Gale Watch 18, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
854 PM PDT TUE JUN 21 2011

.DISCUSSION...AFTER A SUNNY AND FAIRLY HOT DAY, NOT MUCH GOING ON
ACROSS THE MEDFORD FORECAST AREA THIS EVENING. SEEING SOME
ALTOCUMULUS DRIFTING ACROSS WHICH INDICATES THE PRESENCE OF SOME
MID LEVEL INSTABILITY AND SOME OF THESE CLOUDS ARE PRODUCING A
LITTLE VIRGA THAT IS SHOWING UP ON RADAR. HOWEVER, GIVEN THE VERY
DRY LOW LEVELS (DEWPOINT DEPRESSIONS ON THE ORDER OF 30C) IT IS
NO SURPRISE THAT THIS STUFF ISN'T REACHING THE GROUND. THE TROUGH
OFF THE BC COAST CONTINUES TO DIG SOUTH AND WILL MOVE OVER THE
PACNW OVER THE NEXT 36 HRS. THE THERMAL TROUGH IS SITTING RIGHT
OVER THE WEST SLOPES OF THE CASCADES AND WILL SHIFT INTO EASTERN
OREGON OVERNIGHT. THIS WILL ALLOW THE MARINE LAYER TO PUSH IN
ACROSS THE WEST SIDE TONIGHT. NOT EXPECTING THE CLOUDS TO MAKE IT
MUCH PAST THE UMPQUA, BUT THE COOLER AIR WILL. THUS HIGHS TOMORROW
ON THE WEST SIDE WILL BE COOLER (POTENTIALLY MUCH COOLER IN PLACES
WHERE THE STRATUS PERSISTS) BUT THE EAST SIDE WILL SEE SIMILAR
TEMPS TO TODAY. THE MODELS CONTINUE TO INDICATE A FAIR AMOUNT OF
MID LEVEL INSTABILITY TOMORROW OVER MUCH OF THE MEDFORD FORECAST
AREA. LI'S WILL BE WELL BELOW ZERO AND MID LEVEL LAPSE RATES ON
THE ORDER OF 8-9C/KM ARE NOTHING TO SNEEZE AT. THE 00Z NAM ALSO IS
STARTING TO SHOW SOME AFTERNOON QPF INDICATING THAT IT IS A
LITTLE MORE BULLISH WITH THE INSTABILITY NOW. AM NOT PLANNING TO
UPDATE RIGHT NOW, BUT THE NIGHT SHIFT WILL HAVE TO LOOK HARD AT
THE POTENTIAL FOR HIGHER COVERAGE OF THUNDERSTORMS TOMORROW, ESP
OVER THE EAST SIDE, COMPARED TO WHAT WE HAVE NOW. -WRIGHT

&&

.AVIATION...VFR EXPECTED TO CONTINUE THROUGH TOMORROW EXCEPT ALONG
THE IMMEDIATE COAST WHERE THE MARINE LAYER WILL KEEP IFR CIGS IN
PLACE. SHOULD SEE AT LEAST MVFR CIGS SPREAD INTO UMPQUA BASIN OVN
AND THEN RETREAT TO THE COAST BY AFTERNOON. COULD SEE ISOLD TS
TOMORROW AFTERNOON, ESP EAST SIDE. EXPECT STORMS TO BE ELEVATED
AND DRY THUS VFR LIKLEY TO PREVAIL DESPITE CONVECTION. HOWEVER,
GUSTY WINDS, DOWNDRAFTS, AND TURBULENCE COULD BE AN ISSUE INVOF
STORMS. -WRIGHT

&&

.PREV DISCUSSION... /ISSUED 258 PM PDT TUE JUN 21 2011/

DISCUSSION...LATEST VISIBLE IMAGE SHOWS SOME ACCAS ACTION ALIGNED
SOUTHWEST TO NORTHWEST OVER THE CWA AND IS GENERALLY MOVING
NORTHEAST. THIS IS IN RESPONSE TO A WEAK SHORTWAVE MOVING INTO THE
AREA. A QUICK LOOK AT THE RADAR DOES SHOW SOME RETURNS NEAR
REEDSPORT WHICH IS MOST LIKELY VIRGA. AT THIS TIME...DO NOT EXPECT
MUCH TO COME OUT OF THIS WITH MODELS SHOWING WEAK INSTABILITY.
500 MB HEIGHTS GRADUALLY DECREASE TONIGHT AS THE UPPER TROF NEAR 140
W MOVES EAST WHICH WILL BRING IN INCREASING ONSHORE FLOW TO THE
COAST AND WEST OF THE CASCADES. THE MARINE STRATUS IS EXPECTED TO
MOVE INTO THE UMPQUA BASIN TONIGHT....BUT IT NOT EXPECTED TO MOVE
INTO THE ROGUE VALLEY.

WEDNESDAY WILL BE A TRICKY DAY WITH RESPECT TO THE POTENTIAL FOR
ISOLATED THUNDERSTORMS. AT THIS TIME...NORTHERN CAL AND ALONG AND
EAST OF THE CASCADES ARE MOST FAVORABLE FOR ISOLATED THUNDERSTORMS
TO DEVELOP BY MID AFTERNOON THROUGH EARLY EVENING AND ANY STORMS
THAT DEVELOP ARE EXPECTED TO MOVE EAST TO NORTHEAST. MEANWHILE THE
ATMOSPHERE SHOULD BECOME STABLE ENOUGH TO KEEP ISOLATED
THUNDERSTORMS FROM DEVELOPING WEST OF THE CASCADES AND NORTH OF THE
SISKIYOUS.

THE TROF AXIS MOVES THROUGH THE AREA THURSDAY. THIS WILL BRING A
REINFORCING MARINE PUSH RESULTING IN COOLER TEMPERATURES. THIS
TIME...THE MARINE STRATUS COULD MAKE IT INTO THE ROGUE VALLEY. MOST
OF PRECIPITATION THURSDAY WILL BE IN THE MORNING AND MAINLY CONFINED
TO COOS AND DOUGLAS COUNTY. HOWEVER THE 18Z NAM SUGGEST QPF ALONG
THE CASCADES AND SISKIYOUS. SUSPECT THIS MAY BE A BIT
OVERDONE...EXCEPT FOR THE WEST FACING SLOPES ALONG THE NORTHERN
CASCADES.

A WESTERLY FLOW ALOFT CONTINUES OVER THE CWA WITH DRY CONDITIONS
EXPECTED. HOWEVER THE COAST AND NORTHWEST DOUGLAS COUNTY COULD PICK
UP PATCHY AREAS OF DRIZZLE DUE TO THE DEEP MARINE LAYER.
TEMPERATURES ARE EXPECTED TO REMAIN SLIGHTLY BELOW NORMAL.
-PETRUCELLI

LONG TERM...
SATURDAY JUNE 25TH INTO WEDNESDAY JUNE 29TH...
THE TREND DURING THIS FORECAST PERIOD WILL BE FOR SLIGHTLY ABOVE
AVERAGE TEMPERATURES COOLING TO TEMPERATURES 5 TO 10 DEGREES BELOW
NORMAL BY EARLY NEXT WEEK. THIS MEANS PLENTY OF 70S AND 80S IN THE
VALLEYS WILL BE REPLACED BY MOSTLY LOWER 70S.

HIGH PRESSURE ON SATURDAY WILL GRADUALLY TRANSITION TO AN UPPER
LEVEL TROUGH SETTING UP SOMEWHERE ALONG OR NEAR THE WEST COAST
SUNDAY THROUGH TUESDAY. THE GFS40 MODEL GUIDANCE IS THE MOST
AGGRESSIVE SOLUTION...BRINGING IN THE TROUGH WITH RAINFALL ACROSS
MOST OF OUR OREGON AREA SUNDAY INTO MONDAY. MEANWHILE THE ECMWF IS
SLOWER...AMPLIFYING THE TROUGH OFFSHORE AND THEN NOT BRINGING IT IN
UNTIL LATE MONDAY INTO TUESDAY. ADJUSTED THE FORECAST TO TREND
TEMPERATURES BETWEEN THESE TWO SOLUTIONS AND ENTERED A SHOWER AND
SOME THUNDER THREAT FOR MOST AREAS FOR THIS PERIOD. ENSEMBLE
GUIDANCE AND ANALYSIS FROM NCEP INDICATES THAT A SOLUTION BETWEEN
THE GFS AND ECMWF IS THE MOST LIKELY OUTCOME.

FIRE WEATHER...
ISOLATED THUNDERSTORMS ARE EXPECTED TO FORM ALONG OR NEAR THE
CASCADES AND TRINITY ALPS ON WEDNESDAY...PROPAGATING OUT TO THE
NORTHEAST DURING THE AFTERNOON AND EVENING. EXPECT THE GREATEST
THREAT TO BE ACROSS OUR EASTERN OREGON AREAS...IN KLAMATH AND LAKE
COUNTIES. WITH FIRE DANGER RATING IN THE MODERATE RANGE EXPECT SOME
FIRE STARTS ARE POSSIBLE. SOME RAIN IS EXPECTED WITH THESE
CELLS...THOUGH NOT MUCH. THERE IS AN UPPER TROUGH AND FRONTAL
BOUNDARY DRIVING THIS...SO EXPECT POTENTIAL FOR SOME ORGANIZATION
ACROSS KLAMATH AND LAKE COUNTIES WEDNESDAY AFTERNOON. WE'VE KEPT
COVERAGE ISOLATED...HOWEVER...AS THE UPPER LEVEL TROUGH LIFTS OUT
AFTER MAXIMIZING OVER THE AREA WEDNESDAY MORNING. THUS...THE BEST
UPPER LEVEL CONDITIONS FOR THUNDERSTORMS WILL BE TO OUR NORTHEAST.
-LUTZ

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT FRIDAY FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT FRIDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THIS
     EVENING FOR PZZ376.