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000
FXAK67 PAJK 031346
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
546 AM AKDT TUE MAY 3 2016

.SHORT TERM...THE REMAINS OF A WEAKENING FRONT LIE STREWN ACROSS
THE SOUTHERN COAST MOUNTAINS. STEADY LIGHT RAIN HAS FALLEN ALL
NIGHT FROM WRANGELL/PETERSBURG SOUTH AND EASTWARD. AS COOLER AND
DRIER AIR ALOFT INFILTRATES THIS PORTION OF THE PANHANDLE, MORNING
STEADY RAINS WILL GIVE WAY TO SCATTERED SHOWERS INTO THE
AFTERNOON. MEANWHILE OVER OUR NORTHERN REACHES, SCATTERED SHOWER
ACTIVITY MOVED EASTWARD OVERNIGHT AS THE ATMOSPHERE CONTINUES TO
DRY OUT ALOFT. THE DAY PROMISES A STEADY EROSION OF SKY COVER. IR
IMAGERY INDICATES JUST SUCH A TREND. FARTHER NORTHWEST, A BAND OF
SHOWERS PASSED NORTH OF YAKUTAT A COUPLE OF HOURS AGO. ANOTHER
WEAK TROUGH OFFSHORE MAY DRAW MORE CLOUDINESS INTO THE AFTERNOON
WITH THE RISK OF ISOLATED SHOWERS INCREASING. LOOKING FORWARD TO
TONIGHT, THE FLOW ALOFT VEERS MORE SOUTHWEST. LAPSE RATES AND
HUMIDITIES INCREASE AND MOISTURE PROFILES DEEPEN ACROSS SOUTHEAST.
THUS WE EXPECT THICKER CLOUDINESS AND EXPANDING COVERAGE OF
SHOWERS.

A SURFACE RIDGE OVER THE PANHANDLE AND THE EASTERN GULF PERSISTS
TODAY INTO TONIGHT, WITH ALL BUT A WEAK FRONTAL SYSTEM MOVING INTO
THE CENTRAL GULF AFFECTING THE PATTERN. THEREFORE, WITH THE
EXCEPTION OF THE TIGHTER GRADIENT ACROSS THE NORTHERN INNER
CHANNELS WHERE SKAGWAY AND HAINES MAY BLOW SOUTHERLY 10 TO 20 MPH,
MOST AREA WINDS WILL BE RELATIVELY LIGHT WITH SOME MESOSCALE
AFFECTS ALLOWING FOR CHANNEL SEA BREEZE CIRCULATIONS. A 25-KT
BARRIER JET NEAR CAPE SUCKLING AND YAKATAGA WILL BE THE ONLY WIND
SMALL CRAFT TODAY, AND THIS WEAKENS INTO THE AFTERNOON.

MORE RAGGED SKY COVER ACROSS THE WESTERN ZONES ALLOWED FOR SOME
LOCAL PATCHY FOG TO DEVELOP IN SPOTS, NOTABLY HOONAH. BUT THIS IS
EXPECTED TO BE ONLY TEMPORARY AND THUS NOT SO IMPACTFUL. GIVEN THE
CONVECTIVE ATMOSPHERE, THIS SHOULD DISSIPATE SOON. TEMPERATURES
SHOULD RISE BETWEEN THE UPPER 40S TO THE MIDDLE 50S THIS
AFTERNOON. TONIGHT LOWS WILL DIP BETWEEN 35 AND 40 DEGREES.

FEW CHANGES WERE REQUIRED FOR TODAY`S FORECAST. WE DID SLIDE RAIN
CHANCES TO CERTAINTY ACROSS THE FAR SOUTHEAST FOR THE MORNING
HOURS AND MODIFIED THE SKY COVERAGE ACCORDING TO THE LATEST NASA
SPORT NIGHT MICROPHYSICS IMAGERY WITH SOME CONFIRMATION FROM THE
FAINT LIGHT OF EARLY MORNING WEBCAMS. WE USED NAM AND GFS FOR
MINOR UPDATES.

.LONG TERM...A WEAK RIDGE OF HIGH PRESSURE WILL REMAIN OVER THE
PANHANDLE AT THE BEGINNING OF THE EXTENDED RANGE ON WEDNESDAY
MORNING. ONSHORE FLOW WITH EMBEDDED WEAK IMPULSES MOVING FROM SW-NE
ACROSS THE AREA WILL KEEP SCATTERED SHOWERS ONGOING THROUGH
WEDNESDAY NIGHT. WINDS WILL GENERALLY BE LIGHT EXCEPT FOR NORTHERN
INNER CHANNELS WHERE THE PRESSURE GRADIENT WILL BE TIGHTER AS A
RESULT OF RIDGING OFFSHORE AND A WEAK THERMAL LOW OVER THE YUKON.

MODELS ARE IN GOOD AGREEMENT WITH ANOTHER STRONGER SYSTEM MOVING
INTO THE GULF ON THURSDAY WITH ITS ASSOCIATED FRONT TRACKING ACROSS
THE PANHANDLE ON FRIDAY. MAIN CHANGE TO THE FORECAST WAS TO
INCREASE RAIN CHANCES ACROSS THE NORTHERN HALF OF THE PANHANDLE ON
THURSDAY AHEAD OF THE FRONT AS THE RIDGE FLATTENS OUT. THIS WILL
RESULT IN INCREASING SOUTHWESTERLY FLOW AND MOISTURE FLUX INTO THE
PANHANDLE. MODELS CONTINUE TO SHOW PRECIPITABLE WATER VALUES 3-4
STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF YEAR WITH THIS
SYSTEM. THEREFORE CAN EXPECT A PERIOD OF MODERATE TO HEAVY RAIN
ACROSS A LARGE PORTION OF THE PANHANDLE THURSDAY NIGHT INTO FRIDAY.
THERE STILL REMAINS SOME DISAGREEMENT ON WHERE THE HEAVIEST RAIN
WILL FALL AS ANY POTENTIAL WAVE DEVELOPMENT ALONG THE FRONT AND ITS
TRACK WOULD IMPACT THIS. THE DETAILS WILL BE FINE-TUNED OVER THE
NEXT FEW DAYS. GALE FORCE WINDS CAN BE EXPECTED WITH THE FRONT OVER
THE EASTERN GULF AND A PERIOD OF GUSTY WINDS FOR THE INNER CHANNELS
AS THE FRONT MOVES OVER THE PANHANDLE ON FRIDAY.

PRECIPITATION CHANCES WILL DECREASE OVER THE LATTER HALF OF THE
WEEKEND. DRY WEATHER COULD RETURN TO SOUTHEAST ALASKA FOR THE FIRST
PART OF NEXT WEEK AS MODELS INDICATE A BUILDING RIDGE OF HIGH
PRESSURE OVER THE INTERIOR AND EASTERN GULF. STAY TUNED...

MAINLY USED THE 00Z GFS FOR UPDATES TO THE FORECAST. FORECASTER
CONFIDENCE IS ABOVE AVERAGE ON SYNOPTIC PATTERN THROUGH THE
WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051.
&&

$$

JWA/TPS

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