Severe Thunderstorm Warning 4, NWS Pendleton, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
215 PM PDT SAT MAY 28 2005

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...LATEST WATER VAPOR
IMAGERY SHOWS AN UPPER LEVEL CLOSED LOW OFF THE NORTHERN CALIFORNIA
COAST WITH MOISTURE SPREADING NORTHEAST INTO CENTRAL AND SOUTHERN
SECTIONS OF OREGON.  THE MAIN FORECAST CONCERN CONTINUES TO BE THE
THREAT FOR ISOLATED SEVERE THUNDERSTORMS THIS EVENING.  THE STORM
PREDICTION CENTER CURRENTLY HAS NORTH CENTRAL OREGON...CENTRAL
OREGON...THE OCHOCO-JOHN DAY HIGHLANDS...AND THE JOHN DAY BASIN IN A
SLIGHT RISK FOR SEVERE THUNDERSTORMS THROUGH THE EVENING.  SO FAR
MOST OF THE LIGHTNING HAS BEEN CONCENTRATED CLOSE TO THE CENTER OF
CIRCULATION IN SOUTHWEST OREGON WITH A FEW LIGHTNING STRIKES IN
DESCHUTES COUNTY.  HOWEVER LIGHTNING COVERAGE WILL INCREASE THROUGH
THE EVENING AS A SHORT WAVE AHEAD OF THE LOW LIFTS NORTH TOWARDS THE
AFOREMENTIONED AREAS WITH A SEVERE THREAT.  THE MAIN THREAT FROM THE
THUNDERSTORMS THIS EVENING WILL BE LARGE HAIL.  A FEW OTHER POSSIBLE
THREATS INCLUDE LOCALLY HEAVY RAIN IN GRANT COUNTY AND THE NE OREGON
MOUNTAINS WHERE STORM MOTIONS ARE ONLY IN THE 2-5 MPH RANGE. ANOTHER
THREAT WILL BE GUSTY WINDS IN CENTRAL OREGON WHERE STRONGER WINDS
ALOFT MAY MIX DOWN WITH THUNDERSTORMS. MODEL SOUNDINGS INDICATE A
RISK FOR A FEW NOCTURNAL THUNDERSTORMS IN THESE AREAS BUT WILL LEAVE
OUT FOR NOW GIVEN UNCERTAINTY IN THIS PANNING OUT.
ELSEWHERE...AFTERNOON HEATING IS LEADING TO SOME CUMULUS DEVELOPMENT
OVER THE BLUE AND WALLOWA MOUNTAINS.  A FEW LIGHTNING STRIKES MAY
OCCUR OVER THESE AREAS THIS EVENING BUT ARE NOT EXPECTED TO BE
STRONG NOR SEVERE.  WITH THE LOW MOVING INLAND ACROSS NORTHERN
CALIFORNIA TONIGHT AND WITH HIGH PRESSURE OVER SOUTHERN BRITISH
COLUMBIA...A DEFORMATION ZONE IS EXPECTED TO DEVELOP ACROSS CENTRAL
OREGON OVERNIGHT BRINGING NUMEROUS RAIN SHOWERS.

ON SUNDAY MORNING...A DEFORMATION ZONE WILL PERSIST OVER CENTRAL
OREGON LEADING TO RAIN SHOWERS BEING LIKELY.  THEN RESIDUAL MOISTURE
AND AFTERNOON/EARLY EVENING HEATING WILL LEAD TO A SLIGHT CHANCE OF
THUNDERSTORMS MAINLY OVER CENTRAL OREGON AND THE OCHOCO-JOHN DAY
HIGHLANDS.  THE UPPER LOW WILL THEN MOVE SOUTH AND EAST OF THE AREA
WITH SHORT WAVE RIDGING EXPECTED TO PROVIDE DRY CONDITIONS THROUGH
MONDAY NIGHT.  TEMPERATURES WILL COOL SLIGHTLY THROUGH MONDAY BUT
WILL REMAIN ABOVE AVERAGE.  WOLF

.LONG TERM...TUESDAY THROUGH SATURDAY...MEDIUM RANGE MODELS DEPICT
RIDGING CONTINUING TO MOVE EAST OF THE REGION...WITH A WAVE
APPROACHING THE AREA TUESDAY NIGHT/WEDNESDAY. ECMWF/UKMET STILL
THE STRONGEST WITH THE SYSTEM...WITH A CLOSED LOW CROSSING THE AREA
ON WED...WHILE THE GFS IS MOST OPEN WITH THE SYSTEM AND THE CANADIAN
MODEL STILL LEANING TOWARD THE ECMWF/UKMET. WITH RECENT PERFORMANCE
SHOWING A BLEND LEANING TOWARD THE GFS BEING THE BEST
SOLUTION...WILL KEEP SOME CHC (MAINLY SLIGHT) OF SHWRS FOR TUE NIGHT
THROUGH WED NIGHT. THU/FRI LOOK MAINLY DRY FOR LOWLANDS...WITH
PERHAPS SOME NE OREGON MTN SHWRS AS W/NW FLOW WILL PREVAIL.THE NEXT
SYSTEM APPROACHES BY FRI NIGHT/SAT WITH THE NEXT CHANCE AT PRECIP
FOR MOST AREAS. TEMPERATURES WILL CONTINUE TO COOL TO NEAR/SLIGHTLY
ABOVE NORMAL BY WEDNESDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  55  87  52  82 /  10  10  10  10
ALW  59  88  55  82 /   0   0  10  10
PSC  54  91  50  86 /   0   0   0  10
YKM  54  89  51  84 /   0   0   0  10
HRI  56  89  52  83 /   0   0   0  10
ELN  52  89  50  83 /   0   0   0  10
RDM  53  75  42  76 /  60  60  10  10
LGD  49  82  48  79 /  10  10  10  10
5J0  53  78  47  77 /  30  30  10  10
DLS  62  83  58  81 /  10  10  10  10

&&

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

TI:GGG
FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON
86/89

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
245 PM PDT SAT MAY 28 2005

WAZ024>030-ORZ041>050-291215-
EAST SLOPES OF THE SOUTHERN CASCADES-KITTITAS VALLEY-
YAKIMA VALLEY-LOWER COLUMBIA BASIN OF WASHINGTON-
FOOTHILLS OF THE BLUE MOUNTAINS OF WASHINGTON-
NORTHWEST BLUE MOUNTAINS-EASTERN COLUMBIA RIVER GORGE OF OREGON-
NORTH CENTRAL OREGON-CENTRAL OREGON-
LOWER COLUMBIA BASIN OF OREGON-
FOOTHILLS OF THE BLUE MOUNTAINS OF OREGON-BLUE MOUNTAINS-
JOHN DAY BASIN-OCHOCO-JOHN DAY HIGHLANDS-GRANDE RONDE VALLEY-
WALLOWA COUNTY-
245 PM PDT SAT MAY 28 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.

.DAY ONE...TODAY AND TONIGHT

SLIGHT RISK OF SEVERE THUNDERSTORMS
     NORTH CENTRAL OREGON, CENTRAL OREGON, JOHN DAY BASIN,
     OCHOCO-JOHN DAY HIGHLANDS

THUNDERSTORMS
     NORTHWEST BLUE MOUNTAINS, BLUE MOUNTAINS, WALLOWA COUNTY

AN UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE EAST THROUGH EXTREME
NORTHERN CALIFORNIA TODAY AND TONIGHT. THE CIRCULATION ASSOCIATED
WITH THE LOW WILL BRING MID LEVEL MOISTURE AND INSTABILITY INTO
CENTRAL AND NORTH CENTRAL OREGON...THUS TRIGGERING CONVECTION
BEGINNING THROUGH THIS EVENING.

THE ATMOSPHERE WILL BECOME MODERATELY UNSTABLE WITH 30-40 KNOTS OF
DEEP LAYER SHEAR IN CENTRAL AND NORTH CENTRAL OREGON THIS EVENING.
THESE CONDITIONS WILL FAVOR THUNDERSTORMS THAT ORGANIZE INTO
SUPERCELLS WITH STRONG...SUSTAINED UPDRAFTS. A FEW STORMS IN CENTRAL
AND NORTH CENTRAL OREGON AND IN THE OCHOCO-JOHN DAY HIGHLANDS AND
THE JOHN DAY VALLEY MAY BECOME SEVERE WITH ISOLATED LARGE HAIL UP TO
ONE INCH IN DIAMETER AND DAMAGING WINDS.

A FEW ISOLATED LATE AFTERNOON AND EVENING THUNDERSTORMS WILL ALSO
OCCUR IN THE BLUE AND WALLOWA MOUNTAINS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS SUNDAY
     NORTH CENTRAL OREGON, CENTRAL OREGON, JOHN DAY BASIN,
     OCHOCO-JOHN DAY HIGHLANDS

LINGERING LOW LEVEL MOISTURE AND AFTERNOON HEATING WILL LEAD TO A
SLIGHT CHANCE OF THUNDERSTORMS.

HIGH PRESSURE WILL GIVE DRY CONDITIONS ON MONDAY AND TUESDAY.

A WEAK UPPER LEVEL SHORT WAVE WILL MOVE THROUGH THE REGION TUESDAY
NIGHT THROUGH WEDNESDAY NIGHT FOR A SLIGHT CHANCE OF SHOWERS IN
NORTHEAST OREGON AND THE BLUE MOUNTAINS IN SOUTHEAST WASHINGTON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

PROTOTYPE GRAPHICAL FORECASTS OF WEATHER HAZARDS OUT TO SEVEN DAYS
ARE DISPLAYED ON THE WORLD WIDE WEB AT:

WWW.WRH.NOAA.GOV/PENDLETON/CURRENTHAZARDS/HWO.HTML

ALL LETTERS IN THE ABOVE URL ARE LOWER CASE...EXCEPT THE H IN
CURRENTHAZARDS.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PENDLETON OR
517 PM PDT SAT MAY 28 2005

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0512 PM     HAIL             5 SSW THREE RIVERS      43.75N 121.52W
05/28/2005  0.75 INCH        DESCHUTES          OR   TRAINED SPOTTER

&&

JAS