Storm Warning 20, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
557 AM AKST THU NOV 21 2013

.SHORT TERM...STRONG WEATHER FRONT EXTENDING FROM A 990 MB LOW
SOUTH OF THE ALEUTIANS IS MOVING OVER THE AK GULF AND PANHANDLE.
WITH LONG FETCH OF TROPICAL MOISTURE THIS FRONT HAS BEEN
PRODUCING HEAVY PRECIPITATION OVER THE ENTIRE PANHANDLE. AS THE
PARENT LOW BEGINS TO TRACK NEAR KODIAK FRONTAL BANDS WILL
CONTINUE TO MOVE OVER THE REGION. AT THIS TIME THE RAIN-SNOW LINE
IS NEAR SUMNER STRAIT AND UP ALONG THE COAST UP TO SITKA. AS THE
FRONT ADVANCES NORTHWARD TODAY THROUGH TONIGHT SNOW WILL BEGIN TO
TRANSITION TO RAIN WITH TEMPERATURES STEADILY RISING OVERNIGHT
AND THROUGH FRIDAY. COLD AIR DAMMING NEAR HYDER SHOULD KEEP THEM
WITH HEAVY SNOW BIT LONGER THROUGH THE DAY. DEW POINTS NEAR
PETERSBURG AND WRANGLE STILL IN THE UPPER 20S WITH TEMPERATURES
JUST BELOW FREEZING. WHILE THERE WILL BE A TRANSITION TO RAIN
THINKING IS THE COLD POOL OF AIR, ESPECIALLY NEAR PETERSBURG WILL
LAST AND KEEP SNOW THROUGH THE LATE AFTERNOON BEFORE CHANGING
OVER TO RAIN.

 SNOW INCREASED IN INTENSITY OVERNIGHT WITH SNOW FALL AMOUNTS
THROUGH MIDNIGHT OF 1 TO 3 INCHES FOR THE CENTRAL PANHANDLE WITH
AMOUNTS UPWARDS OF 8 INCHES NEAR HYDER. EXPECTING ADDITIONAL SNOW
AMOUNTS TODAY IN THE 3 TO 8 INCH RANGE. AS TEMPERATURES RISE
THROUGH THE DAY SNOW WILL TRANSITION FROM THE FINER GRAINS TO
LARGER FLAKES AND WITH THE HEAVY PRECIP RATES AND QPF VALUES THIS
SHOULD PRODUCE THE HIGHER SNOWFALL ACCUMULATION. SNOW AMOUNTS
LATER TONIGHT WILL BE LOWER THAN THE DAY WITH WARMING TEMPS AND
AS THE HEAVY WET SNOW COMPACTS. THE WINTER STORM WARNINGS WILL
END AS PRECIP TRANSITIONS FROM SNOW TO RAIN.

 TIGHT PRESSURE GRADIENT BETWEEN THE ADVANCING FRONT AND HIGH
PRESSURE OVER THE YUKON PRODUCING STRONG NORTHERLY AND OUTFLOW
WINDS. THESE GALE FORCE WINDS WILL BEGIN TO DIMINISH AS THE HIGH
MOVES EASTWARD. WINDS WILL BEGIN TO SHIFT TO THE SOUTH AS THE
FRONT MOVES OVER THE PANHANDLE LATE TONIGHT.

 NOT MUCH VARIATION IN 00Z MODEL RUNS WITH ONLY MINOR CHANGES TO
THE WIND AND PRESSURE FORECAST. MAIN MODEL DIFFERENCE WAS THE QPF
VALUES FOR THE NORTHERN PANHANDLE WITH NAM AND ECMWF SHOWING
HIGHER AMOUNTS OVER THE NORTHERN PANHANDLE. WITH THESE VALUES AND
COLDER AIR IN PLACE OVER THE NORTHERN PANHANDLE INCREASED SNOW
AMOUNTS FOR THE HAINES AND KLONDIKE HIGHWAYS. DELAYED SNOW LEVEL
INCREASE FOR PETERSBURG AND HYDER ENOUGH TO EXTEND THOSE WINTER
STORM WARNINGS. FORECAST CONFIDENCE IS ABOVE AVERAGE FOR SYNOPTIC
PATTERN WITH SOME UNCERTAINTY ON TIMING OF ADVANCING WARM AIR AND
SNOW AMOUNTS.

 &&

 .LONG TERM...STRONG FRONT APPROACHING THE EASTERN GULF ON FRIDAY
AS A SURGE OF WARM AIR MOVES NORTHWARD ACROSS THE PANHANDLE. THE
RESULTING AIR MASS DISPLACEMENT WILL HAVE TURNED ALL BUT LYNN
CANAL ZONES INTO RAIN BY FRIDAY MORNING. THERE WILL BE THE FOCUS
AS WE SHALL SEE OUR LAST WINTER STORM EVENT FOR THIS
ROUND...SQUARELY ON THE HAINES HIGHWAY. THE WARNING STATEMENT
ISSUED CALLS FOR 7 TO 24 INCHES OF SNOW FOR THE HAINES
ZONE...WITH 7 INCHES TOTAL FOR HAINES, BUT 24 INCHES NEAR THE
BORDER...AS THE COLD AIR WILL REMAIN ENTRENCHED IN THE CHILKAT
VALLEY EVEN AS THE WARM AIR WILL CAUSE TEMPERATURES TO RISE ABOVE
FREEZING NEAR LYNN CANAL, TURNING HAINES ITSELF TO RAIN AROUND
MID-DAY FRIDAY. THINK SNOW AMOUNTS WILL RISE FOR FRIDAY WITH A
POSSIBLE 1 TO 8 INCHES FOR THE HAINES ZONE...AGAIN LIGHTER
AMOUNTS NEAR LYNN CANAL. WHITE PASS IN TURN HAS BEEN PLACED UNDER
A WINTER WEATHER ADVISORY...FOR POSSIBLE 4 TO 12 INCHES THROUGH
FRIDAY EVENING. JUST AS COLDER TEMPERATURES AND FLUFFIER FLAKES
WILL BE THE BIG REASON FOR WARNING/ADVISORY AMOUNTS UP NORTH FOR
THURSDAY NIGHT, HIGHER QPF IN ADVANCE OF THE FRONT WILL PUSH
SNOW TOTALS EVEN HIGHER FOR FRIDAY INTO FRIDAY EVENING.

 ELSEWHERE EXPECT FRIDAY TO BE A VERY MESSY, WET, RAINY DAY OVER
HEAVY SNOWFALL ALREADY ON THE GROUND. IF THURSDAY'S COMMUTE WILL
BE BAD, FRIDAY'S WILL NOT BE A CAKEWALK. DID PUSH INSIDE PASSAGE
WINDS TO GALE FORCE FOR MUCH OF THE NORTH-SOUTH CHANNELS IN
ADVANCE OF THIS FRONT...THINKING MODELS MAY HAVE UNDERDONE THE
GRADIENTS, AND ADDING 5 KT TO COMPENSATE FOR THE FRONTAL PASSAGE.
IN ADDITION, 850 MB WINDS ARE UP TO 60 KTS IN AREAS OF THE
PANHANDLE MID-DAY FRIDAY. BY THE SAME TOKEN A LOT OF COMMUNITIES
WILL SEE WIND RISES...SUCH AS JUNEAU FROM THE SOUTHEAST,
KETCHIKAN FROM THE SOUTHEAST. ELFIN COVE AND SITKA FROM THE EAST
AND SOUTHEAST AS WELL. EXPECT A BRIEF PERIOD OF 55 KT FRIDAY
MORNING ACROSS MUCH OF THE OUTSIDE WATERS AND THEN A SLOW DECLINE
THROUGH FRIDAY EVENING AS GRADIENTS RELAX.

 BEYOND...SOME COOL AIR ALOFT WILL MOVE INTO THE NORTHERN
PANHANDLE ON SATURDAY THUS TURNING MUCH OF THE PRECIPITATION INTO
RAIN AND SNOW SHOWERS. BEYOND THIS FOR SIMPLICITY, WENT WITH
STRATIFORM. ACTIVE PATTERN REMAINS WITH THE POSSIBILITY OF SOME
CLEARING AND AGAIN COOLING TEMPERATURES ON SUNDAY WITH MORE
PRECIPITATION MOVING IN WITH A SYSTEM FROM THE SOUTH ON MONDAY.
FORECAST BEYOND SUNDAY LARGELY LEFT UNCHANGED.

 MODELS OF CHOICE WERE ECMWF AND GFS WITH SOME ELEMENTS OF NAM
USED AS WELL. MODELS DIVERGE RUN TO RUN ON THE WAY THEY HANDLE
THE BUILDING RIDGE POST-FRONTAL...SO ELECTED NOT TO CHANGE
PRESSURE FIELD FOR SATURDAY AND BEYOND. CONFIDENCE IN FORECAST
AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 6 PM AKST THIS EVENING FOR AKZ026-029.
         STRONG WIND UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ018-027.
         WINTER STORM WARNING UNTIL MIDNIGHT AKST TONIGHT FOR AKZ022-024.
         WINTER STORM WARNING UNTIL 6 AM AKST FRIDAY FOR AKZ020-021-025.
         STRONG WIND UNTIL NOON AKST TODAY FOR AKZ022.
         STRONG WIND UNTIL 6 AM AKST EARLY THIS MORNING FOR AKZ020-023.
         WINTER STORM WARNING UNTIL 9 PM AKST FRIDAY FOR AKZ019.
         WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 9 PM AKST
     FRIDAY FOR AKZ018.
         STRONG WIND THROUGH THIS AFTERNOON FOR AKZ017.
         WINTER STORM WARNING UNTIL 6 AM AKST FRIDAY FOR AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011>013-021-022-031-036-041>043-051>053.
         SMALL CRAFT ADVISORY FOR PKZ032>035.

&&

PRB/JWA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
249 PM AKST THU NOV 21 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 AM     HEAVY SNOW       15 ESE JUNEAU           58.21N 134.03W
11/21/2013  M9.5 INCH                           AK   CO-OP OBSERVER

            SNETTISHAM

0600 AM     SNOW             CRAIG                   55.47N 133.13W
11/21/2013  M2.0 INCH                           AK   PUBLIC

            SNOW ACCUMULATION BEFORE CHANGEOVER TO RAIN.

0600 AM     HEAVY SNOW       PETERSBURG              56.81N 132.96W
11/21/2013  M7.0 INCH                           AK   CO-OP OBSERVER

            9 MILES OUT OF PETERSBURG

0620 AM     HEAVY SNOW       JUNEAU                  58.30N 134.41W
11/21/2013  M6.8 INCH                           AK   NWS EMPLOYEE

            SNOW THROUGH 620AM STILL SNOWING A GOOD RATE. IN
            MENDENHALL VALLEY.

0700 AM     HEAVY SNOW       OUTER POINT             58.30N 134.69W
11/21/2013  M10.0 INCH                          AK   CO-OP OBSERVER

0700 AM     SNOW             38 WNW HAINES           59.45N 136.44W
11/21/2013  M1.0 INCH                           AK   CO-OP OBSERVER

0700 AM     SNOW             WHITE PASS              59.62N 135.14W
11/21/2013  M3.0 INCH                           AK   OTHER FEDERAL

            BLOWING AND DRIFTING SNOW.

0800 AM     HEAVY SNOW       CANYON ISLAND           58.55N 133.68W
11/21/2013  M6.7 INCH                           AK   CO-OP OBSERVER

0800 AM     HEAVY SNOW       2 S EAGLECREST          58.25N 134.51W
11/21/2013  M7.0 INCH                           AK   CO-OP OBSERVER

            TOP OF EAGLECREST.

0800 AM     HEAVY SNOW       EAGLECREST              58.27N 134.51W
11/21/2013  M7.3 INCH                           AK   CO-OP OBSERVER

            BASE OF EAGLECREST

0800 AM     SNOW             JUNEAU                  58.30N 134.41W
11/21/2013  M4.0 INCH                           AK   NWS EMPLOYEE

            BLUEBERRY HILL IN WEST JUNEAU.

0800 AM     HEAVY SNOW       GUSTAVUS                58.41N 135.80W
11/21/2013  M20.0 INCH                          AK   CO-OP OBSERVER

0800 AM     SNOW             HAINES                  59.24N 135.44W
11/21/2013  M2.0 INCH                           AK   CO-OP OBSERVER

0800 AM     HEAVY SNOW       2 SE JUNEAU             58.28N 134.37W
11/21/2013  M8.0 INCH                           AK   CO-OP OBSERVER

            WASTE WATER TREATMENT PLANT

0830 AM     HEAVY SNOW       5 NW GUSTAVUS           58.46N 135.90W
11/21/2013  M30.0 INCH                          AK   CO-OP OBSERVER

0900 AM     HEAVY SNOW       HOONAH                  58.11N 135.44W
11/21/2013  M16.0 INCH                          AK   CO-OP OBSERVER

0930 AM     SNOW             YAKUTAT                 59.54N 139.73W
11/21/2013  M2.0 INCH                           AK   NWS EMPLOYEE

            FREEZING RAIN STARTED AT 1208 PM AKST.

1000 AM     HEAVY SNOW       AUKE BAY                58.38N 134.65W
11/21/2013  M10.0 INCH                          AK   CO-OP OBSERVER

1030 AM     HEAVY SNOW       TENAKEE SPRINGS         57.78N 135.22W
11/21/2013  M24.0 INCH                          AK   PUBLIC

1030 AM     SNOW             SKAGWAY                 59.48N 135.33W
11/21/2013  E0.0 INCH                           AK   CO-OP OBSERVER

            BLOWING SNOW WITH LITTLE OR NO SNOW ACCUMULATION.

1100 AM     SNOW             PELICAN                 57.95N 136.21W
11/21/2013  M5.6 INCH                           AK   CO-OP OBSERVER

            BLOWING AND DRIFTING SNOW. FREEZING RAIN STARTED AT 1 PM.

1100 AM     SNOW             HYDER                   55.91N 130.02W
11/21/2013  M24.5 INCH                          AK   CO-OP OBSERVER

            SNOW ACCUMULATION BEFORE CHANGEOVER AT 1130 AM.

1100 AM     SNOW             5 SE SITKA              57.00N 135.24W
11/21/2013  E7.0 INCH                           AK   PUBLIC

            SNOW ACCUMULATION AROUND 6 TO 8 INCHES.

1200 PM     HEAVY SNOW       LENA LOOP               58.39N 134.77W
11/21/2013  M11.0 INCH                          AK   CO-OP OBSERVER

            9 INCHES SINCE MIDNIGHT ON THURSDAY MORNING.

1200 PM     HEAVY SNOW       10 NW JUNEAU            58.40N 134.61W
11/21/2013  M10.0 INCH                          AK   CO-OP OBSERVER

            JUNEAU FORECAST OFFICE

1200 PM     HEAVY SNOW       8 NW JUNEAU             58.38N 134.57W
11/21/2013  M10.0 INCH                          AK   OFFICIAL NWS OBS

            JUNEAU AIRPORT

1230 PM     HEAVY SNOW       ANGOON                  57.50N 134.59W
11/21/2013  M14.0 INCH                          AK   PUBLIC

0100 PM     HEAVY SNOW       ELFIN COVE              58.19N 136.34W
11/21/2013  M16.0 INCH                          AK   CO-OP OBSERVER

            2 INCHES BEFORE 3 PM WEDNESDAY, 14 INCHES OVERNIGHT
            THROUGH THURSDAY MORNING, CURRENT TEMPERATURE 26 F

0100 PM     HEAVY SNOW       PETERSBURG              56.81N 132.96W
11/21/2013  M15.0 INCH                          AK   CO-OP OBSERVER

            PETERSBURG AIRPORT

&&

RCL