Blizzard Watch 1, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST MON DEC 22 2014

.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO PRODUCE CLOUDS AND SHOWERS OVER THE
WESTERN HALF OF THE ISLAND CHAIN TODAY...WITH ACTIVE WEATHER
DEVELOPING LATE THIS AFTERNOON AND TONIGHT. A STRONG DISTURBANCE
ALOFT WILL DROP OVER THE ISLANDS TONIGHT AND LINGER THROUGH AT LEAST
WEDNESDAY...CREATING THE POTENTIAL FOR HEAVY FLOODING RAINFALL AND
STRONG THUNDERSTORMS. DRIER AND INCREASINGLY STABLE WEATHER IS
EXPECTED THURSDAY AND FRIDAY.

&&

.DISCUSSION...
WET WEATHER FOR THE WESTERN HALF OF THE ISLAND CHAIN TODAY WILL TURN
ACTIVE STATE-WIDE TONIGHT...WITH FLOODING RAINFALL AND STRONG
THUNDERSTORMS POSSIBLE THROUGH WEDNESDAY.

IN THE SHORT TERM...THE LEADING EDGE OF A SLOW-MOVING COLD FRONT IS
OVER OAHU THIS MORNING. THIS FEATURED DROPPED OVER 2 INCHES OF
RAINFALL ACROSS NORTHERN SLOPES OF KAUAI LAST NIGHT...WITH A COUPLE
OF STANDOUTS MEASURING OVER SIX INCHES. HEAVY SHOWERS ALONG THE
LEADING EDGE WILL REMAIN FOCUSED ALONG NORTH FACING TERRAIN ON OAHU
TODAY WITH SHOWERS PERIODICALLY SPILLING OVER TO LEEWARD AREAS...
ESPECIALLY EAST HONOLULU. STRONG AND GUSTY NORTH TO NORTHEAST WINDS
WILL FILL IN BEHIND THE FRONT...WHICH SHOULD ADVANCE TO MOLOKAI
LATER. EXPECT LIGHT WINDS WITH A LAND AND SEA BREEZE PATTERN OVER
THE BIG ISLAND AND MAUI TODAY. SOME SPOTTY AFTERNOON SHOWERS COULD
BECOME HEAVY.

ACTIVE WEATHER WILL DEVELOP AS EARLY AS LATE THIS AFTERNOON WITH
THUNDERSTORM AND HEAVY RAIN CHANCES INCREASING SIGNIFICANTLY THIS
EVENING. A STRONG MID TO UPPER LEVEL DISTURBANCE CURRENTLY CENTERED
ABOUT 350 MILES NORTHWEST OF KAUAI WILL MOVE OVER THE ISLANDS
TONIGHT AND WILL LIKELY PRODUCE A POTENT CUTOFF LOW ALOFT ON
TUESDAY. THE INITIAL COLD POOL IN THE CORE OF THE DISTURBANCE WILL
BRING 500 MB TEMPS BELOW -15C...WHICH IS EXTREMELY RARE OVER HAWAII.
WHILE THE GREATEST THUNDERSTORM THREAT WILL BE ALONG FRONT NEAR THE
CENTRAL ISLANDS TONIGHT...THUNDERSTORMS COULD POP UP ANYWHERE
WITHIN THE CORE OF THE LOW OVER THE WESTERN ISLANDS. THESE
THUNDERSTORMS COULD BE STRONG...WITH THE POTENTIAL TO PRODUCE
HAIL...STRONG AND GUSTY WINDS...AND HEAVY RAINFALL.

THE THREAT FOR HEAVY SHOWERS AND THUNDERSTORMS WILL PERSIST THROUGH
AT LEAST WEDNESDAY. THE FRONTAL BOUNDARY WILL LIKELY WASH OUT ON
TUESDAY. HOWEVER...THE CUTOFF LOW WILL MEANDER NEARBY...AND THE GFS
AND ECMWF DEPICT DEEP MOISTURE BEING DRAWN OVER THE ISLANDS FROM THE
SOUTHEAST WITH A SURFACE LOW POSSIBLY DEVELOPING OVER THE ISLANDS.
THE THREAT FOR HEAVY FLOODING RAINFALL WITH THUNDERSTORMS WILL
CONTINUE THROUGH AT LEAST WEDNESDAY...AND A FLASH FLOOD WATCH IS IN
PLACE FROM THIS EVENING THROUGH WEDNESDAY AFTERNOON ALONG WITH A
WINTER STORM WATCH FOR THE BIG ISLAND SUMMITS.

THE UNCERTAINTY IN THE FORECAST MODELS EXTENDS INTO THE SECOND HALF
OF THE WEEK...FOR WHICH THE PREVIOUS FORECAST TREND HAS BEEN FOR THE
MOST PART KEPT IN PLACE WITH NE WINDS AND A DRYING TREND GRADUALLY
RETURNING ACROSS THE AREA. SURELY THE LONG RANGE FORECAST WILL BE
ADJUSTED...DEPENDING ON THE FINAL OUTCOME OF THE AFOREMENTIONED
LOW/TROUGH COMPLEX. STAY TUNED.

&&

.AVIATION...
CLOUDS AND SHOWERS ASSOCIATED WITH A COLD FRONT CONTINUE TO AFFECT
KAUAI AND OAHU...WITH THE MAJORITY OF THE SHOWERS NOW OVER OAHU.
EXPECT PERIODS OF TEMPO MVFR WITH POSSIBLE ISOL IFR TO MOVE THROUGH
OAHU AND KAUAI TODAY...INCLUDING PHLI...PHJR...AND PHNL. AIRMET
SIERRA FOR MOUNTAIN OBSCURATION REMAINS POSTED FOR KAUAI AND OAHU.
CLOUDS TOPS ARE MAINLY BETWEEN 8 AND 15 KFT. SOME CLOUDS AND SHOWERS
ARE BEGINNING TO REACH MOLOKAI...N THRU E AREAS MAY EXPERIENCE
PASSING MVFR CONDITIONS...BUT NOT AS WIDESPREAD AS OAHU AND KAUAI.
AIRMET TANGO IS POSTED FOR LOW LEVEL TURB OVER KAUAI...DUE TO GUSTY
N WINDS THAT WILL CONTINUE AT LEAST INTO TONIGHT BEFORE SPREADING
EAST.

OVER THE OTHER ISLANDS TODAY...VFR WILL PREVAIL FOR THE MOST PART.
THE FRONT IS EXPECTED TO BECOME STATIONARY NEAR MAUI COUNTY LATER
TONIGHT. TONIGHT INTO TUESDAY HOWEVER...A DEVELOPING LOW ALOFT
WILL BRING THE STATEWIDE POSSIBILITY OF THUNDERSTORMS AND THEIR
ASSOCIATED AVIATION HAZARDS...INCLUDING ICING...TURBULENCE...WIND
SHEAR AND IFR CONDITIONS.

&&

.MARINE...
A LARGE NORTHWEST SWELL IS KEEPING WARNING LEVEL SURF OVER NORTH AND
WEST FACING SHORES OF THE SMALLER ISLANDS AND WEST FACING SHORES OF
THE BIG ISLAND UNTIL 6 AM HST TUESDAY. THIS SWELL WILL ALSO GENERATE
SMALL CRAFT ADVISORY CONDITIONS OVER MOST COASTAL WATERS DUE TO
HAZARDOUS SEAS.

STRONG NORTH TO NORTHEAST WINDS ARE IN PLACE OVER KAUAI AND OAHU AND
MAY SPREAD EASTWARD TO MAUI COUNTY LATE TODAY. BUT IT IS NOT CLEAR
IF SMALL CRAFT ADVISORY CONDITIONS WILL BE EXPERIENCED AGAIN BEYOND
TUESDAY MORNING. THEREFORE...THE SMALL CRAFT ADVISORY WILL BE
ALLOWED TO EXPIRE AT 6 AM HST TUESDAY AND REISSUED LATER ON IF
CONDITIONS WARRANT IT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM THIS EVENING THROUGH WEDNESDAY AFTERNOON
FOR ALL HAWAII ISLANDS.

HIGH SURF WARNING UNTIL 6 AM HST TUESDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU
KOOLAU-OLOMANA-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-
WINDWARD HALEAKALA-KONA-KOHALA.

WINTER STORM WATCH FROM THIS EVENING THROUGH WEDNESDAY AFTERNOON
FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR ALL HAWAIIAN
WATERS EXCEPT MAALAEA BAY-

&&

DISCUSSION...WROE
AVIATION...EATON
MARINE...REYNES