Weather Service Report


843 
FXAK67 PAJK 252347
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
347 PM AKDT FRI JUL 25 2014

.SHORT TERM...THIS SHIFT RELIED LARGELY ON CONCEPTS AND PRIOR
EXPERIENCES...WITH SOME HELP FROM HOW WINDS RESPONDED TO THE
FRONTAL PASSAGE MOVING NORTH ACROSS THE SOUTHERN HALF OF THE
PANHANDLE.  

 LET US BEGIN WITH WHAT WE KNOW. RAIN. WHETHER IT FALLS AT TIMES
IN BURSTS LIKE SHOWERS OWING TO SOME VERTICAL
ACCELERATIONS/INSTABILITY IN LAYERS ALOFT OR WHETHER IT FALLS
MORE STEADILY AT TIMES...AFTER ATTEMPTING TO ANALYZE SUBTLE
ATMOSPHERIC REGIMES AND FAILING, DECIDED TO DESCRIBE THINGS HOW
IT IS...RAIN FALLING IN PERIODS. DID BRIEFLY COORDINATE WITH RFC
BASED ON RAINFALL TOTALS, AND SEE NO THREATS OF ANY RISES EVEN TO
ACTION IN THE SHORT-TERM. BUT IT WILL BE WET.  

 THE LARGEST TIME SPENT WAS FOR WINDS. TRIED TO USE THE 850 NAM
WINDS FOR TIMING ISSUES IN REGARDS TO JETS THAT MAY SUPPORT
SURFACE LEVEL BURSTS. ARRIVED AT MORE SMALL CRAFT ESPECIALLY OVER
THE CENTRAL PANHANDLE...AS SOUTHERN PANHANDLE WAS ALREADY
COVERED. STIKINE VESSEL CALLED OUR ATTENTION EARLY ON THAT WINDS
WERE GOING TO BLOW STRONGER THAN FORECAST TODAY AS CLARENCE
STRAIT WAS ALREADY BLOWING SUSTAINED AT 30 KT. A QUICK MORNING
UPDATE TO BOOST WINDS FOR THE DAY COUPLED WITH GUSTS EXCEEDING
50 KT AT LINCOLN ROCK LEAD US TO POST A GALE WARNING FOR THIS
EVENING. NAM INTERESTINGLY ADVERTISING ANOTHER 850 MB JET MOVING
ACROSS SATURDAY AFTERNOON. WHILE BOOSTED CLARENCE TO 30 HERE...WE
MAY NEED TO SERIOUSLY THINK OF THE POSSIBILITY OF ANOTHER GALE.
STEPHENS PASSAGE IS ANOTHER AREA OF ANTICIPATION. IN THE END DID
NOT GO SMALL CRAFT BUT INCLUDED SOME GUSTY LANGUAGE FOR THIS
EVENING AS THE FRONT PROBABLY STARTS TO GO ALOFT SOMEWHERE
BETWEEN FIVE FINGERS AND JUNEAU.  

 COOLED TEMPS JUST A TAD AGAIN TO LOWER INTO THE 50S OVER THE FAR
NORTH...FOR RAIN COOLED AIR. LOW 50S LOOKED GOOD FOR LOWS.  

 USED NAM AND A LITTLE ECMWF FOR UPDATES. FORECAST CONFIDENCE
EXCELLENT ON PERIODS OF RAIN...SKETCHY ON WIND GUSTS REGARDING
TIMING/SPATIAL SPREAD.  

 .LONG TERM...VERY GOOD MODEL AGREEMENT IN THE UPPER LEVELS WITH
A LOW OVER THE GULF THAT REMAINS STATIONARY AND WEDGED IN BETWEEN
UPPER LEVEL RIDGES TO THE WEST AND EAST. ECMWF BREAKS DOWN THIS
PATTERN TOWARDS THE END OF THE MODEL RUN AND ALLOWING A MORE
PROGRESSIVE PATTERN TO DEVELOP. GFS NOT SHOWING THIS YET, BUT
THERE ARE SEVERAL DAYS YET TO WATCH FOR THIS POSSIBLE DEVELOPMENT.
UPDATED MONDAY MORNING THROUGH WEDNESDAY MORNING WITH A
NAM/GFS/ECMWF BLEND TO BETTER DEPICT THE LOCATION OF THE NEXT WEAK
LOW TO DEVELOP AND ROTATE CYCLONICALLY AROUND THE GULF. CYCLONIC OFFSHORE
WINDS 20 KTS OR LESS THROUGHOUT THE ENTIRE EXTENDED RANGE FORECAST
PERIOD. HAVE A DIMINISHING SOUTHEASTERLY SMALL CRAFT IN CLARENCE
STRAIT AT THE VERY BEGINNING OF THE EXTENDED RANGE FORECAST PERIOD
SATURDAY EVENING. 

CURRENTLY THERE ARE PERIODS OF MODERATE TO HEAVY PRECIPITATION IN
THE VARIOUS MODELS THAT OCCUR OVER THE COURSE OF THE NEXT WEEK,
BUT NO STORM TOTALS THAT ARE EXPECTED TO CAUSE ANY RIVERS
TO GET INTO FLOOD STAGE. ONE THING TO WATCH OUT FOR WILL BE
WHETHER A FORMER TYPHOON GETS BLOCKED AND SHUNTED TO THE NORTH
WELL WEST OF OUR AREA OR PASSES FAR ENOUGH SOUTH TO BE ABLE TO
TRACK EAST AND THEN GET CAUGHT UP IN THE UPPER LEVEL LOW
CIRCULATION OVER THE GULF. WERE THAT TO HAPPEN, THERE COULD BE
WIDE SPREAD HEAVY PRECIPITATION OVER THE PANHANDLE. WILL KEEP A
CLOSE WATCH ON THIS. UPDATES TO POP MADE FROM SUNDAY NIGHT
THROUGH MONDAY NIGHT USING A BLEND OF ECMWF, GFS, AND GEM. QPF
PRIMARILY FROM RFC WITH SOME ECMWF. 

 TEMPERATURE GUIDANCE CONTINUES TO FORECAST TOO MUCH DIURNAL
VARIATION - TOO WARM DURING THE DAY, AND TOO COOL AT NIGHT -
BASED ON EXPECTED CLOUD COVER AND LOW LEVEL AIRMASS TEMPERATURES.
EXISTING VALUES LOOKED GOOD, SO DID NOT MAKE AND CHANGES TO TEMPS.

FORECAST CONFIDENCE IN CONTINUED WET WEATHER BASED ON A STATIONARY
UPPER LOW OVER THE GULF IS ABOVE AVERAGE. CONFIDENCE IN TIMING OF
BANDS OF HEAVIER PRECIPITATION BELOW AVERAGE DUE TO MODEL
DIFFERENCES IN TRACKING WEAK TROUGHS OVER THE FORECAST AREA. 

 &&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ036. 
         SMALL CRAFT ADVISORY FOR PKZ022-032>035-041>043. 


$$

JWA/FRITSCH




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