433
FXUS66 KMFR 280907
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
207 AM PDT MON APR 28 2025
SHORT TERM
HIGH PRESSURE WILL BUILD INTO THE AREA TODAY WITH
DRY WEATHER. ONSHORE FLOW AND A MARINE PUSH INTO THE UMPQUA VALLEY
IS BRINGING CLOUDY SKIES TO MUCH OF COOS, DOUGLAS AND NORTHERN
CURRY COUNTIES THIS MORNING, BUT NO RAIN. THE DEPTH OF THE MOIST
LAYER EXTENDS UP TO AROUND 3500 FEET, AND THIS IS WELL-SHOWN BY
THE LATEST NIGHTTIME MICROPHYSICS RGB SATELLITE IMAGERY, WHICH
SHOWS THIS STRATUS BANKING UP AGAINST THE ROGUE-UMPQUA DIVIDE.
SOUTH OF THERE, CLOUDS ARE PATCHY AT BEST. THERE IS A CHANCE SOME
OF THE STRATUS "SPILLS OVER" INTO THE ROGUE BASIN (BANKING UP
AGAINST THE SISKIYOUS) TOWARD SUNRISE. EVEN IF IT DOES, THESE
CLOUDS WILL BE SHORT-LIVED, BREAK UP INTO STRATOCUMULUS LATER
THIS MORNING AND THEN SCATTER OUT THIS AFTERNOON YIELDING SUNNY
SKIES FOR MOST. IT'LL BE MILDER THAN YESTERDAY WITH MAXTS IN THE
UPPER 60S AND LOW 70S FOR MOST WEST SIDE VALLEYS (75-80F IN THE
LOWER KLAMATH VALLEY FROM HAPPY CAMP TO SOMES BAR) AND IN THE 60S
OVER THE EAST SIDE. OVERALL, FAIRLY TYPICAL AFTERNOON N-NW BREEZES
CAN BE EXPECTED AREA WIDE THAT'LL LAST THROUGH EARLY EVENING.
A WEAK TROUGH WILL MOVE SOUTHEASTWARD FROM THE NE PACIFIC TONIGHT
AND SWING THROUGH THE AREA ON TUESDAY. THIS WILL BRING SOME CLOUDS
AND SLIGHT CHANCE TO CHANCE POPS (~15-50%) FOR SHOWERS FROM THE
COAST TO THE CASCADES AND OVER THE EAST SIDE (BEST CHANCE IS IN
THE MOUNTAINS). IF IT RAINS AT ALL, AMOUNTS WILL BE LIGHT,
GENERALLY ONLY A HUNDREDTH OR TWO. THIS SYSTEM WILL EXIT TO THE
SOUTH AND EAST OF THE AREA TUESDAY EVENING WITH HIGH PRESSURE RE-
ESTABLISHING WEDNESDAY INTO THURSDAY. EXPECT COOL (WEST SIDE) TO
CHILLY (EAST SIDE) MORNINGS BOTH DAYS, BUT WITH NICE, WARM
AFTERNOONS. PEAK OF THE WARMTH IS EXPECTED ON THU WITH HIGHS IN
THE VALLEYS WEST OF THE CASCADES IN THE 80-85F RANGE (UPPER 80S
LOWER KLAMATH). EAST SIDE LOCATIONS WILL HAVE HIGHS LARGELY IN THE
MID AND UPPER 70S.
NEXT TROUGH IS STILL SLATED TO ARRIVE FRIDAY INTO NEXT WEEKEND.
DETAILS TO FOLLOW IN LONG TERM SECTION BELOW. -SPILDE
LONG TERM
ON FRIDAY, A DEEPER NEGATIVELY TILTED TROUGH IS
ANTICIPATED TO DEVELOP WITH THE TROUGH AXIS EXTENDING DOWN
THROUGH THE PACNW FROM BRITISH COLUMBIA. THE BASE OF THE TROUGH
AND VORTICITY MAXIMUM WILL PASS OVER THE FORECAST AREA. THIS
COUPLED WITH WITH AMPLE CAPE (UPWARDS OF 600 J/KG) WILL LIKELY
LEAD TO SHOWERS AND ISOLATED THUNDERSTORMS. HOWEVER, IT SHOULD BE
NOTED THAT INSTABILITY HAS DECREASED IN AREAL COVERAGE, WITH
INSTABILITY NOW BEING CONFINED TO AREAS ALONG AND NEAR THE
CASCADE, AND AREAS TO THE EAST OF THE CASCADES (INCLUDING NORTHERN
CALIFORNIA. BULK SHEAR VALUES (ALSO DECREASED) AROUND 30-40 KNOTS
WOULD ALLOW FOR UPDRAFTS TO MAINTAIN, SO WE COULD HAVE A COUPLE
STRONG STORMS; HOWEVER, ITS TOO EARLY TO SAY WITH MUCH CONFIDENCE
THE COVERAGE OF THESE THUNDERSTORMS GIVEN FLUCTUATIONS IN UPPER
LEVEL DYNAMICS. DCAPE VALUES REMAIN ON THE LOWER END, AND THIS IS
EVIDENT WITH FORECAST SOUNDINGS INDICATING MOIST LOW LEVELS. IN
FACT, EXTENDED RANGE FORECAST SOUNDINGS SHOW A "TROPICAL" LIKE
SOUNDINGS WITH A VERY MOIST COLUMN. WILL CONTINUE TO MONITOR THIS
BECAUSE FRIDAY COULD BE IMPACTFUL FROM A RAIN AND LIGHTNING POINT
OF VIEW, BUT SMALL HAIL CANNOT BE RULED OUT EITHER AT THIS POINT.
PWATS ARE APPROACHING AN INCH IN SOME AREAS, SO WE WILL NEED TO
ALSO KEEP AN EYE ON HEAVY RAINFALL POTENTIAL. EARLY INDICATION
SUGGEST THE SYSTEM IS PROGRESSIVE, AND THE MEAN FLOW COULD RESULT
IN FAST MOVING CELLS WHICH WOULD LIMIT RAINFALL AMOUNTS OVER ONE
AREA. WE WILL CONTINUE TO MONITOR FRIDAY FOR IMPACTS AS THIS
REMAINS THE DAY WITH THE HIGHEST POTENTIAL.
-GUERRERO
AVIATION...28/06Z TAFS
MARINE STRATUS IS SUPPORTING CONTINUED
MVFR LEVELS ALONG THE OREGON COAST NORTH OF CAPE BLANCO, WITH
MVFR/VFR LEVELS CONTINUING FOR INLAND AREAS. SATELLITE IMAGERY
DOES INDICATE CLOUDS ARE FILLING THE UMPQUA VALLEY AS WELL AS THE
SLIGHTEST HINT OF DEVELOPMENT IN THE SOUTHERN ROGUE VALLEY.
PERIODS OF MVFR CEILINGS HAVE BEEN INCLUDED IN THE ROSEBURG AND
MEDFORD TAFS, WITH SOME UNCERTAINTY IN MEDFORD'S CHANCES OF SEEING
THOSE CEILINGS. THE ROGUE AND UMPQUA CEILINGS LOOK TO CLEAR OUT
LATE THIS MORNING. THE COASTAL AREA LOOKS TO CLEAR OUT THIS
AFTERNOON, BUT COULD RETURN IN THE EVENING.
OTHER AREAS LOOK TO REMAIN AT VFR THROUGH THE TAF PERIOD. -TAD
MARINE...UPDATED 200 AM MONDAY, APRIL 28, 2025
THE STRONGEST
NORTHERLY WINDS AND STEEPEST SEAS WILL BE FOUND SOUTH OF CAPE
BLANCO AS A WEAK THERMAL TROUGH PERSISTS TODAY THROUGH MONDAY
NIGHT.
STABLE UPPER LEVEL CONDITIONS WILL ALLOW FOR MORE IMPROVEMENT IN THE
MIDDLE OF THE WEEK. A STRONG THERMAL TROUGH IS NOT FORECAST, SO
PERIODS OF BELOW ADVISORY SEAS WILL BE POSSIBLE. AN APPROACHING
FRONT MAY BRING STEEP SWELL AND MARINE SHOWERS NEAR THE END OF THE
WEEK. -TAD/SPILDE
MFR WATCHES/WARNINGS/ADVISORIES
OR...CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY
FOR PZZ356-376.
MAS/JWG/TAD
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