degrees. Temperatures will then begin to settle Tuesday as the next system moves in bringing temperatures back to 5-10 degrees above normal

Winds will be the next concern for the forecast period as the region becomes sandwiched between two upper level systems. The upper level low to the north will continue to break down the ridge as it moves in from the north later this evening. In house pressure gradient tool shows a tightening of the surface gradients across the area with a 10-14 mb spread. This will bring increased winds to the Kittitas Valley where a Wind Advisory is in effect from 5 AM through 5 PM Tuesday for 25-35 mph sustained winds and gusts to 45 mph (70- 80% confidence). Winds will be breezy across the Simcoe Highlands as well as the foothills of the southern Blues with 60-80% of the raw NBM ensembles in agreement for gusts 30-35 mph in those locations. Winds will also be elevated along the ridgetops of the Ochoco John- Day Highlands, Horse Heaven Hills and along portions of the Northern Blues.

Models begin to diverge after Tuesday with the next pattern solution. The cut-off low in the Pacific and the incoming trough is proving difficult for models to resolve. However, there does appear to be come congruency with a split flow pattern occurring with the trough to the northwest and the incoming cut-off low to the south of the region. This will keep temperatures to neat or above normal with slight chances (15-30%) of precipitation mainly across the mountains ans the southern portion of the region (Deschutes, Grant and Crook Counties through Friday. NBM raw ensembles also keep in 10- 15% probabilities of those same areas seeing slight chances of isolated thunderstorms. Thereafter, models begin to show another trough is set to move into the region, however, clusters are showing a timing and positioning separation between ensembles. Looking at the CPC guidance, temperatures look to be at or slightly above normal with above normal seasonal precipitation for days 6-10. 90

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

VFR conditions to prevail through the period. There remains a 10% chance or less of an isolated thunderstorm impacting sites RDM/BDN through early this evening. Winds will be light, 12kts or less, through this evening at sites PDT/ALW/PSC and will remain light through the period at site YKM. Winds of 12-17kts with gusts 20-25kts will continue at sites DLS/RDM/BDN, but will become light in the evening. Winds will increase again 12-20kts with gusts 20-30kts at sites PDT/DLS/ALW/PSC by or after 10Z as a cold front approaches and passes through the region. Winds will increase further to 20-25kts with gusts 30-35kts at sites DLS/PDT after 16Z. Expect wind shifts around 16Z for sites PDT/ALW/PSC. Otherwise, light winds tonight then increasing to the 12-15kts with gusts up to 25kts at sites RDM/BDN. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 47 65 35 65 / 0 0 0 0 ALW 50 65 39 65 / 0 0 0 0 PSC 47 69 37 68 / 0 0 0 0 YKM 42 66 35 67 / 0 0 0 0 HRI 49 68 36 68 / 0 0 0 0 ELN 38 57 32 62 / 10 0 0 0 RDM 37 68 32 68 / 0 0 0 0 LGD 43 65 34 65 / 0 0 0 0 GCD 42 68 34 67 / 20 0 0 0 DLS 46 65 39 70 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...Wind Advisory from 5 AM to 5 PM PDT Tuesday for WAZ026. OR...None.