270 FXHW60 PHFO 121646 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 645 AM HST SUN JAN 12 2014 .SYNOPSIS... A TROUGH ALOFT NORTH OF THE ISLANDS WILL KEEP THE ATMOSPHERE UNSTABLE ENOUGH TO BRING A THREAT OF HEAVY RAIN AND THUNDERSTORMS THROUGH THIS EVENING. THE ATMOSPHERE WILL BECOME MORE STABLE OVER THE NEXT COUPLE OF DAYS AS THE TROUGH WEAKENS AND MOVES OFF TO THE NORTHEAST. A RIDGE ALOFT IS EXPECTED TO PRODUCE MUCH DRIER WEATHER THROUGH THE REST OF NEXT WEEK. && .UPDATE... UPDATED FORECAST TO EXPAND AREA OF THUNDERSTORMS. && .DISCUSSION... SATELLITE LOOPS SHOW A STRONG TROUGH ALOFT NORTH OF THE ISLANDS AND THE MORNING BALLOON SOUNDINGS CONTINUE TO SHOW AN UNSTABLE ATMOSPHERE OVER THE AREA THANKS TO THE TROUGH. RADAR AND SATELLITE LOOPS SHOW HEAVY SHOWERS AND THUNDERSTORMS NEAR THE ISLANDS... ESPECIALLY AROUND THE BIG ISLAND AND MAUI. THE THREAT OF HEAVY SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THIS EVENING...AND POSSIBLY LONGER. TEMPERATURES WILL BE COLD ENOUGH FOR SNOW ON THE SUMMITS OF MAUNA KEA AND MAUNA LOA BUT SIGNIFICANT ACCUMULATIONS ARE NOT EXPECTED. THE GLOBAL MODELS ARE IN GOOD AGREEMENT SHOWING THE TROUGH ALOFT WEAKENING AND MOVING OFF TO THE NORTHEAST OVER THE NEXT FEW DAY AND RIDGING ALOFT SPREADING OVER THE AREA FROM THE WEST. THE ATMOSPHERE WILL DRY OUT AND STABILIZE. BY TUESDAY NIGHT THE ATMOSPHERE WILL BE DRY AND STABLE ENOUGH SO THAT ONLY LIGHT RAIN CAN BE EXPECTED FROM TUESDAY NIGHT THROUGH THE END OF THE COMING WEEK. MEANWHILE A SERIES OF FRONTS WILL APPROACH THE ISLANDS FROM THE NORTHWEST THROUGH THE COMING WEEK KEEPING THE SUBTROPICAL RIDGE WEAK AND CLOSE TO THE ISLANDS. WITH THE RIDGE CLOSE TO THE ISLANDS WINDS WILL REMAIN GENTLE THROUGH NEXT WEEK. && .AVIATION... A SLIGHT CHANCE OF THUNDERSTORMS WILL CONTINUE TODAY THANKS TO A TROUGH ALOFT NORTH OF THE AREA. LOW LEVEL FLOW FROM THE SOUTHEAST IS CONCENTRATING CLOUDS AND SHOWERS OVER THE BIG ISLAND BUT THUNDERSTORMS WILL BE POSSIBLE ELSEWHERE AS WELL...ESPECIALLY OVER MAUI. SIGMET PAPA IS IN EFFECT FOR THUNDERSTORMS. AIRMETS FOR MT OBSC MAY BE NEEDED TODAY. && .MARINE... A MODERATE NORTHWEST SWELL ARRIVING MONDAY WILL PRODUCE SURF BELOW THE ADVISORY THRESHOLD THROUGH TUESDAY. A LARGER NORTHWEST SWELL ARRIVING TUESDAY NIGHT WILL PRODUCE SURF NEAR THE ADVISORY LEVEL WEDNESDAY. A VERY LARGE NORTHWEST SWELL ARRIVING WEDNESDAY NIGHT WILL LIKELY PRODUCE WARNING LEVEL SURF THROUGH FRIDAY. LIGHT TO MODERATE WINDS...WELL BELOW THE SMALL CRAFT ADVISORY THRESHOLD...ARE EXPECTED THROUGH THE COMING WEEK. && .HFO WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DONALDSON