Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 121020
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
320 AM PDT SAT JUL 12 2014

.DISCUSSION...LARGE SCALE RIDGING OVER THE WESTERN CONUS WILL
KEEP VERY WARM TEMPERATURES IN PLACE OVER THE AREA FOR THE NEXT
SEVERAL DAYS AT LEAST. HOWEVER...A SMALL TROUGH CURRENTLY LOCATED
OFF THE WEST COAST WILL RIDE NORTHEAST ALONG THE WESTERN PERIPHERY
OF THE RIDGE...SKIRTING THE NORTHWEST PORTIONS OF THE FORECAST
AREA SUNDAY. THE TIMING OF THIS SYSTEM IS NEARLY PERFECT...IN THAT
THE BEST LIFT...PROVIDED BY DIVERGENCE AND FAVORABLE JET DYNAMICS
ALOFT...WILL PASS THROUGH THE AREA AROUND THE TIME OF MAXIMUM
HEATING. MODELS HAVE CONSISTENTLY SHOWN THIS TIMING...LEADING TO
INCREASED CONFIDENCE IN A BUSY THUNDERSTORM DAY. THE FOCUS OF
STORMS WILL BE FARTHER NORTH THAN THE PREVIOUS EVENT ON
FRIDAY...AS THAT IS WHERE THE ATMOSPHERE WILL FAVOR CONVECTIVE
DEVELOPMENT...BUT THERE IS SLIGHT CHANCE OF THUNDER FOR JUST ABOUT
ALL OF THE FORECAST AREA THROUGH THE DAY SUNDAY.

BEYOND SUNDAY...THE RIDGE OVERHEAD WILL RETROGRADE FURTHER WEST AS A
VERY DEEP AND STRONG TROUGH DIGS INTO THE CENTRAL AND EASTERN CONUS.
THIS WILL EVENTUALLY LEAD TO BROAD TROUGHING OVER MOST OF THE
CONTINENT BY MID TO LATE WEEK...WITH THE MAIN BELT OF WESTERLIES
JUST NORTH AND EAST OF THE FORECAST AREA. UNTIL THAT TIME...VERY
WARM TEMPERATURES WILL REMAIN IN PLACE...WITH THE THERMAL TROUGH
OVER NORTHERN CALIFORNIA STRENGTHENING AND EXPANDING TO THE NORTH BY
TUESDAY. IN FACT...TUESDAY WILL BE THE WARMEST DAY OF THE
WEEK...WITH HIGHS LIKELY REACHING 10 TO 15 DEGREES ABOVE
NORMAL...WHICH WOULD EQUAL RECORD HIGHS FOR SOME LOCATIONS. WITH THE
ARRIVAL OF LOWER HEIGHTS UNDER NORTHWEST FLOW LATER IN THE
WEEK...TEMPERATURES SHOULD RETURN TO NEAR OR SLIGHTLY ABOVE NORMAL
VALUES. THIS NEW PATTERN WOULD ALSO OPEN THE AREA UP TO POSSIBLE WAVES
WITHIN THE WESTERLIES THAT COULD BRING WEATHER MAKERS TO THE AREA
INTO NEXT WEEKEND. THE LATEST GFS SOLUTION DEPICTS ONE SUCH TROUGH
TOPPING THE RIDGE OVER THE EASTERN PACIFIC AND PUSHING INTO THE
PACIFIC NORTHWEST BY FRIDAY...SHOWING THAT SUCH A SCENARIO IS NOT
OUT OF THE QUESTION. WITH UNCERTAINTY AS IT IS...HAVE LEFT THE
FORECAST DRY FOR NOW...AND WILL WAIT FOR CONFIDENCE TO IMPROVE IN
LATER FORECAST CYCLES BEFORE ADDING ANY PRECIPITATION CHANCES. -BPN


&&

.AVIATION...BASED ON THE 12/06Z TAFS...ALONG THE COAST...IFR
CIGS/VSBYS WITH HIGHER TERRAIN OBSCURED WILL PERSIST INTO
SATURDAY MORNING...MANY AREAS WILL CLEAR TO VFR SATURDAY AFTERNOON,
BUT IFR/MVFR CIGS MAY HOLD ALL DAY AT THE IMMEDIATE COAST (INCLUDING
NEAR KOTH). EITHER WAY EXPECT IFR TO RETURN SATURDAY EVENING. UMPQUA
BASIN...AREAS OF MVFR CIGS WILL DEVELOP LATE TONIGHT AFTER AROUND
10Z AT KRBG. CIGS WILL CLEAR TO VFR BY LATE MORNING SATURDAY. VFR
CONDITIONS WILL PREVAIL ELSEWHERE THROUGH SATURDAY EVENING...THOUGH
ISOLATED THUNDERSTORMS MAY DEVELOP FROM THE CASCADE CREST EASTWARD
SATURDAY AFTERNOON. -SPILDE


&&

.MARINE...UPDATED FRIDAY 12 JULY 300 AM PDT...A WEAK PRESSURE
PATTERN AND SLIGHT SWELL WILL PERSIST INTO SUNDAY...THEN A THERMAL
TROUGH WILL DEVELOP NEAR THE COAST.  THIS WILL BRING A RETURN OF
STRONG NORTH WINDS AND STEEP SEAS BEGINNING MONDAY AFTERNOON.  THE
WINDS WILL PEAK MONDAY NIGHT...THEN THE TROUGH WILL WEAKEN.
HOWEVER...STRONG WINDS AND STEEP SEAS WILL STILL OCCUR IN THE
AFTERNOONS AND EVENING TUESDAY THROUGH WEDNESDAY. -RES


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FIRE WEATHER WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING
     FOR ORZ616-617-623>625.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

BPN/RES/MAS





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