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000
FXUS66 KMFR 222157
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
257 PM PDT WED MAY 22 2013

.SHORT TERM...AN UPPER LOW WILL REMAIN OVER THE REGION THROUGH
FRIDAY...WEAKENING AND SHIFTING NORTH SLIGHTLY ON SATURDAY. THIS
LOW WILL GRADUALLY FILL AND THE AIR MASS WILL GRADUALLY WARM.
CONTINUED MOISTURE AND SHORTWAVES WILL MOVE INTO THE CWA OVER THE
NEXT FEW DAYS AND BRING SHOWERS. THE PREFERRED AREA FOR SHOWER
ACTIVITY WILL BE ACROSS THE COAST AND THE UMPQUA AS WELL AS THE
SOUTHERN OREGON CASCADES WITH AREAS OF SHOWERS MOVING INTO OTHER
WEST SIDE LOCATIONS AND EAST OF THE CASCADES AT TIMES.

A SHORTWAVE IS MOVING INLAND THIS AFTERNOON AND EVENING AND IS
BRINGING SCATTERED SHOWERS TO AREAS FROM THE CASCADES WEST.
SHOWER ACTIVITY IS EXPECTED TO INCREASE ACROSS THE WEST SIDE IN
THIS AFTERNOON AND EVENING AND SPREAD INTO SOME EAST SIDE LOCATIONS AS
WELL.  SOME OF THE SHOWERS MAY BRING SMALL HAIL AND GUSTY WINDS
THIS AFTERNOON INTO THIS EVENING.  MODELS  SHOW SOME MARGINAL
INSTABILITY IN NORTHERN LAKE COUNTY. EXPECT MAINLY SCATTERED
SHOWERS TO DEVELOP THERE BUT THINK THE CHANCE FOR ANY
THUNDERSTORMS IS LOW.

SHOWER ACTIVITY IS EXPECTED TO CONTINUE INTO THE EVENING FOR MANY
LOCATIONS WITH SHOWERS DECREASING OVERNIGHT. COLD OVERNIGHT
TEMPERATURES ARE EXPECTED AGAIN TONIGHT INTO THURSDAY MORNING.
SKIES WILL LIKELY STAY CLOUDY OVERNIGHT WITH SOME PARTIAL
CLEARING OVER INLAND AREAS DURING THE EARLY MORNING. TEMPERATURES
THURSDAY MORNING WILL LIKELY BE SIMILAR OR JUST A COUPLE DEGREES
WARMER THAN THIS MORNING. PARTIAL CLEARING THOUGH MAY ALLOW MORE
FROST FORMATION THURSDAY MORNING. HAVE INCLUDED MENTION OF PATCHY
FROST IN THE WESTERN OREGON VALLEYS INCLUDING THE ROGUE AND
ILLINOIS VALLEYS AND AREAS OF FROST INTO THE SHASTA VALLEY IN
CALIFORNIA. OVER THE KLAMATH BASIN EXPECT FREEZING AND BELOW
FREEZING CONDITIONS.

ON THURSDAY...EXPECT SOME SCATTERED SHOWERS DURING THE DAY. THEN
MODELS SHOW INCREASED SHOWER ACTIVITY DURING THE EVENING AND
CONTINUING INTO FRIDAY MORNING AS A MODERATE VORT MAX ASSOCIATED
WITH THE UPPER LOW MOVES INTO THE AREA. THE BEST CHANCE FOR SHOWERS
WILL BE FROM THE SOUTHERN OREGON CASCADES WEST WITH ISOLATED TO
SCATTERED SHOWERS EAST OF THE CASCADES AND INTO PORTIONS OF
NORTHERN CALIFORNIA.

SHOWERS ARE EXPECTED TO DECREASE FRIDAY AFTERNOON AND EVENING AS
THE SHORTWAVE MOVES NORTHEAST AND OUT THE AREA. THE UPPER
TROUGH REMAINS OVER THE REGION FRIDAY NIGHT AND SATURDAY...ALTHOUGH
WEAKER AND CENTERED FURTHER NORTH. THIS WILL BRING THE POTENTIAL
FOR ADDITIONAL AREAS OF SCATTERED SHOWERS ON SATURDAY. MODELS HAVE
TRENDED LOWER ON THE SHOWER ACTIVITY THOUGH SO HAVE LOWERED THE
CHANCE OF PRECIPITATION FOR SATURDAY. WEAK INSTABILITY STILL IS
PRESENT EAST OF THE CASCADES SO HAVE KEPT A SLIGHT CHANCE FOR
THUNDERSTORMS...MAINLY IN LAKE COUNTY...SATURDAY AFTERNOON AND
EVENING.

.LONG TERM...


&&

.AVIATION...A WEAKENING DISTURBANCE IS MOVING ACROSS THE AREA
THIS AFTERNOON. SCATTERED SHOWERS...AREAS OF MVFR CIGS AND AREAS
OF OBSCURED MOUNTAINS ARE EXPECTED THROUGH THE EVENING. AREAS OF
MVFR CIGS WILL PERSIST NEAR THE COAST AND IN THE UMPQUA BASIN LATE
TONIGHT THROUGH THURSDAY MORNING. OTHERWISE...CONDITIONS WILL
IMPROVE TO VFR LATE TONIGHT. ANOTHER DISTURBANCE WILL REACH THE
COAST BY THURSDAY AFTERNOON.



&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FREEZE WARNING FROM 2 AM TO 9 AM PDT THURSDAY FOR ORZ029.

CA...FREEZE WARNING FROM 2 AM TO 9 AM PDT THURSDAY FOR CAZ084.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THURSDAY
     FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT THURSDAY
     FOR PZZ370-376.

$$

CC