Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 221551
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
851 AM PDT TUE JUL 22 2014

.DISCUSSION...ALL THINGS SEEM TO BE COMING TOGETHER FOR A
THUNDERSTORM OUTBREAK IN PORTIONS OF OUR AREA TODAY. A LARGE UPPER
TROUGH CONTINUES TO DIG SOUTH ALONG THE B.C. COAST AND ASSOCIATED
SOUTHERLY FLOW AHEAD OF IT CONTINUES TO PUMP MOISTURE IN OVER THE
AREA. A STRONG SHORTWAVE CAN BE SEEN CLEARLY ON SATELLITE MOVING
NORTHWARD THROUGH CENTRAL CALIFORNIA THIS MORNING, AND RADAR SHOWS
THAT CONVECTION HAS ALREADY DEVELOPED FROM THE BAY AREA NORTHWARD
WHICH WILL CONTINUE TO ADVECT TOWARD OUR AREA. UNFORTUNATELY,
THERE IS PLENTY OF CLEARING AHEAD OF THE SHORTWAVE OVER NORTHERN
CALIFORNIA WHICH WILL SERVE TO FURTHER DESTABILIZE AN ALREADY
UNSTABLE AIRMASS. AS IF THAT WEREN`T ENOUGH, THE UPPER JET WILL
INCREASE THROUGH THE DAY AND OUR EAST SIDE OREGON ZONES WILL BE
UNDER THE LEFT EXIT REGION OF THE 100 KT PLUS JET BY THIS
AFTERNOON AND EVENING. ALL THIS ADDS UP TO THUNDERSTORMS FOR US
TODAY, ESPECIALLY CASCADES/SISKIYOUS AND EASTWARD, AND SOME
STORMS MAY BE SEVERE OVER NORTHERN KLAMATH AND LAKE COUNTIES.
INDEED, THE STORM PREDICTION CENTER, HAS THAT AREA IN A SLIGHT
RISK FOR SEVERE TODAY. THE THREAT FROM THESE STORMS WOULD BE
STRONG WINDS AND HAIL, AND WHILE THEY WILL ALSO PRODUCE HEAVY
RAIN, THEY WILL BE MOVING, SO FLOODING SHOULDN`T BE MUCH CONCERN.
WILL BE MAKING SOME UPDATES TO INCREASE POPS IN THESE AREAS AND
POSSIBLY ADD SEVERE WORDING IN THE APPROPRIATE AREAS. -WRIGHT

&&

.AVIATION...BASED ON THE 22/12Z TAFS...AREAS OF IFR CIGS WITH
ISOLATED SHOWERS ALONG THE COAST WILL IMPROVE TO MVFR AROUND 16Z
THIS MORNING. OTHERWISE...CONDITIONS EARLY THIS MORNING WILL REMAIN
VFR ACROSS THE AREA. BY LATE THIS MORNING...CEILINGS WILL REMAIN
MAINLY VFR BUT SHOWERS WILL INCREASE WITH ISOLATED THUNDERSTORMS
DEVELOPING. DURING THE AFTERNOON AND THROUGH THE EVENING, SCATTERED
TO NUMEROUS THUNDERSTORMS ARE EXPECTED WITH THE MOST FREQUENT
ACTIVITY FROM WESTERN SISKIYOU COUNTY NORTHEASTWARD ACROSS THE
SISKIYOU AND CASCADE MOUNTAINS INTO NORTHERN PORTIONS OF KLAMATH AND
LAKE COUNTIES. THESE THUNDERSTORMS MAY PRODUCE MODERATE TO HEAVY
RAIN WITH MVFR CIGS/VSBYS, GUSTY WINDS, AND FREQUENT LIGHTNING.

&&

.PREV DISCUSSION... /ISSUED 340 AM PDT TUE JUL 22 2014/

SHORT TERM...AN UPPER LOW CENTERED WEST OF BRITISH COLUMBIA ALONG
130W WILL GRADUALLY SHIFT SOUTHWARD TODAY WHILE A RIDGE BUILDS INLAND.
MEANWHILE, AN UPPER LEVEL SHORTWAVE WILL MOVE UP THE COAST OF
CALIFORNIA AND INTO THE AREA THIS AFTERNOON AND EVENING AND
SOUTHERLY MONSOONAL FLOW WILL INCREASE OVER THE AREA. THIS PATTERN
IS EXPECTED TO BRING MOIST AND UNSTABLE CONDITIONS WITH SCATTERED
THUNDERSTORMS DEVELOPING OVER MANY INLAND AREAS TODAY. FURTHER,
THERE IS A SLIGHT CHANCE OF SEVERE STORMS WITH DAMAGING HAIL OR
WIND WITH THESE THUNDERSTORMS TODAY. THEN ON WEDNESDAY, THE CHANCE
FOR THUNDERSTORMS SHIFTS NORTHWARD AND THE UPPER LOW MOVES INTO
THE PACNW COAST BRINGING A FRONT INTO THE AREA WITH RAIN SHOWERS.

MODEL FORECASTS HAVE REMAINED ON TRACK SHOWING THAT THE BEST CHANCE
FOR THUNDERSTORMS TODAY IS ACROSS NORTHERN CALIFORNIA AND FROM
NEAR THE I-5 CORRIDOR EASTWARD IN SOUTHERN OREGON AS THE UPPER
SHORTWAVE PUSHES INTO THE AREA. LIFTED INDICES ARE GENERALLY
FORECAST TO BE AROUND -2 TO -4 AND STEEP MID LEVEL LAPSE RATES OF
7 TO 8 ARE FORECAST. MUCAPE VALUES OF NEAR 500 OR GREATER ARE
INDICATED AS WELL. AS UPPER LEVEL JET WILL PUSH INTO THE EASTERN
HALF OF THE AREA BRINGING AREAS OF DIVERGENCE ALOFT. BULK SHEAR
OF 30 KTS IS ALSO POSSIBLE OVER THE AREA. AS A RESULT, EXPECT A
SLIGHT CHANCE FOR SEVERE STORMS WITH DAMAGING HAIL OR WINDS.

HAVE INCREASED THE THUNDERSTORM COVERAGE IN THE AREA FROM CRATER
LAKE TO CHEMULT FROM SCATTERED TO NUMEROUS COVERAGE SINCE MODELS
SHOW GOOD AGREEMENT FOR LIKELY THUNDERSTORMS. ALSO INCREASED THE
SCATTERED THUNDERSTORM COVERAGE IN WESTERN SISKIYOU COUNTY GIVEN THE
TRAJECTORY OF THE SHORTWAVE UP FROM THE COAST.

DURING THE LATE EVENING AND TUESDAY NIGHT, THUNDERSTORMS ARE
EXPECTED TO DECREASE AND SHIFT NORTHWARD.

THEN, THE UPPER LOW MOVES TOWARDS THE PACNW COAST TONIGHT AND
INLAND WEDNESDAY. THE GFS, NAM, ECMWF, AND SREF ALL ARE IN GOOD
AGREEMENT AND INDICATE RAIN DEVELOPING ALONG THE COAST AND
SPREADING INLAND INTO AREAS WEST OF THE CASCADES IN OREGON AS
THIS SYSTEM BRINGS A FRONT INLAND ON WEDNESDAY. EAST OF THE
CASCADES EXPECT LITTLE SHOWER ACTIVITY AND ONLY A SLIGHT CHANCE
FOR THUNDERSTORMS OVER NORTHERN-MOST KLAMATH AND LAKE COUNTIES.
HOWEVER WINDS WILL BECOME VERY GUSTY IN THE AFTERNOON AND INTO THE
EVENING WITH GUSTS AROUND 30 TO 40 MPH POSSIBLE. COOLER
TEMPERATURES ARE EXPECTED ON WEDNESDAY AND WEDNESDAY NIGHT. HIGHS
IN THE 70S TO LOWER 80S ARE FORECAST DURING THE DAY WEDNESDAY.
ALSO TEMPERATURES ARE FORECAST TO LOWER INTO THE MID 30S FOR
AREAS IN NORTHERN KLAMATH AND LAKE COUNTIES WEDNESDAY NIGHT INTO
EARLY THURSDAY MORNING. ELSEWHERE, FOR AREAS EAST OF THE CASCADES,
EXPECT LOWS IN THE 40S AND FOR WEST SIDE VALLEYS, EXPECT LOWS IN
THE LOWER TO MID 50S.

THE UPPER LOW IS FORECAST TO SHIFT OFF TO THE NORTHEAST THURSDAY
AND A SURFACE THERMAL TROUGH DEVELOPING ALONG THE COAST THURSDAY.
THIS MAY BRING SOME STRONG GUSTY NORTHERLY WINDS TO THE COASTAL
WATERS AND ALONG THE COAST THURSDAY.

LONG TERM...FRIDAY THROUGH SUNDAY, EXPECT A DRY AND HOT
PATTERN TO DEVELOP AS AN UPPER LEVEL RIDGE BUILDS OVER THE
REGION. ALSO A THERMAL TROUGH WILL PERSIST ALONG THE COAST AND
BRING CONTINUED GUSTY WINDS TO THE COASTAL WATERS AND TO AREAS
ALONG  THE COAST. THEN EARLY NEXT WEEK, THE GFS AND ECMWF ARE
INDICATING MONSOON MOISTURE MOVING UP FROM THE SOUTH. THIS
COMBINED WITH DAYTIME INSTABILITY AND SHORTWAVE ACTIVITY MAY BRING
SOME THUNDERSTORMS TO THE AREA. SO HAVE ADDED ISOLATED
THUNDERSTORMS TO THE FORECAST, MAINLY FOR AREAS FROM THE CASCADES
EASTWARD FOR MONDAY AND TUESDAY.

MARINE...UPDATED 230 AM PDT 21 JULY 2014...WEAK LOW PRESSURE WILL
MOVE TOWARDS THE WATERS TODAY...THEN A FRONT WILL MOVE ONSHORE
WEDNESDAY. THIS WILL RESULT IN MAINLY LIGHT WINDS AND SEAS THROUGH
WEDNESDAY. A THERMAL TROUGH PATTERN WILL REDEVELOP THURSDAY AND
REMAIN IN PLACE THROUGH NEXT WEEKEND RESULTING IN STRONG NORTH
WINDS AND STEEP TO VERY STEEP WIND DRIVEN SEAS INTO THE WEEKEND.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ625.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR
     ORZ617-621>623.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ624.

CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ285.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ280-281.
     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ284.

PACIFIC COASTAL WATERS...NONE.

$$






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