Hail in Oregon, July 19, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
135 PM PDT THU JUL 19 2012

.DISCUSSION...THINGS CONTINUE TO DESTABILIZE OVER SW OREGON AND
NORCAL THIS AFTERNOON. WE ARE SEEING A LOT OF HEATING WITHIN A DRY
SLOT ORIENTED SE TO NW ACROSS THE WESTERN 2/3RDS OF MY FORECAST
AREA, AND CONVECTIVE TEMPS ARE JUST NOW BEING REACHED. THE RICHER
MID LEVEL MOISTURE CONTINUES TO STREAM NORTHWARD ACROSS THE EAST
SIDE, AND THE ASSOCIATED CLOUDS HAVE LIMITED HEATING SOMEWHAT OVER
THERE. HOWEVER, THERE ARE SUFFICIENT BREAKS TO ALLOW CONTINUED
DESTABILIZATION THROUGH THE AFTERNOON.

I HAVE YET TO DETECT ANY MOVEMENT OF THE LOW OFFSHORE, BUT IT
SHOULD BEGIN LIFTING TOWARD THE NE ANY MOMENT NOW AS A VERY DEEP
UPPER LOW APPROACHING THE CENTRAL BC COAST CONTINUES TO MOVE
EASTWARD AND PICKS OUR LOW UP. MODELS CONTINUE TO SHOW OUR LOW
ATTAINING A NEGATIVE TILT THIS EVENING AND THEN RAPIDLY PUNCHING
INLAND OVERNIGHT. THE CONFLUENCE OF INCREASING INSTABILITY FROM
DAYTIME HEATING, THE PRESENCE OF UNUSUALLY HIGH PWATS (125-150%
OF NORMAL OVER MUCH OF THE AREA), AND INCREASING JET DYNAMICS AS
THE SYSTEM BEGINS TO COME ASHORE WILL LEAD TO ANOTHER ROUND OF
SCATTERED THUNDERSTORMS. MOST AREAS COULD SEE A THUNDERSTORM, BUT
THE FOCUS CONTINUES TO BE OVER THE NORTHERN MOST AREAS WHERE ALL
THE PARAMETERS BECOME COINCIDENT THROUGH THE EVENING. LIKE
PREVIOUS DAYS, WE WILL PROBABLY SEE STORMS BREAK OUT OVER THE FAR
SW OREGON MOUNTAINS OVER THE NEXT FEW HOURS AND MOVE OUT ACROSS
THE WEST SIDE AND CASCADES THIS EVENING. FORECAST SOUNDINGS ON
THE WEST SIDE ACTUALLY HAVE SLIGHTLY CURVED HODOGRAPHS INDICATING
MARGINAL DIRECTIONAL SHEAR. INSTABILITY IS NOT OVERWHELMING, BUT
THIS SHEAR COULD PROMOTE A FEW SPLITTING STORMS ALONG WITH AN
ATTENDANT THREAT FOR LARGE HAIL AND STRONG WINDS. GIVEN THE
MOISTURE PROFILES, ALL STORMS, ESPECIALLY FROM THE CASCADES WEST,
WILL BE CAPABLE OF PRODUCING HEAVY DOWNPOURS, BUT THEY SHOULD BE A
LITTLE LESS PERSISTENT THAN YESTERDAY AS STEERING FLOW WILL
INCREASE.

AS WE GET INTO THE EVENING, AREAS FURTHER NORTH INCLUDING THE
CASCADES, EASTERN DOUGLAS COUNTY, AND NORTHERN PORTIONS OF
KLAMATH AND LAKE COUNTIES WILL BECOME FAVORED LOCATIONS. MODELS
SHOW ACTIVITY IN THESE LOCATIONS CONTINUING WELL INTO THE NIGHT,
AND THIS SEEMS REASONABLE GIVEN THAT OUR UPPER LOW MOVES OVER
THESE AREAS TONIGHT.

THIS WHOLE MESS FINALLY ENDS TOMORROW AS THE UPPER LOW MOVES
NORTHEAST AWAY FROM US. THIS ALLOWS SUMMER TO RETURN OVER THE REST
OF THE FORECAST PERIOD. WE ARE CURRENTLY FORECASTING TEMPERATURES
NEAR TO SLIGHTLY ABOVE NORMAL THIS WEEKEND INTO NEXT WEEK, BUT
THERE REALLY ISN'T MUCH UPPER LEVEL RIDGING IN THE OFFING, SO A
LOT OF HEAT IS NOT EXPECTED AROUND HERE. IN FACT, ALL THE MODELS
SHOW AT LEAST WEAK TROUGHING HANGING OUT OFF THE PACNW COAST FOR
THE NEXT 10 DAYS, WITH FAIRLY LOW HEIGHTS OVER US. WHILE THIS
ISN'T GOOD NEWS FOR THE PARCHED AREAS IN THE CENTRAL PART OF THE
COUNTRY (THEY'LL CONTINUE TO BAKE AWAY UNDER THE DOWNSTREAM
RIDGE), IT WILL KEEP OUR TEMPERATURES IN CHECK. -WRIGHT

&&

.AVIATION...EXPECT MOSTLY VFR ACROSS INLAND TAF SITES THIS
AFTERNOON...BUT INSTABILITY WILL IGNITE SHOWERS AND THUNDERSTORMS
BEGINNING AFTER 21Z AND CONTINUING THROUGH 06Z. COVERAGE OF STORMS
WILL BE CONCENTRATED OVER SOUTHWEST OREGON/NW CALIFORNIA
NORTHEASTWARD UP ALONG THE CASCADES DURING THIS TIME AND MAY BRIEFLY
LOWER CIGS TO MVFR IN AREAS OF RA/+RA. ISOLATED TO SCATTERED STORMS
WILL ALSO DEVELOP OVER THE EAST SIDE. GUSTY, ERRATIC WINDS AND HAIL
MAY ACCOMPANY ANY OF THE STRONGER STORMS. STORMS COULD LINGER
THROUGH THE OVERNIGHT FARTHER NORTH IN KLAMATH AND LAKE COUNTIES AND
ALONG THE NORTH CASCADES, BUT THESE SHOULD LIFT NORTH OF THE AREA BY
OR SHORTLY AFTER 12Z FRIDAY. MUCH MORE STABLE CONDITIONS WILL MOVE
IN FRIDAY AFTERNOON WITH VFR FOR MOST INLAND AREAS INLAND. A DEEP
MARINE LAYER PERSISTS ALONG THE COAST. EXPECT AREAS OF IFR CIGS
THERE. A BRIEF SHOWER OR EVEN THUNDERSTORM THAT DEVELOPS INLAND MAY
DRIFT OVER KOTH THIS EVENING AS AN UPPER LEVEL LOW PASSES BY.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 5 AM PDT FRIDAY FOR ORZ027>031.

CA...NONE.

PZ...NONE.