211
FXUS66 KMFR 281128
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
427 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...28/12Z TAFS
ONSHORE FLOW AND A MARINE PUSH IS
BRINGING A MIX OF VFR/MVFR TO THE COAST NORTH OF PORT ORFORD AND
INTO MOST OF COOS AND DOUGLAS COUNTIES, INCLUDING NORTH
BEND/ROSEBURG THIS MORNING. AREAS OF HIGHER TERRAIN ARE OBSCURED.
MOIST LAYER DEPTH OF 3000-4000 FEET IS CAUSING SOME "SPILL OVER"
INTO THE ROGUE BASIN WITH CEILINGS FORMING AROUND 3500 FEET IN THE
LAST HOUR OR SO. THIS COULD BRING LOCAL MVFR FOR A FEW HOURS THIS
MORNING. ALSO, LOCAL IFR CEILINGS ARE PRESENT THIS MORNING NEAR
BROOKINGS. AS THE SUN RISES, CEILINGS WILL BREAK UP INTO
STRATOCUMULUS, EVENTUALLY SCATTERING OUT TO VFR BY THIS AFTERNOON.
THE REMAINDER OF THE AREA WILL BE VFR.
A WEAK FRONT WILL APROACH THE COAST TONIGHT, THEN MOVE THROUGH ON
TUESDAY. LOCAL MVFR CEILINGS ARE POSSIBLE TUESDAY ALONG WITH A
CHANCE OF SHOWERS, BUT MOST OF THE TIME WILL BE DRY WITH VFR.
-SPILDE
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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