Damaging Wind in Oregon, July 30, 2022

Area Forecast Discussion
National Weather Service Pendleton OR
355 PM PDT Sat Jul 30 2022

.Updated aviation discussion

.SHORT TERM...Rest of Today through Monday night...Heat and fire
weather concerns comprise the forecast challenges in the short term
period. With a strong upper-level ridge in place over the Pacific
Northwest, excessive heat remains a concern through the weekend for
our entire forecast area. Additionally, ensemble and
deterministic guidance have continued to trend slower with the
arrival of the cut-off low that remains parked offshore. As such,
the breakdown of the ridge will likely not occur until at least
Tuesday, with only modest suppression of the ridge on Monday due
to a shortwave trough passing across the Canadian Rockies. Have
extended the Excessive Heat Warning until 11PM Monday for the
Lower Columbia Basin, Yakima Valley, and Foothills of the Blue
Mountains zones as HeatRisk remains elevated. That said, afternoon
high temperatures should moderate somewhat Monday, around 5
degrees cooler than Sunday, though still eclipsing the century
mark in most areas.

Regarding fire weather concerns, moderate to high confidence exists
in thunderstorms developing each afternoon across the Cascade crest,
central Oregon, and portions of the eastern mountains. Some elevated
instability with steep mid-level lapse rates, mid-level moisture,
and a deep boundary layer with strong daytime surface heating
will facilitate afternoon and evening convection with strong,
gusty outflow winds and abundant lightning. HREF neighborhood
probabilities suggest a decent chance of strong outflow (30-50%
chance of gusts exceeding 30 kts for central Oregon this afternoon
and evening, and 50-70% chance for central Oregon and the eastern
mountains on Sunday with a 10% chance of exceeding 50 kts for
central Oregon on Sunday). Monday, moisture will continue to
advect across the region with another round of thunderstorms
forecast for central Oregon through the eastern mountains. Red
Flag Warnings have been issued for fire weather zones 611 and 610
for this afternoon, and 611, 610, 640, 642, and 644 for Sunday and
Monday. Lastly, breezy winds are forecast through the Cascade
gaps on Monday, but RH values are not expected to reach critical
thresholds. Plunkett/86

.LONG TERM...Tuesday through Saturday...Poor run-to-run continuity
in the deterministic and ensembles have made for a challenging long
term forecast.  The models are not handling a closed low off the
eastern Pacific well, and the GFS is determined to fill the low and
push in northeast across Oregon on Thursday.  The Canadian and ECMWF
are in slightly better agreement with the center of the low about
550 miles west of the OR/CA coast Tuesday-Wednesday, although the
Canadian is much farther east than the ECMWF from Thursday-Friday.
Despite these significant differences, they are all in agreement
that a broad and flat trough will set up over western Canada and the
interior NW during the long term period.  This will lower heights
and increase the westerly flow.  We will be looking at near to below
seasonal temperatures late in the week.  However, it will be breezy
to windy for areas in and around the Columbia Basin. The relative
humidity will respond with the cooler temps, but there will not be a
significant increase. The ECMWF EFI hints that winds in the Lower
Columbia Basin south of the Tri-Cities will be climatologically high
for Tues-Wed, so this may be addressed in the near future for fire
weather.

Another fire weather concern, particularly at the start of the long
term period, will be the threat of thunderstorms.  Central and
northeast Oregon and southeast Washington will be under an unstable
southwest flow aloft.  Based on WPC's Cluster of the multi-mean QPF
and a majority of the EC-ENS and GEFS members QPF, there is a chance
that these area will have occasional showers and thunderstorms
although the amounts vary from one member to another. Wister/85

&&

.AVIATION...00Z TAFs...VFR conditions will prevail for the next 24
hours. Skies will be mostly clear with mostly light terrain driven
winds though the period. However there may be periods of breezy
winds 10-20 kts from the NW this evening at KPDT, KDLS, KRDM and
KBDN, and again after 21Z Sunday. Skies will become BKN-OVC with a
very slight chance of thunderstorms after 21Z Sunday over KRDM and
KBDN. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  70 108  73 100 /   0   0   0  10
ALW  72 109  75 103 /   0   0   0   0
PSC  73 110  75 105 /   0   0   0   0
YKM  67 108  68 103 /   0   0   0   0
HRI  72 112  76 105 /   0   0   0   0
ELN  67 105  69  99 /   0   0   0  10
RDM  66 104  67  95 /  20  20  20  20
LGD  68 103  69  97 /   0   0   0  10
GCD  69 105  68  97 /   0  20  20  20
DLS  74 109  75  98 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 11 PM PDT Sunday for ORZ041-505-508-
     510-511.

     Heat Advisory until 11 PM PDT Sunday for ORZ049-050-502-503-506-
     509.

     Red Flag Warning from 2 PM Sunday to 11 PM PDT Monday for ORZ610-
     611-640-642-644.

     Excessive Heat Warning until 11 PM PDT Monday for ORZ044-507.

     Red Flag Warning until 11 PM PDT this evening for ORZ610-611.

WA...Excessive Heat Warning until 11 PM PDT Sunday for WAZ024-026-521.

     Heat Advisory until 11 PM PDT Sunday for WAZ030.

     Excessive Heat Warning until 11 PM PDT Monday for WAZ027>029.

     Heat Advisory from 11 PM this evening to 11 PM PDT Sunday for
     WAZ520.

     Excessive Heat Warning until 11 PM PDT this evening for WAZ520.

&&

SHORT TERM...86
LONG TERM....85
AVIATION...88