Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 242246
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
246 PM PST SAT JAN 24 2015

.SHORT TERM...A STRONG HIGH PRESSURE RIDGE CONTINUES TO BUILD OVER
THE AREA THROUGH SUNDAY...THEN WILL GRADUALLY SHIFT EASTWARD
MONDAY. THIS PATTERN WILL BRING WARM AND DRY CONDITION TO THE
AREA WITH STAGNANT AIR FOR INLAND VALLEYS. ON TUESDAY HIGH
PRESSURE WEAKENS WITH A WEAK PACIFIC FRONT FORECAST TO PUSH INTO
THE COAST LATE IN THE DAY WILL A LOW TO THE SOUTH WILL MOVE UP
INTO NORTHERN CALIFORNIA AND NEVADA, BRINGING A CHANCE FOR RAIN
MAINLY TO AREAS EAST OF THE CASCADES.

ALONG THE COAST, A THERMAL TROUGH WILL BRING LIGHT TO MODERATE
OFFSHORE FLOW TONIGHT INTO SUNDAY. THEN THE THERMAL TROUGH WILL
EXPAND NORTH LATE SUNDAY AND SHIFT INLAND ON MONDAY. A CONTINUED
STRONG EAST- WEST SURFACE PRESSURE GRADIENT WILL BRING SOME BREEZY
EAST TO SOUTHEAST WINDS OVER THE MOUNTAINS LATE SUNDAY INTO
MONDAY. OFFSHORE FLOW IS EXPECTED TO KEEP MAINLY CLEAR SKIES ALONG
THE COAST WITH WARM DAYTIME TEMPERATURES ON SUNDAY, WITH SLIGHTLY
COOLER CONDITIONS ON MONDAY AND WINDS NEAR SHORE BECOME
SOUTHERLY.

INLAND, STRONG HIGH PRESSURE COMBINED WITH OFFSHORE FLOW WILL
ALSO BRING VERY WARM AND SUNNY CONDITIONS TO THE MOUNTAINS ON
SUNDAY AND INTO MONDAY. ON SUNDAY MODELS SHOW 850 MB TEMPERATURES
WARMING INTO THE UPPER 60S WEST OF THE CASCADES AND TO AROUND 60
EAST OF THE CASCADES. HIGH TEMPERATURES ON SUNDAY WILL BE WARMEST
IN THE MOUNTAINS, ESPECIALLY WEST OF THE CASCADES, WITH HIGHS IN
THE 60S TO LOW 70S.

VALLEY LOCATIONS WILL ALSO SEE WARM TEMPERATURES WITH HIGHS IN THE
UPPER 50S TO LOW 60S FOR MOST VALLEY LOCATIONS. VALLEY FOG IS
EXPECTED AGAIN TONIGHT AND SUNDAY MORNING FOR INLAND WEST SIDE
VALLEYS. FOG MAY BE DENSE IN THE UMPQUA VALLEY, ILLINOIS VALLEY
AND IN PORTIONS OF THE ROGUE VALLEY. STRENGTHENING OFFSHORE FLOW
THOUGH IS EXPECTED TO KEEP VALLEY FOG OUT OF THE TALENT AND
ASHLAND AREAS. SIMILAR CONDITIONS ARE EXPECTED SUNDAY NIGHT AND
MONDAY AS THE HIGH PRESSURE RIDGE PERSISTS OVER THE AREA BUT GRADUALLY
SHIFTS EASTWARD. HOWEVER INCREASING SOUTHEAST WINDS MAY RESULT IN
LESS FOG DEVELOPING IN THE MEDFORD AREA. ON MONDAY THE INVERSION
IS NOT EXPECTED TO BE AS STRONG, SO WILL SEE SLIGHTLY LESS WARM
DAYTIME TEMPERATURES, ESPECIALLY IN THE MOUNTAINS.

ON TUESDAY, A COUPLE DISTURBANCES WILL MOVE INTO THE AREA AND
WEAKEN THE HIGH PRESSURE. A WEAKENING PACIFIC FRONT IS EXPECTED TO
GRADUALLY PUSH INTO THE COAST LATE TUESDAY. THIS WILL BRING A
CHANCE OF RAIN TO THE COAST AND COASTAL WATERS. MEANWHILE A LOW
TO THE SOUTH WILL PUSH INTO NEVADA AND NORTHEAST CALIFORNIA ON
TUESDAY BRINGING A SLIGHT CHANCE OR CHANCE OF RAIN TO SOUTHEAST
PORTIONS OF THE CWA. EXPECT MOST THE MOISTURE TO REMAIN SOUTHEAST
OF THE CWA THOUGH AND CURRENT MODELS ARE SHOWING THAT THE BEST
CHANCE FOR ANY LIGHT PRECIPITATION WITH THIS LOW WILL BE IN
WESTERN SISKIYOU, MODOC, AND EXTREME SOUTHEAST LAKE COUNTIES.

AS HIGH PRESSURE BREAKS DOWN OVER THE AREA EXPECT INCREASED MIXING
AND A BRIEF BREAK IN THE STAGNANT AIR PATTERN, ESPECIALLY FOR
AREAS EAST OF THE CASCADES. WEST SIDE VALLEYS MAY CONTINUE TO
EXPERIENCE STAGNANT AIR THOUGH ON TUESDAY WITH ONLY LIMITED
IMPROVEMENT DURING THE AFTERNOON. ALSO HIGH PRESSURE IS EXPECTED
TO REBUILD INTO THE AREA IN THE LATTER PORTION OF THE WEEK WITH A
RETURN TO STAGNANT AIR CONDITIONS.

.LONG TERM...WEDNESDAY THROUGH SATURDAY...UPPER RIDGING WILL
GRADUALLY BUILD OVER THE REGION THROUGH THE EXTENDED FORECAST PERIOD
AND DRY WEATHER WILL CONTINUE. TEMPERATURES WILL JUMP BACK UP TO
WELL ABOVE NORMAL READINGS THROUGH THE BEGINNING OF THE WEEKEND. THE
5000 FOOT TEMPERATURES...A GOOD INDICATOR OF HOW WARM AN AIR MASS
WILL BE...SUGGEST TOP 10 PERCENT WARMTH FOR THIS TIME OF YEAR FROM
THURSDAY THROUGH SATURDAY. THE COAST COULD REACH TOP 5 PERCENT
WARMTH...AND READINGS IN THE MID TO UPPER 60S ARE A GOOD POSSIBILITY
FOR THE COAST BY SATURDAY.

AS WE HEAD TOWARDS FEBRUARY...OCCURRENCES OF OVERNIGHT AND MORNING
FOG DECREASE SHARPLY IN MOST PLACES...DUE TO SHORTER NIGHTS AND
INCREASING SUN ANGLE...AND LESS PRECIPITATION TOO. THEREFORE...AS
RIDGING BUILDS AGAIN LATER THIS WEEK WE HAVE ONLY KEPT FOG IN THE
FORECAST FOR RIVER VALLEYS LIKE THE UMPQUA...ILLINOIS...AND THE
GRANTS PASS AREA. EVEN THESE AREAS COULD BE FOG-FREE GIVEN THE DRY
ANTECEDENT CONDITIONS AND DECREASING SOIL MOISTURE.


&&

.AVIATION...BASED ON THE 24/18Z TAF CYCLE...CONDITIONS THIS
AFTERNOON ARE MAINLY VFR WITH ONLY ISOLATED IFR/MVFR CIGS
LINGERING INTO THIS AFTERNOON NEAR GRANTS PASS. THEN...WITH HIGH
PRESSURE BUILDING OVER THE AREA...EXPECT ANOTHER NIGHT OF FOG AND
LOW CLOUDS. CONFIDENCE IN LIFR CONDITIONS IN THE UMPQUA AND
ILLINOIS VALLEYS...AS WELL AS THE GRANTS PASS AREA...IS HIGH LATE
TONIGHT INTO SUNDAY MORNING. FOG AND LOW CLOUDS SHOULD LIFT TO VFR
LATE SUNDAY MORNING OR EARLY AFTERNOON. FURTHER SOUTH...THERE IS
POTENTIAL FOR ENOUGH SOUTHEAST WINDS TO DISRUPT FOG FORMATION IN
MEDFORD AND ESPECIALLY IN ASHLAND...SO CONFIDENCE IN IFR
CONDITIONS TONIGHT AND SUNDAY MORNING IS LOWER THERE.
LASTLY...THERE IS SOME POTENTIAL FOR A BRIEF PERIOD OF IFR
CEILINGS IN NORTH BEND TONIGHT BEFORE INCREASING EASTERLY OFFSHORE
FLOW CLEAR OUT THAT AREA. ELSEWHERE ACROSS THE FORECAST
AREA...EXPECT VFR CONDITIONS THROUGH SUNDAY. /SK

&&

.MARINE...UPDATED AT 211 PM SATURDAY 24 JANUARY 2015...WEAK HIGH
PRESSURE WILL REMAIN OVER THE WATERS THROUGH THE WEEKEND WITH STEEP
SEAS DOMINATED BY A LONG PERIOD WEST SWELL. WINDS WILL BECOME SOUTH
ON SUNDAY NIGHT AND REMAIN LIGHT TO MODERATE WHILE SEAS DIMINISH
MONDAY INTO WEDNESDAY. A WEAK FRONT IS FORECAST TO BRUSH ACROSS THE
WATERS ON TUESDAY WITH A SLIGHT CHANCE OF SHOWERS. HIGH PRESSURE
WILL FOLLOW WITH LIGHT TO MODERATE NORTHERLY WINDS DEVELOPING ON
THURSDAY. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 11 AM PST TUESDAY FOR
     ORZ023-024-026-616-620-622.
     AIR STAGNATION ADVISORY UNTIL 11 AM PST TUESDAY FOR
     ORZ029>031-623>625.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST THIS
     EVENING FOR PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 PM TO 10 PM PST
     SUNDAY FOR PZZ350-356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 10 AM TO 10 PM PST
     SUNDAY FOR PZZ370-376.

$$

CC/SK


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