Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 032344
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
343 PM PST TUE MAR 3 2015

UPDATED TO ADD CLIMATE AND FIRE WEATHER SECTIONS

.CLIMATE... THERE IS HIGH CONFIDENCE IN A PATTERN CHANGE TO WETTER
AND LESS WARM CONDITIONS FOR THE WEEK 2 PERIOD, WHICH IS MARCH 10TH
TO THE 17TH. THERE ARE SEVERAL REASONS TO HAVE HIGH CONFIDENCE IN
THIS CHANGE OCCURRING, AS THE ARCTIC OSCILLATION IS EXPECTED TO GO
FROM POSITIVE TO VERY POSITIVE AND THE MADDEN JULIAN OSCILLATION IS
EXPECTED TO BECOME ACTIVE AGAIN AS IT PROPAGATES THROUGH THE WESTERN
PACIFIC OCEAN. LOW PRESSURE NEAR HAWAII IS LIKELY TO INTERACT WITH
THIS FLOW SENDING STORM ACTIVITY INTO THE REGION. WITH THE STORM
TRACK COMING FROM THE HAWAIIAN ISLAND AREA SNOW LEVELS USUALLY END
UP 6,000 TO 8,000 FOOT RANGE. BEYOND WEEK 2 MODEL GUIDANCE IS
GENERALLY INDICATING AN ACTIVE STORM TRACK ALONG THE WEST COAST
FOCUSED ACROSS CALIFORNIA. HOW FAR NORTH THIS WILL EXTEND IS
UNCERTAIN, BUT IT DOES APPEAR IT WILL REACH NORTH INTO OUR AREA, AT
TIMES. IT SHOULD BE NOTED THAT, WITH LOW PRESSURE NEAR HAWAII, THAT
PRECIPITATION FROM SINGLE STORMS COULD BE SIGNIFICANT IF A
CONSOLIDATED JET STREAM REACHES INTO OUR AREA. BTL

&&

.FIRE WEATHER... A WARMING AND DRYING TREND UNDERWAY ACROSS THE
FORECAST AREA IS EXPECTED TO CONTINUE THROUGH THIS UPCOMING WEEKEND
BEFORE WET WEATHER RETURNS EARLY TO THE MIDDLE OF NEXT WEEK. BY THIS
WEEKEND TEMPERATURES ARE EXPECTED TO BE 10 TO 15 DEGREES ABOVE
NORMAL FOR HIGHS. THIS IS WILL RESULT IN FURTHER DRYING ACROSS THE
AREA THAT SHOULD BE TAKEN INTO CONSIDERATION FOR THOSE PLANNING AND
CONDUCTING PRESCRIBED BURNING. THERE MAY BE A PERIOD EARLY NEXT WEEK
WHEN SOUTH AND SOUTHWEST WINDS BECOME GUSTY BEFORE WARM AND DRY
CONDITIONS TRANSITION TO COOLER AND WETTER. BTL

&&

.DISCUSSION...03/12Z NAM/GFS IN.

THE LOW CLOUDS HAVE CLEARED. ALL THAT REMAINS IS AN AREA OF HIGH
CLOUDS MOVING THROUGH FROM NORTH TO SOUTH. THOSE WILL CLEAR OUT
LATER THIS AFTERNOON.

THE WAVE NUMBER IS A BIT DIFFICULT TO DETERMINE...BUT IT LOOKS
LIKE A 3-4 WAVE PATTERN AROUND THE NORTHERN HEMISPHERE. THIS WOULD
ARGUE FOR A SLOW PROGRESSION OR STATIONARY PATTERN AROUND THE
GLOBE. OVER TIME THIS PATTERN CHANGES LITTLE...REMAINING A 3 TO 4
WAVE PATTERN THROUGH THE WEEK WITH THE COLDEST AIR GENERALLY
RETREATING TOWARDS THE POLE.  LOOKS LIKE A SEASONAL CHANGE.

CURRENTLY A LONG WAVE RIDGE REMAINS OFFSHORE ALONG 14OW WITH DRY
NORTHERLY FLOW ALOFT OVER THE PACIFIC NORTHWEST. THE RIDGE WILL
MOVE SLOWLY WEST THROUGH WEDNESDAY WHILE SLOWLY WEAKENING. THIS
MAY ALLOW SOME HIGH LEVEL MOISTURE TO MOVE OVER THE RIDGE...BUT
THAT WILL JUST BRING SOME HIGH CLOUDS TO THE AREA. EXPECT DRY
CONDITIONS TO CONTINUE WITH A GRADUAL WARMING TREND...ALONG WITH
SOME MORNING FOG IN THE WEST SIDE VALLEYS. MARINE STRATUS WILL
LIKELY INCREASE IN COVERAGE WITH TIME...BUT THE MARINE INVERSION
WILL REMAIN LOW DUE TO SUBSIDENCE ALOFT. HIGHER RESOLUTION MODELS
ARE SUGGEST A SOUTHERLY MARINE PUSH THURSDAY AND FRIDAY. THIS
WOULD BRING WIDESPREAD LOW CLOUDS AND FOG TO THE COAST.

THE COLDEST TEMPERATURES ARE EXPECTED TONIGHT INTO TOMORROW
MORNING, WITH BELOW FREEZING TEMPERATURES LIKELY IN PORTIONS OF
THE WEST SIDE VALLEYS. AGRICULTURAL INTERESTS MAY NEED TO TAKE
PRECAUTIONS TO PROTECT NEW GROWTH RESULTING FROM THE WARMER THAN
NORMAL TEMPERATURES OF THE PAST SEVERAL WEEKS. OVERNIGHT LOWS WILL
BE SLIGHTLY ABOVE SEASONAL NORMALS BY THIS WEEKEND...BUT INLAND
HIGHS WILL BE 10 TO 15 DEGREES ABOVE NORMAL BY THAT TIME.

THE RIDGE WILL BECOME STATIONARY ALONG THE WEST COAST AND
STRENGTHEN THURSDAY INTO THE WEEKEND...THEN WEAKEN IN PLACE SUNDAY
INTO MONDAY BEFORE MOVING OFF TO THE EAST NEXT TUESDAY. EXPECT THE
DRY CONDITIONS AND WARMING TREND TO CONTINUE THROUGH THE WEEKEND.
TUESDAY IS WHEN THE NEXT CHANCE OF PRECIPITATION CREEPS INTO THE
FORECAST. EVEN THAT IS LOOKING IFFY AT THIS TIME...IT MIGHT NOT
ACTUALLY HAPPEN UNTIL NEXT WEDNESDAY OR THURSDAY.
HOWEVER...MEDIUM-RANGE MODELS ARE MAKING STRONG INDICATIONS THAT
WET CONDITIONS WILL DEVELOP IN THE 7-14 DAY PERIOD.

&&

.AVIATION...FOR THE 03/18Z TAF CYCLE...EXPECT VFR THE REST OF
TODAY THROUGH WEDNESDAY MORNING FOR KOTH, KMFR, KLMT. AREAS OF IFR
LOW CLOUDS/FOG COULD REDEVELOP IN THE UMPQUA VALLEY TOWARD SUNRISE
WEDNESDAY, BURNING OFF TO VFR BY MID-LATE MORNING. SPILDE

&&

.MARINE...UPDATED 0600 PST MONDAY 2 MAR 2015...SEAS ARE PRIMARILY
WIND-DRIVEN AS NORTH WINDS HAVE INCREASED DUE TO A DEVELOPING
THERMAL TROUGH AND HIGH PRESSURE OFFSHORE. NORTH WINDS WILL WEAKEN
WEDNESDAY AS THE SURFACE HIGH PRESSURE SHIFTS EASTWARD.

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL
        10 PM PST THIS EVENING FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS
        EVENING FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 3 AM PST
        THURSDAY FOR PZZ370-376.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM PST WEDNESDAY
        FOR PZZ376.

$$

BTL/15/10


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