449
FXUS66 KMFR 161127
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
327 AM PST SUN FEB 16 2025
SYNOPSIS
A FRONT IS MOVING INLAND EARLY THIS MORNING AND RADAR
IMAGERY SHOWS THE MAIN BAND OF PRECIPITATION ACROSS SOUTHEAST
PORTIONS OF THE CWA. SHOWERS WILL INCREASE AND SPREAD INLAND THIS
MORNING INTO THIS AFTERNOON. THIS EVENING INTO MONDAY, A LOW
GRADUALLY NEARS THE PACIFIC NORTHWEST COAST. THIS WILL RESULT IN
CONTINUED MOIST ONSHORE FLOW AND WIDESPREAD SHOWERS ACROSS THE
AREA, WITH IMPACTFUL SNOWFALL ACROSS THE SOUTHERN OREGON CASCADES.
THE LOW MOVES ONSHORE JUST NORTH OF THE AREA SUNDAY NIGHT INTO
MONDAY MORNING, THEN SHIFTS EASTWARD AS A TROUGH MONDAY NIGHT.
WEAK HIGH PRESSURE BUILDS IN MONDAY NIGHT WITH A RELATIVE BREAK IN
THE ACTIVE PATTERN INTO TUESDAY MORNING.
DISCUSSION
WITH THIS SHOWERY PATTERN AND STRONG, MOIST ONSHORE
FLOW, THE MAIN CONCERN IS FOR PERSISTENT SNOW ACROSS THE SOUTHERN
OREGON CASCADES. RADAR IMAGERY INDICATES INDICATES THE MAIN BAND
OF PRECIPITATION IS ACROSS SOUTHEAST PORTIONS OF THE AREA WITH
SHOWERS BEGINNING TO MOVE INLAND ACROSS COASTAL AREAS AND INTO
DOUGLAS COUNTY. MOIST WESTERLY FLOW WILL PROVIDE OROGRAPHIC LIFT,
AND SUPPORT FOR HIGHER SNOWFALL RATES ACROSS THE CASCADES AS
SHOWERS CONTINUE TODAY INTO MONDAY. HIGH RESOLUTION ENSEMBLES
INDICATE SNOWFALL RATES WILL BE HIGHEST SUNDAY AND SUNDAY NIGHT
WITH A CHANCE (60-80%) FOR SNOWFALL RATES UP TO AN INCH PER HOUR
OVER HIGHER PORTIONS OF THE CASCADES, MAINLY NORTH OF HIGHWAY 140
AND NEAR THE CRATER LAKE AND DIAMOND LAKE AREAS. TOTAL SNOWFALL
ACCUMULATIONS (TODAY THROUGH MONDAY) OF 6 TO 18 INCHES ARE
EXPECTED IN THE SOUTHERN OREGON CASCADES, WITH HIGHEST AMOUNTS
NORTH OF HIGHWAY 140 AND LOCALLY HIGHER AMOUNTS NEAR CRATER LAKE
AND OVER HIGHER MOUNTAINS. A WINTER STORM WARNING (WSWMFR) REMAINS
IN EFFECT FOR THE SOUTHERN OREGON CASCADES THROUGH MONDAY
AFTERNOON.
OTHERWISE, MOIST ONSHORE FLOW WITH A LOW/TROUGH MOVING INTO THE
REGION THROUGH MONDAY WILL KEEP THE SHOWERS GOING. HEAVIEST
SHOWERS WILL BE FAVORED ON UPSLOPE AREAS ACROSS THE COASTAL
MOUNTAINS AND ALONG THE SOUTHERN OREGON CASCADES. WITH SNOW LEVELS
AROUND 4000-5000 FEET TODAY, LOWERING TO 3500-4000 FEET TONIGHT
AND MONDAY MORNING, EXPECT SNOW SHOWERS (MAINLY LIGHT) ACROSS THE
SISKIYOU MOUNTAINS AND MOUNTAINS IN SISKIYOU COUNTY AS WELL AS
EAST OF THE CASCADES. ALONG THE COAST AND IN VALLEYS WEST OF THE
CASCADES, RAIN SHOWERS ARE EXPECTED.
BREEZY TO GUSTY WINDS (WITH GUSTS OF AROUND 30 TO 40 MPH) ARE
ALSO LIKELY TODAY INTO MONDAY ACROSS THE MOUNTAINS. LOCALLY GUSTY
WINDS ARE ALSO EXPECTED IN THE SOUTHERN SHASTA VALLEY THIS
MORNING.
AS THE UPPER TROUGH SHIFTS EASTWARD MONDAY NIGHT, EXPECT SHOWERS
TO DIMINISH. THIS BREAK WILL BE BRIEF THOUGH AS ENSEMBLES SUPPORT
A FRONTAL SYSTEM MOVING INTO THE AREA LATE TUESDAY INTO WEDNESDAY.
SEE THE LONG TERM DISCUSSION BELOW FOR MORE DETAILS.
AVIATION...16/06Z TAFS
MVFR CEILINGS WILL BEGIN TO SPREAD
ACROSS THE AREA TONIGHT AS A FRONT APPROACHES. SHOWERS ALONG THE
COAST THIS EVENING WILL SPREAD EASTWARD OVERNIGHT, THEN MORE
UNIFORM STEADY RAIN IS EXPECTED ALONG WITH MVFR/IFR CONDITIONS FOR
MUCH OF THE DAY TOMORROW, WITH THE HEAVIEST PRECIPITATION ALONG
THE COAST AND OVER THE CASCADES. SNOW LEVELS WILL STEADILY RISE
TO 4000-5000 FEET THROUGH THE TAF PERIOD, ALTHOUGH THERE WILL BE
ISOLATED AREAS WITH MORE PERSISTENT LOWER SNOW LEVELS.
THE FRONT WILL ALSO BRING PERIODS OF LOW LEVEL WIND SHEAR AS IT
MOVES OVER THE AREA, ESPECIALLY OVER ELEVATED TERRAIN. WHILE
ROSEBURG DOES NOT HAVE SHEAR NOTED IN THE TAF FORECAST, SHEAR IS
PRESENT AROUND THE UMPQUA VALLEY AT ABOUT THE SAME TIMEFRAME AS
NORTH BEND. LOW LEVEL WIND SHEAR IS GENERALLY ABSENT ACROSS THE AREA
BY MORNING, WITH A FEW ISOLATED POCKETS OVER LAKE AND MODOC
COUNTIES, WHERE MOUNTAIN WAVE TURBULENCE IS POSSIBLE.
-TAD/BPN
MARINE...UPDATED 230 AM PST SUNDAY, FEBRUARY 16, 2025
HAZARDOUS
SEAS WILL PERSIST THROUGH THIS MORNING WITH VERY STEEP SEAS OBSERVED
NEAR BUOY 229 JUST OFF OF REEDSPORT. WINDS EASE LATER THIS MORNING,
BUT LONG-PERIOD WESTERLY SWELL WILL BUILD IN THE WATERS AND SUSTAIN
STEEP SEAS THROUGH THE START OF NEXT WEEK. SEAS OF 12 TO 15 FEET AT
14 TO 15 SECONDS ARE FORECAST THROUGH MOST OF MONDAY, WITH SEAS
IMPROVING INTO TUESDAY.
THERE IS A LOW CHANCE OF GALE FORCE WINDS IN THE WATERS WEDNESDAY
MORNING AS A STRONG COLD FRONT COULD MOVE THROUGH THE WATERS. THIS
WOULD INCREASE WAVE HEIGHTS THURSDAY AND BRING ANOTHER ROUND OF VERY
HIGH AND STEEP SEAS.
-SMITH
PREV LONG TERM DISCUSSION
/ISSUED 227 PM PST SAT FEB 15 2025/
UPPER RIDGING BUILDS INTO THE AREA BRIEFLY TUESDAY MORNING WHICH
SHOULD GIVE US A BREAK IN PRECIPITATION. THIS WON'T LAST LONG WITH
STRONGER EVIDENCE POINTING TOWARDS WARM FRONTAL PRECIPITATION MOVING
INTO THE AREA (CASCADES WEST) TUESDAY AFTERNOON. SNOW LEVELS TUESDAY
AFTERNOON WILL BE ON THE RISE TO AROUND 5500 FEET TUESDAY AFTERNOON
AND NEAR 6000 FEET TUESDAY EVENING.
A COLD FRONT AND UPPER TROUGH WILL MOVE IN EARLY WEDNESDAY MORNING
WITH SNOW LEVELS FALLING IN THE MORNING, THEN REBOUNDING SOME IN THE
AFTERNOON DUE TO DIURNAL EFFECTS. HOWEVER SNOW LEVELS WILL VARY
DEPENDING ON PRECIP INTENSITY SINCE WE'LL BE IN A CONVECTIVE
ENVIRONMENT.
THERE ARE SIGNS POINTING TOWARDS A QUIETER PATTERN THE LATTER PART
OF NEXT WEEK. THE CLUSTERS ARE ALL POINTING TOWARDS UPPER RIDGING
WITH THE STORM TRACK NORTH OF THE AREA, AND THE MAJORITY OF THE
INDIVIDUAL ENSEMBLE MEMBERS POINT TOWARDS DRY WEATHER WITH THE STORM
TRACK STAYING NORTH, THEN SHIFTING JUST FAR ENOUGH SOUTH TO WARRANT
A SLIGHT CHANCE OF PRECIPITATION FOR THE NORTHWEST PART OF THE
FORECAST AREA. -PETRUCELLI
MFR WATCHES/WARNINGS/ADVISORIES
OR...WINTER STORM WARNING UNTIL 4 PM PST MONDAY FOR ORZ027-028.
CA...NONE.
PACIFIC COASTAL WATERS...HAZARDOUS SEAS WARNING UNTIL 10 AM PST THIS
MORNING FOR PZZ350-356-370-376.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 4 PM PST MONDAY
FOR PZZ350-356-370-376.
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