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000
FXUS66 KPDT 051740 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1045 AM PDT Tue Jul 5 2022

Updated Aviation Discussion

.MORNING UPDATE...A remnant band of showers from overnight
activity continues to push north across OR Cascades and the far
western half of the forecast area this morning, however these
showers are only producing only a trace to a couple hundreths of
inch of rain. Today, an upper low will persist over the northeast
Pacific, placing the forecast area in a southwest flow aloft. Day
time heating and subtle impulses rounding the low will support
chances of rain showers mainly across the east slopes of the
Cascades and the eastern mountains. Weak, isolated thunderstorms
will also be mixed in with the rain showers this afternoon, but
will be mostly confined to the eastern mountains and portions of
central OR. Made minor updates to PoPs and temperatures, with the
rest of the morning forecast package on track. Lawhorn/82

&&

.AVIATION...18Z TAFs...Mid level altocumulus clouds are blanketing
the region with CIGS BKN-OVC070-100.  This will continue for the
next 24 hours.  Weak impulses in a southwest flow aloft will bring a
few showers--one over central OR this afternoon and another tracking
across the Columbia Basin tonight.  Cloud cover will inhibit the
instability for thunderstorms, but cannot rule out an isolated storm
if there is enough breaks in the clouds. Most instability will be
along the OR Cascades.  Winds remain 10-15 kts or less for most TAF
sites. 85



&&


.PREV DISCUSSION... /issued 431 AM PDT Tue Jul 5 2022/

Updated Aviation Discussion.

SHORT TERM...Today through Thursday night... A low pressure
system over the epac will spin a disturbance and moisture into
portions of our area this morning. The latest radar was showing
showers developing across central Oregon and expect this area of
pcpn to track north along the WA/OR cascades. A challenge is with
the eastward extent of the pcpn into portions of the basin by
midday. The moisture increases across our region and combining
with daytime heating will make the atmosphere unstable by
afternoon and thunderstorms are possible. The best chances of
thunderstorms are expected across central Oregon through Grant
county and extending ne into the Blue/Wallowa mountains into the
evening. Tuesday night the bulk of the pcpn remains over the
western half of our area into Wednesday morning.

Meanwhile the low pressure system remains nearly stationary over
the epac and will keep our region in a moist southerly flow and
showers and thunderstorms are expected to develop again Wednesday
afternoon and evening with the best chances over the area
mountains. This pattern will likely continue into Thursday with
showers and thunderstorms developing again by afternoon and
continuing into the evening.

Afternoon temperatures are forecast to be warmer today climbing
into the mid to upper 80s across the basin and 70s in the area
mountains.

LONG TERM...Friday through Tuesday... The region undergoes a
transition away from daytime shower/thunderstorm development over
the mountains to a dry and warmer weather pattern Saturday into next
week. On Friday models are in good agreement regarding the overall
synoptic pattern with a closed low previously off the coast of
Washington undergoing a transition to an open wave and progressing
into British Columbia, while a ridge persists over the high plains.
Southwesterly flow remains overhead as a result. Persistent mid-
level moisture in combination with daytime heating and 400-800 J/kg
of CAPE may facilitate yet another chance for pop-up showers/T-
storms over the central Oregon Cascades and the Ochoco-John Day
highlands up through the Blues/Wallowas. Otherwise, the rest of the
region looks dry. Friday night and Saturday a secondary upper level
wave moves through the Pacific Northwest although the deterministic
models show more variance in the timing and amplitude of this
feature. Nevertheless most deterministic guidance and the ensemble
means keep conditions dry Saturday, even over the mountains, holding
any precipitation just to the east of the CWA where the environment
is more conducive to shower/T-storm development. Should this wave
arrive later on Saturday and be more robust compared to the
consensus, as depicted by the deterministic ECMWF, one more round of
showers and T-storms may be possible over the northeastern
mountains; something to keep an eye on.

Zonal flow returns to the Pacific Northwest Saturday night and
Sunday as dry weather prevails locally. The stronger westerly flow
likely leads to breezy conditions for the Cascade Gap areas; nothing
anomalous.  Models are in fairly good agreement for an area of high
pressure centered over the four corners region to amplify and
slightly retrograde west Sunday night into Monday and Tuesday,
putting us under the influence of a robust ridge. Expect daytime
temperatures to increase during this time period with the majority
of ECMWF/GEFS Ensemble Members projecting highs in the low triple-
digits across the lower Columbia Basin by Tuesday afternoon. 99


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  86  59  85  60 /  10  20  20  20
ALW  86  61  88  62 /  10  20  20  20
PSC  88  65  91  65 /  10  20  20  20
YKM  84  60  85  58 /  10  30  30  20
HRI  88  60  90  63 /  10  20  20  20
ELN  81  58  82  59 /  10  30  30  20
RDM  80  51  79  53 /  40  30  20  20
LGD  80  55  83  56 /  30  20  30  20
GCD  82  52  86  53 /  20  20  20  20
DLS  85  61  83  61 /  20  40  20  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

MORNING UPDATE...82
SHORT TERM...97
LONG TERM....99
AVIATION...85