979
FXUS66 KPDT 172316
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
416 PM PDT Wed Jul 17 2024

.UPDATED AVIATION...18Z TAFs...VFR across the TAF sites with
elevated winds at DLS/PDT/BDN/RDM/YKM with gusts to 25 being
reported/ There have also been thunderstorms near PDT and some
expected near YKM around now through 02Z. Monitoring thunderstorms
for PSC with a tempo group now until 2Z. Things should begin to
calm with regards to winds and TS between 2-5Z. Bennese/90


&&

.PREV DISCUSSION... /issued 215 PM PDT Wed Jul 17 2024/

SHORT TERM...Today through Saturday...All eyes are on radar and
satellite this afternoon as a low pressure system currently centered
on the OR/WA border around Portland slowly lurches its way NNE-ward,
bringing with it a round of broken showers and some isolated
thunderstorms. So far, activity this afternoon has been concentrated
primarily along the spine of the southern WA Cascades, but even then
lightning strikes have been relatively infrequent. Across the
eastern mountains and portions of the Basin, light showers to virga
have prevailed thus far. With clearing on the back end of this
morning`s showers, there is a potential for another round of
isolated showers and storms to form heading into the evening hours
tonight, namely across the Washington Columbia Basin and even into
the eastern mountains.

Or at least that is what is being suggested by recent runs from CAMs
such as the 18z NAMNest and HRRR. Confidence is shaky, however, as
latest SPC mesoanalysis keeps instability concentrated primarily
over the Cascades, with moisture still being pretty limited. It
doesn`t take much moisture or instability to trigger convection
given the right pattern, however this system`s performance outside
of central Oregon does not particularly inspire confidence. Either
way, the 4-10pm time window will be key, and we`ll have to keep a
close eye on how convection develops under clearer skies. Until
then, Red Flag Warnings remain in effect for both Basin zones and
zones around the east slopes of the Washington Cascades.

Quieter, albeit hotter, weather prevails Friday onward. Once the low
moves out, high pressure stemming from the Four Corners will slowly
begin to dominate, fighting against a weak shortwave trailing
today`s low on Friday. Not seeing much of any impacts in the way of
this wave, so looking at primarily increasing temps, the usual gap
flows, and continued dry conditions. Heat headlines remain in
effect, with more possible over the weekend should models prove
correct in depicting the influence of this building Four Corners
high. Evans/74

LONG TERM...Saturday through Wednesday...A ridge continues to
amplify across the PacNW on Saturday and Sunday. Hot temperatures
are expected (70-90%) with HeatRisk demonstrating wide swaths of
Moderate risk by Saturday, and developing pockets of Extreme risk on
Sunday, especially across the lower elevations. Audiences
susceptible to heat should consider preparations ahead of this
incoming heat. This round of heat is anticipated to be shorter than
the one experienced in early July, though additional audiences could
be impacted with the weekend. Sunday is expected to be the hottest
day through the forecast period. Currently, analysis is
demonstrating a 80-100% chance of temperatures of at least 100
degrees F for the lower elevations of Sunday, with a low chance (10-
30%) chance of temperatures of 110 or greater. To offer support, the
ECMWF Extreme Forecast Index also highlights a significant portion
of the forecast area as abnormally warm for the weekend.

As the ridge amplifies, it does produce a tightened pressure
gradient for Sunday, with gusty wind developing across the western
half of the forecast area by the afternoon/evening hours. This
gradient will receive an extra boost from a passing wave to help
produce additional gusty winds on Sunday. The favored areas of
Yakima and Kittitas Valleys are current showing a 30-50% chance of
wind gusts of 30-35 mph. Generally quiet conditions anticipated for
Monday with this pattern with a return of gusty afternoon wind
possible (30-50%).

Another area of low pressure will influence conditions across the
PacNW by Tuesday. This system will help to flatten the ridge
allowing temperatures to cool down to near normal values. Meanwhile,
this system will again result in a tightened pressure gradient
across the forecast area, with gusty winds possible (20-50%).
Influences from this system will continue through the remainder of
the forecast period, with near yo slightly above normal(within 5
degrees) temperatures forecast. Cluster analysis through the later
forecast periods all remain fairly supportive of the progression of
this area of low pressure. Branham/76

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  63  98  63  97 /  20   0   0   0
ALW  67 102  68 101 /  20   0   0   0
PSC  67 103  67 102 /  20   0   0   0
YKM  63 101  63 100 /  20   0   0   0
HRI  67 103  67 102 /  20   0   0   0
ELN  66 101  65  98 /  20   0   0   0
RDM  54  95  54  94 /   0   0   0   0
LGD  60  97  60  96 /  10   0   0   0
GCD  58  98  59  98 /   0   0   0   0
DLS  66  96  66  98 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 10 PM PDT this evening for ORZ641.

     Heat Advisory until 10 PM PDT this evening for ORZ041-505-507-
     508-510.

     Heat Advisory until 10 PM PDT Thursday for ORZ044.

WA...Red Flag Warning until 10 PM PDT this evening for WAZ690-691-694-
     695.

     Heat Advisory until 10 PM PDT this evening for WAZ024-029-521.

     Heat Advisory until 10 PM PDT Thursday for WAZ028.

     Excessive Heat Warning until 10 PM PDT Thursday for WAZ026-027.

&&

$$

SHORT TERM...74
LONG TERM....76
AVIATION...90