Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 022205
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
305 PM PDT TUE JUN 2 2015

.SHORT TERM...A WEAK SHORT WAVE ROTATING AROUND AN UPPER LOW
CENTERED OVER SEATTLE WILL CONTINUE TO BRING SHOWERY CONDITIONS
TO THE SISKIYOUS AND THE SOUTHERN CASCADES THIS AFTERNOON AND
EVENING. RADAR RETURNS INDICATE SHOWERS DEVELOPING OVER THE
MEDICINE LAKE AREA, WHICH WILL MOVE NORTHEASTWARD INTO LAKE AND
MODOC COUNTY. THUNDERSTORMS IN AREAS EAST OF THE CASCADES CAN`T BE
RULED OUT, BUT GIVEN BORDERLINE INSTABILITY AND LOW MID TO HIGH
LEVEL RH, CONFIDENCE IS LOW THAT ANY WILL OCCUR.

WEAK OFFSHORE RIDGING EARLY WEDNESDAY WILL CAUSE OFFSHORE FLOW AND
TEMPERATURES WILL RISE TO JUST A FEW DEGREES BELOW NORMAL. A CLOSED
LOW WILL START TO FORM OFF THE COAST...BRINGING SOUTHEASTERLY
MOISTURE ADVECTION AND THE CHANCE OF AFTERNOON SHOWERS ON WEDNESDAY.
THE LOW WILL CLOSE AND BEGIN TRACKING SOUTH ALONG THE CALIFORNIA
COAST. MOISTURE WILL WRAP AROUND, BRINGING POSSIBLE SHOWERS AND
THUNDERSTORMS THURSDAY. THE HIGHEST CHANCE FOR SHOWERS WILL BE IN
THE AFTERNOON. STORMS SHOULD DEVELOP FROM EAST TO WEST AND MAINLY
AFFECT THE EAST SIDE AND SISKIYOUS. CONFIDENCE THAT THUNDERSTORMS
WILL DEVELOP IS MODERATE AS HIGH LEVEL CLOUDS MAY PREVENT SURFACE
TEMPERATURES FROM REACHING THE TRIGGER TEMPERATURE.

THE LOW WILL MOVE TOWARDS SOUTHERN CALIFORNIA ON FRIDAY. THE CWA
WILL BE BISECTED FROM NORTHWEST TO SOUTHEAST...DRY OFFSHORE FLOW
OVER THE CASCADES AND WESTWARD WILL BRING TEMPERATURES IN THE
NORTHWESTERN PORTION OF THE CWA UP TO 10 DEGREES ABOVE NORMAL FRIDAY
AFTERNOON. SOUTHEASTERLY FLOW ON THE NORTH SIDE OF THE LOW WILL
BRING POSSIBLE AFTERNOON SHOWERS AND THUNDERSTORMS FRIDAY AFTERNOON
IN THE SOUTHEASTERN PORTION OF THE CWA. -MSC/MAS

.LONG TERM...SATURDAY THROUGH TUESDAY...CONSIDERING THE FACT THAT WE
WILL BE DEALING WITH A CLOSED LOW IN THE EXTENDED, THE MODELS ARE IN
REMARKABLE AGREEMENT. NOT ONLY ARE THEY IN AGREEMENT WITH EACH
OTHER, BUT ENSEMBLE SPREADS ARE VERY LOW. ALL THIS LEADS TO
UNUSUALLY HIGH CONFIDENCE IN THE EXTENDED FORECAST.

A CLOSED UPPER LOW OVER SOUTHERN CALIFORNIA WILL BEGIN TO LIFT OUT
INTO THE GREAT BASIN OVER THE WEEKEND, AND AT THE SAME TIME, A
POSITIVELY TILTED RIDGE OF HIGH PRESSURE WILL LEAN IN OVER THE
PACIFIC NORTHWEST. THIS WILL RESULT IN DEEP OFFSHORE FLOW WHICH
LEADS TO HOT, DRY WEATHER WEST OF THE CASCADES. MOISTURE AND ENERGY
WILL WRAP AROUND THE LOW AND RESULT IN A CHANCE FOR THUNDERSTORMS
OVER THE EAST SIDE AND NORTHERN CALIFORNIA OVER THE WEEKEND. GIVEN
THE HIGH CONFIDENCE, I RAISED POPS IN THESE AREAS FOR SUNDAY.

THE UPPER LOW THEN ELONGATES EARLY NEXT WEEK AS A PORTION OF THE LOW
CONTINUES NORTHWARD AND SOME NEW ENERGY FEEDS INTO THE TROUGH OFF
CALIFORNIA. AT THIS POINT THE SYSTEM MAY BREAK INTO TWO SEPARATE
LOWS, ONE OFF CALIFORNIA AND THE OTHER OVER THE NORTHERN ROCKIES.
THE MODELS ALSO AGREE ON THIS WITH THE MAIN DIFFERENCE BEING THAT
THE ECMWF DOES THIS A LITTLE FURTHER SOUTH THAN THE GFS. THE NET
RESULT IS THAT WE WILL BE IN THE WEAK TROUGHING, OR COL, BETWEEN THE
TWO. THIS WILL WEAKEN THE OFFSHORE FLOW AND ALLOW TEMPERATURES TO
MODERATE ON THE WEST SIDE. HOWEVER, THERE WILL STILL BE A CHANCE FOR
THUNDERSTORMS OVER NORTHERN CALIFORNIA AND THE EAST SIDE MONDAY AND
TUESDAY. -WRIGHT

&&

.AVIATION...FOR THE 02/18Z TAF CYCLE...CONDITIONS WILL BE VFR MOST
OF TODAY OVER MOST OF THE AREA. BRIEF MVFR CIGS/VIS ARE POSSIBLE IN
SHOWERS WHICH WILL BE MOST LIKELY ALONG THE COAST, THE UMPQUA BASIN
(INCLUDING KOTH AND KRBG), AND INTO THE CASCADES. ELSEWHERE, SHOWERS
WILL BE MUCH MORE ISOLATED. THERE IS A SLIGHT CHANCE FOR
THUNDERSTORMS FROM AROUND MT. SHASTA EAST INTO THE WARNERS THIS
AFTERNOON AND EVENING. SHOWERS DIMINISH TONIGHT WITH A MIX OF VFR
AND MVFR CIGS. -WRIGHT

&&

.MARINE...UPDATED 220 PM PDT, TUESDAY, 2 JUNE 2015...SHOWER CHANCES
WILL CONTINUE TO DIMINISH THIS AFTERNOON AND TONIGHT. WINDS AND SEAS
WILL REMAIN LIGHT THROUGH WEDNESDAY MORNING. CONDITIONS WILL CHANGE
SUBSTANTIALLY FOR THE SECOND PORTION OF THE WEEK. HIGH PRESSURE WILL
BEGIN BUILDING OFFSHORE...AND WILL COUPLE WITH LOW PRESSURE INLAND
TO ALLOW NORTHERLY WINDS AND STEEP CHOPPY SEAS TO REACH ADVISORY
LEVEL BY WEDNESDAY EVENING FOR THE WATERS SOUTH OF CAPE BLANCO. THEN
AS THE PRESSURE GRADIENT INCREASES, EXPECT WINDS TO INCREASE FURTHER
ON THURSDAY. AS A RESULT, SMALL CRAFT WINDS AND STEEP SEAS ARE
FORECAST TO DEVELOP OVER MOST THE COASTAL  WATERS BY LATE THURSDAY
AFTERNOON AND THURSDAY EVENING. AREAS OF GALES AND HAZARDOUS SEAS
WILL BECOME POSSIBLE SOUTH OF CAPE BLANCO. THESE STRONG WINDS AND
STEEP TO VERY STEEP SEAS ARE FORECAST TO PERSIST INTO SATURDAY
BEFORE DECREASING BELOW ADVISORY LEVELS ON SUNDAY. ALTHOUGH
CONFIDENCE IS LOW AT THIS TIME, ANOTHER SET OF ADVISORY LEVEL WINDS
AND SEAS COULD BE POSSIBLE EARLY TO THE MIDDLE OF NEXT WEEK AND WILL
NEED TO BE MONITORED. -SCHAAF/SVEN

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...GALE WATCH FROM THURSDAY MORNING THROUGH
     LATE FRIDAY NIGHT FOR PZZ376.
     HAZARDOUS SEAS WATCH FROM THURSDAY MORNING THROUGH SATURDAY
     AFTERNOON FOR PZZ376.

$$

MAS/TRW/SBN/MSC/BMS



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