Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 301734 AAC
AFDPDT

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PENDLETON OR
1034 AM PDT SAT MAY 30 2015

UPDATED FOR AVIATION DISCUSSION

.UPDATE...THE LATEST RADAR WAS SHOWING A FEW SHOWERS SOUTH OF THE
STATE LINE THIS MORNING AND THE AREA OF PCPN WAS EXPANDED TO
INDICATE THIS. A DISTURBANCE IS FORECAST TO WORK ITS WAY ACROSS THE
REGION LATER TODAY WHICH MAY HELP TO INCREASE POPS ACROSS CENTRAL
OREGON...JOHN DAY HIGHLANDS...BLUE/WALLOWA MTNS WHERE THE BEST
CHANCES FOR CONVECTION COULD OCCUR. ELSEWHERE ABUNDANT LOW LEVEL
MOISTURE ALONG WITH ABOVE NORMAL TEMPS MAY COMBINE TO PRODUCE ISOLD
TSRA. OTHERWISE THE PRESENT SHORT TERM FORECAST APPEARS ON TRACK FOR
NOW.

&&

.AVIATION...18Z TAFS...VFR CONDITIONS EXPECTED AT ALL TAF SITES OVER
THE NEXT 24 HOURS.  SCT-BKN 10-15KFT CLOUD DECKS CAN BE EXPECTED.
WINDS WILL RANGE FROM 5 TO 15 KTS...WITH SOME GUSTS OVER 20 KTS.
CANT RULE OUT -TSRA AT KPDT...KRDM...KBDN...OR KALW...AND MAYBE VCTS
AT KPSC.  BUT INSTABILITY LOOKS BEST OVER THE NORTHEAST MOUNTAINS.
HAVE HELD OFF ON ANY SHOWER ACTIVITY AND WILL MONITOR RADAR TO SEE
HOW THINGS DEVELOP...AND WILL AMEND TAFS IF NECESSARY FOR VCTS OR
POSSIBLE -TSRA.  WEBER

&&

.PREV DISCUSSION... /ISSUED 351 AM PDT SAT MAY 30 2015/

SHORT TERM...TODAY THROUGH MONDAY...AN UPPER RIDGE WILL KEEP
TEMPERATURES VERY WARM THROUGH THE SHORT TERM PERIOD. HOWEVER...THE
MAIN CONCERN OVER THE NEXT FEW DAYS WILL BE AFTERNOON AND EVENING
INSTABILITY WITH WIDESPREAD AREAS OF NEGATIVE LI`S...CAPE AND SHEAR.
TODAY THE BEST SHEAR AND INSTABILITY WILL BE OVER THE HIGH TERRAIN
FROM THE BLUE MOUNTAINS SOUTH AND EASTWARD. WILL HAVE A CHANCE OF
SHOWERS AND AFTERNOON AND EVENING THUNDERSTORMS TODAY AS A RESULT
WITH A SOUTHWEST FLOW ALOFT AND 45-50 KTS OF SHEAR. THE UPPER RIDGE
AXIS WILL MOVE TO THE EAST ALLOWING A SOUTHERLY FLOW TO INCREASE.
THERE WILL BE A DECENT AMOUNT OF SHEAR OF 45-50 KTS ALONG WITH CAPE
AND NEGATIVE LI`S. WILL AVE A CHANCE OF SHOWERS AND AFTERNOON AND
EVENING THUNDERSTORMS AGAIN ON SUNDAY IN MUCH THE SAME AREAS AS
TODAY...I.E. FROM THE BLUE MOUNTAINS AND NORTH CENTRAL OREGON SOUTH
AND EASTWARD. THUNDERSTORMS MAY PERSIST OVERNIGHT SUNDAY INTO MONDAY
AS THE ATMOSPHERE REMAINS UNSTABLE OVERNIGHT. MONDAY LOOKS TO BE THE
BEST DAY OVERALL FOR THUNDERSTORMS WITH THE GREATEST AMOUNT OF
SHEAR, NEGATIVE LI`S AND CAPE. HOWEVER THE SHEAR IS EXPECTED TO
DECREASE IN THE AFTERNOON WHICH MAY HELP TO INHIBIT ORGANIZED
THUNDERSTORMS. HOWEVER MONDAY COULD STILL HAVE THE MOST AND THE
STRONGEST STORMS WITH SOME POSSIBLY EVEN SEVERE DUE TO A POTENT LOW
PRESSURE SYSTEM ALOFT ON THE OREGON COAST AND A DEEP SOUTHERLY FLOW
ALOFT OVER THE CWA. TEMPERATURES THROUGH THE NEXT FEW DAYS WILL BE
IN THE 80S TO AROUND 90 IN THE LOWER ELEVATIONS WITH 70S TO LOWER
80S IN THE MOUNTAINS EACH DAY THROUGH MONDAY. LOW LEVEL WESTERLY
WINDS WILL INCREASE MONDAY AFTERNOON IN THE LOWER COLUMBIA BASIN
WHICH ALSO MAY HELP TO INHIBIT ORGANIZED STORMS...AS DRIER AND MORE
STABLE AIR MOVES IN FROM THE WEST OF THE CASCADES IN THE AFTERNOON.
AS A RESULT THE STRONGEST STORMS MAY BE IN THE MORNING...DECREASING
IN THE AFTERNOON MONDAY. ELSEWHERE WINDS WILL BE LIGHT THROUGH THE
SHORT TERM PERIOD. 88

LONG TERM...MONDAY NIGHT THROUGH FRIDAY...THE MONDAY SYSTEM IS
EXPECTED TO CONTINUE TO SWING THROUGH THE REGION MONDAY NIGHT AND
TUESDAY. FAIRLY WIDE COVERAGE OF ISOLATED TO SCATTERED THUNDERSTORMS
SHOULD CONTINUE INTO MONDAY EVENING. OVERNIGHT MONDAY THROUGH
TUESDAY SHOULD SEE A GRADUAL DECREASE IN SHOWERS COVERAGE,
ESPECIALLY ACROSS THE COLUMBIA BASIN. EXPECTED THUNDERSTORMS TUESDAY
AFTERNOON AND EVENING SHOULD BE LIMITED TO OUR EASTERN MOST MOUNTAIN
ZONES. WEAK WAVES LOOK MOVE INTO THE REGION WEDNESDAY THROUGH FRIDAY.
AT THIS TIME THE LOW LEVEL FLOW LOOKS TO REMAIN WESTERLY AND
SOMEWHAT STABLE. THUS WILL SEE SHOWERS MAINLY NEAR THE CASCADE CREST
AND OVER OUR EASTERN ZONES. THUNDERSTORMS LOOK TO BE EVEN MORE
LIMITED, MAINLY OVER WALLOWA COUNTY AND/OR THE BLUE MOUNTAINS,
DEPENDING ON THE DAY. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  85  56  85  59 /  20  10  10  20
ALW  88  60  87  62 /  20  10  10  20
PSC  91  57  90  62 /  10  10  10  20
YKM  88  56  86  59 /  10   0  10  20
HRI  90  58  89  61 /  20  10  10  20
ELN  84  53  85  57 /  10   0  10  20
RDM  83  46  83  53 /  20  20  30  40
LGD  78  51  83  55 /  30  30  20  30
GCD  84  50  88  49 /  30  30  20  30
DLS  87  57  88  61 /  10  10  10  30

&&

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

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

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