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000
FXUS66 KMFR 170410
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
910 PM PDT THU MAY 16 2013

.SHORT TERM...AN UPPER TROUGH MOVING ACROSS THE REGION IS
BRINGING CONTINUED AREAS OF LIGHT SHOWERS TONIGHT. EXPECT MUCH OF
THE SHOWER ACTIVITY TO BE ISOLATED TO SCATTERED IN NATURE. SO HAVE
ADJUSTED POPS AND WEATHER DOWN THIS EVENING INTO FRIDAY MORNING.
IN ADDITION TO SHOWERS TONIGHT...MODELS ARE SHOWING LOW CLOUDS
DEVELOPING FOR MANY AREAS TONIGHT INTO FRIDAY MORNING...ESPECIALLY
WEST OF THE CASCADES. THE TROUGH SHIFTS EAST ON FRIDAY AND SHOWERS
ARE EXPECTED TO BE ISOLATED FOR MUCH THE WEST SIDE WITH LINGERING
SCATTERED SHOWERS POSSIBLE EAST OF THE CASCADES.


&&

.AVIATION...WEAK INSTABILITY REMAINS OVER THE AREA INTO TONIGHT
WITH SCATTERED SHOWERS. THIS WILL RESULT IN A MIX BETWEEN MVFR AND
VFR CIGS BETWEEN NOW AND 5-6Z. THE CHANCE FOR MVFR CIGS WILL BE
HIGHER NEAR AND UNDER SHOWERS WITH MTNS PARTLY OBSCURED THROUGH
THIS EVENING. SHOWERS WILL CONTINUE TO DIMINISH TONIGHT BUT MVFR
CIGS ARE EXPECTED TO RETURN TO COASTAL AREAS AND THE UMPQUA VALLEY
THIS EVENING AND OVERNIGHT. IT WILL BE A CLOSE CALL IN THE ROGUE
VALLEY AND KLAMATH BASIN. GUIDANCE SUGGEST THERE IS THE POTENTIAL
FOR MVFR CIGS TO DEVELOP AFTER 08Z WHICH COULD BE THE RESULT OF
LINGERING LOW LEVEL MOISTURE. CONDITIONS SHOULD IMPROVE TO VFR AT
MOST LOCATIONS BY TOMORROW LATE MORNING. SK


&&

.PREV DISCUSSION... /ISSUED 252 PM PDT THU MAY 16 2013/

SHORT TERM...THE UPPER LEVEL TROUGH WILL CONTINUE TO SHIFT EAST
OVERNIGHT WITH THE MAIN ENERGY CONCENTRATED TO THE EAST OF THE
CASCADES. AS A RESULT SHOWERS WILL BE MORE PREVALENT FROM THE
KLAMATH/TULELAKE BASINS EAST WITH ONLY ISOLATED SHOWERS TO THE
WEST OF THE CASCADES. HIGH PRESSURE WILL BRIEFLY INTO THE AREA
FRIDAY BUT WITH PLENTY OF LOW LEVEL MOISTURE AND SLIGHTLY UNSTABLE
AIR MASS, SOME SHOWERS WILL LINGER ACROSS OUR FORECAST AREA
ESPECIALLY IN UPSLOPE AREA OF WEST TO NORTHWESTERLY FLOW. HIGH
TEMPERATURES WILL NUDGE UP A FEW DEGREES BUT SHOULD STILL BE A FEW
DEGREES BELOW SEASONAL NORMS. ANOTHER SHORT WAVE TROUGH WILL BRING
MORE SHOWERS TO THE AREA ON SATURDAY.

THE UPPER LEVEL RIDGE WILL BUILD INTO THE AREA SUNDAY AND MONDAY.
THIS WILL LEAD TO CLEARING AND WARMING WITH OFFSHORE EAST TO NORTHEAST
WINDS ACROSS SOUTHWEST OREGON AND NORTHERLY WINDS INTO THE
SACRAMENTO VALLEY FOR THE CALIFORNIA ZONES. THE FLOW IS EXPECTED
TO TURN ONSHORE MONDAY AFTERNOON IN RESPONSE TO THE NEXT LOW
PRESSURE THAT WILL AFFECT OUR WEATHER IN THE EXTENDED PERIOD. /FB

LONG TERM...CONFIDENCE IS HIGH AN UPPER LOW WILL DROP SOUTH INTO
THE PAC NW TUESDAY AND REMAINING THERE INTO THE END OF NEXT WEEK
WITH BELOW NORMAL TEMPERATURES AND POPS ABOVE CLIMO...ESPECIALLY
WEST OF THE CASCADES. CONFIDENCE IS NOT AS HIGH REGARDING THE
DETAILS ON THE EXACT POSITION OF THE UPPER LOW AND WHERE MOST OF THE
SIGNIFICANT PRECIPITATION WILL BE CENTERED AT. THIS MAY SEEM UNUSUAL
FOR THIS TIME OF THE YEAR...ESPECIALLY WITH THE RECENT WARM AND DRY
CONDITIONS WE HAVE EXPERIENCED THE PAST FEW WEEKS...HOWEVER THE
RETURN INTERVAL FOR THIS TYPE OF PATTERN DOES OCCUR EVERY 0-1 YEARS.
THE GOOD NEWS IS THAT IT COULD BRING THE POTENTIAL FOR MUCH NEEDED
PRECIPITATION. -PETRUCELLI

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

CC