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FXAK67 PAJK 232251
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
251 PM AKDT WED APR 23 2014

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING A WEAK
BUT RATHER COMPLEX INTERACTION BETWEEN LOW PRESSURE OVER THE
NORTHERN PANHANDLE, HIGH PRESSURE OVER THE AK GULF AND A
DEVELOPING INVERTED TROUGH OVER THE SOUTHERN PANHANDLE EXTENDING
FROM A LOW MOVING TOWARDS THE COAST OF WASHINGTON. THE NORTHER
LOW THAT PRODUCED SHOWERS OVER THE PANHANDLE LAST NIGHT IS
TRACKING NORTHWESTWARD WITH DIMINISHING SHOWERS AND CLEARING
SKIES BEHIND. SOME MORE STRATIFORM CLOUDS OVER THE AK GULF UNDER
THE HIGH PRESSURE RIDGE BUT WITH COLDER AIR MOVING IN FROM THE
SOUTH ALREADY SEEING MORE CONVECTIVE TYPE CLOUDS IN THE SOUTHERN
GULF. THE DEVELOPING INVERTED TROUGH WILL ENHANCE CLEARING OVER
THE SOUTHERN REGIONS WITH SUNNY SKIES EXPECTED FOR THURSDAY.
NORTHERN PANHANDLE WILL STILL HAVE SOME LINGERING REMNANTS OF THE
CURRENT SHORT WAVE FOR THURSDAY, ENOUGH TO KEEP SOME CLOUDS IN
THE FORECAST WITH ISOLATED SHOWERS FOR THE FAR NORTHERN
PANHANDLE. TEMPERATURES DICTATED BY CLOUD COVER TONIGHT AND
TOMORROW WITH THE NORTHERN REGIONS THAT REMAIN CLOUDY SHOWING
SMALLER DIURNAL RANGE WHILE THE SOUTHERN AREAS WHERE SKIES WILL
BE CLEAR WILL HAVE LOWER OVERNIGHT TEMPS AND HIGHS RISING INTO
THE MID TO UPPER 50S ON THURSDAY.

 SOUTHERLY WIND FLOW WILL SHIFT TO THE NORTH AS THE INVERTED
TROUGH DEVELOPS AND SHIFTS THE PRESSURE GRADIENT. WINDS OVER THE
SOUTHERN PANHANDLE AND INNER CHANNELS WILL INCREASE TO THE 15 TO
20 MPH RANGE WITH WITH THIS ADVANCING FEATURE BUT THE WEAK
GRADIENT FOR THE CENTRAL AND NORTHERN REGIONS WILL KEEP WINDS
LESS THAN 15 MPH. WAVES IN THE AK GULF WILL INCREASE THROUGH
THURSDAY FROM SOUTHWEST SWELL PRODUCED BY A LOW IN THE FAR
WESTERN GULF.

 MINOR DIFFERENCES BETWEEN MODELS TODAY. KEPT WITH THE ECMWF DUE
TO ITS CONSISTENCY AND BLENDED SOME 12Z ECMWF WITH INHERITED
GRIDS FOR PRESS WITH A BLEND OF NAM/ECMWF FOR POP. OVERALL
CHANGES WERE MINOR. FORECAST CONFIDENCE IS ABOVE AVERAGE.

&&

.LONG TERM...MODELS REMAIN IN GENERAL AGREEMENT THROUGH THE
WEEKEND WITH DECREASING CLOUDS AND CLEARING PROCESS EXPANDING
NORTHWARD ACROSS SOUTHEAST ALASKA THROUGH LATE FRIDAY. A WEAK
INVERTED TROUGH OF LOW PRESSURE MOVING OVER THE SOUTHERN
PANHANDLE FRIDAY EVENING WILL INCREASE CLOUDS AGAIN WITH
SCATTERED SHOWERS...THEN SPREAD NORTH THROUGH THE WEEKEND.
REFRESHED THE INHERITED FORECAST PACKAGE WITH THE 12Z RUN ECMWF
FOR ITS GOOD CONSISTENCY. THE RESULTANT CHANGES WERE SMALL AND
MADE A FEW TOUCHES TO FINE TUNE OVER PRESSURE AND WIND FIELDS.

 ISOLATED SHOWERS OVER THE NORTHERN AREAS THURSDAY EVENING WILL
BE ENDING...FOLLOWED BY DRY WEATHER WITH DECREASING CLOUDS AND A
BIT WARMING TREND. NO SIGNIFICANT WINDS ARE EXPECTED...EXCEPT ROUGH
SMALL CRAFT LEVEL SEAS CONTINUING OVER THE OUTER WATERS DUE TO
LONG PERIODS SOUTHWEST TO WEST SWELLS FROM THE OPEN SEAS.
INCREASING CLOUDS AGAIN ACROSS THE SOUTHERN AREAS WITH INCREASING
POPS OVER THE WEEKEND WILL COOL DOWN TEMPERATURES A BIT.

 MODEL SPREADS BECOME LARGER EARLY NEXT WEEK AS AN UPPER LEVEL
SHORTWAVE TROUGH MOVES ACROSS THE GULF...BUT THE MAIN JET STREAM
WILL REMAIN SOUTH OF THE AREA. BLENDED THE 12Z RUN WPC SOLUTIONS
OF SUPER BLENDING ENSEMBLE APPROACH FOR THE REMAINING LONG TERM
FORECAST PERIODS. MAIN JET STREAM ASSOCIATED WITH THE NEXT DEEP
SHARP UPPER LEVEL SHORTWAVE TROUGH WILL CURVE SOUTHWARD OVER THE
WESTERN GULF INTO NORTH PACIFIC...AND TURN TO NORTH ACROSS THE
EASTERN GULF AND THE PANHANDLE BY MID WEEK. AS THE UPPER LEVEL
PATTERN SHIFTS TO AMPLIFIED MERIDIONAL...UPPER LEVEL DYNAMICS WILL
BRING SOUTHEAST ALASKA A SERIES OF DISTURBANCES ORIGINATING IN
SUB-TROPICS. THIS CAN BE TRANSLATED FOR A SIGNIFICANT WARMING
NEXT WEEK. DAYTIME TEMPERATURES MAY REACH TO THE LOWER 60S OVER
THE SOUTHERN PANHANDLE.

 DUE TO INCREASED UNCERTAINTIES...PREDICTABLE SURFACE FEATURES
ARE DIFFICULT TO PIN POINT BUT A SURFACE LOW PRESSURE SYSTEM
MOVING ACROSS THE GULF IS EXPECTED TO BECOME ACTIVE AS IT MOVES
CLOSER TO SOUTHEAST ALASKA AND INCREASE EASTERLY PRESSURE GRADIENT
TO PRODUCE NEAR SMALL CRAFT LEVEL WINDS AND CONTINUED ROUGH
COMBINED SEAS ACROSS THE OUTER WATERS. IN GENERAL...MAINTAINED
INCREASING CLOUDS AND POPS MAINLY FOCUSING OVER THE SOUTHERN HALF
OF THE PANHANDLE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041>043.

&&

$$

PRB/AHN







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