textproduct: Pendleton

UPDATED AVIATION...12 TAFs

While an ongoing rain shadow keeps rain pinned along the mountains, VFR conditions will prevail during overnight hours for all sites with light rain currently over KDLS. Through most of the day Tuesday, rain is forecast to develop for all sites. KDLS, KPDT, and KRDM may reach to MVFR conditions or lower as VSBYs and/or CIGs drop from the low clouds and potential mist Tuesday morning into early evening hours. KPSC may see MVFR conditions around early Tuesday evening as light rain arrives starting late Tuesday afternoon(<30% confidence). Southwest to west gusty winds are expected to be at 20-30kts or higher for most sites overnight into Tuesday morning. However, winds gusts up to 30kts could return for KBDN late Tuesday morning and for KRDM early Tuesday evening. Feaster/97

DISCUSSION

Key Points:

1. Significant rainfall leading to flooding in some areas through the week. *Flood Advisory and Warnings Active*

2. Breezy conditions through Thursday

3. Warm temperatures will continue through the long term

Current radar shows much of the incoming rainfall to be mostly on the west side of the Cascades with some spill over in portions of Kittitas and Yakima Counties as well as over the higher peaks of the Blues. Winds are expected to begin settling through the morning with ground observation showing gusts to be between 25-35 mph still. Winds are expected to settle after 3-5 AM as the passage of the front continues to move east.

Today through Thursday afternoon...Models show a relatively strong atmospheric river has set up along the coast of WA and OR and persisting through Thursday. This will bring widespread significant rainfall to the region with QPF totals for today through Thursday afternoon totaling to nearly 3 inches along the eastern slopes with higher amounts along the crests. Models also show nearly 1-1.5 inches of precipitable water which is substantially higher than the normal. CAMs raw ensembles (HREF) show the crests to the eastern slopes through Ellensburg and the Dalles as well as the eastern mountains through the Grande Ronde Valley and into Wallowa Valley will see 0.05-1 inch or more of precipitation today (Tuesday)with 80- 90% confidence. This will continue through the day with ensembles showing up to another inch of precipitation in the aforementioned areas again Wednesday. However, backing off along the eastern mountains and the Grande Ronde Valley where only 0.25-0.5 inches are expected (60-80%). NBM raw ensembles show 25-65% chance of the lower elevations such as the Basin and foothills of the Blues will see 0.25-0.30 inches in a 48 hour period and central OR will see 0.10 inches. With the significant rainfall across the WA Cascades, many rivers are expected to reach/exceed bankfull through tomorrow. Naches at Naches, Yakima at Horlick and Easton are all exceeding action stage and into minor so a Flood Warning has been issued for those locations. All other rivers in the area are still at or nearing action stage and are continuing to be monitored as the event continues to unfold.

Models show another cold front to make its way across the region beginning Tuesday night and persisting through Wednesday bringing another round of breezy conditions. Pressure gradients along the Cascades with this front are not as strong as the previous with only 7-9 mb gradient. Winds will be from the southwest between 15-25 mph sustained with gusts to 40 mph and will affect the wind prone Gap areas as well as the eastern slopes, Horse Heaven Hills and the Northern Blues of WA. After Wednesday, models show a more zonal flow will rest over the region bringing winds back to a more diurnal flow.

Lastly, models show that not only did this AR tap into an abundance of moisture, but also in a abu-tropical flow that will bring with it increasing temperatures. With the influx of warm air, temperatures are expected to be 10-15 degrees warmer than seasonal average today increasing to 15-25 degrees above seasonal average Wednesday. Short term raw ensembles show elevations below 3500 feet will see temperatures in the low to mid 50s Tuesday, with the exception of Kittitas Valley where temperatures will be in the mid to upper 40s (70-90% confidence). Moving to Wednesday, raw ensembles show the same areas beginning to see temperatures in the low to mid 60s with Kittitas Valley now seeing low to mid 50s (60-80% confidence). Temperatures will steadily decrease as we move into the later portion of the week, however, temperatures are expected to stay 10- 20 degrees above climatological normal. Essentially saying temperatures will remain in the low to mid 50s. 90

PRELIMINARY POINT TEMPS/POPS

PDT 56 45 65 51 / 100 90 40 20 ALW 54 46 64 54 / 90 90 60 30 PSC 56 44 66 53 / 80 90 20 20 YKM 50 39 60 48 / 80 100 60 50 HRI 57 46 66 52 / 90 90 20 20 ELN 46 35 56 44 / 70 100 70 70 RDM 57 44 63 37 / 70 50 10 0 LGD 51 41 58 45 / 100 100 50 20 GCD 51 45 58 40 / 90 70 10 10 DLS 56 48 63 55 / 100 100 70 60

PDT WATCHES/WARNINGS/ADVISORIES

OR...Wind Advisory until 7 AM PST this morning for ORZ041-044-507-508- 510.

WA...Wind Advisory until 7 AM PST this morning for WAZ024-027>029-521.

Flood Watch through Friday morning for WAZ026-027-521>523.