Storm Warning 15, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
345 PM AKST FRI JAN 23 2015

.SHORT TERM...A GALE FORCE LOW OVER THE NE GULF WILL MOVE ONSHORE NEAR
YAKUTAT THIS EVENING. A HIGH PRESSURE RIDGE WILL BUILD N INTO THE
AREA LATER TONIGHT. ANOTHER GALE FORCE LOW WILL DEVELOP AND MOVE
NE INTO THE SE GULF SAT. GENERALLY USED A GFS/ECMWF/GEM/NAM BLEND
FOR TONIGHT...THEN BASICALLY LEFT SAT AS IS FOR THE MOST PART.

MAIN FORECAST CONCERNS WILL BE WINDS AND PRECIP. RIGHT
NOW...STRONGEST WINDS ARE ON SE SIDE OF LOW...ASSOCIATED WITH
SECOND WRAP OF OCCLUDED FRONT. THESE STRONGER WINDS WILL MOVE
OVER THE NRN PANHANDLE THRU THIS EVENING. MOST PLACES OVER THE NRN
HALF OF THE MAIN PANHANDLE AREA WILL SEE GALES FROM THIS WIND
BAND...WITH POTENTIAL STORM FORCE WINDS FOR A BIT IN CROSS SOUND
THIS EVENING. ALSO...WILL HAVE STRONG WIND HEADLINES FOR THE
ADJACENT PUBLIC ZONES FOR AT LEAST THE EVENING HOURS. THE FAR NRN
INNER CHANNEL AREA WILL STAY WINDY THRU THE NIGHT...SO THEIR
GALES/STRONG WIND HEADLINES WILL LAST INTO EARLY SAT MORNING.
WINDS SHOULD DROP OFF EARLY SAT MORNING OVER THE NRN AREA.
THEN...NEXT LOW MOVING IN WILL INCREASE WINDS OVER THE SRN AREA
SAT. MORE GALES ARE EXPECTED OVER THE FAR SE GULF AND SRN INNER
CHANNELS BY SAT AFTERNOON...AND WILL ALSO HEADLINE ZONES 27 AND 28
FOR STRONG WINDS. AM A BIT CONCERNED THAT THE MODELS MAY BE
UNDERESTIMATING THE STRENGTH OF THIS LOW AS IT WILL HAVE STRONG
JET SUPPORT...180+ KT JET MAXIMA WITH SYSTEM IN LEFT EXIT REGION.
LATER SHIFTS WILL NEED TO MONITOR THIS CLOSELY.

AS FOR PRECIP...THE HEAVIEST RAIN WILL BE OVER THE NRN AREAS THIS
EVENING AS SECOND WRAP FRONTAL BAND MOVES THRU. LOOKS LIKE 1/2 TO
1 INCH OF RAIN OVER THE NRN THIRD OF THE AREA...MAINLY THIS
EVENING. WILL STILL HAVE SOME RAIN AFTER THE SECOND WRAP MOVES
AWAY FROM THE AREA...BUT IT WILL DIMINISH OVERNIGHT AND EARLY SAT
MORNING. MORE RAIN WILL SPREAD NNE INTO THE SRN AREA SAT AHEAD OF
THE NEXT LOW. THE SRN THIRD OF THE AREA COULD GET LOCALLY HEAVY
RAIN IN THE AFTERNOON...WITH 1/2 TO 1 INCH AMOUNTS LIKELY THERE.
THINK THE RAIN IN BOTH EVENTS WILL NOT LAST LONG ENOUGH TO CAUSE
ANY FLOODING CONCERNS...BUT SOME SMALLER STREAMS WILL RISE TO
NEAR BANKFULL CONDITIONS. AN SPS WAS ISSUED TO COVER THE HYDRO
IMPACTS FROM THESE SYSTEMS.

OTHERWISE...WILL REMAIN FAIRLY MILD OVER THE AREA THRU SAT. TEMPS
WILL NOT MOVE MUCH FROM THEIR CURRENT READINGS TONIGHT ESPECIALLY
OVER THE NRN AREA. NOT MUCH RISE IS EXPECTED ON SAT EITHER AS SOME
SLIGHTLY COOLER AIR TRIES TO FILTER IN ON N SIDE OF THE NEXT LOW.

.LONG TERM...985 LOW MOVES IN FROM THE SOUTH LATE SATURDAY NIGHT
ACCOMPANIED BY GALE-FORCE WINDS OFFSHORE AND OVER THE SOUTHERN
INNER CHANNELS ALONG WITH STRONG WINDS IN THE SOUTHERN ZONES. THE
POSITION OF THE LOW CHANGED AND IT STRENGTHENED A BIT ON TODAY'S
MODELS...NECESSITATING NEW PRESSURE/WIND FIELDS IN THE GRIDS. THE
LOW WEAKENS ON THE LATEST GUIDANCE DURING THE DAY SUN AND PRECIP
AMOUNTS WILL BE LARGEST OVER THE SOUTHERN THIRD...ALTHOUGH ALL OF
THE PANHANDLE WILL LIKELY SEE RAIN AS MOIST POSTFRONTAL CONDITIONS
ACCOMPANY THE BACK SIDE OF THE FRONTAL SYSTEM. RAIN SHOULD NOT BE
PERSISTENT ENOUGH FOR FLOODING PROBLEMS THOUGH. LATE SUNDAY OUR
ONSHORE COMPONENT FINALLY WEAKENS SIGNIFICANTLY AS COLDER AIR
BEGINS TO FILTER IN BEHIND THE WEAKENING LOW. SOME LIGHT SNOW IS
POSSIBLE AT THE END OF THE PRECIP EVENT ON SUNDAY NIGHT. GRADIENT
WEAKENING PERMEATES THE WHOLE AREA SUNDAY NIGHT. A SECONDARY COLD
FRONT IS POISED ALONG THE NORTHERN BORDER IN THE MODEL PROGS
SUNDAY NIGHT AND MONDAY AND SHOULD MAKE SOME PROGRESS SOUTHWARD.
MONDAY NIGHT APPEARS TO PRESENT A CHANCE OF SNOW OVER EVEN THE
CENTRAL PANHANDLE AS A WEAK LOW SKIRTS THE PANHANDLE, CROSSING THE
SOUTHERN PORTION...THIS SCENARIO WILL DEPEND ON THE NORTHWARD
EXTENT OF ITS PRECIP. ANOTHER WEAK LOW MOVES IN FROM THE SOUTH
WITH ANOTHER POSSIBLE SNOW SCENARIO FOR AT LEAST THE NORTHERN
PANHANDLE FOR WEDNESDAY. WE HAVE SNOW MENTIONED IN THE WET
PORTIONS OF THE FORECASTS FOR THE NORTHERN HALF FROM ABOUT SUNDAY
NIGHT THROUGH WEDNESDAY.

ON MONDAY THE MODELS' JET-LEVEL FIELDS SHOW GENERAL AGREEMENT WITH
RIDGING ALOFT DOMINATING ALONG WITH THE ARCTIC FRONT IN PLACE OVER
OUR NORTHERN PORTION. THE COLD AIR OVER THE NORTH PERSISTS RIGHT
ON THROUGH MIDWEEK WITH THE WEAK WED SYSTEM AT THE SURFACE. BY WED
PM THE EC AND GFS BOTH SHOW GENERAL UPPER RIDGING CONTINUING WITH
THE EC ON THE STRONGER END...THIS WOULD TEND TO KEEP THE COLD AIR
IN AS A FACTOR IN PRECIP TYPE FOR ANY WEAK DISTURBANCE PRESENT AT
THE SURFACE. HOWEVER AT THIS POINT (WED) THE GEM MODEL HAS ALREADY RE-
STRENGTHENED WARM LOW-LEVEL SWLY FLOW OVER THE GULF. BY NEXT FRI
THE EC AND GFS ARE GENERALLY SIMILAR WITH THE RIDGE GIVING WAY TO
SIGNIFICANT GULF TROUGHING AND A TRANSITION BACK TO WARM/WINDY
CONDITIONS OVER THE PANHANDLE.

UTILIZED PRIMARILY NAM/EC/GEM PROGS FOR UPDATES ON DAYS 2-4 AND THEN
MIGRATED TO WPC GUIDANCE FOR DAY 5 ONWARDS, WHICH UTILIZED AN
ENSEMBLE APPROACH. THE SOLUTION DEVELOPS EXTENSIVE SOUTHEASTERLY
GULF SURFACE FLOW AGAIN BY THURS BUT MAINTAINS THE PROXIMITY OF
THE ARCTIC FRONT ON THE NORTH END OF THE PANHANDLE THROUGH DAYS
7-8. OVERALL FORECAST CONFIDENCE IS AVERAGE WITH SIGNIFICANT MODEL
DIVERGENCE PRESENT BY ABOUT TUES.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND SATURDAY AFTERNOON FOR AKZ027.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ020-021-024.
         STRONG WIND UNTIL 3 AM AKST SATURDAY FOR AKZ025.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ022.
         STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ023.
         STRONG WIND SATURDAY AFTERNOON FOR AKZ028.
         STRONG WIND THROUGH SATURDAY MORNING FOR AKZ018-019.
MARINE...STORM WARNING FOR PKZ022.
         GALE WARNING FOR PKZ012-013-021-031-032-034>036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011-033-051>053.

&&

RWT/WESLEY

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