Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 290349
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
849 PM PDT SAT MAR 28 2015

.SHORT TERM...A FLAT RIDGE OVER THE AREA WILL BRING DRY
CONDITIONS TONIGHT AND SUNDAY WHILE A FRONTAL SYSTEM WILL REMAIN
WELL TO THE NORTHWEST WITH A WARM FRONT MOVING INTO BRITISH
COLUMBIA AND A COLD FRONT OFFSHORE. MODELS CONTINUE TO SHOW A WEAK
DISTURBANCE MOVING INLAND TONIGHT AND EARLY SUNDAY MORNING. THIS
WILL RESULT IN SOME HIGH CLOUDS MOVING INTO THE AREA. AS A RESULT
EXPECT VALLEY FOG DEVELOPMENT TO BE LIMITED IN EXTENT EARLY
SUNDAY MORNING, WITH LIKELY ONLY PATCHY VALLEY FOG, MAINLY IN
LOWER RIVER VALLEYS WEST OF THE CASCADES INCLUDING THE UMPQUA
VALLEY AND NEAR GRANTS PASS. OTHERWISE EXPECT A WARM AFTERNOON
SUNDAY ACROSS INLAND AREAS.

THEN MODELS REMAIN ON TRACK SHOWING A PACIFIC FRONTAL SYSTEM
APPROACHING THE COAST LATE MONDAY AND MOVING INLAND MONDAY NIGHT.
THIS IS FOLLOWED BY A COLD UPPER TROUGH SHIFTING OVER THE REGION
TUESDAY AND DEEPENING ON WEDNESDAY AS A SHORTWAVE TROUGH SHIFTS
DOWN INTO THE AREA. EARLY MODEL RUNS  TRENDED SLIGHTLY SLOWER
WITH THE MOVEMENT OF THE FRONT INLAND MONDAY NIGHT AND THE RECENT
00Z NAM INDICATES SIMILAR TIMING WITH THE FRONT PUSHING INLAND
MONDAY NIGHT INTO TUESDAY MORNING. BEHIND THE FRONT EXPECT A COLD
AND SHOWERY AIRMASS TO MOVE INTO PLACE TUESDAY. ALSO MODELS
CONTINUE TO SHOW THAT THE COLD AIR ALOFT WILL BRING THE POTENTIAL
FOR SOME INSTABILITY OVER THE AREA WITH A SLIGHT CHANCE FOR
THUNDERSTORMS DURING THE DAY TUESDAY, MAINLY FOR COOS AND DOUGLAS
COUNTIES. THEN THE COLD SHOWERY PATTERN CONTINUES WEDNESDAY WITH
A SHORTWAVE TROUGH MOVING INTO THE AREA AND DEEPENING THE OVERALL
TROUGH PATTERN OVER THE REGION. ALSO A DEEPER COLD POOL ALOFT IS
POSSIBLE WEDNESDAY AND MAY BRING ADDITIONAL CHANCES FOR ISOLATED
THUNDERSTORMS.


&&

.AVIATION...FOR THE 29/00Z TAF CYCLE...VFR CONDITIONS WILL CONTINUE
FOR THE NEXT 24 HOURS. THERE IS A CHANCE THAT A SHALLOW LAYER OF LOW
CLOUDS AND PATCHY FOG COULD DEVELOP IN THE UMPQUA BASIN, INCLUDING
ROSEBURG, AND POSSIBLY IN THE GRANTS PASS AREA, BEGINNING AROUND 14Z
SUNDAY, BUT CONFIDENCE ON THIS IS LOW. FOR NOW WE`LL LEAVE IT OUT
OF THE KRBG TAF, BUT WILL NEED TO MONITOR. -PETRUCELLI/CC



&&

.MARINE...UPDATED 200 PM PDT SATURDAY 28 MAR 2015...HIGH PRESSURE
PERSIST THROUGH MONDAY MORNING. MODERATE WEST SWELL WILL BUILD
SUNDAY AFTERNOON AND SUBSIDE LATE SUNDAY NIGHT. THIS WILL BRING A
SMALL AREA OF SMALL CRAFT ADVISORY SEAS TO THE SOUTHERN WATERS SOUTH
OF CAPE SEBASTIAN. A STRONGER COLD FRONT WILL MOVE ONSHORE MONDAY
NIGHT. THIS WILL BRING IN SMALL CRAFT ADVISORY SEAS. HOWEVER THE
MODELS ARE IN GOOD AGREEMENT SUGGESTING SOUTHERLY WINDS WILL LIKELY
REMAIN JUST BELOW SMALL CRAFT CRITERIA. HIGH PRESSURE WILL BRIEFLY
BUILD SOUTHWEST OF THE WATERS TUESDAY... THEN A WEAK FRONT WILL MOVE
ONSHORE WEDNESDAY MORNING. -PETRUCELLI


&&

.PREV DISCUSSION... /ISSUED 251 PM PDT SAT MAR 28 2015/

SHORT TERM...THE REST OF THIS AFTERNOON THROUGH TUESDAY
NIGHT...WESTERLY FLOW ALOFT AND HIGH PRESSURE AT THE SURFACE ARE
BOTH PROVIDING DRY WEATHER ACROSS THE AREA THIS AFTERNOON.
TEMPERATURES INLAND ARE RUNNING ABOUT 10-15 DEGREES COOLER THAN
THEY WERE AT THIS TIME YESTERDAY, BUT WILL STILL END UP AROUND
5-10 DEGREES ABOVE AVERAGE FOR THIS TIME OF YEAR. EXPECT DRY,
TRANQUIL WEATHER TONIGHT WITH TEMPERATURES DOWN NEAR 40 AT THE
MEDFORD AIRPORT...PERHAPS A FEW DEGREES COOLER IN THE TYPICALLY
COLDER OUTLYING SPOTS AROUND THE VALLEY. PATCHY FOG MAY FORM IN
SOME OF THE DEEPER RIVER VALLEYS WEST OF THE CASCADES...LIKE THE
COQUILLE OR UMPQUA BASIN.

THE MAIN JET AXIS WILL REMAIN DIRECTED INTO SOUTHERN BRITISH
COLUMBIA THROUGH THE REST OF THE WEEKEND AND THIS WILL ALLOW FOR
FLAT RIDGING OVER SOUTHWEST OREGON AND NORTHERN CALIFORNIA. A
WEAK DISTURBANCE WILL MOVE THROUGH THE RIDGE ON SUNDAY, BUT WE`RE
NOT EXPECTING ANY PRECIPITATION...PROBABLY JUST SOME MID AND HIGH
LEVEL CLOUDS. EXPECT A WARMER AFTERNOON FOR MOST AREAS AWAY FROM
THE COAST WITH HIGHS IN THE LOW TO MID 70S OVER THE WEST SIDE
VALLEYS AND IN THE MID TO UPPER 60S OVER THE EAST SIDE.

THE RIDGE WILL SHARPEN A BIT AS IT MOVES INTO THE INTERMOUNTAIN
WEST MONDAY AND SOUTHWEST FLOW ALOFT WILL STRENGTHEN OVER THE AREA.
THIS WILL PROVIDE ANOTHER WARM DAY FOR MOST AREAS WITH SOME GUSTY
AFTERNOON BREEZES, ESPECIALLY EAST OF THE CASCADES.

THE NEXT UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WILL MOVE
ONSHORE MONDAY NIGHT. MODELS HAVE BEEN FAIRLY CONSISTENT IN THEIR
DEPICTIONS OF THIS SYSTEM, THOUGH LOOK TO BE JUST A TAD SLOWER
THAN PREVIOUS RUNS. HAVE GONE WITH A BLEND OF THE EC/GFS TO
ACCOUNT FOR THE SLIGHT TIMING DIFFERENCES. RAIN WILL PROBABLY
ARRIVE AT THE COAST IN THE EVENING, THEN SPREAD INLAND TO THE
CASCADES OVERNIGHT. POST-FRONTAL SHOWERS WILL PERSIST ON TUESDAY
AS THE 500MB COLD POOL MOVES OVERHEAD. THE COLDEST AIR ALOFT
(AROUND -30C) WILL RESIDE OVER THE NORTHERN PART OF THE CWA.
MODELS ARE INDICATING STEEP LAPSE RATES OVER THE WATERS NORTH OF
CAPE BLANCO AND ALSO NORTHWEST DOUGLAS COUNTY. SO, HAVE INTRODUCED
SLIGHT CHANCE/ISOLATED THUNDER IN THOSE AREAS. SHOWERS MAY
DECREASE BRIEFLY AFTER THE SUN SETS TUESDAY EVENING, BUT ANOTHER
SHORTWAVE AND ONSHORE FLOW WILL RE-ENERGIZE SHOWER
ACTIVITY...ESPECIALLY ALONG THE COAST LATER TUESDAY NIGHT. SPILDE

LONG TERM...WEDNESDAY THROUGH SATURDAY...THE GFS AND ECMWF ARE IN
FAIRLY GOOD AGREEMENT ADVERTISING COOLER WEATHER WITH UNSETTLED
ONSHORE FLOW AND UPPER TROUGHING IN THE EXTENDED.
WEDNESDAY...ABOVE AVERAGE CONFIDENCE EXISTS WITH A SHORT WAVE
COMING THROUGH BRINGING RAIN CHANCES. POPS HERE RANGE FROM 25-50
PERCENT FROM THE CASCADES TO THE COAST WITH THOSE VALUES WANING
WEDNESDAY NIGHT THROUGH EARLY THURSDAY. FEELING IS THESE VALUES
WILL RISE WITH THE NEXT FEW FORECAST CYCLES. FAIRLY COOL MIN TEMPS
LOOK LIKELY THURSDAY MORNING WITH SOME WEST SIDE FROST POTENTIAL.
THEN THERE LOOKS LIKE A FAIR POTENTIAL FOR A PERIOD OF SHORT WAVE
RIDGING LATER THURSDAY THROUGH FRIDAY. CLEARING SKIES THERE MAY
ALLOW MIN TEMPS TO DIP CLOSER TO FREEZING FOR THE ROGUE VALLEY
FRIDAY MORNING. FOR NEXT WEEKEND...THE PAST 10 RUNS OF THE GFS
HAVE INDICATED A DIGGING TREND OF THE ADVERTISED TROUGH VALID
SATURDAY. WE`RE CONTINUING TO STEER WITH THE COOLER WETTER
FORECAST FOR NOW. WE`LL KEEP AN EYE ON THE EUROPEAN FORECAST WHICH
INDICATES THE TROUGH AXIS WILL BE FURTHER WEST. THUS THERE IS
LOWERED CONFIDENCE OF THE TIMING OF THE MAIN RAIN PUSH AND COOLING
WITH THE ONSET OF THIS NEXT TROUGH. STAVISH


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 11 AM TO 11 PM PDT
     SUNDAY FOR PZZ356-376.

$$

CC


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