High Wind Watch 5, NWS Medford, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
920 AM PDT FRI SEP 27 2013

.DISCUSSION...NO UPDATE IS NECESSARY THIS MORNING. IT WAS THE
COLDEST NIGHT THUS FAR FOR MANY AREAS WITH TEMPERATURES DOWN INTO
THE UPPER 30S HERE AT THE MEDFORD AIRPORT. SAW EVIDENCE OF FROST
IN SOME LOCATIONS ON THE DRIVE IN THIS MORNING.

THE WEATHER PATTERN IS ABOUT TO CHANGE THOUGH...AND CHANGE
ABRUPTLY THIS WEEKEND AS A STRONG PACIFIC JET CARRIES A STRONG
EARLY FALL STORM SYSTEM IN OUR DIRECTION. THIS STORM IS ALREADY
HAVING ITS EFFECTS DOWNSTREAM AS A WEAK FRONTAL SYSTEM OFFSHORE
WILL GET A PUSH EASTWARD AND MOVE INTO NORTHERN AREAS THIS
AFTERNOON AND TONIGHT WITH SOME LIGHT RAIN. BUT THIS WILL PALE IN
COMPARISON FOR WHAT'S TO COME THIS WEEKEND. A SERIES OF POTENT
FRONTS WILL HAVE ENERGY/MOISTURE ADDED FROM WHAT WAS ONCE TYPHOON
PABUK. THE FIRST WILL ARRIVE AT THE COAST SATURDAY, THEN MOVE
INLAND TO THE CASCADES SATURDAY NIGHT, THEN ANOTHER IMPULSE WILL
MOVE IN BEHIND IT SUNDAY INTO SUNDAY EVENING WITH ANOTHER SHOT OF
HEAVY RAIN/WIND. THIS WILL BE MORE LIKE SOMETHING WE WOULD SEE
DURING THE MIDDLE OF THE WET SEASON WITH VERY HEAVY RAIN AT THE
COAST...SPREADING INLAND TO THE CASCADES AND ALSO STRONG WINDS AT
THE COAST, SHASTA VALLEY AND THE EAST SIDE. WE WON'T HAVE TO WORRY
ABOUT SNOW WITH THIS SYSTEM THOUGH, EXCEPT AT THE HIGHEST
PEAKS...SINCE SNOW LEVELS WILL BE VERY HIGH UP ABOVE 8500 FEET.
COORDINATION WITH THE NWRFC THIS MORNING INDICATES WE WILL SEE
SIGNIFICANT RIVER RISES (5-6 FEET) AND MODERATE TO HIGH FLOWS OF
AREA STREAMS/CREEKS/DRAINAGES ALONG THE COAST/JUST INLAND. BUT
MAIN STEM RIVERS SHOULD REMAIN IN THEIR BANKS SINCE THEY ARE
STARTING OUT LOW AND THERE REALLY ISN'T MUCH/IF ANY SNOW TO MELT
TO RESULT IN ADDED RUNOFF. THERE IS THE POTENTIAL THOUGH FOR
DEBRIS FLOWS AND ROCK SLIDES THROUGH SOME OF STEEPER TERRAIN ALONG
THE COAST AND AREAS BURNED FROM THE WILDFIRES THIS SUMMER. BY THE
TIME THIS SYSTEM EXITS THE REGION, THIS COULD BE A RECORD
PRECIPITATION EVENT FOR SOME AREAS.

FOCUS FOR THIS AFTERNOON WILL BE ON THE SHORT TERM RAINFALL AND
ALSO POTENTIALLY UPGRADING THE WIND WATCHES WE CURRENTLY HAVE
OUT. SPILDE

&&

.AVIATION...BASED ON THE 27/12Z TAF CYCLE.

AREAS OF FOG AND LOW IFR CIGS WILL CONTINUE ALONG THE COAST AND INTO
THE UMPQUA WITH ISOLATED IFR CIGS/FOG EXPECTED IN OTHER WESTERN
VALLEYS AND IN THE KLAMATH BASIN.  ALSO AREAS OF MVFR CIGS ARE
PRESENT IN EASTERN LAKE COUNTY. IFR/MVFR CIGS ARE EXPECTED TO CLEAR
TO VFR AROUND 16Z THIS MORNING. THEN VFR CONDITIONS PERSIST THROUGH
THIS AFTERNOON AND EVENING FOR MOST INLAND AREAS. HOWEVER LOW CLOUDS
AND LIGHT RAIN WILL SPREAD INTO THE COAST AND THE UMPQUA BASIN WITH
AREAS OF MVFR CIGS DEVELOPING BETWEEN 22-02Z AND BECOMING WIDESPREAD
ALONG THE COAST AND IN UMPQUA DURING THE EVENING. CC

&&

.PREV DISCUSSION... /ISSUED 444 AM PDT FRI SEP 27 2013/

DISCUSSION...
IN SUMMARY, TRANQUIL AUTUMN WEATHER TODAY WILL TURN UNUSUALLY
STORMY DURING THE COURSE OF THIS WEEKEND, WITH EXCEPTIONALLY HIGH
RAINFALL AMOUNTS EXPECTED SATURDAY NIGHT THROUGH EARLY MONDAY PER
SEPTEMBER STANDARDS. RAINFALL AMOUNTS DURING THIS TIME PERIOD MAY
MEET OR EXCEED WHAT WE HAVE ALREADY SEEN THUS FAR THIS MONTH IN
MOST AREAS FROM THE UPPER KLAMATH BASIN AND CASCADES WESTWARD. THE
VALUES OBSERVED THUS FAR THIS MONTH ARE ALREADY THE HIGHEST VALUES
SEEN FOR THE MONTH OF SEPTEMBER SINCE THE LATTER HALF OF THE
1980S. THUS, THE POTENTIAL FOR MODERATE TO HIGH FLOWS IN AREA
DRAINAGE DITCHES, STREAMS, CREEKS, AND RIVERS IS HIGH. AT THE
CURRENT TIME NO MAIN STEM RIVER FLOODING IS EXPECTED.

THAT BEING SAID, COOL TEMPERATURES THIS MORNING ARE GETTING
COLDER, WITH THE FIRST FROST OF THE SEASON DEVELOPING IN SOME
AREAS. TEMPERATURES ARE NOW IN THE MID-30S IN THE SHASTA VALLEY TO
MOUNT SHASTA CITY AND IN PORTIONS OF THE ILLINOIS VALLEY. IN THE
BEAR CREEK PORTION OF THE ROGUE VALLEY AN AREA OF CLOUD COVER
SOUTHEAST OF MEDFORD IS KEEPING TEMPERATURES MOSTLY STEADY IN THE
UPPER 30S TO LOWER 40S. CURRENT FORECAST LOWS LOOK PRETTY MUCH
RIGHT ON TRACK, SO SUSPECT WE WILL AT LEAST SEE SOME PATCHY FROST
FOR OUTLYING AREAS OF THE ROGUE VALLEY THIS MORNING.

WHAT A DIFFERENCE 3-4 DAYS HAVE MADE IN THE MODEL GUIDANCE! THE
REMNANTS OF WESTERN PACIFIC TYPHOON PABUK ARE RAPIDLY SPREADING
FROM NORTHERN JAPAN AND KAMCHATKA ACROSS THE BERING SEA, ALEUTIANS
AND OVER THE GULF OF ALASKA THIS MORNING. A FRONTAL BOUNDARY
CURRENTLY ALONG THE WASHINGTON COAST IS ALREADY GETTING A FORWARD
BOOST FROM THE JET ENERGY ASSOCIATED WITH THE REMNANTS OF THE
TYPHOON. THE GFS40 MODEL IS THE FASTEST AND FURTHEST SOUTH WITH
THIS FRONTAL BOUNDARY, PUSHING IT INTO MAINLY NORTHERN PORTIONS OF
THE FORECAST AREA TODAY. I HAVE INCREASED PRECIPITATION
PROBABILITIES ACROSS NORTHERN AND WESTERN PORTIONS OF THE AREA
FOR TODAY, AS THIS SOLUTION SEEMS REASONABLE AND IS BACKED, IN
PART, BY OTHER GUIDANCE.

TONIGHT THROUGH SATURDAY THE CORE OF AN ATMOSPHERIC RIVER EVENT
WILL TAKE AIM ON VANCOUVER ISLAND AND THEN WILL LIKELY SPREAD
SOUTHWARD ALONG THE COAST. MAINLY EXPECT LIGHT OVERRUNNING ALONG
THE COAST AND UMPQUA BASIN DURING THE DAY. HOWEVER, SATURDAY NIGHT
INTO SUNDAY RAINFALL AMOUNTS ARE LIKELY TO RAPIDLY INCREASE OVER
SOUTHWESTERN OREGON. EXPECT 6 HOUR AMOUNTS ALONG AND NEAR THE
COAST AND COAST RANGE TO REACH 1 TO 3 INCHES FOR ABOUT A 24 HOUR
PERIOD. THIS MEANS STORM TOTALS THERE ARE LIKELY TO BE IN THE 4 TO
12 INCH RANGE. OBVIOUSLY, THIS IS A LARGE SPREAD, BUT REALISTIC
FOR THIS TYPE OF ATMOSPHERIC RIVER EVENT. FUTURE SHIFTS WILL
NEED TO HONE IN ON THE EXACT LOCATION AND DURATION OF THE HEAVIEST
RAIN WITH THIS SYSTEM, AS TOTALS SUCH AS THESE COULD PUSH SOME
WATERWAYS CLOSE TO BANK FULL. EXPECT COORDINATION WITH THE RIVER
FORECAST CENTER TO BE NECESSARY TODAY. NAEFS DATA SUGGESTS
PRECIPITABLE WATER VALUES WITH THIS EVENT TO BE AROUND 2.5
STANDARD DEVIATIONS ABOVE NORMAL WITH A RETURN INTERVAL OF 5 TO 10
YEARS. THE GEFS, ON THE OTHER HAND, PUTS THE PRECIPITABLE WATER
RETURN INTERVAL FOR THIS EVENT FOR OUR AREA AT MORE LIKE ONCE
EVERY 30 YEARS FOR THREE CONSECUTIVE 3 HOUR PERIODS! SAID ANOTHER
WAY, THE MEX AND ECX BULLETINS FOR MEDFORD ARE INDICATING STORM
TOTAL AMOUNTS IN THE 1 TO 2 INCH RANGE, WHICH ALONE WOULD SURPASS
SEPTEMBER TOTAL MONTHLY RAINFALL BACK TO THE LATE 1980S.

ANOTHER NOTABLE ANOMALY THAT SHOWS UP ON THE NAEFS IS 700MB WINDS
ON THE EAST SIDE REACHING 4 TO 5 STANDARD DEVIATIONS ABOVE NORMAL
CENTERED IN THE 18Z SUNDAY THROUGH 06Z MONDAY TIME FRAME. IN SOME
AREAS, THOSE SORT OF VALUES HAVE NOT BEEN OBSERVED AS HIGH AS THEY
ARE EXPECTED TO BE IN THE PERIOD OF COMPARISON. DECIDED TO ISSUE
SOME WIND HEADLINES THIS MORNING WITH MAXIMUM LEAD TIME, AS
EXPECTATIONS ARE THAT THESE WILL LIKELY NEED TO BE EXPANDED TO
OTHER AREAS AND THAT WORK LOAD PRIOR TO THE SATURDAY NIGHT THROUGH
MONDAY PERIOD WILL BE HIGH.

IT SHOULD BE NOTED THAT, WHILE ALL MODELS INDICATE A MAJOR
PRECIPITATION EVENT FOR THE COAST, THE WETTER GFS40 AND ECMWF
MODELS HAVE BEEN FAVORED FOR THE FORECAST PERIOD. THIS IS BECAUSE,
FOR EVENTS SUCH AS THESE, THE HIGHER END VALUES TEND TO HAVE A
HIGHER CHANCE OF VERIFYING. THAT BEING SAID, THE NAM12 DOES SHOW
LESSER AMOUNTS AS THE ATMOSPHERIC RIVER OF MOISTURE INTO OUR
AREA IS FORECAST BY IT TO BE HERE FOR SHORTER DURATION AND WITH A
BIT LESS INTENSITY.

DURING THE DAY ON MONDAY A COLD FRONT WILL PUSH THROUGH SENDING
THE DEEP SUBTROPICAL MOISTURE SOUTHEASTWARD, SNOW LEVELS
DOWNWARD, AND PUTTING US UNDER A SHOWERY NORTHWEST FLOW. THUS, A
BIT OF A REPRIEVE FROM OUR SEPTEMBER PRECIPITATION ONSLAUGHT IS
EXPECTED. BTL

AVIATION...
BASED ON THE 27/06Z TAF CYCLE.

WE MAY SEE SOME STRATUS WITH MVFR TO IFR CIGS DEVELOP AT THE COAST
AND IN THE UMPQUA LATE TONIGHT. PATCHY STRATUS AND FOG IS POSSIBLE
OVER INLAND VALLEYS AS WELL, BUT LESS LIKELY. ANY STRATUS THAT DOES
FORM WILL CLEAR OUT BY MID MORNING FRIDAY, LEAVING VFR. WE WILL SEE
INCREASING MID AND HIGH CLOUD OVER THE NORTH COAST THROUGH THE DAY
FRIDAY AND PERHAPS EVEN A LITTLE LIGHT RAIN TOWARD DAY'S END AS A
WARM FRONT APPROACHES. /FB

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...WIND ADVISORY FROM 5 PM SATURDAY TO 11 PM PDT SUNDAY FOR
     ORZ030-031.
     FROST ADVISORY UNTIL 8 AM PDT THIS MORNING FOR ORZ024-026.
     FREEZE WARNING UNTIL 9 AM PDT THIS MORNING FOR ORZ029.

CA...FREEZE WARNING UNTIL 9 AM PDT THIS MORNING FOR CAZ084.
     FROST ADVISORY UNTIL 9 AM PDT THIS MORNING FOR CAZ081-082.
     FREEZE WARNING UNTIL 9 AM PDT THIS MORNING FOR CAZ081-082.
     WIND ADVISORY FROM 5 PM SATURDAY TO 11 PM PDT SUNDAY FOR CAZ081.

PACIFIC COASTAL WATERS...GALE WATCH FROM SATURDAY MORNING THROUGH SUNDAY
     EVENING FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR WINDS FROM 2 AM TO 11 AM PDT SATURDAY
     FOR PZZ350-370.
     HAZARDOUS SEAS WATCH FROM SATURDAY MORNING THROUGH MONDAY
     AFTERNOON FOR PZZ350-370.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 AM TO 11 AM PDT
     SATURDAY FOR PZZ350-370.
     GALE WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY EVENING FOR
     PZZ356-376.
     SMALL CRAFT ADVISORY FOR WINDS FROM 8 AM TO 2 PM PDT SATURDAY
     FOR PZZ356-376.
     HAZARDOUS SEAS WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY
     AFTERNOON FOR PZZ356-376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 AM TO 2 PM PDT
     SATURDAY FOR PZZ356-376.

MAS/BTL/CMC