Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 011639
AFDMFR

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

.DISCUSSION...BUMPED UP POPS THIS MORNING PARTICULARLY FOR THE
MEDFORD AREA AND ALSO REMOVED FOG WORDING FOR THE WEST SIDE
VALLEYS. NO OTHER UPDATES WERE MADE AS THE GOING FORECAST LOOKS
ON TRACK. RADAR SHOWS SOME SHOWERS MOVING THROUGH THE AREA WITH A
FEW SITES MEASURING A COUPLE HUNDRETHS AT BEST. THE 01/12Z KMFR
SOUNDING SHOWS A FAIRLY DRY SUB-CLOUD LAYER HOWEVER, PRECIPITATION
HAS MADE IT TO THE GROUND HERE AT THE KMFR AIRPORT. SUSPECT THAT
WHAT IS FALLING IS MAKING IT TO THE GROUND ALBEIT VERY LIGHT.
PRECIPITATION CHANCES AND TOTALS WILL INCREASE AS THE DAY
PROGRESSES. FOR MORE DETAILS SEE THE PREVIOUS DISCUSSION BELOW.
MND

&&

.AVIATION...BASED ON THE 01/12Z TAF CYCLE...MAINLY VFR CONDITIONS
ARE EXPECTED THIS MORNING WITH ISOLATED MVFR VISIBILITIES IN PATCHY
FOG FOR INLAND WEST SIDE VALLEYS THROUGH 16Z. THEN AN INCOMING WEAK
FRONTAL SYSTEM WILL BRING SHOWERS AND SOME WEST SIDE MVFR CIGS
THROUGH THE DAY, MAINLY COAST AND UMPQUA BASIN. ALSO EXPECT PARTIAL
TERRAIN OBSCURATIONS CASCADES WEST TODAY. THEN THIS EVENING AND
TONIGHT, MVFR CIGS ARE EXPECTED TO BECOME MORE WIDESPREAD AS AREAS
OF RAIN CONTINUE OVER THE AREA. ALSO EXPECT WIDESPREAD MOUNTAIN
OBSCURATIONS TO DEVELOP THIS EVENING INTO TONIGHT. /CC

&&

.MARINE...UPDATED 815 AM PST SUNDAY, FEBRUARY 1, 2015...LIGHT SOUTH
WINDS AND PERIODS OF RAIN ARE EXPECTED TODAY AS A WEAK FRONT PUSHES
IN FROM THE WEST. MODERATE WEST SWELL WILL BUILD AS A SOMEWHAT
STRONGER FRONT APPROACHES THE COASTAL WATERS TONIGHT, THEN GUSTY
SOUTH WINDS AND STEEP SEAS ARE LIKELY AS THIS FRONT PASSES ON
MONDAY. UNSETTLED CONDITIONS WILL THEN CONTINUE THROUGH MIDWEEK,
WITH A STRONG STORM SYSTEM POSSIBLY RESULTING IN AND EXTENDED PERIOD
OF GALES THURSDAY AND FRIDAY. MODEL GUIDANCE CONTINUES TO SHOW THE
POTENTIAL FOR SEAS OF 15 TO 20 FT DEVELOPING LATE THURSDAY INTO
FRIDAY DUE TO WIND SEAS AND FRESH SOUTH TO SOUTHWEST SWELL.
-CC/BPN

&&

.PREV DISCUSSION... /ISSUED 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. ADDITIONALLY...WINDS WILL BECOME
GUSTY...ESPECIALLY EAST OF THE CASCADES MONDAY AFTERNOON WITH
700MB FLOW REACHING 50KT FROM THE WEST ON BOTH THE NAM AND GFS
MODELS.

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. WINDS WILL ALSO BE SIGNIFICANT WITH
THIS SYSTEM...WITH 700MB WINDS PEAKING AT 55KT PER THE GFS...SO
EAST SIDE WINDS WILL BECOME VERY GUSTY AND WOULD NOT BE SURPRISED
IF ADVISORY CRITERIA ARE MET...OR MORE. 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 TIME FRAME.

&&

.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.

$$

MND/NSK/CC



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