Area Forecast Discussion
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FXAK67 PAJK 281427 AAA
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JUNEAU AK
527 AM AKST SAT FEB 28 2015

.SHORT TERM...EARLY MORNING SATELLITE IMAGE SHOWS HIGH PRESSURE
OVER THE CENTRAL AND EASTERN GULF...A WEAKENING INVERTED TROUGH
OF LOW PRESSURE OVER THE SOUTHERN PANHANDLE...AND ANOTHER HIGH
ACROSS YUKON AND BRITISH COLUMBIA. THE INVERTED TROUGH SLOWLY
MOVES SOUTHEAST AS THE HIGH OVER THE GULF DRIFTS EAST A LITTLE.
MID TO HIGH LEVEL CLOUD SHIELDS CONTINUE SPREADING ACROSS THE
NORTHEASTERN GULF COAST EAST TO OVER THE NORTHERN PANHANDLE.
RELAXED PRESSURE GRADIENT HAS RESULTED LIGHT AND VARIABLE WINDS
ACROSS SOUTHEAST ALASKA. OVERNIGHT TEMPERATURES REMAIN SLIGHTLY
ABOVE FREEZING ALONG THE IMMEDIATE COASTAL SECTIONS AND SOUTHERN
AREAS. ELSEWHERE...EARLY MORNING MERCURY READINGS RANGE FROM THE
MID 20S TO AROUND 30.

MODELS REMAIN IN GENERAL AGREEMENT FOR THE HIGH PRESSURE OVER THE
CENTRAL AND EASTERN GULF CONTINUES TO WEAKEN AND MOVES SOUTHWARD
THROUGH TONIGHT AS A DEVELOPING LOW NEAR KODIAK THIS AFTERNOON MOVES
SOUTHEASTWARD ACROSS THE EASTERN GULF AND PANHANDLE. REFRESHED THE
INHERITED FORECAST WITH THE NAM AND ECMWF FOR THEIR GOOD
CONSENSUS. AS THE LOW MOVES FARTHER SOUTHEAST...AN INVERTED TROUGH
OF LOW PRESSURE WILL FORM ACROSS THE OUTER WATERS TO HAIDA GWAII
LATE TONIGHT. NO SIGNIFICANT WINDS/SEAS ARE EXPECTED. AS THE
DEVELOPING LOW NEAR KODIAK DRIFTS ACROSS SOUTHEAST ALASKA...CLOUDS
WILL THICKEN AND POPS GRADUALLY INCREASES THROUGH LATE TONIGHT.

CONTINUED INCREASING INSOLATION WILL WARM UP AFTERNOON TEMPERATURES
TO THE LOWER 40S OVER THE NORTHERN PANHANDLE TO THE MID 40S ACROSS
THE CENTRAL PANHANDLE TO AROUND 50 ACROSS THE SOUTHERN AREAS. WITH
INCREASING CLOUDS AND INCOMING RAIN BAND...OVERNIGHT TEMPERATURES
WILL BE IN THE MID TO UPPER 30S OVER THE CENTRAL AND SOUTHERN
PANHANDLE. AN IMPULSE OF UPPER LEVEL TROUGH MOVES SOUTHEAST THIS
EVENING AND BREAK THE NEAR ZONAL UPPER LEVEL FLOW OVER THE AREA
AND BRING COLDER AIR MASS ACROSS THE NORTHERN PANHANDLE. EXPECTING
SNOW LINE WILL BE OVER THE NORTHEASTERN GULF COAST SOUTHEAST TO
GLACIER BAY TO JUNEAU AREA EAST TO ALONG COAST MOUNTAIN RANGE
SOUTHEAST TO HYDER REGION. THE LOW IS EXPECTED TO MOVE SOUTHEAST
RATHER QUICKLY THROUGH LATE TONIGHT WITH LIMITED QPF VALUES FOR
SNOW ACCUMULATION UP TO ABOUT 1 INCH.

.LONG TERM...ALL MAJOR MODELS HAVE COME INTO BETTER AGREEMENT
TONIGHT ON THE EVOLUTION OF THE WEAK LOW MOVING SOUTHEASTWARD
ACROSS THE PANHANDLE TONIGHT AND SUNDAY MORNING. TREND OF MOVING
PRECIP FURTHER SOUTH AND ENDING IT QUICKER CONTINUED ON THE
00Z/06Z RUNS...WE HAVE ONLY 0.1 TO PERHAPS 0.3 LIQUID TOTAL
PREDICTED NOW WITH ONLY THE NORTHERN FRINGE GETTING ANY THREAT OF
SNOWFALL OR MIXED PRECIP...WITH CLEARING SKIES SPREADING NORTH TO
SOUTH ON SUNDAY MORNING. PRECIP IS MAXIMIZED OVER THE SOUTHERN
COASTAL ZONES. IF THE TREND IN MODEL SOLUTIONS CONTINUES TODAY
THEN NORTHERN AREAS MAY SEE NO PRECIP AT ALL. 00Z NAM RUN WAS
STILL RELATIVELY WET WITH THIS SYSTEM (OUTLIER) WHILE THE 06Z RUN
WAS MORE IN LINE WITH OTHER MODELS ON THE DRIER/QUICKER SCENARIO.
CHOSE TO UPDATE WITH AN EC/NAM COMBO BUT THIS ONLY INTRODUCED
SLIGHTLY LIGHTER POPS AND A QUICKER EXIT. THIS WHOLE SCENARIO OF
A DRIER/QUICKER SYSTEM STARTED WITH THE SAME TREND NOTED IN THE
DAY SHIFT LOG TODAY.

AFTER A SHARP POST-TROUGH RIDGE ALOFT DOMINATES SUNDAY AFTERNOON
THROUGH MONDAY NIGHT WITH DRY WEATHER...AND THE INTERIOR
ANTICYCLONE GENERATING SOME MODERATE OUTFLOW WINDS OVER A FEW OF
THE CHANNELS AND EASTERN ZONES...MODELS BRING A NEW UPPER TROUGH
IN FOR TUESDAY BUT IT IS NOT ENERGETIC. IN THE MEANTIME OUTFLOW
WINDS WILL LIKELY LEAD TO SCA WINDS OVER SEVERAL NORTHERN INNER
CHANNELS SUN PM THROUGH MONDAY. MOST OF THE ENERGY WITH THE NEW
TROUGH IS HEADING SOUTHEAST INTO THE CENTRAL PACIFIC. AREAS OF
LIGHT QPF REACH THE NORTHERN PORTIONS DURING THE DAY AND THE REST
OF THE PANHANDLE TUES NIGHT. THE ONLY PRESSURE/WIND UPDATE
NECESSARY WAS ON MON WHERE THE NEW MODEL RUNS INDICATED LIKELY
STRONGER SURFACE OCEANIC WINDS OVER WESTERN PORTIONS. ON WEDNESDAY
WEAK TROUGHING REMAINS OVER THE GULF ON THE EC/GFS MODELS WITH
MOIST ONSHORE FLOW OVER THE PANHANDLE. WEDNESDAY MARKS THE DAY IN
THIS CYCLE WHERE MODEL SOLUTIONS BEGIN TO DIVERGE ON THE LOW-LEVEL
DETAILS WITHIN THE WEAK UPPER TROUGHING. THE GFS IS A BIT FURTHER
WEST THAN THE EC WITH THE SURFACE LOW WHILE THE GEM SHOWS A MORE
ORGANIZED SYSTEM SOUTHEAST OT THE ALEUTIANS WITH STRONGER ONSHORE
FLOW OVER THE PANHANDLE. BY EARLY THURSDAY ONE LOW COMES ONSHORE
ON THE GFS WITHIN CONTINUED GENERAL GULF TROUGHING. THE EC
CONTINUES TO SHOW WEAK, MOIST ONSHORE FLOW WITH A WEAK LOW OVER
THE WESTERN GULF. THE GEM CONTINUES TO SHOW A MORE ORGANIZED LOW
OVER THE WESTERN/CENTRAL GULF. WITH ALL THIS IN MIND COULD NOT
SPECIFY TIMING OF THESE SYSTEMS WITH ANY ACCURACY IN THE EXTENDED
PERIOD AND WENT WITH THE WPC GUIDANCE FROM WEDNESDAY ONWARD. THIS
LEFT THE GRIDS WITH WIDESPREAD CHANCE TO LIKELY POPS DURING THE
WED-SAT PERIOD. APPEARS AT THIS POINT THAT MOST OR ALL OF THE
PRECIP WILL BE LIQUID AT SEA LEVEL WITH THE ONLY DOUBTS BEING THE
SKAGWAY/HAINES AREA AND POSSIBLY YAKUTAT...PER USUAL. NO EVIDENCE
OF ANY ORGANIZED INFLUX OF COLD AIR INTO THE TROUGH THRU PERIOD.
MODEL CONFIDENCE WAS AVERAGE THROUGH THE PERIOD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

AHN/WESLEY

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