Gale Warning 294, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
405 PM AKDT TUE SEP 29 2015

.SHORT TERM...THE RATHER ACTIVE WEATHER PATTERN WILL BEGIN TO EXIT
THE REGION OVER THE NEXT 24 HOURS. 984 MB LOW IN THE NORTHWEST
GULF WILL CONTINUE TO TRACK EASTWARD THROUGH THURSDAY WHILE
WEAKENING. THERE WERE TWO MAIN FRONTAL WAVES ASSOCIATED WITH THE
LOW MOVING EASTWARD. THE FIRST CROSSED OVER THE PANHANDLE TODAY
PRODUCING HEAVY RAIN AND STRONG WINDS. THE SECOND WAVE WILL MOVE
OVER THE REGION EARLY THIS EVENING BRINGING THE NEXT ROUND OF
STRONG WINDS AND HEAVY RAIN AFTER A BRIEF LULL THIS AFTERNOON. THE
SECOND WAVE WILL CROSS MOVE TO THE SOUTH PRODUCING SOME OF THE
HIGH RAINFALL AMOUNTS SEEN OVER THE NORTH TO THE SOUTH, WITH
DIMINISHING RAIN RATES BEHIND. RAIN FALL AMOUNTS FROM THE SYSTEM
RANGED FROM 2 TO NEARLY 6 INCHES SO FAR, WITH ANOTHER 1 TO 2
INCHES EXPECTED THIS EVENING. SOME QUESTION ON THE TIMING OF THIS
WAVE MOVING OUT OF THE SOUTH SOONER THAN LATER. LAST WRAP AROUND
THE LOW WILL MOVE OVER THE NORTHERN AND CENTRAL PANHANDLE THROUGH
WEDNESDAY. UNSTABLE ATMOSPHERE WITH COLD AIR ALOFT BEHIND THE
FRONT WILL TRANSITION RAIN TO SHOWERS OVERNIGHT WITH THIS LAST
WRAP. ENOUGH INSTABILITY WITH CAPE VALUES AROUND 400 J/KG AND LI
NEAR -1 C TO PUT IN MENTION OF THUNDERSTORMS MOVING ACROSS THE
GULF AND REACHING THE NORTHEAST COAST BY TOMORROW AFTERNOON.

GALE FORCE WINDS AROUND THE LOW OVER THE AK GULF WILL DIMINISH
TONIGHT AS THE LOW WEAKENS. OVER THE INNER CHANNELS WINDS DROPPED
SLIGHTLY THIS AFTERNOON BETWEEN THE TWO WAVES BUT WILL PICK BACK
UP AGAIN THIS EVENING. SOUTHERLY GRADIENT BETWEEN PAGY AND PAJN
REACHED -7.4 RESULTING IN STORM FORCE WIND GUSTS FOR N LYNN
CANAL. GALE FORCE WINDS OVER MOST OF THE CENTRAL AND NORTHERN
INNER CHANNELS THROUGH THE DAY WITH HIGHER GUSTS. CAPE SPENCER
GUSTS REACHED UP TO 60 KTS AT ONE POINT. PAGY REACHED ITS HIGH
WIND WARNING CRITERIA WITH 60 MPH GUSTS THIS AFTERNOON. THE
GRADIENT WILL DECREASE AS THE SYSTEM MOVE EAST WITH WINDS
DIMINISHING THROUGH WEDNESDAY. IN ADDITION TO THE TIGHT SURFACE
GRADIENT LLJ MOVING OVER THE PANHANDLE ENHANCED THE STRONGER
WINDS. THE SOUTHERN PANHANDLE WINDS WILL MUCH WEAKER COMPARED TO
THE NORTH TODAY BUT WITH A 700 MB 50 KT JET MOVING OVER EXPECT
WINDS IN ZONE 27 AND 28 ALONG WITH WINDS IN CLARENCE STRAIT TO
PICK UP.

NEW MODELS HAD A HANDLE ON THE CURRENT SYSTEM AND STILL MATCHED UP
OVERALL FROM PRESS AND WINDS. DID BUMP UP WINDS SPEEDS SLIGHTLY
THIS EVENING. WHILE MOST MODELS KEPT RAIN OVER THE SOUTHERN
PANHANDLE THROUGH THE DAY WED POSSIBLE THEY ARE TOO HIGH WITH THE
SPEED OF THE SYSTEM. FORECAST CONFIDENCE IS AVERAGE

.LONG TERM...WEAKENING LOW WILL MOVE ACROSS THE NE GULF WED NIGHT
THEN TURN SE ALONG THE OUTER COAST THU BUT WILL LIKELY DISSIPATE
BY LATE THU AFTERNOON. HIGH PRESSURE WILL BUILD OVER THE YUKON WED
NIGHT INTO THU...THEN WEAKEN AND SHIFT E FRI INTO THE WEEKEND.
UPPER RIDGE WILL BUILD OVER THE ERN GULF FOR LATE WEEK...BUT WILL
LIKELY FLATTEN ESPECIALLY BY SUN. MODELS DIFFER ON THIS HOWEVER.
ENDED UP USING THE 12Z NAM FOR THE WED NIGHT THRU FRI
PERIODS...WITH MOSTLY LATEST WPC FOR FRI NIGHT ONWARD.

SHOWERS WILL CONTINUE OVER THE NW HALF OF THE AREA WED
NIGHT...WITH SOME SHOWERS SPREADING SE INTO THE SRN AREA LATE WED
NIGHT AND THU MORNING. THE SHOWERS WILL DIMINISH THU AS SFC LOW
DISSIPATES AND LOWER LEVEL NLY FLOW INCREASES. THU NIGHT AND FRI
LOOK TO BE DRY UNDER PARTLY CLOUDY OR BETTER CONDITIONS FOR MOST
OF THE AREA. ALSO WILL HAVE SOME COLDER AIR MOVE IN FROM THE N THU
NIGHT. SOME AREAS COULD SEE TEMPS DROP BELOW FREEZING THU
NIGHT...MAINLY IN WIND SHELTERED AREAS OVER THE N. 25-35 KT NLY
WINDS ARE LIKELY ESPECIALLY OVER THE NRN HALF OF THE AREA THU
NIGHT AND FRI MORNING.

FOR THE WEEKEND...A WEAKENING SHORTWAVE WILL MOVE THRU THE RIDGE
BUT MODELS DIFFER ON HOW MUCH OF THE SYSTEM WILL SURVIVE INTO SE
AK. ATTM...DID BRING IN LOW POPS TO MAINLY THE FAR NW PART OF THE
AREA FOR FRI NIGHT AND SAT. WPC KEEPS POPS GENERALLY LOW THRU THE
WEEKEND INTO EARLY NEXT WEEK...BUT LATER SHIFTS WILL NEED TO
MONITOR THIS AS SOME MODELS SUGGEST MORE SHORTWAVE ENERGY WILL GET
THRU THE RIDGE INTO SE AK SUN INTO EARLY NEXT WEEK.

&&

.AVIATION...WIND PROGS OF 35-50 KNOTS AT 2000 FEET MSL HAVE
PROMPTED WIND SHEAR ALERTS IN MOST OF THE TAFS THROUGH 18 TO 24
HOURS.

&&

.HYDROLOGY...FOR YAKUTAT SOUTHWESTERLY STORM SURGE, ALONG WITH
VERY HIGH TIDE AND HEAVY RAIN FALL WARRANTED A COASTAL FLOOD
WARNING. REPORTS OF WASHED OUT ROADS WERE ALREADY REPORTED FOR THE
AREA. PUT IN A BROAD FLOOD ADVISORY FOR MOST OF THE CENTRAL AND
NORTHERN PANHANDLE DUE TO THE HEAVY RAINFALL. MOST RIVERS AND
STREAMS SAW RAPID RISES TODAY, THEN LEVELED OUT DURING THE
RAINFALL LULL BETWEEN FRONTAL BANDS, BUT ARE EXPECTED TO RISE
AGAIN WITH THE NEXT ROUND. RIVERS OF NOTE ARE THE SITUK NEAR
YAKUTAT WHICH HIT BANKFULL OF 70 FT TO DAY, RISING 3 FEET, AND
EXPECTED TO HIT ABOVE MINOR FLOOD STAGE TO 72 FEET TONIGHT. IN
JUNEAU JORDAN CREEK HAD A QUICK RISE BUT LOTS OF FLUCTUATION
AROUND BANKFULL AT 9 FT, EXPECTED TO RISE ABOVE MINOR FLOOD STAGE
TO 9.9 FEET. WHILE THE MENDENHALL IS NOT EXPECTED TO REACH
BANKFULL TONIGHT IT HAS BEEN SHOWING A 24 HOUR DELAY, SO
POTENTIAL RISES CONTINUING INTO WEDNESDAY WHILE OTHER RIVERS HAVE
ALREADY DROPPED. THE TAIYA RIVER NEAR SKAGWAY HAS BEEN TRICKIEST
SINCE MODEL QPF OVER THE RIVER BASIN HAS SHOWN LARGE VARIATIONS.
THE RIVER, AS MOST OTHERS, HAS SHOWN A RAPID RISE JUST NEARING
BANKFULL. CURRENT NUMBER PUT THE RIVER ALMOST AT MODERATE FLOOD
STAGE OF 17 FEET, BUT AS THESE FRONTAL WAVES ARE PREDICTED TO
START MOVING SOUTH MAY NOT BE ENOUGH RAINFALL TO REACH THAT HIGH.

THE HEAVY RAIN, SATURATED GROUND, AND STRONG WINDS ALSO HAVE MADE
POTENTIAL FOR MUD SLIDES. SMALL MUD SLIDES ALREADY REPORTED NEAR
THE THANE CAMPGROUND IN JUNEAU.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 7 PM THIS EVENING TO 1 AM AKDT WEDNESDAY FOR
     AKZ027.
         AREAL FLOOD ADVISORY UNTIL 9 AM AKDT WEDNESDAY FOR AKZ017>025.
         STRONG WIND UNTIL 10 PM AKDT THIS EVENING FOR AKZ025.
         STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ017-022-023.
         STRONG WIND UNTIL 1 AM AKDT WEDNESDAY FOR AKZ019.
         HIGH WIND WARNING UNTIL 1 AM AKDT WEDNESDAY FOR AKZ018.
         STRONG WIND FROM 7 PM AKDT THIS EVENING THROUGH WEDNESDAY
     MORNING FOR AKZ018.
MARINE...STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-034-036-042-043-051>053.
         SMALL CRAFT ADVISORY FOR PKZ032-033-035-041.

&&

PRB/RWT

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