Flood in Alaska, July 4, 2014

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
528 AM AKDT FRI JUL 4 2014

.SHORT TERM...VERTICALLY STACKED LOW OVER THE FAR SE GULF WILL
WEAKEN AND DRIFT WWD TONIGHT AS ANOTHER LOW MOVES UP FROM THE S.
MID-LEVEL WAVY BAROCLINIC BAND EXTENDS FROM THE SERN YUKON INTO
NRN SE PUBLIC...AND WILL REMAIN THERE TODAY BEFORE IT BEGINS TO SHIFT
WNW TOWARD THE NE GULF COAST LATE TONIGHT. MODEL PREFERENCE FOR
TODAY WAS A 00Z GEM/EC BLEND...BUT MODELS WERE ALL STRUGGLING
WITH  THE WAVY NATURE OF THE BAROCLINIC BAND. THE GEM AND EC HAD
BEST OVERALL HANDLE ON THIS FEATURE THOUGH.

 MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL AND AMOUNTS. THE
2 MAIN AREAS OF PRECIP ARE ASSOCIATED WITH THE BAROCLINIC BAND
OVER THE N AND NEAR THE VERTICALLY STACKED LOW OVER THE S. THE
NRN AREA SHOULD REMAIN WET INTO AT LEAST THE EVENING TIME FRAME
AS MULTIPLE MINOR MID-LEVEL SHORTWAVES RIDE SW ALONG THE
BAROCLINIC BAND. PRECIP WILL TRY TO SHIFT TO THE W LATE TONIGHT
AS BAND MOVES IN THAT DIRECTION...WITH HELP OF STRONGER SHORTWAVE
MOVING AROUND THE STACKED LOW TO THE S. MODEL TIMING ON THIS WWD
SHIFT VARIED  QUITE A BIT THOUGH ON THE 00Z MODEL RUNS...ALTHOUGH
THE GEM AND EC WERE FAIRLY CLOSE. UNTIL THIS WWD SHIFT
OCCURS...RAINFALL COULD BE LOCALLY MODERATE AT TIMES WITH
RAINFALL AMOUNTS WELL OVER 1 INCH LIKELY OVER THE FAR NRN
PANHANDLE THRU TONIGHT. THIS WILL CAUSE HYDRO CONCERNS THAT WILL
BE COVERED IN THE HYDRO SECTION OF THE AFD.

 OVER THE S...PRECIP WILL CONTINUE TO WRAP IN FROM THE SSE AROUND
THE STACKED LOW TODAY...BUT A DIMINISHING TREND SHOULD OCCUR
TONIGHT AS LOW WEAKENS AND DRIFTS WWD IN RESPONSE TO ANOTHER LOW
MOVING N TO JUST W OF HAIDA GWAII...AND FLOW TURNS MORE ELY.

 THE AREA IN BETWEEN...FROM N OF PAPG TO S OF PAJN...WILL SEE
SPOTTY PRECIP AT MOST. THIS WILL GENERALLY DIMINISH TONIGHT AS
OFFSHORE FLOW INCREASES.

 .HYDROLOGY...GIVEN THE RAINFALL RATES (NEAR/OVER 0.1 INCH PER
HOUR AT TIMES) AND EXPECTED CONTINUATION OF THESE RATES THRU MOST
OF TODAY INTO THIS EVENING OVER THE FAR N...RIVERS HAVE BEGUN
RISING QUICKLY AND THE TAIYA RIVER HAS REACHED MINOR FLOOD LEVEL
(16.5 FEET). THINK IT WILL CONTINUE RISING TO SOME DEGREE. CALLED
RFC ON-DUTY PERSON AND THEY ARE HEADING IN EARLY TO CHECK ON
THINGS. AFTER COORDINATING WITH THEM LATER THIS MORNING...WILL
LIKELY PUT OUT A FLOOD ADVY OR WARNING FOR THE TAIYA RIVER. WILL
NEED TO KEEP AN EYE ON SUICIDE BASIN AS WELL DUE TO THE EXTRA
WATER GOING INTO THE BASIN FROM RAINFALL. IT HAS REACHED 73 FEET.
MENDENHALL LAKE HAS GONE OVER THE 5 FOOT LEVEL THIS MORNING AND
WILL LIKELY CONTINUE RISING SLOWLY DUE TO THE RAIN.

&&

.LONG TERM...ELONGATED MID LEVEL LOW IN THE SOUTHEAST GULF WITH
SURFACE LOW MOVING UP FROM THE N PACIFIC FRO THE START OF THE
WEEKEND. THE MID LEVEL LOW WILL BEGIN TO RETROGRADE WESTWARD WITH
THE SURFACE LOW MOVING UP THE PANHANDLE COAST BEFORE PULLING OFF
TO THE WEST BY SUNDAY. OVER THE NORTHERN PANHANDLE THE CURRENT
WEATHER FRONT WILL MOVE WESTWARD. FOR NEXT WEEK STILL SOME
UNCERTAINTY WITH THE DETAILS OF THE NEXT SYSTEM. MODELS ARE IN
AGREEMENT WITH OVERALL SYNOPTIC PATTERN OF A MID LEVEL TROUGH MOVING
OVER THE AK GULF THEN FORMING A CLOSED LOW TRACKING TOWARDS THE
SOUTHEAST GULF LATE IN THE WEEK AS A RIDGE OF HIGH PRESSURE BUILDS
OVER THE WESTERN GULF. MODELS ARE NOT IN GOOD AGREEMENT WITH THE
SURFACE LOW POSITION AND STRENGTH.

PRECIP OVER THE NORTHERN PANHANDLE WILL DIMINISH AS THE WEATHER FRONT
EXITS TO THE WEST. FOR THE SOUTHERN PANHANDLE PRECIP RATES WILL
BEGIN TO INCREASE AS THE NEXT LOW MOVES UP FROM THE NORTH PACIFIC,
THEN DECREASE AS THE LOW MOVES WESTWARD AND WEAKENS. KEEPING JUST
CHANCE POPS LATER IN THE WEEK DUE TO THE MODEL SPREAD AND RUN TO
RUN INCONSISTENCIES.

THE LIGHT WINDS OVER THE SOUTHERN PANHANDLE WILL INCREASE WITH THE
NEXT ADVANCING LOW. FOR NOW KEEPING LAND WINDS IN THE 10 TO 20 MPH
RANGE WITH SMALL CRAFT WINDS DEVELOPING OVER CLARENCE STRAIT.
ECMWF AND GFS ARE MORE IN LINE WITH THE 850 MB WINDS NOW IN THE
40 TO 50 KT RANGE. WILL KEEP WATCH IF WINDS NEED TO BE INCREASED
WITH THIS DEVELOPING WAVE.

KEPT WITH A ECMWF/GEM BLEND THROUGH DAY 3 THEN USED THE INHERITED
WPC GRIDS TO DAY 8. GFS WAS IN FAIR AGREEMENT WITH THE ECMWF/GEM
THAN PREVIOUS RUNS WHILE NAM BECAME AND OUTLIER EARLY ON. CHANGES
WERE MINOR WITH PRESS AND WINDS LEFT MAINLY AS IS. NEW POP BLEND
HAD MORE OF A DRY SLOT OVER THE CENTRAL PANHANDLE ON SAT. FORECAST
CONFIDENCE IS AVERAGE THROUGH THE WEEKEND THEN DROPS BY THE START OF
NEXT WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

RWT/PRB