Small Craft Advisory 30, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
250 PM PST THU MAR 3 2016

.DISCUSSION...

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...TODAY AND TOMORROW
MARK THE CALM BEFORE THE STORM. WARM AND PLEASANT WEATHER WILL
CONTINUE THROUGH AT LEAST THE FIRST HALF OF FRIDAY, WITH HIGH
PRESSURE IN CONTROL AND LITTLE IN THE WAY OF EXCITING WEATHER.
HOWEVER, BEGINNING FRIDAY NIGHT, TWO STRONG STORMS WILL BRING
HEAVY RAIN AND STRONG WINDS TO THE FORECAST AREA. WHILE THERE WILL
BE A BREAK BETWEEN THE TWO FRONTS, IT WILL BE VERY BRIEF, THUS FOR
THE SAKE OF SIMPLICITY AND EASE OF COMMUNICATION, THE TWO HAVE
BEEN COMBINED INTO ONE EVENT FOR THE PURPOSES OF OUR WATCHES AND
OTHER HEADLINES.

MODELS HAVE BEEN IN GOOD AGREEMENT WITH THE OVERALL PATTERN AND
TRENDS, BUT THERE HAS BEEN SOME DISAGREEMENT REGARDING THE
LOCATION AND STRENGTH OF THE TWO SYSTEMS' ASSOCIATED SURFACE LOWS.
DIFFERENCES IN THESE FACTORS WILL MAKE A BIG IMPACT ON THE
RESULTING WIND STRENGTHS, ESPECIALLY ALONG THE COAST. GIVEN
SIMILAR SYSTEMS IN THE PAST, AND THE OVERALL CONSENSUS OF THE
MODELS, HAVE OPTED TO ISSUE A HIGH WIND WATCH FOR MUCH OF THE
REGION, WITH A FOCUS ON THE COAST, THE HIGH TERRAIN OF THE
CASCADES AND SISKIYOUS, THE EAST SIDE, AND THE SHASTA VALLEY.
WHILE CONFIDENCE IS MODERATE IN DETAIL, THERE IS HIGH CONFIDENCE
THAT ONE OR BOTH OF THESE SYSTEMS WILL HAVE A DEEPENING LOW JUST
OFFSHORE, EITHER OF WHICH WOULD RESULT IN VERY STRONG WINDS ACROSS
THE AREA.

THERE IS SIGNIFICANT MOISTURE INFLOW INTO THESE SYSTEMS AS WELL,
AS SHOWN BY MODEL VAPOR TRANSPORT IMAGERY. HOWEVER, THESE ARE
FAST MOVING FRONTS. IN FACT, THE TRAILING EDGE OF THE FIRST WILL
BARELY BE OUT OF THE EAST SIDE BEFORE THE NEXT BEGINS MOVING
ONSHORE. THIS SHOULD KEEP PRECIPITATION AMOUNTS ON THE LOWER END,
SO WHILE TOTAL AMOUNTS HAVE BEEN BUMPED UP FROM THE PREVIOUS
FORECAST, EXCEPTIONAL AMOUNTS ARE NOT EXPECTED. CREEKS AND
STREAMS MAY RISE QUICKLY, AND PONDING IS LIKELY ON AREA ROADS,
BUT NO OTHER HYDROLOGIC CONCERNS ARE ON THE TABLE AT THIS TIME.

WARMER THAN NORMAL TEMPERATURES WILL KEEP SNOW LEVELS HIGH INTO
FRIDAY, BUT A MUCH COLDER AIR MASS WILL ENTER THE REGION SATURDAY
NIGHT, BRINGING MORE SEASONAL TEMPERATURES BACK TO THE FORECAST
AREA. SNOW LEVELS SHOULD DROP TO 3000 TO 3500 FEET ON THE BACK
END OF THE SECOND FRONT, AND THIS WILL ALLOW FOR SEVERAL INCHES OF
SNOW ON AREA PASSES SUNDAY MORNING INTO THE AFTERNOON. SOME
WINTER HEADLINES MAY BE NEEDED AT THAT TIME, BUT CONFIDENCE
REMAINS LOW AT THIS TIME RANGE.

ANOTHER NEW FEATURE OF CONCERN WILL BE YET ANOTHER WAVE SUNDAY
EVENING, WHICH PUSHES A CLOSED SURFACE LOW RIGHT INTO THE SOUTHERN
OREGON COAST. THIS IS A NEW FEATURE IN THE MODELS, AND PLACEMENT
AND STRENGTH HAVE CHANGED IN THE PAST TWO RUNS. DUE TO LOW CONFIDENCE,
HAVE NOT ADDED IN SOME OF THE STRONGER EFFECTS POSSIBLE WITH SUCH
A SYSTEM, BUT WILL KEEP A WARY EYE ON IT IN THE COMING DAYS.

HIGH PRESSURE FINALLY RETURNS MONDAY, GIVING US A MUCH NEEDED
BREAK, JUST IN TIME FOR ACTIVE WEATHER TO RETURN IN THE EXTENDED
TERM. -BPN

.LONG-TERM...TUESDAY THROUGH THURSDAY NIGHT...TUESDAY STARTS WITH
RIDGING OVERHEAD AND SOME DRY WEATHER LIKELY. BOTH THE GFS AND EC
HAVE PUSHED BACK THE ARRIVAL OF THE NEXT UPPER TROUGH BY 6 TO 12
HOURS. THUS...WIND IMPACTS WITH THE APPROACHING FRONT IN THE MIDDLE
OF THE WEEK HAVE BEEN PUSHED BACK 6 TO 12 HOURS BASED ON THESE MODEL
TRENDS.

BY LATE TUESDAY...SOME SIGNIFICANT DIFFERENCES BETWEEN THE EC AND
GFS BEGIN TO SHOW...WITH THE EC FLATTENING THE RIDGE WHILE THE GFS
MAINTAINS RIDGING AND MOSTLY DRY CONDITIONS THROUGH WEDNESDAY NIGHT.
ESSENTIALLY...THE EC IS WETTER AND COLDER LATE TUESDAY INTO THURSDAY
WITH AN ATMOSPHERIC RIVER (AR) TRAINED OVER THE FORECAST AREA.
EXAMINING THE GEFS MEMBERS AND THE SPREAD BETWEEN THEM IN TERMS OF
H5 HEIGHT...THERE IS HIGH UNCERTAINTY IN THE PLACEMENT OF THE AR AND
OUR PRECIPITATION CHANCES REPRESENT A CONSENSUS AMONGST THE EC AND
GFS.

THIS UNCERTAINTY HAS SIGNIFICANT IMPLICATIONS ON SNOWPACK IN THE
MIDDLE OF THE WEEK. THE EC SUGGESTS SIGNIFICANT SNOW ABOVE 5000 FEET
WHILE THE GFS WOULD SUGGEST GENERALLY DRY CONDITIONS OVER MOST OF
THE MOUNTAINS. AGAIN...WILL TRY TO HONE IN ON A SOLUTION AS ENSEMBLE
SPREAD HOPEFULLY DECREASES IN THE NEXT FEW MODEL RUNS. -SK

&&

.AVIATION...FOR THE 03/18Z TAF CYCLE...THERE IS ISOLATED IFR IN THE
UMPQUA VALLEY THIS MORNING THAT WILL LINGER INTO MID-MORNING AND MAY
FORM AGAIN EARLY FRIDAY MORNING. OTHERWISE...IT WILL REMAIN MAINLY
VFR ACROSS THE AREA INTO FRIDAY MORNING. THE OTHER EXCEPTION WILL BE
LOCAL BRIEF MVFR CEILINGS ASSOCIATED WITH A FEW LIGHT SHOWERS TODAY
OVER NORTHERN CALIFORNIA AND EAST OF THE CASCADES. SK

&&

.MARINE...UPDATED 245 PM PST WED 03 MAR 2016...A FRONTAL SYSTEM WILL
SET UP ALONG THE COAST FRIDAY AND REMAIN THERE THROUGH AT LEAST
SUNDAY NIGHT. A SERIES OF LOW PRESSURE SYSTEMS WILL RIDE ALONG THIS
FRONT AND BRING PERIODS OF GALE TO STORM FORCE WINDS AND EXTREMELY
STEEP SEAS TO THE WATERS DURING THE PERIOD. THE BASIC SETUP IS
CERTAIN TO OCCUR, BUT CONFIDENCE IS LOWER IN THE DETAILS OF EACH
PARTICULAR LOW PRESSURE SYSTEM.

CURRENTLY, LOW PRESSURE SYSTEMS ARE EXPECTED TO PASS FROM SOUTH TO
NORTH FRIDAY AND SATURDAY EVENINGS, AND A THIRD MAY MOVE DIRECTLY
INTO THE COAST FROM THE WEST ON SUNDAY. ALL OF THESE LOWS WILL BE
STRENGTHENING TO SOME DEGREE AS THEY PASS. GALES ARE LIKELY WITH
EACH OF THESE SYSTEMS, BUT STORM FORCE WINDS ARE ALSO POSSIBLE WITH
EACH SYSTEM. A BACKGROUND WEST TO SOUTHWEST SWELL OF AROUND 15 FEET
IS LIKELY TO BE PRESENT FRIDAY THROUGH THE WEEKEND, AND THIS WILL BE
OBVIOUSLY AUGMENTED TO A LARGE DEGREE BY WIND WAVES AS EACH SYSTEM
PASSES. THUS, SEAS WILL BE VERY HIGH NO MATTER WHAT PATH THESE
SYSTEMS TAKE.

CONDITIONS OVER THE WATERS FROM FRIDAY THROUGH SUNDAY NIGHT WILL BE
VERY DANGEROUS AT TIMES. THERE WILL BE TIMES WHEN WINDS EASE, BUT
CONDITIONS WILL DETERIORATE RAPIDLY AS THE NEXT SYSTEM ARRIVES. IT
WILL BE EASY TO GET CAUGHT OFF GUARD, SO MARINERS ARE URGED TO PLAN
ON STAYING IN PORT THIS WEEKEND. STAY TUNED FOR FURTHER UPDATES ON
THIS COMPLEX AND RAPIDLY EVOLVING WEATHER PATTERN. -WRIGHT

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR
     ORZ029>031.
     HIGH WIND WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY EVENING
     FOR ORZ022.
     HIGH WIND WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY EVENING
     FOR ORZ021.
     HIGH WIND WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY EVENING
     FOR ORZ023>028.

CA...HIGH WIND WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR
     CAZ084-085.
     HIGH WIND WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY EVENING
     FOR CAZ081.

PACIFIC COASTAL WATERS...STORM WATCH FROM FRIDAY AFTERNOON THROUGH LATE SUNDAY NIGHT FOR
     PZZ350-356-370-376.
     SMALL CRAFT ADVISORY UNTIL 4 AM PST FRIDAY FOR PZZ350-356.
     GALE WARNING FROM 1 PM FRIDAY TO 4 AM PST SATURDAY FOR
     PZZ356-370-376.
     HAZARDOUS SEAS WARNING FROM 4 AM TO 1 PM PST FRIDAY FOR
     PZZ350-356-370-376.

BPN/NSK/TRW