Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 311537
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
837 AM PDT FRI OCT 31 2014

.DISCUSSION...A COLD FRONT IS BISECTING THE FORECAST
AREA...CURRENTLY SITUATED FROM EASTERN DOUGLAS COUNTY SOUTH INTO
SISKIYOU COUNTY...WITH MODERATE RAIN ALONG THE FRONT. AHEAD OF THE
FRONT OVER LAKE AND MODOC COUNTIES CONDITIONS ARE DRY...WITH
GENERALLY SIMILAR CONDITIONS BEHIND THE FRONT TOWARDS THE COAST.

AS THE DAY PROGRESSES...RAIN WILL TAPER OFF FROM WEST TO
EAST...WITH WET WEATHER AFFECTING MAINLY EASTERN
KLAMATH...LAKE...AND MODOC COUNTIES THIS EVENING AROUND TRICK-OR-
TREAT TIME. THERE WILL BE A FEW SHOWERS TO CONTEND WITH WEST OF
THE CASCADES BUT THESE SHOULD BE FOCUSED PRIMARILY AROUND HIGH
TERRAIN. IN SUMMARY...WEST OF THE CASCADES SHOULD BE MAINLY DRY
THIS EVENING...WHILE EAST OF THE CASCADES FEATURES A GOOD CHANCE
OF RAIN.

PLEASE SEE THE PREVIOUS DISCUSSION BELOW FOR DETAILS ON THIS
WEEKEND AND BEYOND...WHICH WILL FEATURE THE POTENTIAL FOR WEST
SIDE FROST SUNDAY MORNING.


&&

.AVIATION...FOR THE 31/12Z TAF CYCLE...MOUNTAINS WILL BE OBSCURED
THROUGH THE MORNING AS THE COLD FRONT CONTINUES TO MOVE EAST OF THE
CASCADES THIS MORNING WITH RAIN TAPERING TO SHOWERS ON THE WEST SIDE
WITH IMPROVING CONDITIONS. WIDESPREAD RAIN WITH MVFR TO IFR
CIGS/VIS AND MOUNTAIN OBSCURATION ARE EXPECTED EAST OF THE CASCADES THIS
MORNING THROUGH EARLY AFTERNOON AS THE FRONT MOVES THROUGH.
FREEZING LEVELS WILL DROP BY ABOUT 1500 FT FROM THIS MORNING
THROUGH SATURDAY MORNING ACROSS MUCH OF THE FORECAST AREA. MVFR
CEILINGS ARE LIKELY IN THE WEST SIDE VALLEYS TOMORROW MORNING.
-SVEN


&&

.MARINE...UPDATED 320 AM PDT FRI OCT 31 2014...WEAK LOW PRESSURE
WILL REMAIN OVER THE WATERS THROUGH THE MORNING. A LONG PERIOD WEST SWELL
WILL MOVE INTO THE COASTAL WATERS LATE THIS MORNING. HIGH PRESSURE
WILL THEN BUILD SOUTHWEST OF THE WATERS ON SATURDAY...MOVING OVER
THE WATERS SUNDAY. MODELS ARE FAIRLY CONSISTENT SHOWING ANOTHER
LONG PERIOD NORTHWEST SWELL MOVING INTO THE WATERS MONDAY MORNING
THAT PEAKS MONDAY NIGHT. -SVEN


&&

.PREV DISCUSSION... /ISSUED 436 AM PDT FRI OCT 31 2014/

DISCUSSION...A SURFACE LOW HAS MOVED INTO NORTHEAST OREGON WITH
ITS RELATIVELY SLOW MOVING ASSOCIATED COLD FRONT NOW BRINGING A STEADY RAIN
TO MOST OF OUR AREA. THE FRONT IS NOW ROUGHLY ALONG THE INTERSTATE
5 CORRIDOR AND EXPECTED TO EXIT ACROSS THE EAST SIDE THIS
AFTERNOON. THERE WILL BE SCATTERED TO NUMEROUS POST-FRONTAL SHOWERS
THAT WILL BE MAINLY ON THE WEST SIDE THIS MORNING. THUS, RAINFALL
TOTALS WILL BE HIGHEST FROM THE CASCADES WESTWARD THIS MORNING
WITH AFTERNOON AND EARLY EVENING PRECIPITATION AMOUNTS HIGHEST ON
THE EAST SIDE. WITH ADDITIONAL LIFT FROM THE HEATING OF THE DAY,
ISOLATED THUNDERSTORMS MAY DEVELOP ALONG THE FRONT ACROSS THE EAST
SIDE THIS AFTERNOON.

THE NEXT FEATURE OF INTEREST IS A LOW CENTERED OFFSHORE FROM
WASHINGTON WITH A SURFACE TROUGH ALONG 130W THAT WILL BRING
ENHANCED INSTABILITY WITH AN INCREASE IN SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE COASTAL WATERS INTO THE COASTAL COUNTIES
THIS EVENING.

IN SUMMARY, THE HALLOWEEN FORECAST HAS RAIN FOCUSED ON THE WEST
SIDE THROUGH AROUND 11 AM, IN KLAMATH AND EASTERN SISKIYOU
COUNTIES IN THE EARLY AFTERNOON THEN IN LAKE AND MODOC COUNTIES IN
THE LATE AFTERNOON AND EVENING. THERE WILL BE SOME POST-FRONTAL
SHOWERS/RAIN DROPS TO DODGE ON THE WEST SIDE IN THE AFTERNOON AND
EARLY EVENING THEN GETTING TOWARD 7 OR 8 PM THE FREQUENCY AND
COVERAGE OF SHOWERS WILL INCREASE WITH SHOWERY/WET WEATHER AND
DROPPING SNOW LEVELS THROUGH SATURDAY MORNING. THE SNOW LEVEL WILL
BE NEAR 7000 FEET THIS MORNING THEN FALL TO 5500 FEET THIS
EVENING AND 5000 FEET SATURDAY MORNING. GIVEN THAT THE LOWER SNOW
LEVELS WILL OCCUR WITH SCATTERED TO NUMEROUS SHOWERS...ACCUMULATIONS
ARE EXPECTED TO BE AROUND AN INCH OR TWO.

THE WEATHER PATTERN WILL REMAIN ACTIVE DURING THE NEXT WEEK.
LINGERING ISOLATED SHOWERS ON SATURDAY AFTERNOON WILL BE MAINLY
ACROSS LAKE AND MODOC COUNTIES. THE LOWER LEVELS OF THE ATMOSPHERE
WILL REMAIN MOIST SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON AS A
RIDGE BUILDS FROM THE EASTERN PACIFIC INTO THE PACIFIC NORTHWEST
WITH STUBBORN LOW LEVEL CLOUD COVER AND LIGHT OVERRUNNING/DRIZZLY
SHOWERS POSSIBLE IN THE COASTAL ZONES INTO DOUGLAS COUNTY.

A WARM FRONT IS EXPECTED TO SEND MODERATE RAIN TO WASHINGTON AND
NORTHERN OREGON ON SUNDAY NIGHT WITH THE SOUTHERN EDGE OF THE
FRONT LIKELY TO ALSO BRING PERIODS OF LIGHT RAIN TO AREAS WEST AND
NORTH OF JACKSON COUNTY THROUGH MONDAY.

FOR MONDAY AFTERNOON THROUGH TUESDAY EVENING, THERE IS CONFIDENCE THAT
THE FRONT WILL GRADUALLY WEAKEN WITH THE MOST SUBSTANTIAL RAIN
REMAINING NORTH OF OUR AREA. BUT THERE IS MODERATE TO HIGH
UNCERTAINTY ON HOW FAR TO THE SOUTH THE FRONT WILL SAG. THE
PROBABILITY OF RAIN WILL BE HIGHER AS ONE TRAVELS TO THE WEST AND
NORTH. BUT, SOUTHERN OREGON RAINFALL MAY BE VERY LIGHT PER THE
ECMWF MODEL, OR IT MAY BE MORE SUBSTANTIAL PER THE GFS.

THE GFS AND ECMWF ARE STILL IN AGREEMENT ON THE BIG PICTURE AT
MID-WEEK WITH A CHANCE OF VERY LIGHT SOUTHWEST OREGON SHOWERS DUE
TO LINGERING LOW LEVEL MOISTURE BUT STRONGER RIDGING THAT SHOULD
MAKE WEDNESDAY THE WARMEST DAY OF THE WEEK.

THEREAFTER, THE NEXT FRONTAL SYSTEM IS EXPECTED. BUT, MODEL
SOLUTIONS QUICKLY DIVERGE WITH LOW CONFIDENCE IN THE SYSTEM`S
CHARACTERISTICS, INCLUDING ITS STRENGTH, TIMING, AND SNOW LEVELS.

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 AM PDT SATURDAY
     FOR PZZ350-356-370-376.

$$

NSK/DW/SBN






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