Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 252337

Area Forecast Discussion
National Weather Service Pendleton OR
436 PM PDT Tue Jul 25 2017

Updated to add Red Flag Warning for fire zone 611

.SHORT TERM...Tonight through Friday...The upper low continues
pumping moisture north into southern Oregon. Another round of
isolated thunderstorms will occur in the southern portion of
Deschutes, Crook, and Grant counties this evening. All models show
the slow moving upper level low near the northern CA coast
transitioning to an open wave on Wednesday and moving northeast
across southeast and east central Oregon Wednesday night and
Thursday. As this happens, the chance for thunderstorms will
increase and move north and east into the Blue mountains and
Wallowa mountains. Looking at a fire weather watch for mountain
areas south of the Columbia Basin. See Fire Weather discussion for
additional details. Nearly all of Washington and the Columbia
river counties of Oregon will remain hot and dry. As the wave
moves east, a more westerly flow will bring a drier pattern to
Oregon. This westerly flow will produce gusty winds in the
Columbia Gorge and Kittitas valley areas Thursday afternoon. This
westerly flow will also drop temperatures slightly on Thursday and
Friday compared to Wednesday.

.LONG TERM...Friday night through Tuesday...Models in fair agreement
with the overall pattern.  However, they differ in position of upper
level high which affects the flow over the Pacific Northwest.  The
GFS Ensemble members show a general ridge over the area with
predominant southwest flow as they keep the high farther south.  The
ECMWF shows southwest flow early in the period becoming more
westerly as the upper ridge builds over central Nevada.  At this
time, will lean towards the drier ECMWF solution as it handled the
current pattern better. With limited low level moisture, the weather
should remain dry and hot through the period. However, there could
be some afternoon buildups over Central Oregon and the Elkhorns each
late afternoon and early evening, but not expecting them to develop
beyond towering cumulus.  Daytime highs will be well above
normal.  Earle


.AVIATION...00Z TAFs...VFR conditions will continue for the next
24 hours. Isolated thunderstorms may approach Central Oregon this
evening, but they are not expected to impact any TAF sites.
Thunderstorms will become more widespread Wednesday in Central
Oregon, but will leave mention out of KRDM and KBDN at this time.
Winds will generally remain 10 kts or less...except KDLS 10-15 kts
Wednesday afternoon. Earle


.FIRE WEATHER...Thunderstorms that have developed southeast of
Prairie City and in central Oregon this afternoon are producing
about 5-10 lightning strikes every 15 minutes.  A Red Flag Warning
for Fire zone 611 and 642 is in effect through this evening.

Fire Weather Watches will be issued shortly for the fire zones
across central and northeast Oregon (OR610, OR611, OR640, OR642,
OR643, OR644 and OR645) for thunderstorms producing abundant
lightning Wednesday afternoon and Wednesday night.  Confidence is
high that there will be scattered thunderstorms across central and
northeast Oregon, but the uncertainty lies on where the cluster of
lightning strikes will occur.  The track of the wave associated with
the low pressure trough over northern California that gets absorbed
in the southwest flow is questionable and decisions on what to do
with the watches will be made by Wednesday morning.  Due to the high
precipitable water on Wednesday (approx. 1 inch), believe some
storms could bring a 0.25 inch...possibly 0.5 inch...that will occur
underneath the core of the storms. Despite the possibility of
wetting rain, there will also be abundant lightning.

A weak marine surge on Thursday will cause winds to increase in the
Eastern Columbia River Gorge, the Kittitas Valley and over portions
of the Lower Columbia Basin.  The wind and RH threat is marginal and
fire weather highlights may be needed if the marine surge is
stronger than currently advertised by the models. Wister


PDT  63  96  64  95 /   0   0  10  10
ALW  68  98  69  97 /   0   0   0  10
PSC  61  99  64  98 /   0   0   0   0
YKM  65  99  65  96 /   0   0   0   0
HRI  64  98  66  97 /   0   0   0   0
ELN  61  96  63  91 /   0   0   0   0
RDM  57  93  55  92 /  10  30  20   0
LGD  55  94  57  93 /   0  20  20  10
GCD  61  94  60  94 /  10  30  20  10
DLS  67  95  66  90 /   0   0   0   0


OR...Red Flag Warning until 10 PM PDT this evening for ORZ611 and

     Fire Weather Watch from Wednesday afternoon through late
     Wednesday night for ORZ610-611-640-642>645.



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