Small Craft Advisory 17, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
947 PM PST WED FEB 3 2016

UPDATED AVIATION SECTION

.DISCUSSION...SATELLITE IMAGERY THIS EVENING IS SHOWING THE FRONT
MOVING EAST OF THE CASCADES. GIVEN RECENT RADAR TRENDS SHOWING A
RAPID DECREASE IN PRECIPITATION, THE WINTER WEATHER ADVISORIES
HAVE BEEN CANCELLED. SOME SNOW SHOWERS WILL PERSIST THROUGH ABOUT
10 PM...ESPECIALLY IN THE FAVORED UPSLOPE AREAS OF THE CASCADES
AND ALSO OVER THE WARNER MOUNTAINS...BUT MOST AREAS WILL HAVE LESS
THAN AN INCH OF ADDITIONAL SNOW ACCUMULATION. SOME ONSHORE FLOW
AND A TRAILING SHORTWAVE DISTURBANCE WILL KEEP SHOWERS IN THE
FORECAST FROM THE COAST TO THE CASCADES, MAINLY FROM THE UMPQUA
DIVIDE NORTHWARD OVERNIGHT INTO THURSDAY MORNING. ANY SHOWERS
WILL MOVE NORTH OF THE AREA THURSDAY AFTERNOON AS A WEAK RIDGE
BUILDS IN. SPILDE

&&

.AVIATION...FOR THE 04/06Z TAF CYCLE...LIGHT WINDS AND PLENTY OF
MOISTURE LEFT BEHIND WEDNESDAY'S FRONT WILL BRING TERRAIN
OBSCURATION OVERNIGHT INTO THURSDAY WITH CIGS LOWERING IN THE
VALLEYS TO AT LEAST MVFR AT THE MAIN TERMINALS. IFR IS EXPECTED AT
KLMT AT TIMES OVERNIGHT INTO THURSDAY MORNING AND IFR IS POSSIBLE
AT KRBG AND KMFR IN THE 12-17Z TIME FRAME. EXPECT IMPROVEMENT TO
VFR EXCEPT AT KLMT WHERE MVFR MAY LINGER THROUGH THE AFTERNOON.
SPILDE

&&

.MARINE...UPDATED 800 PM PST WED FEB 3 2016... SOUTHWEST AND WEST
WINDS WILL CONTINUE TO DIMINISH BEHIND THE COLD FRONT THIS AFTERNOON
AND EVENING, BUT HEAVY LONG PERIOD WEST SWELL WILL BUILD IN THIS
EVENING THROUGH TONIGHT PERSISTING INTO THURSDAY EVENING. ANOTHER
FRONTAL SYSTEM WILL MOVE THROUGH FRIDAY WITH GALES POSSIBLE IN
PORTIONS OF THE AREA. HIGH PRESSURE IS THEN EXPECTED TO BUILD IN
SATURDAY WITH LIGHT WINDS CONTINUING THROUGH EARLY NEXT WEEK. BTL

&&

.PREV DISCUSSION... /ISSUED 218 PM PST WED FEB 3 2016/

DISCUSSION...THE COLD FRONT IS NOW JUST MOVING INTO THE OUTER
MARINE WATERS AND IS EXPECTED TO REACH THE COAST LATE THIS
AFTERNOON AND MOVE INLAND TONIGHT. RAINFALL HAS ALREADY BEGUN AT
THE COAST AND WILL PUSH INLAND THIS EVENING. THIS FRONT SHOULD
MOVE FAIRLY QUICKLY, THUS LIMITING THE AMOUNT OF PRECIPITATION.
EVEN SO, THE HEAVIEST AMOUNTS WILL BE IN THE USUAL LOCATIONS:
ALONG THE COAST, COAST RANGE AND CASCADES. SNOW LEVELS ARE
EXPECTED TO BE AROUND 4000 FEET THIS EVENING, BUT COULD BRIEFLY
LOWER TO 3500 FEET IN HEAVIER PRECIPITATION. THE FRONT WILL MOVE
EAST OF THE CASCADES TONIGHT, BUT A SHORTWAVE TROUGH WILL FOLLOW
THE FRONT BRINGING ENHANCED PRECIPITATION EAST OF THE CASCADES AND
AT THE SAME TIME SNOW LEVELS WILL LOWER TO AROUND 3500 FEET,
THEREFORE HAVE EXPANDED THE COVERAGE AREA OF THE WINTER WEATHER
ADVISORY. SEE WSWMFR FORE MORE DETAILS. SNOW LEVELS WILL CONTINUE
TO LOWER TO AROUND 3000 FEET LATE TONIGHT, BUT THE BULK OF THE
PRECIPITATION WILL HAVE MOVED OUT OF THE AREA.

WINDS HAVE INCREASED IN THE SHASTA VALLEY AND EXPECT THIS TO
CONTINUE INTO THIS EVENING, THEN WILL DECREASE AS 850 MB WINDS
SHIFT EAST AND DECREASE. WINDS EAST OF THE CASCADES WILL
INCREASE LATE THIS AFTERNOON AND CONTINUE INTO LATE THIS EVENING
AND WILL BE STRONGEST NEAR SUMMER LAKE. EVEN THEN WERE ONLY
EXPECTING ADVISORY CRITERIA BECAUSE PRECIPITATION SHOULD HELP TO
KEEP WIND SPEEDS IN CHECK.

WEAK RIDGING WILL BUILD INTO THE AREA THURSDAY THROUGH THURSDAY
NIGHT PROVIDING ANOTHER BREAK IN THE WEATHER. TEMPERATURES
THURSDAY AFTERNOON WILL BE MILDER, BUT THE MORNINGS COULD END UP
COOLER THAN WHAT'S FORECAST IF THERE'S LESS CLOUD COVER.
-PETRUCELLI

FRIDAY AND SATURDAY...THE MODELS ARE IN A LITTLE BETTER AGREEMENT
TODAY REGARDING A FRONT MOVING THROUGH OUR AREA LATE THIS WEEK
AND EARLY IN THE WEEKEND. WHILE THERE IS STILL SOME DISAGREEMENT
CONCERNING THE STRENGTH OF AND AMOUNT OF MOISTURE ASSOCIATED WITH
THE FRONT, IT LOOKS LIKE WEST SIDE AREAS STAND A GOOD CHANCE OF
GETTING SOME RAIN, SO POPS WERE RAISED. THE MAIN STICKING POINT
REMAINS HOW MUCH PRECIPITATION WILL COME WITH THE FRONT. THE GFS
IS STILL THE WETTEST AND THE ECMWF THE DRIEST, BUT THE GEM IS NOW
STARTING TO LOOK A LITTLE WETTER. QPF WAS ALSO RAISED IN THE USUAL
SPOTS (COAST AND COASTAL MOUNTAINS), BUT KEPT RELATIVELY LOW
ELSEWHERE. WINDS, ESPECIALLY OVER THE WATERS, COULD BE AN ISSUE
WITH THIS FRONT, AND THOSE WERE ALSO INCREASED. SNOW LEVELS LOOK
FAIRLY HIGH, SO SNOW SHOULD NOT BE MUCH OF AN IMPACT EXCEPT
PERHAPS AT THE CRATER AND DIAMOND LAKE AREA. -WRIGHT

SUNDAY INTO NEXT THURSDAY...BOTH EC AND GFS SHOW A REX BLOCK
FORMING OVER THE WEST COAST/ JUST WEST OF CALIFORNIA AND BAJA
CALIFORNIA. THIS WILL KEEP CONDITIONS DRY IN THE MEDFORD CWA EARLY
NEXT WEEK, LIKELY THROUGH NEXT WEDNESDAY. A STRONG UPPER RIDGE
WOULD SEEM LIKE AN EASY FORECAST, BUT THIS ONE HAS HIGH BUST
POTENTIAL, ESPECIALLY IN THE VALLEYS. THIS KIND OF PATTERN IS
NOTORIOUS FOR PRODUCING VALLEY FOG UNDER LOW LEVEL INVERSIONS, BUT
WE ARE A LITTLE PAST THE PEAK FOG SEASON. IT IS ALSO COMPLICATED
BY OFFSHORE FLOW ON MONDAY, WHICH WILL SERVE TO DRY OUT THE
AIRMASS AND MAY LIMIT FOG DEVELOPMENT. THE HIGH TEMPERATURES IN
MANY VALLEY LOCATIONS COULD LITERALLY BE 25-30 DEGREES DIFFERENT
MONDAY AND TUESDAY DEPENDING ON WHETHER FOG FORMS AND/OR BREAKS
DURING THE DAY OR NOT. FOR NOW, WE'LL TAKE THE MIDDLE ROAD AND
KEEP NIGHT TIME FOG IN AND BREAK IT OUT DURING THE DAY WITH MILD
HIGH TEMPERATURES. BUT KEEP IN MIND THAT IF THIS CHANGES, IT WILL
CHANGE TO THE COOLER, FOGGIER SIDE. THE FORECAST FOR THE MOUNTAINS
IS MUCH MORE STRAIGHTFORWARD: IT WILL BE SUNNY AND UNSEASONABLY
WARM EARLY NEXT WEEK, AND CONFIDENCE IN THAT IS HIGH. WPC GUIDANCE
FAVORED THE GFS FOR THE EXTENDED...AND ACCORDING TO THE LAST TWO
RUNS OF THE GFS, THE RIDGE WILL PERSIST OVER US UNTIL NEXT
THURSDAY OR FRIDAY. -MSC

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY UNTIL 4 PM PST THURSDAY FOR ORZ021-022.
     WIND ADVISORY UNTIL 10 PM PST THIS EVENING FOR ORZ031.

CA...WIND ADVISORY UNTIL 10 PM PST THIS EVENING FOR CAZ085.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
     FROM 10 AM THURSDAY TO 10 AM PST FRIDAY FOR PZZ350-356-370-376.
     HAZARDOUS SEAS WARNING UNTIL 10 AM PST THURSDAY FOR
     PZZ350-356-370-376.
     GALE WATCH FROM FRIDAY MORNING THROUGH FRIDAY EVENING FOR
     PZZ370-376.

MAS/MAP/TRW/MSC/BTL