Small Craft Advisory 145, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
612 AM AKST TUE FEB 11 2014

.SHORT TERM...COMPLEX WINTER WEATHER PATTERN FOR SOUTHEAST
ALASKA. SATELLITE IMAGERY CURRENTLY SHOWING AN AREA OF HIGH
PRESSURE STILL OVER THE YUKON THAT HAS BEEN CAUSING STRONG
OUTFLOW WINDS AND COLD ARCTIC AIR TO MOVE SOUTHWARD. THIS HIGH
WILL WEAKEN AS IS SHIFTS TO THE EAST. THERE ARE REMNANTS OF A
WEAK LOW IN THE NORTHEAST GULF BUT THIS IS MAINLY EFFECTING THE
OFFSHORE AREAS BUT STILL HAS A PRESSURE GRADIENT BETWEEN THE
YUKON HIGH FOR OUTFLOW WINDS FROM DISENCHANTMENT BAY. IN THE
NORTHERN GULF ANOTHER ELONGATED LOW WITH DUAL 992 MB CENTERS IS
MOVING EASTWARD. THE FIRST LOW CENTER IS APPROACHING HAIDA GWAII
AND WILL CROSS OVER DIXON ENTRANCE TONIGHT AND MOVE INTO SOUTHERN
BRITISH COLUMBIA EARLY WEDNESDAY MORNING. THE ASSOCIATED WEATHER
FRONT WILL MOVE OVER THE SOUTHERN PANHANDLE THROUGH THE DAY THEN
EXIT THE REGION LATE TONIGHT.

 A BAND OF CLOUDS CAN BE SEEN OVER KUPREANOF ISLAND AND MATCHES
WITH A 500 MB MODEL VORT MAX. THIS FIRST BAND IS PRODUCING SOME
LOWER CLOUDS AND BRIEF PERIOD OF SNOW BEFORE IT SHEARS APART. THE
MAIN FRONTAL BAND IS JUST ALONG THE SOUTHERN PANHANDLE BORDER
WITH SNOW DEVELOPING FROM WEST TO EAST THIS AFTERNOON THROUGH THE
EVENING. BETWEEN THESE TWO BANDS THERE WAS A BIT OF WARMING ALOFT
THAT PRODUCED SOME LIGHT FREEZING RAIN OVER THE KETCHIKAN AREA
BUT THIS SHOULD BE SHORT LIVED AS MODEL PROFILES KEEP TEMPS BELOW
FREEZING. BIGGEST CHANGE WAS HOW FAR NORTH PRECIP WOULD MOVE.
WHILE MODELS ARE STILL SHOWING A SPREAD IN POP THE LATEST RUNS
DID SHOW A TREND OF KEEPING POPS MAINLY SOUTH OF FREDERICK SOUND.
06Z NAM/SREF ARE TOO DRY WITH THE 00Z UKMET MOVING PRECIP TOO FAR
NORTH. WHILE THE 00Z ECMWF DID SHOW MORE OF A SHIFT IT FELL IN
LINE WITH THE GFS. IN ADDITION THE FRONT LOOKS TO MOVE OVER THE
REGION BIT FASTER AND THERE IS NOT A SIGNIFICANT MOISTURE FEED.
AT THIS TIME HAVE WINTER WEATHER ADVISORIES FOR AKZ26, 27 AND
29 WITH A WINTER STORM WARING FOR AKZ28. THE SOUTHERN INNER
CHANNELS AND HYDER AREAS WILL GET THE HIGHEST SNOW AMOUNTS IN THE
THE 4 TO 10 INCH RANGE AS THE FRONT WILL BE OVER THESE AREAS THE
LONGEST. HAVE LOWER SNOW AMOUNTS FOR PRINCE OF WALES ISLAND AS
HIGHEST QPF VALUES WILL BE WHERE TEMPS ARE THE WARMEST AND THUS
HAVE LOWEST SNOW ACCUMULATION. FOR AKZ26 MAJORITY OF SNOW WILL
FALL OVER SOUTHERN KUPREANOF ISLAND THIS EVENING. THE REMAINDER
OF THE PANHANDLE WILL STAY DRY BUT HAVE KEPT CHANCE POPS FOR THE
CENTRAL PANHANDLE DUE TO SOME UNCERTAINTY WITH HOW FAR NORTH THE
FRONT WILL MOVE.

 OUTFLOW WINDS HAVE DROPPED OFF OVERNIGHT BUT AS THE NORTHERLY
GRADIENT WILL PICK UP AGAIN THROUGH THE DAY AS THE LOW MOVES
EASTWARD KEEPING STRONG NORTHERLY WINDS FOR THE NORTHERN AND
CENTRAL INNER CHANNELS THROUGH THE NIGHT. STRONGEST WINDS
CURRENTLY OVER NORTHERN LYNN CANAL AND WITH THE LONG FETCH WILL
HAVE SEA HIGHEST UPWARDS OF 9 TO 11 FEET DOWN LYNN CANAL INTO
NORTHERN CHATHAM STRAIT. DOWNTOWN JUNEAU WINDS STILL GUSTING TO
45 MPH. FOR THE SOUTHERN PANHANDLE WINDS WILL INCREASE WITH THE
APPROACHING LOW. 850 MB WINDS IN THE 50 TO 60 KT RANGE SO NOT
EXPECTING SURFACE WIND GUSTS TO BE MUCH MORE THAN 40 MPH.

 THERE WILL BE A SPLIT BETWEEN THE SOUTHERN REGIONS WITH
TEMPERATURES WARMING THROUGH THE DAY THEN REMAINING FAIRLY STEADY
OVERNIGHT WITH THE INCOMING FRONT, PRECIP AND CLOUD COVER AND THE
NORTHERN REGIONS WHERE ARCTIC TEMPS WILL STILL BE IN PLACE AND
EXPECT LOWS IN THE SINGLE DIGITS OVERNIGHT WITH CLEAR SKIES AND
RADIATIONAL COOLING.

 GENERAL AGREEMENT BETWEEN MODELS FOR SYNOPTIC PATTERN WITH STILL
VARIATIONS IN DETAILS. LIKED THE 00Z ECMWF/ 06Z NAM FOR PRESSURE
AND WINDS AND USED THAT BLEND WITH INHERITED GRIDS. DISCOUNTED
THE NAM POP AS IT KEEP PRECIP TO FAR SOUTH BUT LIKED THE 00Z
ECMWF COMPARED TO THE 12Z RUN AS IT KEPT THE CENTRAL PANHANDLE
DRIER AND WAS MORE IN LINE WITH THE GFS. THINK THE NORTHERLY
GRADIENT AND OUTFLOW WINDS SUPPORT THE IDEA OF KEEPING THINGS
DRIER FOR LOCATIONS NORTH OF FREDERICK SOUND. FORECAST CONFIDENCE
IS ABOVE AVERAGE FOR THE SYNOPTIC PATTERN BUT DUE TO SOME CURVE
BALLS WITH THE PERIOD OF FREEZING RAIN THIS MORNING THERE IS SOME
QUESTION WITH OVERALL SNOW TOTALS.

 &&

 .LONG TERM...GENERAL TREND OF THE MID TO LONG RANGE FORECAST.
OVERALL I DO NOT THINK THERE WERE SIGNIFICANT CHANGES TO THE MID
TO LATER PERIODS BUT SOME MINOR ADJUSTMENTS WERE DONE. FIRST THE
SURFACE LOW FROM THE WESTERN GULF WILL MOVE ACROSS THE GULF AND
THEN OVER THE SOUTHERN PORTION OF THE PANHANDLE WEDNESDAY
MORNING. WHILE THIS IS GOING ON A TROUGH/LOW ALOFT WILL BE MOVING
SOUTH TO ANCHOR OVER THE NORTHERN GULF OF ALASKA AND REMAIN THERE
THROUGH THE REST OF THE WEEK.

 THE FLOW PATTERN AROUND THE LOW WILL CONTINUE TO SWING
SHORTWAVES AROUND WITH ONE FOR LATE THURSDAY NIGHT AND A SECOND
WHICH SEEMS BETWEEN THAT SHORT WAVE THE UPPER TROUGH LEADING BACK
TO THE MAIN LOW WILL BE USHERING THE COLD AIR THAT HAS SPILLED
INTO THE WESTERN GULF OUT OF THE BERING SEA TO ACROSS THE CENTRAL
GULF THROUGH FRIDAY. THE SYSTEM ON LATE FRIDAY TO EARLY SATURDAY
HAVING DUG ITS WAY TO TH THE NORTH CENTRAL PACIFIC MAY HAVE
TAPPED INTO SOME OF THE TROPICAL MOISTURE AND QPF VALUES ARE ON
THE HALF TO THREE QUARTER INCH IN A 6 HOUR PERIOD FOR SOME
LOCATIONS.

 THE 00Z OPERATIONAL MODELS ON THE WHOLE LINED UP WITH THE IDEAS
OF THE WPC SOLUTION THAT WAS USED IN THE LONG RANGE FORECAST SO
MAINTAINED THAT PLAN WILL ONLY LITTLE ADJUSTMENT. FORECAST
CONFIDENCE THROUGH THE MID RANGE IS AVERAGE OR SLIGHTLY BETTER.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM AKST
     WEDNESDAY FOR AKZ026.
         WINTER WEATHER ADVISORY FROM NOON TODAY TO MIDNIGHT AKST TONIGHT
     FOR AKZ027.
         STRONG WIND THROUGH THIS EVENING FOR AKZ025.
         WINTER STORM WARNING UNTIL 5 AM AKST WEDNESDAY FOR AKZ028.
         WINTER WEATHER ADVISORY FROM NOON TODAY TO 5 AM AKST WEDNESDAY
     FOR AKZ029.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ018-019.
         WIND CHILL ADVISORY UNTIL NOON AKST WEDNESDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012-013-031.
         GALE WARNING FOR PKZ012-013-022-031.
         SMALL CRAFT ADVISORY FOR PKZ011-021-032>036-041>043-051.

&&

PRB/BEZENEK