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  Forecast Discussion for Southern Oregon and Northern California  

Forecast: Forecast Discussion | 7 Day Forecast

Forecast Discussion for MFR NWS Office

000
FXUS66 KMFR 281721
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
921 AM PST WED JAN 28 2015

.DISCUSSION...CURRENT VISIBLE IMAGE SHOWS HIGH CLOUDS MOVING OVER
THE AREA WITH SCATTERED HIGH CLOUDS IN NORTHERN CAL AND EAST OF
THE CASCADES. WITH THE EXCEPTION OF LOW CLOUDS IN THE WESTSIDE
VALLEYS, HAVE REDUCED CLOUD COVER FOR THIS MORNING AND AFTERNOON.
THE MORNING SOUNDING SHOWS THE MOISTURE LAYER SIMILAR TO
YESTERDAY, BUT TEMPERATURES ALOFT ARE COOLER THAN YESTERDAY (DUE
IN PART TO THE WEAK COLD FRONT THAT MOVED THROUGH YESTERDAY). LOW
CLOUDS AND AREAS OF FOG WILL LINGER THROUGH THE MORNING HOURS,
THEN EXPECT A SLOW BURN OFF EARLY THIS AFTERNOON. ALSO ADJUSTED
MAX TEMPERATURES DOWN A FEW DEGREES IN GRANTS PASS, MEDFORD AND
ILLINOIS VALLEY DUE TO THE EXPECTED LATER BREAK UP OF LOW CLOUDS.
REST OF THE FORECAST IS STILL ON TRACK AND OTHER THAN WHAT`S NOTED
ABOVE NO OTHER CHANGES WERE MADE. -PETRUCELLI

&&

.AVIATION...BASED ON THE 28/18Z TAF CYCLE...IFR CIGS/VSBYS OVER THE
WEST SIDE VALLEYS WILL CLEAR TO VFR THIS AFTERNOON...THEN THE LOWER
CONDITIONS WILL RETURN TO THE SAME AREAS LATE TONIGHT THROUGH LATE
MORNING THURSDAY.  THE REMAINDER OF THE AREA WILL REMAIN VFR THROUGH
THURSDAY...BUT SOME HIGHER TERRAIN MAY BE OBSCURED FROM THE CASCADES
WEST.

&&

.MARINE...UPDATED AT 900 AM WEDNESDAY 28 JANUARY 2015...WEST SWELL
WILL CONTINUE TO SUBSIDE WITH LIGHT SOUTH WINDS TODAY. A WEAK
FRONT ACROSS THE NORTHERN PART OF THE WATERS WILL DISSIPATE
TODAY. MODERATE NORTHERLY WINDS WILL DEVELOP THURSDAY INTO FRIDAY
AS OFFSHORE HIGH PRESSURE BUILDS...RESULTING IN INCREASED
CHOP...ESPECIALLY SOUTH OF CAPE BLANCO. SMALL CRAFT CONDITIONS MAY
DEVELOP THERE. THE HIGH WILL WEAKEN SATURDAY NIGHT INTO SUNDAY AS
THE NEXT FRONT APPROACHES...AND THAT FRONT WILL MOVE ONSHORE SUNDAY
NIGHT.


&&

.PREV DISCUSSION... /ISSUED 405 AM PST WED JAN 28 2015/

DISCUSSION... THE INVERSION ACROSS THE AREA WEAKENED SIGNIFICANTLY
TUESDAY AFTERNOON WITH AIR QUALITY IMPROVING WELL INTO THE GOOD
RANGE. IMPROVEMENT WAS GREATEST EAST OF THE CASCADES WHERE PM2.5
VALUES FELL TO SINGLE DIGITS AT BOTH KLAMATH FALLS AND LAKEVIEW.
OVERNIGHT, THE NOCTURNAL INVERSION HAS SETTLED IN, AND AREAS OF FOG,
LOCALLY DENSE, HAVE FORMED ACROSS THE ROGUE AND ILLINOIS VALLEYS. A
DENSE FOG ADVISORY HAS BEEN ISSUED FOR THESE AREAS AS WELL AS THE
APPLEGATE VALLEY. INFRARED SATELLITE IMAGERY INDICATES THAT A
RELATIVE BREAK IN MID AND HIGH CLOUD OVER THE AREA WILL CONTINUE AND
LIKELY INCREASE THROUGH THE MORNING IN THE ADVISORY AREA, SO THE
ADVISORY IS OUT THROUGH 10AM PST. DUE TO A WEAKER INVERSION, WE DO
EXPECT MILD AFTERNOON TEMPERATURES TO YIELD ENOUGH MIXING IN THE
VALLEYS TO SCOUR OUT AT LEAST SOME OF THE VALLEY AIR, ESPECIALLY ON
THE EAST SIDE. HOWEVER, TONIGHT THROUGH SATURDAY THE INVERSION WILL
STRENGTHEN SOME, ESPECIALLY ON THE WEST SIDE.

IT IS BECOMING CLEAR THAT EARLY NEXT WEEK, POSSIBLY AS EARLY AS
SUNDAY, STORM ACTIVITY WILL RETURN TO THE REGION AND STAGNATION
WILL END. THE TIMING AND INTENSITY OF THIS STORM ACTIVITY IS VERY
MUCH IN FLUX AT THIS TIME, BUT IT APPEARS THE FIRST FRONTAL SYSTEM
TO BRING MEASURABLE PRECIPITATION TO US IN QUITE SOME TIME WILL
ARRIVE SUNDAY INTO MONDAY. GEFS ENSEMBLE INTEGRATED VAPOR TRANSPORT
AND OTHER LONGER RANGE MODEL FORECASTS DO INDICATE AT LEAST SOME
STORM ACTIVITY CONTINUING IN THE PACIFIC NORTHWEST AND, POSSIBLY,
CALIFORNIA IN THE 7 TO 14 DAY RANGE, BUT DETAILS ARE UNCLEAR. THE
BOTTOM LINE IS THAT A CHANGE IN THE WEATHER IS ON THE MORE IMMEDIATE
HORIZON, BUT NOT UNTIL EARLY NEXT WEEK. BTL

CLIMATE...
JANUARY 2015 IS LIKELY TO END WITH MONTHLY PRECIPITATION TOTALS IN
THE LOWEST 20TH PERCENTILE OF CLIMATOLOGY ACROSS MUCH OF THE
FORECAST AREA. OF NOTE, IN MEDFORD THIS WILL BE THE 3RD
CONSECUTIVE JANUARY WITH BELOW NORMAL PRECIPITATION, BUT IT HAS
BEEN WETTER THAN JANUARY 2014 AND 2013 WERE, WHEN UNDER AN INCH
OF WATER FELL. WHILE IT IS VERY RARE TO HAVE 3 CONSECUTIVE DRY
JANUARIES IN A ROW, RECORDS INDICATE THAT WE HAD EXACTLY THAT
OCCUR IN 1983, 1984, AND 1985, AND IT WAS ACTUALLY DRIER THAN THIS
CURRENT DRY JANUARY STREAK. BTL


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 1 PM PST SATURDAY FOR
     ORZ023-024-026-616-620-622.
     AIR STAGNATION ADVISORY UNTIL 1 PM PST SATURDAY FOR
     ORZ029>031-623>625.
     DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR
     ORZ024-026-620-622.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

NWS MFR Office Area Forecast Discussion