Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 172154
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
254 PM PDT FRI APR 17 2015

.SHORT TERM...THINGS ARE ON TRACK FOR SIGNIFICANT WARMING ACROSS
OUR INLAND AREAS THIS WEEKEND AS THE RIDGE OF HIGH PRESSURE BUILDS
INTO THE PAC NW. FORECAST HIGHS OF LOWER TO MID 80S FOR THE ROGUE
VALLEY AND LOWER TO MID 70S FOR THE KLAMATH BASINS STILL LOOK
REASONABLE AS 850MB TEMPERATURES WILL RISE TO 15-17C. AT THE
COAST THE THERMAL TROUGH WILL CONTINUE TO SHIFT BACK AND FORTH
MOVING OFFSHORE AT NIGHT. ONSHORE DURING THE DAY IS QUITE SHALLOW
WITH BROOKINGS SHOWING MID 50S FOR HIGHS AND RED MOUND RAWS
NORTHEAST OF TOWN AT 1800 FEET SHOWING 69.

ON SATURDAY A DISTURBANCE ROTATE SOUTH ALONG THE EAST SIDE OF THE
RIDGE. THE ATMOSPHERE BECOMES SLIGHTLY MORE UNSTABLE. THERE IS
NOT AS MUCH MOISTURE ON THE OREGON SIDE BUT THERE IS SOME MID AND
HIGH LEVEL MOISTURE ACROSS SOUTHWESTERN SISKIYOU COUNTY, WITH MORE
INSTABILITY SOUTH OF MOUNT SHASTA. FORECAST SOUNDINGS OF THE
MARBLE MOUNTAINS SHOW MOISTURE IN THE MIXED LAYER IS ENOUGH TO
GENERATE DEEP CUMULUS CLOUDS. WE WILL HAVE TO TAKE ANOTHER LOOK AT
THIS TONIGHT BUT CURRENTLY WE FEEL THAT THE AREA WOULD MOST LIKELY
SEE PLENTY OF CUMULUS CLOUDS. ELSEWHERE IN OUR AREA THERE IS TOO
MUCH WARMING ALOFT AND THE ATMOSPHERE IS TOO STABLE ABOVE 3000
FEET.

ON SUNDAY THE THERMAL TROUGH MOVES EAST OF THE CASCADES. THIS WILL
BE THE WARMEST DAY IN KLAMATH AND GOOSE LAKE BASINS. NORMAL THIS
LEADS TO A MORE ONSHORE FLOW FOR THE COASTAL ZONES BUT MODELS
CONTINUE TO SHOW EASTERLY WIND AND A WARM POCKET JUST ABOVE
GROUND. HAVE KEPT BROOKINGS TEMPERATURES WARM AGAIN BUT CONFIDENCE
IS NOT AS HIGH ON SUNDAYS TEMPERATURE AS FOR SATURDAYS HIGH.

ONSHORE SHOULD BE MORE PROMINENT AT THE COAST AND INTO THE UMPQUA
BASIN ON MONDAY AS THE RIDGE SHIFTS MORE TO THE EAST. MOST OF
INLAND VALLEYS WILL STILL BE WARM BUT MONDAY WILL BE A
TRANSITIONAL DAY. INCREASED MOISTURE AND SOME INSTABILITY WILL
LEAD TO MOUNTAIN SHOWERS /FB

.LONG TERM...TUESDAY THROUGH FRIDAY...THE EXTENDED PERIOD
OF THE FORECAST WILL BE SIGNIFICANTLY COOLER AND WETTER THAN THE
SHORT-TERM. GFS ENSEMBLE MEMBERS SUGGEST WITH HIGH CONFIDENCE THAT
THE UPPER RIDGE AXIS THAT PROVIDED WEEKEND WARMTH WILL PUSH EAST ON
TUESDAY...BRINGING COOLER TEMPERATURES AND THE POTENTIAL FOR
THUNDERSTORMS TUESDAY AFTERNOON FROM THE CASCADES EASTWARD. BOTH THE
EC AND GFS KEEP THE WEST SIDE GENERALLY DRY ON TUESDAY...BUT WITH A
POTENT TROUGH AND FRONT APPROACHING...WE HAVE A CHANCE OF SHOWERS
WEST OF THE CASCADES FOR TUESDAY AS WELL. COOL AND SHOWERY
CONDITIONS WILL CONTINUE THROUGH THURSDAY AS UPPER TROUGHING
CONTINUES OVER THE AREA.

BY FRIDAY MODEL SOLUTIONS DIFFER SIGNIFICANTLY...BETWEEN THE 12Z EC
AND GFS OPERATIONAL RUNS. ALMOST ALL GFS ENSEMBLE MEMBERS SHOW A
LARGE CLOSED UPPER LOW OR TROUGH IN THE VICINITY OF SOUTHERN OREGON
AND NORTHERN CALIFORNIA. THIS SHOULD MAINTAIN COOL AND SHOWERY
CONDITIONS FOR ANOTHER DAY. SK

&&

.AVIATION...FOR THE 17/18Z TAF CYCLE...MARINE STRATUS AND A MIX OF
MVFR AND IFR CEILINGS CONTINUE AT THE COAST...AND THESE CONDITIONS
WILL BRIEFLY CLEAR THIS AFTERNOON BEFORE RETURNING THIS EVENING.
OFFSHORE FLOW WILL KEEP THE COAST BETWEEN GOLD BEACH AND CAPE BLANCO
VFR THROUGH TOMORROW. INLAND...IN THE UMPQUA VALLEY...MODELS SUGGEST
A SLIGHT CHANCE FOR MVFR CEILINGS AT ROSEBURG EARLY SATURDAY
MORNING...SO SINCE THE CHANCE IS SO SMALL WE HAVE ONLY INCLUDED
SCATTERED CLOUDS IN THE MORNING. ELSEWHERE...VFR CONDITIONS WILL
CONTINUE THROUGH TOMORROW.

GIVEN THE THERMAL TROUGH PATTERN AT THE COAST...A STRONG NORTH TO
SOUTH PRESSURE GRADIENT WILL MAINTAIN GUSTY AFTERNOON NORTH WINDS AT
THE COAST...EAST OF THE CASCADES...AND OCCASIONALLY IN WEST SIDE
VALLEYS. /NK

&&

.MARINE...


&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT MONDAY FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT MONDAY
     FOR PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 2 AM PDT SUNDAY FOR PZZ356-376.
     HAZARDOUS SEAS WARNING UNTIL 2 AM PDT SUNDAY FOR PZZ350-370.
     GALE WARNING UNTIL 2 AM PDT SUNDAY FOR PZZ376.

$$

FJB/NSK/NSK


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