Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 250305

Area Forecast Discussion
National Weather Service Pendleton OR
805 PM PDT Mon Jul 24 2017

.UPDATE...A thick cirrus shield has moved north over the CWA into
southeast Washington due to anvil blow off cirrus from those
thunderstorms over our CWA southern border area. Will update
forecast to increase cloud cover overnight...and may have to
increase temps to compensate too for the cloud cover. Main threat
with these storms are the lightning strikes with very little
precipitation along the southern border. A Red Flag Warning remains
in effect until 11 PM those area. At this time am still thinking it
can be expired at that time, but it will need to be watched.
Otherwise a warm and dry pattern remains over the rest of the CWA
north of the Red Flag Warning area (north central Oregon, northeast
Oregon and all of our Washington zones). Tuesday looks to be a
quieter day with less thunderstorms due to a dry upper trough that
will sag southward over the CWA overnight tonight and suppress the
moisture and instability to the south. Tuesday looks to be a rather
benign day, except along our southern border where there could still
be an isolated thunderstorm or two. Tuesday looks to be warmer. Then
on Wednesday moisture will work its way back northward and eastward
to include the northeast mountains for a slight chance of afternoon
and evening thunderstorms as an upper low opens up and moves into
northern California. The rest of the extended forecast period looks
to be dry and very warm to hot. 88


.AVIATION...06Z TAFs...Thick cirrus shield from thunderstorm anvil
blow off will cover most TAF sites tonight, but will remain well
above VFR minimums. Winds will be generally light...though they
could be gusty and erratic near any thunderstorms that may move into
the KRDM/KBDN area this evening. 88


.PREV DISCUSSION... /issued 204 PM PDT Mon Jul 24 2017/

SHORT TERM...Tonight through Thursday...Upper low off CA coast
continues to transport moisture into southern Oregon. Models
slowly move upper low onto CA shore by Wednesday. Daytime heating
will allow isolated to scattered thunderstorms to develop or move
across mainly southern Deschutes, Crook, and Grant counties this
evening and Tuesday and then spread into the higher elevations of
Union and Wallowa counties on Wednesday. As the upper lows opens
up into a wave and moves out of the area on Thursday, a few
parting thunderstorms are not out of the question for mainly the
southern Blue mountains and Wallowas. The northern 2/3 of the area
including nearly all of Washington and the Columbia river
counties of Oregon will continue to experience dry weather with
above normal temperatures through Thursday. Also, as the low pulls
off to the east, the pressure gradient will increase enough on
Wednesday and Thursday to give breezy conditions to the Columbia
Gorge. Otherwise, winds will be rather light, except locally gusty
near thunderstorms.

LONG TERM...Thursday night through Monday. Hot and dry conditions
will continue through the extended period as a ridge of high
pressure remains over the western U.S.  Southwest flow will be seen
over the area and there is the potential for some limited moisture
to move across the northeast Oregon mountains at times, depending on
the position of the high pressure.  Temperatures will continue to be
above normal with highs in the 90s and 80s in the mountains. 93.

AVIATION...00Z Tafs. VFR conditions will prevail over the next 24
hours. Moisture will continue to move north into central Oregon
and combine with daytime heating for a slight chance of
thunderstorms near KBDN and KRDM this afternoon and evening with
mid and high clouds extending from central Oregon northeast
through the Blue Mountains. Otherwise mostly clear skies. Winds
5-10kts through the period. 93

FIRE WEATHER...Red Flag Warnings are in effect from 2 PM to 11 PM
today for thunderstorms producing gusty outflow winds and abundant
lightning  for our central Oregon fire zones...OR611, OR640 south-
southeast of Prineville, and OR642.  Isolated Thunderstorms have
developed in southeast Oregon this afternoon.  Storms will either
travel north or additional storms will develop over central Oregon.
The westerly flow across Washington and northern Oregon should keep
most storms confined to our far southern zones. The chance of
wetting rain is slim, although one or two storms could bring a tenth
of an inch underneath the core.  On Tuesday...any thunderstorms
that develop will be south of the forecast area but there could be
isolated thunderstorms in our far southern zones.  As the flow
shifts to the southwest on Wednesday, the threat of thunderstorms
will extend farther north across the Blue Mountains.  Precipitable
Water will increase to an inch on Wednesday, so some of the storms
could bring moderate to heavy rain showers but it will definitely be
a hit-or-miss with wetting rain. No wind concerns are anticipated
through Wednesday. Wister


PDT  60  95  63  95 /   0   0   0   0
ALW  64  96  67  97 /   0   0   0  10
PSC  58  98  61  99 /   0   0   0   0
YKM  62  96  63  97 /   0   0   0   0
HRI  60  97  63  98 /   0   0   0   0
ELN  58  94  61  94 /   0   0   0   0
RDM  54  93  56  92 /  10  10  10  20
LGD  54  92  54  93 /  10  10   0  10
GCD  58  93  59  94 /  20  10  10  20
DLS  64  97  65  94 /   0   0   0   0


OR...Red Flag Warning until 11 PM PDT this evening for ORZ611-640-642.




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