325
FXUS66 KPDT 052309
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
409 PM PDT Fri Jul 5 2024

Updated Aviation Discussion

.AVIATION...00z TAFs...VFR conditions expected. Skies will remain
clear amidst the ongoing heat wave, with winds light and terrain-
driven across most sites. Some sites along the Cascades, namely
BDN and RDM, may see locally breezy conditions tomorrow afternoon,
with gusts approaching 20-25 kts out of the NW. Pilots should be
aware that unseasonably hot temperatures can also promote High
Density Altitude. Evans/74

&&

.PREV DISCUSSION... /issued 239 PM PDT Fri Jul 5 2024/

SHORT TERM...Tonight through Sunday...High pressure ridge will
now be firmly entrenched over the region well into next week,
promoting significantly hot conditions and enhanced fire weather
concerns. At this point confidence is very high (90-100%) in
temperature across the weekend reaching at or above triple digits
for most of our lower elevation locations; The Dalles has already
hit 100 as of this writing, and with peak heating still a little
bit away, we`re likely to see portions of the Columbia Basin and
Yakima Valley achieve these temperatures today. Temperatures
should slowly rise through the weekend about 1-3 degrees each day,
with widespread triple digits the certainty for Sunday. These hot
afternoon highs coupled with increasing overnight lows rising
across the 60`s for the lower elevations will lead to widespread
moderate to major HeatRisk values with pockets of extreme. Excessive
heat warnings and advisories will continue into next week.

A pair of disturbances rounding the ridge overhead are also
tightening the pressure gradient leading to some locally enhanced
breezes for the Kittitas Valley today and into Central Oregon
tomorrow. This alongside the bone dry airmass will promote some
elevated fire weather concerns, detailed in further in the Fire
Weather section below. Goatley/87

FIRE WEATHER...Red flag warning remains in effect until 9 PM this
evening for WA Fire Weather Zone 690 (Kittitas Valley); Red flag
warnings in effect for OR Fire Weather Zones 610, 611, 640, and
642 valid Saturday 2 to 9 PM. Both of these are in effect for
critically low relative humidity values into the teens and single
digits, and breezy winds around 10 to 20 mph with gusts to 25 mph.
Enhanced winds are expected thanks to a pair of passing shortwave
troughs to the northeast rounding the dominant ridge over our
region, tightening the pressure gradient and bringing elevated
winds. Sunday winds should decline, but some elevated winds may be
possible in Central Oregon once again. Expect this will be brief
and should not coincide long enough with lowered RH values to
necessitate any fire weather products, but we continue to monitor
for the potential. Goatley/87

LONG TERM...Monday through Friday...The ridge remains in place
through much of the long term forecast period. This system will
continue to produce hot temperatures across the lower elevations.
Temperatures of 100 degrees or greater are likely (60-100%) through
the forecast period. Tuesday is anticipated to be the hottest day,
with a 80-100% chance of temperatures above 100 degrees for the
lower elevations, and a 30-50% chance for temperatures of 110
degrees or greater, mainly across the Columbia Basin.

The ridge will generally move east of the area by Wednesday,
allowing southwest flow develop across the region. Models do have
variances with the progression of this ridge, with the clusters
showing some timing differences. Additionally, the clusters show some
disagreement with the timing and strength of the approaching
southwest flow in the latter portion of the week. Moisture is
currently present within this flow, allowing temperatures to remain
high, though a few degrees of cooling is noted between Wednesday and
Friday. Even with this cooling, temperatures will be 10-15 degrees
above normal.

The last mentionable concern will be wind during the latter half of
next week. As the southwest flow develops, there could be an
increase in afternoon winds, with a 60-90% chance of gusts of 25 mph
noted across the western half of the CWA on Wednesday, and a 30-50%
chance for 25 mph gusts for the same area into Friday. Branham/76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  60  95  62  99 /   0   0   0   0
ALW  63  98  64 102 /   0   0   0   0
PSC  64 100  65 103 /   0   0   0   0
YKM  62 100  62 101 /   0   0   0   0
HRI  62 101  64 103 /   0   0   0   0
ELN  64  98  63 101 /   0   0   0   0
RDM  56 100  56 100 /   0   0   0   0
LGD  58  91  58  95 /   0   0   0   0
GCD  57  96  58  98 /   0   0   0   0
DLS  66 103  68 106 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 10 PM PDT Thursday for ORZ041-044-
     507-508-510.

     Heat Advisory from noon Monday to 10 PM PDT Thursday for ORZ050.

     Red Flag Warning from 2 PM to 9 PM PDT Saturday for ORZ610-611-
     640-642.

     Heat Advisory until 10 PM PDT Thursday for ORZ505-511.

WA...Excessive Heat Warning until 10 PM PDT Thursday for WAZ024-
     026>029-521.

     Heat Advisory until 10 PM PDT Thursday for WAZ523.

     Red Flag Warning until 9 PM PDT this evening for WAZ690.

&&

$$

SHORT TERM...87
LONG TERM....76
AVIATION...74