Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
082 FXUS66 KPDT 262309 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 409 PM PDT Wed Jun 26 2024 .UPDATED AVIATION...00Z TAFs...Primary concern for TAF sites this period revolve around winds. All TAF sites will experience sustained winds of 15-25 kts withs gusts to 30 kts through much of the period with a brief reprieve at TAF sites YKM/RDM/BDN near 05/06Z decreasing below 10 kts until 18-20Z when winds will again pick up above 10 kts and gusts 25 kts. Mostly high clouds above 10-25kft. Bennese/90 && .PREV DISCUSSION... /issued 309 PM PDT Wed Jun 26 2024/ SHORT TERM...Today through Friday... Bottom Line Up Front 1. Thunderstorms along the eastern mountains this afternoon. 2. Breezy to windy conditions today through the Cascades Gaps. 3. Dry and warm conditions return Thursday night. Current radar shows that the thunderstorms have since decreased over the east slopes of the Cascades from this morning. Some cells are beginning to pop up over Wallowa but ground observations are showing very lite rain as well as no lightning. Thunderstorms will continue to develop along the eastern mountains with 30-50% probabilities, highest probabilities in Wallowa County this afternoon with orographic lifting assisting in the formation of the cells over the mountains. The storms that do develop over Wallowa County will put down some precipitation with model derived soundings showing PWATs of 0.80 inches, MUCAPEs of greater than 200 J/kg, lifted index between -2 to -4 and lapse rates over 8.5 C/km. Models are in firm agreement with the upper level low continuing to push onshore. Clusters are showing no variances between the models so the forecast outcome is pretty on par. Southwesterly flow aloft will dominate through the remainder of today and continue to tighten the cross Cascade pressure gradient. Looking at the pressure gradient in office, the pressure gradient change between PDX to GEG ranging from 9 to nearly 11 mb through 8 PM tonight. Looking at the raw ensemble data it shows there to be over an 80% probability of the Simcoe Highlands, lower Columbia Basin and the southern foothills of the Blues to see gusts nearing and just over 40 mph. Ground observations along those areas have already confirmed the speeds already. Models remain in firm agreement with alignment within the clusters showing little to no variances in the track of the exiting low and incoming ridge. To start, showers will affect mainly the mountains as the upper level low continues to traverse across the area. Ensembles show a 20% probability of 0.05 inches of rain along the eastern slopes increasing steadily as you head towards the crests with 60-80% chances of 0.05 inches of rain along Snoqualmie and Stampede Passes. Probabilities of 0.05 inches along the Northern Blues is less than 10%. Once the upper level low moves off towards the east, and upper level ridge begins to build back over the region. This will bring warming temperatures and dry conditions back to the region. Thursday will also be the coolest day of the short term with over 50% of the ensembles showing a 5 to 10 degree drop from todays highs of upper 70s to mid 80s. Bennese/90 LONG TERM...Saturday through Wednesday...The main sensible weather highlights include: - Elevated fire weather conditions possible (50-70%) Sunday owing to the combination of dry and windy conditions alongside low chances for isolated thunderstorms in the eastern mountains. - Broadly seasonable temperatures with Sunday and Wednesday looking to be more likely than not the warmest in the period. The large scale pattern early Saturday will be characterized by a somewhat progressive synoptic pattern. Guidance is in good agreement with a shortwave trough moving in behind a transient shortwave ridge early Saturday. The former associated with an upper- level low in the eastern North Pacific offshore BC. This feature will lift across the PacNW and move north into Alberta to then be followed by another shortwave trough that will amplify and deepen across the PacNW on Sunday. A weak marine push late Saturday/Saturday night associated with the initial feature will be followed by a stronger cold front crossing late Sunday/Sunday Night. The latter day will support stronger, increased winds along and ahead of the front. Increased confidence (~70%) with clustering solutions showing good agreement, which support the favorable combination of dry and windy conditions more so Sunday compared to Saturday. Chances for 24-hr peak daily gusts exceeding 39 mph surpass 75% across Kittitas Valley, Simcoe Highland, Cascade gaps, and the eastern Gorge spilling into north central OR and parts of the foothills of the Blues. Most likely peak gusts (50th percentile) are seen to be around 35-45 kts (40-50 mph) on Sunday. Meantime, large scale forcing for ascent ahead of this impulse with marginal instability and modest mid-level lapse rates will support the potential for low-end (15-25%) storm chances confined mainly to the eastern mountains Sunday. Limited instability on Saturday but could see slight chances for showers across the upper slopes of the WA Cascades and eastern mountains late Saturday and Saturday night. Northwest and upper-level cyclonic flow dominates Monday with breezy conditions likely to continue, albeit slightly cooler with drier conditions more likely than not area-wide. Thereafter guidance in moderate agreement between either near zonal (50%) to a northwest flow regime with upstream ridging (50%) taking hold offshore the PacNW on Tuesday. Nonetheless, a less active pattern looks to take shape Tuesday and Wednesday with highs starting to warm back up by midweek. && .PRELIMINARY POINT TEMPS/POPS... PDT 52 73 48 79 / 10 0 0 0 ALW 56 77 53 83 / 10 10 0 0 PSC 58 80 54 84 / 10 10 0 0 YKM 51 75 48 81 / 0 10 0 0 HRI 57 79 52 84 / 10 0 0 0 ELN 52 71 50 81 / 0 10 0 0 RDM 45 72 41 79 / 10 0 0 0 LGD 50 69 45 78 / 20 10 0 0 GCD 50 73 45 81 / 0 0 0 0 DLS 56 74 53 84 / 10 10 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...90 LONG TERM....80 AVIATION...90