Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 312115
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
215 PM PDT FRI OCT 31 2014

.DISCUSSION...THE FOCUS ON TODAY`S FORECAST WAS THE HALLOWEEN
EVENING FORECAST...GIVEN THAT A LOT OF FOLKS WILL BE OUT AND
ABOUT...EXPOSED TO THE WEATHER. MOST PEOPLE DON`T WANT RAIN WHILE
TRICK-OR-TREATING...AND FOR THE WESTERN HALF OF OUR FORECAST
AREA...WEST OF THE CASCADES...THAT MEANS GOOD NEWS AS JUST A FEW
SHOWERS WILL BE AROUND AND THESE SHOULD BE SHORT-LIVED AND MORE
MISS THAN HIT. EAST OF THE CASCADES...ESPECIALLY IN LAKE AND MODOC
COUNTIES...A SLOW MOVING FRONTAL SYSTEM WILL BRING A GOOD CHANCE
FOR WETTING RAINS THIS EVENING AND EVEN THE POTENTIAL FOR A
THUNDERSTORM FROM MOUNT SHASTA CITY EAST TO MODOC COUNTY.
TEMPERATURES ARE ABOUT 5 DEGREES COOLER THAN YESTERDAY...SO THE
EVENING WILL FEEL CHILLY IN MANY LOCATIONS. SNOW LEVELS DROP TO
5000 FEET LATE TONIGHT...AND A FEW INCHES OF SNOW IN THE HIGH
TERRAIN FROM THE CASCADES EAST ARE EXPECTED.

ON SATURDAY THE FRONT WILL STILL BRING SOME RAIN TO MAINLY LAKE AND
MODOC COUNTIES...THEN EXIT THE FORECAST AREA COMPLETELY BY LATE
SATURDAY. BEHIND THE FRONT THERE IS STILL A CHANCE OF SHOWERS ALONG
AND WEST OF THE CASCADES...BUT GENERALLY JUST A SLIGHT CHANCE IN THE
VALLEYS AND CHANCE IN THE HIGHER TERRAIN. ADDITIONALLY...GUSTY
NORTHWEST WINDS ARE EXPECTED SATURDAY AFTERNOON EAST OF THE CASCADES.

SUNDAY MORNING`S TEMPERATURE FORECAST WILL HAVE IMPACTS ON
AGRICULTURE AND BACKYARD GARDENS...AS TEMPERATURES IN WEST SIDE
VALLEYS COULD REACH FROST CRITERIA FOR THE FIRST TIME THIS YEAR.
WE THOUGHT IT PRUDENT TO GIVE YOU A HEADS UP FOR THE EXPECTED COLD
TEMPERATURES SO GROWERS COULD USE SATURDAY TO DO THE NECESSARY
WORK TO PREPARE FOR THE FIRST FALL FROST...AND THUS...A FROST
ADVISORY AT NPWMFR HAS BEEN ISSUED TO ACCOUNT FOR THESE TEMPERATURES.
SOME CLEARING IS POSSIBLE...BUT NOT ENOUGH FOR TEMPERATURES TO
DROP TO FREEZING...SO TEMPERATURES GENERALLY IN THE MID 30S ARE
EXPECTED. EVEN WITH LOW CLOUDS OR FOG...AND WE`RE FAVORING LOW
CLOUDS AT THIS TIME...THE AIR MASS SHOULD BE COLD ENOUGH FOR FROST
CONDITIONS. FARTHER SOUTH IN NORTHERN CALIFORNIA...A FREEZE IS
POSSIBLE IN PARTS OF THE SHASTA VALLEY...SO A FREEZE WATCH HAS
BEEN ISSUED FOR THAT AREA. SUNDAY AFTERNOON WILL FEATURE DRY
CONDITIONS AS WEAK RIDGING BUILDS OVER THE AREA.

ON MONDAY SOME WARM FRONTAL OVERRUNNING BEGINS...AFFECTING THE COAST
WITH SOME LIGHT RAIN AND PLENTY OF LOW CLOUDS. FARTHER INLAND OVER
LOCATIONS LIKE MEDFORD...A SLIGHT CHANCE OF LIGHT RAIN EXISTS BUT
THE MAIN IMPACT OF THE OVERRUNNING WILL BE INCREASED CLOUD COVER.

EXTENDED DISCUSSION...TUESDAY THROUGH FRIDAY.

THE ACTIVE WEATHER PATTERN WILL CONTINUE INTO THE EXTENDED PERIOD.

TUESDAY WILL START OFF WITH A FLAT LONG WAVE RIDGE OVER THE FAR
WESTERN U.S. WITH THE RIDGE AXIS NEAR THE COAST. HOWEVER...SHORT
WAVES MOVING OVER THE RIDGE WILL PUSH A FRONT ONSHORE TUESDAY. MOST
OF THE ENERGY WILL BE DIRECTED TO THE NORTH OF THE AREA SO NOT MUCH
IS EXPECTED FROM THIS SYSTEM IN TERMS OF WINDS AND PRECIPITATION.
MOST OF THE AREA FROM THE CASCADES WEST AND SISKIYOUS NORTH WILL GET
WET...BUT OVERALL AMOUNTS WILL BE LIGHT.

THE RIDGE WILL BUILD INTO THE INTERMOUNTAIN STATES WEDNESDAY WHILE A
LONG WAVE TROUGH DIGS OFFSHORE. PRECIPITATION WILL END TUESDAY AND
WEDNESDAY WILL BE DRY AND WARMER OVER THE AREA.

THE EC/GFS/DGEX MODELS ALL PUSH THE TROUGH TOWARD THE WEST COAST
THURSDAY...BUT THERE ARE SIGNIFICANT DIFFERENCES IN STRENGTH AND
TIMING.  THE EC IS SLOWER AND DEEPER WITH THE TROUGH WHILE THE DGEX
IS FASTEST AND SHALLOWEST. ALL MODELS SUPPORT PUSHING A FRONT
ONSHORE THURSDAY...BUT THE UPPER LEVEL SUPPORT MAKES A BIG
DIFFERENCE AS TO HOW WINDY AND WET THE FRONT WILL BE. SO...
CONFIDENCE IS HIGH FOR THE FRONT...CHANCES OF PRECIPITATION...AND
COOLER TEMPERATURES...BUT LOW FOR WINDS AND QPF.

FLAT RIDGING WILL DEVELOP FRIDAY IN THE WAKE OF THE FRONT. EXPECT
SHOWERS TO DIMINISH IF NOT END COMPLETELY WITH WARMER TEMPERATURES.

&&

.AVIATION...FOR THE 31/18Z TAF CYCLE...FROM THE CASCADES WEST...VFR
CONDITIONS WILL PREVAIL INITIALLY WITH ISOLATED SHOWERS AND AREAS OF
HIGHER TERRAIN OBSCURED.  AREAS OF MVFR CIGS WILL DEVELOP THIS
EVENING OVER THE WEST SIDE VALLEYS...CLEARING TO VFR BY SATURDAY
AFTERNOON.  EAST OF THE CASCADES...AREAS OF MVFR CIGS WITH HIGHER
TERRAIN OBSCURED WILL CLEAR TO VFR THIS AFTERNOON...THEN LOCAL MVFR
CIGS WILL REDEVELOP TONIGHT.  THE LOWER CONDITIONS WILL CLEAR TO VFR
BY LATE SATURDAY MORNING.


&&

.MARINE...UPDATED 200 PM PDT FRI OCT 31 2014...WEAK LOW PRESSURE
WILL REMAIN OVER THE WATERS THROUGH TONIGHT, BEFORE SLOWLY MOVING
INLAND TOMORROW. MEANWHILE, MODERATE WEST SWELL WILL CONTINUE,
KEEPING SEAS STEEP ENOUGH TO KEEP A SMALL CRAFT ADVISORY IN PLACE.
HIGH PRESSURE WILL BUILD OVER THE WATERS THIS WEEKEND AND WEAKEN
MONDAY, WITH WINDS AND SEAS REMAINING RELATIVELY CALM. THE NEXT COLD
FRONT WILL MOVE ONSHORE MONDAY NIGHT INTO TUESDAY, MARKING A RETURN
OF GUSTY WINDS AND STEEP SEAS. UNSETTLED CONDITIONS WILL CONTINUE
THROUGH THE WEEK. -BPN



&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...FROST ADVISORY FROM 1 AM TO 8 AM PST SUNDAY FOR ORZ024-026.

CA...FROST ADVISORY FROM 1 AM TO 8 AM PST SUNDAY FOR CAZ080>082.
     FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING FOR
     CAZ081-082.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM PDT SATURDAY
     FOR PZZ350-356-370-376.

$$

NSK/JRS/JRS






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