Hazardous Seas Warning 33, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
800 PM PDT SUN APR 3 2016

.DISCUSSION...04/00Z NAM IN.

THE NORTHERN HEMISPHERIC FLOW PATTERN CONTINUES TO SHOW A
PROGRESSIVE 5 WAVE PATTERN AROUND THE GLOBE THAT WILL PERSIST
THROUGH AT LEAST FRIDAY. HOWEVER...THE PATTERN OVER THE PACIFIC
NORTHWEST WILL SLOW DOWN TUESDAY INTO THURSDAY DUE TO A REX
BLOCK.

A FRONT IS NOW MOVING ONSHORE WITH AREAS OF LIGHT RAIN OVER THE
WEST SIDE UP TO THE CASCADES. AMOUNTS SO FAR HAVE BEEN
LIGHT...RANGING UP TO A THIRD OF AN INCH ALONG THE COAST AND
GENERALLY LESS THAN 0.10 INCHES INLAND. SOME ISOLATED
THUNDERSTORMS HAVE ALSO DEVELOPED...THE HEAVIEST ONE OVER THE
SHASTA VALLEY DURING THE PAST HOUR.

THE UPPER LEVEL LONG WAVE TROUGH SUPPORTING THIS FRONT WILL MOVE
ONSHORE LATER TONIGHT. STRATIFORM PRECIPITATION AHEAD OF AND WITH
THE FRONT WILL GIVE WAY TO SHOWERS BEHIND IT. A TENTH OF AN INCH OR
MORE OF RAINFALL WILL FALL ACROSS MOST AREAS FROM THE CASCADES
WEST THROUGH MONDAY MORNING...WITH A QUARTER TO A HALF INCH IN
THE COASTAL COUNTIES. UP TO A COUPLE OF INCHES OF SNOW WILL FALL
OVER THE HIGHER PEAKS AND POSSIBLY THE CHEMULT AREA. IT WILL ALSO
BE BREEZY MONDAY MORNING OVER HIGHER TERRAIN

MONDAY WILL SEE A RAPID TRANSITION FROM WET TO DRY AS THE TROUGH
MOVES OUT AND A LONG WAVE RIDGE BUILDS INTO THE AREA. A WEAK SHORT
WAVE TRAILING THE TROUGH WILL PROVIDE THE LAST SUPPORT FOR SHOWER
ACTIVITY MONDAY AFTERNOON. SHOWERS WILL END MONDAY EVENING AND
OFFSHORE LOW LEVEL FLOW WILL DEVELOP MONDAY NIGHT. THE RIDGE WILL
STALL OFFSHORE AS IT WILL FORM THE HIGH PORTION OF A REX BLOCK.
THEREFORE...TUESDAY AND THURSDAY WILL BE DRY WITH OFFSHORE FLOW
CONTINUING. THE OFFSHORE FLOW WILL BE LOCALLY STRONG TUESDAY NIGHT
INTO WEDNESDAY SOME EXPOSED MID- ELEVATION AREAS...AS WELL AS
SADDLES AND PASSES WILL SEE WIND GUSTS OF 30 TO 40 MPH WITH MILD
TEMPERATURES AND MODERATE TO POOR RELATIVE HUMIDITY RECOVERIES
DURING THIS TIME PERIOD. THESE EAST WINDS WILL DRY THE AIR MASS
SIGNIFICANTLY...SETTING THE STAGE FOR LIKELY RECORD HIGH AFTERNOON
TEMPERATURES WEDNESDAY AND THURSDAY.

LONG TERM DISCUSSION FROM THE SUNDAY AFTERNOON AFD...THURSDAY
THROUGH SUNDAY. AN UPPER LEVEL RIDGE IS OVER THE PACIFIC NORTHWEST
THURSDAY...WITH OFFSHORE FLOW ACROSS TO THE EAST SIDE WITH A
THERMAL TROUGH ALONG THE SOUTHERN COAST. THE THERMAL TROUGH MOVES
INLAND CONTINUING A SHORT STRETCH OF UNSEASONABLY WARM
TEMPERATURES ACROSS THE REGION WITH HIGH TEMPERATURES WELL ABOVE
RECORD HIGHS. THE TROUGH CONTINUES TO MOVE SLOWLY INLAND WITH
INCREASING SOUTHERLY FLOW INTO THE REGION BRINGING INCREASED
MOISTURE AND INSTABILITY AND A CHANCE OF THUNDERSTORM TO THE EAST
SIDE FRIDAY. THE ECMWF IS COMING MORE IN LINE WITH YESTERDAY'S GFS
POSITION OF THE CLOSED UPPER LEVEL LOW WITH THE GFS COMING IN LINE
WITH THE DEPTH OF THAT UPPER LOW. THE ECMWF AND THE GFS DIFFER ON
THE AMOUNT OF INSTABILITY ON FRIDAY WITH THE GFS INDICATING
COMPUTED FROM 850 MB LI'S OF -5 OVER THE CASCADES AND INSTABILITY
OVER MOST OF THE REGION AND 700MB WINDS FROM THE SOUTHEAST TO EAST
POSSIBLY BRINGING ANY THUNDERSTORMS THAT DO DEVELOP ALL THE WAY TO
THE COAST. THE GFS THEN SWINGS THE UPPER LOW INTO CENTRAL
CALIFORNIA SATURDAY WITH THE ECMWF SWINGING IT INTO SOUTHERN
CALIFORNIA. WITH THE VARIANCE AND RESULTING UNCERTAINTY HAVE KEPT
POPS LOW FOR THE TAIL END. -SVEN

&&

.AVIATION...FOR THE 04/00Z TAF CYCLE...WEST OF THE CASCADES...A COLD
FRONT WILL BRING MVFR CIGS AND LIGHT RAIN TO THE COAST THIS
EVENING. THE LOWER CONDITIONS AND RAIN WILL SPREAD INLAND LATE THIS
EVENING AND OVERNIGHT...WHERE TERRAIN WILL BECOME OBSCURED.
PRECIPITATION WILL TAPER OFF TO SHOWERS LATER TONIGHT AND MONDAY
MORNING BEHIND THE FRONT. CIGS WILL IMPROVE MONDAY AFTERNOON
WITH ISOLATED SHOWERS LINGERING NORTH AND WEST OF THE UMPQUA DIVIDE.

FROM THE CASCADES AND SISKIYOUS EASTWARD...ISOLATED SHOWERS AND
THUNDERSTORMS OVER THE MOUNTAINS MAY BRIEFLY MOVE OUT OVER SOME
OF THE VALLEYS THIS EVENING, BUT CIGS LARGELY REMAIN VFR. CIGS
WILL LOWER A BIT AS THE FRONT MOVES INLAND OVERNIGHT INTO MONDAY
MORNING, BUT WITH ONLY AREAS OF MVFR CIGS AND TERRAIN OBSCURATION.
VFR IS EXPECTED MONDAY AFTERNOON. SPILDE

&&

.MARINE...UPDATED 315 PM PDT SUN 3 APR 2016...A COLD FRONT WILL
BRING RAIN AND FRESH SOUTH WINDS TO THE WATERS INTO THIS EVENING.
WINDS SHIFT TO WESTERLY WITH SHOWERS LINGERING OVERNIGHT INTO
MONDAY. OFFSHORE HIGH PRESSURE WILL REBUILD MONDAY WITH GUSTY
NORTH WINDS DEVELOPING SOUTH OF CAPE BLANCO TUESDAY. THE OFFSHORE
HIGH PRESSURE WILL WEAKEN WEDNESDAY AND WEAK LOW PRESSURE WILL
DEVELOP WEDNESDAY NIGHT INTO THURSDAY. SPILDE

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

15/15/15