Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 011139
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
339 AM PST SUN FEB 1 2015

.DISCUSSION...TODAY REPRESENTS A TRANSITION DAY TOWARDS AN ACTIVE
WEATHER PATTERN AFTER WEEKS OF GENERALLY STAGNANT WEATHER. A WEAK
FRONTAL SYSTEM WILL MOVE THROUGH THE AREA TODAY...BRINGING
GENERALLY LIGHT RAIN TO THE AREA...FOCUSED ALONG AND NORTH OF THE
UMPQUA DIVIDE AND WEST OF THE CASCADES. THIS FRONT WILL MIX UP THE
ATMOSPHERE JUST ENOUGH TO END THE AIR STAGNATION ADVISORIES BY
THIS AFTERNOON. A SECOND...MORE POTENT COLD FRONTAL BOUNDARY WILL
BRING AN INCH OF RAIN TO THE CURRY COUNTY COAST...A QUARTER INCH
TO MOST WEST SIDE VALLEYS...AND A TENTH OF AN INCH OF RAIN TO THE
EAST SIDE. THESE PRECIPITATION AMOUNTS FROM SUNDAY NIGHT THROUGH
MONDAY NIGHT WILL BE VIRTUALLY ALL RAIN...WITH SNOW LEVELS AT 7500
FEET AND HIGHER.

THIS BOUNDARY WILL STALL MONDAY NIGHT OVER NORTHERN CALIFORNIA...AND
THEN GET RE-ENERGIZED AS ANOTHER SHOT OF SIGNIFICANT MOISTURE
ARRIVES TUESDAY MORNING...WAVING NORTH AND BRINGING MODERATE TO
HEAVY RAIN TO THE COAST AND HIGHER TERRAIN WEST OF THE CASCADES.
WE HAVE FAVORED THE HEAVIER RAIN SOLUTIONS OF THE NAM AND GFS FOR
THIS PERIOD...THOUGH HAVE TEMPERED THEM A LITTLE BY BLENDING SOME
OF THE DRIER ECMWF SOLUTION. RIDGING BUILDS OVERHEAD
WEDNESDAY...AND THIS SHOULD BE THE DRIEST DAY OF THE WEEK.
TEMPERATURES COULD GET UNSEASONABLY WARM IN VALLEYS IF FOG DOES
NOT DEVELOP...AND DENSE FOG LOOKS UNLIKELY GIVEN THAT STRONG
INVERSIONS REALLY WON`T HAVE TIME TO SET UP BEHIND THE FRONT.

THURSDAY INTO FRIDAY HAS THE POTENTIAL OF BEING A HEAVY RAIN AND
STRONG WIND EVENT. GEFS-BASED TOOLS THAT HELP GAUGE HOW SIGNIFICANT
A RAIN EVENT WILL BE ARE SHOWING GOOD POTENTIAL FOR A ONCE-IN-TEN-
YEAR TYPE EVENT FOR THE COAST IN TERMS OF RAINFALL. RIVERS ARE
CURRENTLY WELL BELOW NORMAL IN TERMS OF STREAMFLOW...SO ANTECEDENT
CONDITIONS DO NOT FAVOR FLOODING...BUT DO BELIEVE THERE IS STILL
SOME POTENTIAL FOR COASTAL RIVER OR STREAM FLOODING IF THE VERY WET
GFS SOLUTION VERIFIES. CERTAINLY THERE WILL BE MARINE IMPACTS WITH
GALES AND POSSIBLY STORM FORCE WINDS OVER THE WATERS THURSDAY
INTO FRIDAY...AND GUSTY WINDS WILL IMPACT THE COAST...HIGH
TERRAIN...SHASTA VALLEY...AND EAST SIDE DURING THE SAME TIMEFRAME.


&&

.AVIATION...WARMER AFTERNOON TEMPERATURES AND SOME LOWER
DEWPOINTS VERSUS 24 HOURS AGO COUPLED WITH INCREASING HIGH AND MID
LEVEL CLOUDS MEAN THAT ONLY MVFR VIS WITH LOCAL IFR CIG/VIS ARE
EXPECTED IN THE WEST SIDE VALLEYS THIS MORNING, EXCEPT IN THE
ILLINOIS VALLEY AND NEAR GRANTS PASS, WHERE IFR AND LOCAL LIFR
COULD OCCUR EARLY THIS MORNING. AN INCOMING WEAK FRONTAL SYSTEM
WILL BRING SHOWERS AND SOME WEST SIDE MVFR THROUGH THE DAY,
MAINLY COAST AND UMPQUA BASIN. OTHERWISE, EXPECT PARTIAL TERRAIN
OBSCURATIONS CASCADES WEST AS THE DAY PROGRESSES. SVEN


&&

.MARINE...UPDATED 330 AM PST SUNDAY, FEBRUARY 1, 2015... LIGHT
WINDS WILL BECOME SOUTHERLY AROUND SUNRISE TODAY AS A WEAK FRONTAL
SYSTEM PUSHES IN FROM THE WEST WITH PERIODS OF RAIN. TONIGHT
THROUGH MONDAY MODERATE WEST SWELL WILL BUILD AS A SOMEWHAT
STRONGER FRONTAL SYSTEM ARRIVES. UNSETTLED CONDITIONS MID-WEEK
WILL BUILD TO A STRONG STORM SYSTEM WITH GALES AND EVEN STORM
FORCE WINDS POSSIBLE...DURING THURSDAY AND FRIDAY. SVEN


&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...AIR STAGNATION ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR
     ORZ023-024-026-616-620-622.
     AIR STAGNATION ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR
     ORZ029>031-623>625.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

NSK/NSK/SBN



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