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FXAK67 PAJK 231449
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
549 AM AKST SUN NOV 23 2014

.SHORT TERM...WEAK UPPER LEVEL SHORTWAVE TROUGH IS MOVING INTO
SWRN B.C. THIS MORNING. ENHANCED AREA OF ASCENT ON ITS NRN
PERIPHERY SUPPORTED A BRIEF PERIOD OF HEAVY RAINFALL IN
KETCHIKAN DURING THE EARLY MORNING...BUT RATES ARE QUICKLY
DIMINISHING AS THE WAVES MOVES E. FARTHER N...MINOR WAVES OF
ASCENT CONTINUE TO SPREAD ACROSS THE NRN/CNTRL PANHANDLE...AND
WILL YIELD BANDS OF SHOWERS THROUGH THIS AFTERNOON AND TONIGHT.
SMALL CRAFT SEAS RANGING FROM 9-11 FEET ARE PRESENT OVER THE
OUTSIDE WATERS...AND ARE FORECAST TO PERSIST THROUGHOUT THE SHORT
TERM PERIOD.

LATER THIS AFTERNOON INTO TONIGHT...AN UPPER TROUGH WILL MOVE
ACROSS THE N PAC WITH MODEST HEIGHT RISES OCCURRING DOWNSTREAM
FROM THE NERN PAC INTO SWRN CANADA. THIS WILL TIGHTEN THE UPPER
HEIGHT GRADIENT RESULTING IN A WSWLY 300 MB JET STREAK
STRENGTHENING TO AROUND 170 KT. A VORTICITY STREAMER WILL FORM
ALONG THE CYCLONIC SIDE OF THIS JET AND AID IN MODEST SURFACE
CYCLOGENESIS OVER THE SERN GULF TONIGHT. THE POSITION AND
ULTIMATE MAGNITUDE OF THIS LOW IS STILL UNCERTAIN. THE GEM
PRODUCES A DEEPER AND SLOWER SOLUTION...THE GFS AND HI-RES ARW/NMM
ARE FARTHEST S AND MOST PROGRESSIVE...WHILE THE NAM/ECMWF DEVELOP
A LOW THAT LIFTS NNE ALONG THE COAST OF THE PANHANDLE. GIVEN THE
NAM/EC ROUGHLY RESIDE IN BETWEEN THE ENVELOPE OF MODEL
SOLUTIONS...DECIDED TO GO WITH THEIR GUIDANCE. AS A RESULT...SMALL
CRAFT WINDS ARE FORECAST TO DEVELOP LATE TONIGHT OVER MARINE ZONES
41 AND 42 AS WELL AS CLARENCE STRAIT. ATTM...EXPECT WIND GUSTS FOR
LAND ZONES 27 AND 28 TO FALL SHY OF STRONG WIND CRITERIA. IN
ADDITION...A ZONE OF STRENGTHENING LOW-LEVEL WAA OCCURRING AHEAD
OF THE LOW WILL SUPPORT ANOTHER ROUND OF MODERATE RAINFALL RATES
OVER THE SRN PANHANDLE.

.LONG TERM...THE SURFACE LOW DISCUSSED ABOVE WILL PUSH ONSHORE
AND FILL SOMEWHERE IN THE NORTH/CENTRAL PANHANDLE MONDAY MORNING.
THE RESULTING GRADIENT OVER THE SOUTH WILL KEEP SOLID SMALL CRAFTS
GOING FOR CLARENCE STRAIT AND MINIMUM SMALL CRAFT FOR SOUTHERN
CHATHAM AND SUMNER STRAITS. IN ADDITION HIGH SEAS ABOVE 10 FEET
WILL PERSIST IN THE LOW`S WAKE FOR ZONES 41 AND 42 WITH WINDS
TURNING A MORE SOUTHWESTERLY DIRECTION. A TONGUE OF WARM AIR WILL
HAVE SWEPT ACROSS THE PANHANDLE ALONG WITH ASSOCIATED ASCENT. THIS
WILL KEEP THE RAINFALL STRATIFORM PERHAPS FOR THE ENTIRE DAY.
HOWEVER, THE FORECAST TRANSITIONS TO SHOWERS TO COVER ANY
INSTABILITY TRYING TO WORK ITS WAY BEHIND THE SYSTEM.

SOUTHWEST ONSHORE FLOW WITH SOME OROGRAPHIC ENHANCEMENT WILL KEEP
SHOWERS IN THE FORECAST THROUGH THE EARLY WEEK WHILE AT THE SAME
TIME ATMOSPHERIC THICKNESSES SLOWLY DECREASE. AS A PROXY TO
MEASURE THE OVERALL LAYER TEMPERATURE FOR THE ATMOSPHERE, WE LOOK
FOR THICKNESSES, OR TEMPERATURES, LOW ENOUGH TO SUPPORT SNOW
THROUGH THE ENTIRE COLUMN. AT THIS TIME, MODEL THICKNESSES ARE
MARGINAL AT BEST FOR SNOW. SINCE SHOWERS WILL BE DIMINISHING DURING
THE SAME PERIOD AS THICKNESSES WILL BE FALLING, DESPITE FORECAST
LOW TEMPERATURES FALLING JUST BELOW FREEZING, THESE LOW
TEMPERATURES ARE LIKELY TO BE REACHED BETWEEN SHOWERS, AND MOST OF
THE PRECIPITATION SHOULD FALL AS RAIN. HOWEVER, MONDAY MORNING
CANNOT RULE OUT THE POSSIBILITY OF A FEW FLAKES MIXING IN OVER THE
NORTHERN PANHANDLE, BUT IMPACTS SHOULD BE MINIMAL. CONFIDENCE
GROWS FOR SNOWFLAKES MIXING IN WITH RESIDUAL SHOWERS TUESDAY
NIGHT AS 1000-850 MB THICKNESSES BEGIN TO CROSS A 1290-METER
RUBICON.

AS THE UPPER LEVEL RIDGE AXIS PASSES EAST OF SOUTHEAST ALASKA
TUESDAY NIGHT, THE ATMOSPHERE DRIES OUT QUICKLY. RIGHT NOW THE
HOLIDAY LOOKS DRY AND CLOUDS LOOK TO PART. HOWEVER, THIS USUALLY
MEANS FALLING TEMPERATURES THIS TIME OF YEAR. THEREFORE WE HAVE
DROPPED INTERIOR TEMPERATURES WELL INTO THE 20S ACROSS THE
PANHANDLE AND FREEZING TEMPERATURES EVEN TO THE FAR SOUTHERN
COAST. THE RIDGE LOOKS TO PERSIST OVER THE GULF IN SOME FORM OR
ANOTHER THROUGH THE EARLY WEEKEND WHEN PERHAPS A BREAKDOWN BEGINS
TO OCCUR. HOWEVER, GUIDANCE IS NOTORIOUSLY QUICK TO BREAK DOWN
REX BLOCKS. SO CONFIDENCE DROPS FOR THE WEEKEND. ONE DETERMINISTIC
SOLUTION ADVOCATED BY THE ECMWF LOOKS VERY INTERESTING FOR EARLY
NEXT WEEK: A SHORTWAVE DRIVES SOUTHWEST FROM THE NORTHERN BERING
SEA ACROSS THE ALASKA PENINSULA TO SPAWN A SURFACE LOW IN THE
NORTHERN GULF. WITH COLDER AIR HAVING ALREADY SETTLED, A SIGNATURE
SUCH AS THIS USUALLY MEANS SIGNIFICANT SNOW FOR THE NORTHERN
PANHANDLE, BUT THIS IS ONE OF MANY DIVERGENT SOLUTIONS AND WILL
LIKELY BE GONE IN THE MODEL`S NEXT RUN.

FORECAST CONFIDENCE IMPROVING THROUGH THE WEEK INTO THE THANKSGIVING
HOLIDAY WITH A DRYING/COOLING TREND. CONFIDENCE STARTS TO FALL FOR
THE WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-035-036-041-042-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043-051.

&&

$$

GARNER/ADKINS

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