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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 271614
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
914 AM PDT THU AUG 27 2015

.DISCUSSION...CURRENT VISIBLE IMAGE SHOWS A FEW HIGH AND MID LEVEL
CLOUDS MOVING INTO THE AREA. THE MARINE STRATUS EARLIER THIS
MORNING WAS CONFINED TO THE COQUILLE BASIN AND HAS SINCE BURNED
OFF. CURRENT MODELS HAVE BACKED OFF ON THE AMOUNT OF INSTABILITY
FOR THIS AFTERNOON AND EVENING ALONG THE NORTHERN CASCADES AND
SISKIYOUS WITH MOST OF THE 700-500 MB MID LEVEL MOISTURE NEAR
500MB. THUS HAVE REMOVED THE SLIGHT CHANCE FOR THUNDERSTORMS. ALSO
THE MODELS ARE TRENDING SLOWER WITH THE EASTWARD ADVANCEMENT OF
RAIN OVER THE WATERS AND HAVE ALSO BACKED OFF ON THAT. CLOUD COVER
HAS BEEN ADJUSTED TO REFLECT CURRENT SATELLITE TREND.

THE UPPER LOW WILL CONTINUE TO MOVE SOUTHWEST OVER THE NEXT 24
HOURS AND AN UPPER TROUGH ROTATING AROUND THE UPPER LOW WILL MOVE
INTO SOUTHWEST OREGON AND BECOME NEGATIVELY TILTED FRIDAY NIGHT.
THIS WILL LIKELY BRING THE FIRST SIGNIFICANT RAINFALL WE HAVE HAD
IN QUITE SOME TIME ALONG WITH GUSTY WINDS. IN FACT MODERATE TO STRONG
WINDS ARE POSSIBLE FRIDAY NIGHT INTO SATURDAY ALONG AND EAST OF OF
THE CASCADES.

WE`LL REMAIN COOL WITH BELOW NORMAL TEMPERATURES SUNDAY INTO THE
FIRST HALF OF NEXT WEEK WITH A FEW WEAKER SYSTEMS BRUSHING BY THE
AREA, BUT NO BIG RAIN MAKERS AFTER FRIDAY NIGHT/SATURDAY MORNING.
-PETRUCELLI


&&

.AVIATION...FOR THE 27/12Z TAF CYCLE...ALONG THE COAST...VFR
CONDITIONS WILL CONTINUE OVERNIGHT THEN MARINE STRATUS WITH IFR CIGS
MAY COME IN FOR A FEW HOURS EARLY THIS MORNING. EXCEPT FOR
OCCASIONAL MVFR VISIBILITIES IN SMOKE, INLAND AREAS WILL BE VFR
THROUGH THE MOST OF THE DAY INTO THE NIGHT WITH IFR CONDITIONS
RETURNING TO THE COAST BY EARLY FRIDAY MORNING. -SVEN


&&

.MARINE...UPDATED 400 AM PDT THURSDAY 27 AUGUST 2015...WEAK HIGH
PRESSURE OVER THE WATERS WILL RESULT IN LIGHT WINDS AND SEAS THROUGH
EARLY FRIDAY. A FRONTAL SYSTEM WILL ENTER THE WATERS LATER FRIDAY
AND MOVE THROUGH THE WATERS OVER THE WEEKEND. A PERIOD OF MODERATE
SOUTH WINDS IS EXPECTED WITH THE FRONT SATURDAY ALONG WITH
OCCASIONAL HEAVY RAIN AND LOW VISIBILITIES. WIND AND SEAS ARE LIKELY
TO REACH SMALL CRAFT ADVISORY LEVELS SATURDAY, BUT A SHORT PERIOD OF
LOW END GALES AND VERY STEEP SEAS ARE POSSIBLE AS WELL. MULTIPLE
LONG PERIOD SWELLS ARE ALSO EXPECTED THIS WEEKEND WITH POSSIBLE
INCREASED SNEAKER WAVE ACTIVITY. CONDITIONS WILL CALM DOWN MONDAY,
BUT MODERATE NORTHWEST SWELL WILL DEVELOP OVER THE WATERS AS THE
SYSTEM MOVES INLAND. -SVEN

&&

.FIRE WEATHER...UPDATED 401 AM PDT THURSDAY 27 AUGUST 2015...AN
UPPER TROUGH WILL MOVE SOUTH AND SOUTHWEST WINDS ARE EXPECTED TO
INCREASE A LITTLE TODAY EAST OF THE CASCADES, BUT RELATIVE
HUMIDITIES WILL BE HIGHER.

WINDS WILL BECOME MODERATE TO STRONG AT TIMES OVER THE MOUNTAINS AND
EASTSIDE FRIDAY INTO SATURDAY...ACCOMPANIED BY A COOL-DOWN AND A
CHANCE FOR RAIN. THE BEST CHANCE FOR RAIN IS FRIDAY NIGHT INTO
SATURDAY MORNING. CONFIDENCE IS HIGH FOR WETTING RAINS FOR AT LEAST
THE COAST RANGE AND CASCADES FROM CRATER LAKE NORTH AND MODERATE FOR
WESTERN SISKIYOU. WEST SIDE VALLEYS MAY GET DOWNSLOPING WINDS
THROUGH FRIDAY EVENING, THUS LIMITING RAINFALL AMOUNTS. WIDESPREAD
WETTING RAINS ARE UNLIKELY AT THIS POINT EAST OF THE CASCADES. AHEAD
OF THE UPPER LOW THE MODELS SHOW ENOUGH WEAK INSTABILITY TO AT LEAST
KEEP A SLIGHT CHANCE MENTION OF THUNDERSTORMS FOR THE CASCADES
THURSDAY AND FRIDAY AFTERNOON. HOWEVER INSTABILITY ON FRIDAY COULD
SHIFT WEST INTO PORTIONS OF SISKIYOU COUNTY.

IT`S WORTH MENTIONING THAT THIS IS AN UNCOMMON EVENT FOR THIS TIME
OF YEAR. HOWEVER...MODELS CONTINUE TO POINT TO THE IDEA OF
WIDESPREAD WETTING RAINS FROM THE CASCADES WEST. HOWEVER...THIS IS
NOT EXPECTED TO BE A SEASON ENDING EVENT.

SHOWERS CONTINUE INTO MONDAY ON THE WEST SIDE WITH DECREASING
PRECIPITATION AMOUNTS...AND SPREAD INLAND TO THE CASCADES WITH
GENERALLY LIGHT PRECIPITATION AMOUNTS THROUGH THE MIDDLE OF NEXT
WEEK. -SVEN

&&

.PREV DISCUSSION... /ISSUED 435 AM PDT THU AUG 27 2015/

DISCUSSION...
DESPITE BRIEF AIR QUALITY IMPROVEMENT, AT TIMES, IN THE LAST 24
HOURS, AIR QUALITY REDUCTIONS DUE TO SMOKE CONTINUE THIS MORNING.
IN SHORT, WE ANTICIPATE THAT REDUCED AIR QUALITY WILL BE SIMILAR
TODAY AND FRIDAY TO THAT WHICH HAS BEEN EXPERIENCED DURING THE
LAST COUPLE OF DAYS BEFORE MORE CONSISTENT AND SIGNIFICANT
IMPROVEMENT OCCURS THIS WEEKEND. COOLER TEMPERATURES, HIGHER
HUMIDITY, AND RAINFALL WILL DIMINISH BURNING CONDITIONS FOR MOST
AREA WILDFIRES, TO INCLUDE ACROSS MUCH OF NORTHERN CALIFORNIA,
THIS WEEKEND WHERE MOST OF THE SMOKE WE`VE BEEN DEALING WITH
RECENTLY HAS BEEN COMING FROM.

FOR TODAY THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
FROM ABOUT THE TRINITY ALPS INTO AND NEAR THE SCOTT VALLEY AND
ALONG AND NEAR THE OREGON CASCADES FROM ABOUT CRATER LAKE
NORTHWARD. ON WEDNESDAY AFTERNOON WE SAW SOME BUILD-UPS OF NOTE
AND, TODAY, THERE IS ACTUALLY A WEAK UPPER LEVEL SHORTWAVE TROUGH
RIDING THROUGH THE AREA. LIFTED INDICES FROM NUMERICAL MODELS ARE
IN THE 0 TO -2C RANGE FROM ABOUT 18Z-00Z ACROSS THE AREAS WHERE WE
HAVE HIGHLIGHTED A SLIGHT THUNDERSTORM RISK. IT`S MOST LIKELY
THAT SMOKE AND CLOUD COVER WILL MUTE STORMS FROM OCCURRING AND,
INSTEAD, RESULT IN JUST A SPATTERING OF BRIEF RAIN DROPS. THERE
WILL ACTUALLY BE SOMETHING OF A WIND CONVERGENCE ZONE/TROUGH ALONG
AND NEAR THE CASCADES THAT WILL SHIFT EASTWARD AROUND 21Z.

TONIGHT A FRONTAL BOUNDARY IS EXPECTED TO REACH TO ABOUT THE COAST
BRINGING WITH IT A POSSIBILITY OF SOME RAIN THERE. MODELS
INDICATE THAT AREAS FROM GOLD BEACH NORTHWARD ARE MOST LIKELY TO
MEASURE SOME RAIN FROM THIS FEATURE ON FRIDAY MORNING.

FRIDAY AFTERNOON THROUGH SATURDAY- THE PERIOD WHEN WE`VE BEEN
EXPECTING THE BULK OF THE PRECIPITATION TO FALL ACROSS THE
FORECAST AREA- HAS DEVELOPED A BIT OF A WRINKLE THIS MORNING WITH
THE ARRIVAL OF THE 06Z NAM12 AND GFS NUMERICAL MODEL RUNS. BOTH OF
THESE MODELS DEVELOP A MESOSCALE LOW PRESSURE WAVE WEST OF THE
COAST THAT SPLITS THE ATMOSPHERIC RIVER PUSHING INTO THE AREA INTO
TWO PARTS. ONE PART MOVES NORTHWARD WEST OF THE COASTAL WATERS,
WITH THE OTHER ONE REACHING THE WEST SIDE LIKE A BREAKING WAVE.
THIS HAS GREATLY REDUCED EXPECTED RAINFALL AMOUNTS AWAY FROM THE
COAST AND COAST RANGE FROM THOSE FORECAST 24 HOURS AGO. HOWEVER,
IT SHOULD BE NOTED THAT THE LOCATION AND TIMING OF THE RAINFALL
IS ABOUT THE SAME AS BEFORE AND THE FAVORED ECMWF CONTINUES WITH
HEAVIER AMOUNTS. ALL IN ALL, RAINFALL AMOUNTS IN OUR FORECAST
REMAIN CLOSE TO WHAT WAS FORECAST WEDNESDAY AFTERNOON, THOUGH
SOME REDUCTIONS WERE MADE FOR THE INTERIOR WEST SIDE SOUTH OF THE
UMPQUA DIVIDE DUE TO MODEL TRENDS. THE CURRENT FORECAST REFLECTS
THE LATEST NUMERICAL MODEL CONSENSUS, WHICH SHOULD BOTH VERIFY
BEST AND PROVIDE US THE ABILITY TO RAISE OR LOWER AMOUNTS AS
NEEDED OVER THE NEXT COUPLE OF DAYS WITHOUT MAKING RADICAL
CHANGES. BOTH THE FORECAST AND THE SPECIAL WEATHER STATEMENTS HAVE
BEEN UPDATED TO REFLECT THIS NOTED CHANGE. IN SHORT, IT STILL
LOOKS LIKE ENOUGH RAIN TO MAKE AN APPRECIABLE DIFFERENCE ACROSS
THE AREA, WITH AMOUNTS 0.20"+ ACROSS THE ROGUE VALLEY.

SATURDAY THROUGH SUNDAY WE EXPECT SHOWERS, MAINLY FOR THE CASCADES
WESTWARD. AMOUNTS WILL BE LESS THAN A QUARTER OF INCH ALONG AND
NEAR THE COAST AND LESS THAN A TENTH OF AN INCH ELSEWHERE.
WITH TEMPERATURES MOSTLY IN THE 70S FOR HIGHS FOR THE VALLEYS
ALONG WITH HIGHER RELATIVE HUMIDITY, BURNING CONDITIONS WILL BE
MUCH LESS FAVORABLE FOR AREA WILDFIRES. BTL


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

NWS MFR Office Area Forecast Discussion