000
FXUS66 KMFR 200347
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
847 PM PDT SUN MAY 19 2013

.DISCUSSION...STRONG HIGH PRESSURE OFF THE OREGON COAST AND A
THERMAL TROUGH OVER NORTHERN CALIFORNIA WILL PROVIDE TRANQUIL
WEATHER ACROSS THE CWA OVERNIGHT INTO MONDAY MORNING WITH CLEAR
SKIES IN MOST LOCATIONS. A FEW FOG/STRATUS PATCHES MAY PERSIST OR
DEVELOP OVERNIGHT ALONG THE NORTH COAST...PARTICULARLY NEAR THE
COQUILLE RIVER VALLEY...AND ALSO SOUTHERN PORTIONS OF THE UMPQUA
BASIN. A SUNNY, WARM DAY IS EXPECTED MONDAY WITH OFFSHORE FLOW
REVERSING AND BECOMING ONSHORE IN THE AFTERNOON AS THE RIDGE AXIS
SHIFTS TO OUR EAST. HIGHS IN MEDFORD WILL BE IN THE LOW TO MID
80S. AN ABRUPT CHANGE IN THE WEATHER IS COMING TUESDAY AS A SHARP
COLD FRONT MOVES THROUGH. GUSTY WINDS WILL ACCOMPANY THE FRONT
ALONG WITH SOME RAIN. A NOTICEABLE TEMPERATURE DROP WILL ALSO
OCCUR WITH HIGHS IN MEDFORD NO BETTER THAN THE UPPER 60S. A COLD
UPPER LOW WILL MOVE INTO THE PACIFIC NORTHWEST TUESDAY NIGHT
THROUGH THURSDAY RESULTING IN COOL, SHOWERY, UNSETTLED WEATHER
WITH LOW SNOW LEVELS FOR THIS TIME OF YEAR...DOWN AS LOW AS 2500
FEET EARLY WEDNESDAY MORNING. FOR MORE SPECIFIC DETAILS, SEE
PREVIOUS DISCUSSION BELOW. SPILDE

&&

.AVIATION...BASED ON THE 20/00Z TAF CYCLE.

CONDITIONS ARE VFR ACROSS THE AREA. OVERNIGHT NORTHEAST OFFSHORE LOW
LEVEL WINDS ARE EXPECTED TO PREVENT THE FORMATION OF LOW CLOUDS OR
FOG, WITH THE POSSIBLE EXCEPTION OF LATE NIGHT INTO EARLY MORNING
(AROUND 11Z-15Z) PATCHES OF MVFR STRATUS IN THE COQUILLE AND UMPQUA
VALLEYS. VFR CONDITIONS WILL CONTINUE MONDAY THROUGH MONDAY EVENING
THEN CONDITIONS WILL DETERIORATE AT THE COAST AHEAD OF A COLD FRONT
LATE MONDAY NIGHT. DW

&&

.PREV DISCUSSION... /ISSUED 252 PM PDT SUN MAY 19 2013/

DISCUSSION...THE WARM UP CONTINUES OVER THE REGION AS BUILDING
RIDGE SPREADS OFFSHORE FLOW ACROSS THE EAST SIDE TONIGHT. ANOTHER
DAY OF ROUGHLY TEN DEGREE WARMING OVER TODAY IS IN LINE FOR
TOMORROW. THE RIDGE FLATTENS MONDAY WITH FLOW REVERSING LATE.
UNLIKE THE USUAL SOUTHERLY FLOW PATTERN IN THE WARM CONVEYOR AHEAD
OF A COLD FRONT...THIS SYSTEM WILL SEE WESTERLY FLOW THAT WILL
HELP USHER IN THE COOLER AIR AS THE SYSTEM MOVES INLAND
TUESDAY...WITH HIGH TEMPERATURES IN THE EARLY AFTERNOON OVER MOST
OF THE WEST SIDE.BY WEDNESDAY MORNING ALL MODELS HAVE 850 TEMPS
AROUND -4C...WITH 500 MB TEMPS BELOW -30C OVER NORTHWEST PORTIONS
BY WEDNESDAY EVENING. WITH THE WESTERLY 700 MB WINDS AND COLD AIR
MASS SHOWERS WILL CONTINUE THROUGH THE OVERNIGHT HOURS WITH SNOW
LEVELS LOOKING TO DROP TO AROUND 2500 FEET...AND IN HEAVY SHOWERS
POSSIBLY DROPPING TO AROUND 2000 FEET BRIEFLY OVERNIGHT INTO
WEDNESDAY MORNING. HOWEVER...WITH THE LONGER DAYS AND HIGHER SUN
ANGLES...SOIL AND ROAD TEMPS ARE QUITE WARM WITH THE MEDFORD
AGRIMET SHOWING SOIL TEMPS IN THE MID 60S AND BOTH SISKIYOUS AND
SEXTON SUMMIT ROAD TEMPS IN THE UPPER 80S INTO THE 90S. WITH THIS
WARM SOIL AND ROAD TEMPS EVEN A MODERATE TO HEAVY RAIN PRECEDING
THE COOLER AIR MASS WILL NOT COOL SURFACE ENOUGH TO ALLOW ANY SNOW
THAT FALLS TO LAST MORE THAN A COUPLE OF HOURS ON THE PASSES OF
THE I-5 CORRIDOR. IN THE CASCADES THE SNOW MAY LAST A LITTLE
LONGER OFF-ROAD. THIS PATTERN REMAINS THROUGH WEDNESDAY AS VORT
LOBES CYCLE AROUND THE CLOSED LOW...BRINGING INTENSIFIED BANDS OF
SHOWERS THROUGH THE REGION. THE COLDER 500 AIR MASS FINALLY MOVES
OUT OF THE AREA LATE THURSDAY AS THE UPPER LOW CONTINUES TO WOBBLE
ABOUT OVER THE PACIFIC NORTHWEST...CONTINUING AN UNSETTLED PATTERN
INTO THE WEEKEND WHEN THE UPPER LOW LOOKS TO FINALLY MIGRATE TO
THE NORTHEAST BRINGING A WARMING TREND NEXT WEEKEND. SVEN

&&

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

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT
     MONDAY FOR PZZ356.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 11 PM PDT MONDAY
     FOR PZZ356.
     SMALL CRAFT ADVISORY FOR WINDS UNTIL 8 PM PDT MONDAY FOR
     PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 PM PDT MONDAY
     FOR PZZ350-370.
     GALE WARNING UNTIL 8 PM PDT MONDAY FOR PZZ376.
     HAZARDOUS SEAS WARNING UNTIL 8 PM PDT MONDAY FOR PZZ376.

$$

MAS/DW/SBN