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Area Forecast Discussion (AFD)

Issued by Pendleton, OR (PDT)

                            
000
FXUS66 KPDT 231520
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
819 AM PDT Tue Jul 23 2019

.SHORT TERM...Today and tonight...Ridge of high pressure over the 
region today with some monsoonal moisture clipping the region. This 
will lead to some isolated thunderstorms this afternoon. Then a 
shortwave upper level trough will move into the region from off the 
Pacific this evening and overnight. The dynamic forcing of this 
shortwave in the atmosphere will aid to increase thunderstorm 
activity across most of the forecast area through the evening and 
overnight period. 


&&

.AVIATION...18Z TAFs...Increasing mid-level cloudiness today ahead 
of an approaching upper level trough. May initially see some surface-
based convection firing near/just to the north of BDN/RDM by late 
afternoon, but think bulk of the activity will be elevated ahead of 
the stronger forcing moving though the Columbia Basin and Blues 01-
08Z before exiting the region to the northeast. Storms should have 
some decent precipitation cores but given high cloud bases and a 
substantially dry sub-cloud layer, much will evaporate prior to 
reaching the ground with gusty and erratic winds associated with 
rain-cooled downdrafts. Outside of thunderstorms winds will also be 
breezy to locally windy with a strong marine push coming through 
gaps through the Cascades. Winds taper off by late Wednesday 
morning. Peck


&&

.FIRE WEATHER...Red flag warning in effect to cover the potential 
for lightning later today and overnight followed by gusty winds of 
15-30 mph late afternoon into the overnight period. 

&&

.PREV DISCUSSION... /issued 223 AM PDT Tue Jul 23 2019/ 

SHORT TERM...Today through Thursday. Main focus of the short term
forecast will be thunderstorms and winds associated with a weather
system moving across the Pacific northwest. Upper low offshore 
will push a cold front through the region later today and tonight.
There is a chance of thunderstorms ahead of the front with
increasing westerly winds after frontal passage. Showers and
storms will develop in the afternoon and continue through the
evening before moving off to the east overnight. The short wave 
and jet moving through the area are quite strong for this time of 
year. High temperatures will be in the upper 80s and 90s. This may
result in some stronger storms late in the day. West winds will 
then mix down to the surface becoming breezy to windy in the 
evening and overnight. Based on this have upgraded the fire 
weather watch to a warning. For Wednesday and Thursday a dry 
westerly flow over the region with mostly clear skies and cooler 
temperatures. 94

Long Term (Thursday Night through Tuesday)... 
The large scale pattern will generally remain unchanged as we move 
through the extended period. This will feature a dominant Four 
Corners/Southwest US upper ridge, and a persistent upper low off 
British Columbia. Weak shortwave troughs will, at times, move 
through the flow between these two features, allowing weak fronts to 
move through the region with little impact aside from periods of 
breezy to windy conditions. One such shortwave appears probable late 
Friday into Saturday. As little moisture is expected to accompany 
this system, most areas will remain dry outside of perhaps the 
Cascade Crest and adjacent slopes. The main concern with this 
feature will be an increase in west/southwest winds through the 
Columbia Gorge and Lower Columbia Basin. A second weak wave appears 
possible sometime early next week, though models are currently 
rather inconsistent with this feature. Temperatures to generally 
remain at or just above seasonal normals with highs in the lower to 
mid 90s most areas outside of the mountains, where mid 70s and 80s 
will be common.

79/Austin

AVIATION (12z TAFs)...
VFR conditions expected for the first half of the period. Expect 
spotty shra/tsra may develop 22z to 00z near central OR terminals 
and develop/spread northeast. Gusty winds and lightning to accompany 
any storms. A front will sweep through the area after 00z, with 
gusty west/northwest winds spreading west to east through the 
overnight hours.

79/Austin

FIRE WEATHER...Watch has been upgraded to a red flag warning to 
cover the potential for lightning later today followed by gusty 
winds of 15-30 mph late afternoon into the overnight period. 94

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  96  61  83  51 /   0  40   0   0 
ALW  96  64  84  55 /  10  40   0   0 
PSC  98  65  87  53 /  10  40   0   0 
YKM  97  58  85  51 /  10  20   0   0 
HRI  99  64  86  52 /   0  40   0   0 
ELN  90  60  79  49 /  20  20   0   0 
RDM  92  47  82  44 /  20  20   0   0 
LGD  94  58  80  46 /  20  30   0   0 
GCD  96  56  82  49 /  20  20   0   0 
DLS  87  62  84  55 /  10  20   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM this afternoon to 5 AM PDT Wednesday 
     for ORZ640-641.

WA...Red Flag Warning from 2 PM this afternoon to 5 AM PDT Wednesday 
     for WAZ641-675.

&&

$$

91/74/74