Small Craft Advisory 308, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
545 AM AKDT WED APR 6 2016

.SHORT TERM...AN UPPER DISTURBANCE OVER THE NERN PAC IS FORECAST
TO EJECT NEWD DURING THE SHORT TERM PERIOD. AS THIS
OCCURS...SURFACE LOW PRESSURE WILL DEEPEN OVER THE SRN GULF WED
NIGHT...AND A WARM FRONT WILL LIFT N TO THE SERN GULF AND SRN
PANHANDLE. HIGH END SMALL CRAFT WINDS /AROUND 30 KT/ WILL DEVELOP
IN THE WAKE OF THE WARM FRONT WED NIGHT OVER MARINE ZONES 41 AND
42...AS WELL AS CLARENCE STRAIT. IN ADDITION...SELY WINDS GUSTING
TO 40 MPH APPEAR PROBABLE FOR AKZ027. MEANWHILE...GAP WINDS TO 30
KT WILL EMANATE OUT OF CROSS SOUND IMMEDIATELY AHEAD OF THE FRONT.

SATELLITE DERIVED TOTAL PRECIPITABLE WATER SHOWS VALUES NEAR 1
INCH HAVE BEEN ENTRAINED INTO THE NERN PAC FRONTAL WAVE. THIS
WARM/MOIST AIRMASS WILL SPREAD NWD ACROSS THE SRN AND CNTRL
PANHANDLE TONIGHT...AND WITH SLYS STRENGTHENING ALONG AND S OF THE
WARM FRONT...THE ENVIRONMENT IS FORECAST TO BECOME FAVORABLE FOR
MODERATE TO LOCALLY HEAVY RAIN...PARTICULARLY FROM SITKA E TO
PETERSBURG AND N TOWARD JUNEAU /TIMING OF THE ONSET OF
MODERATE/HEAVY RAIN IS MORE UNCERTAIN FOR JUNEAU/.

INHERITED PRESSURE GRIDS WERE NUDGED TOWARD THE NAM/ECMWF. WIND
SPEED/DIRECTION OVER THE GULF WAS FURTHER NUDGED TO THE HI-RES
ARW. MANUAL MODIFICATIONS WERE MADE TO POP AND QPF IN ORDER TO
REFLECT WARM FRONTAL TIMING.

.LONG TERM...ON THURSDAY, FLOW FROM THE NORTH PACIFIC INTO THE
NORTHEAST GULF WILL BE VERY CLOSE TO MERIDIONAL AS THE DEEPLY
SATURATED PLUME OF MOISTURE ADVECTS NORTHWARD. NAM PW VALUES RISE
ABOVE 0.60 INCHES WITHIN THE COLUMN OVER YAKUTAT AND ONLY FALL
SLIGHTLY THURSDAY NIGHT AS JET ENERGY ALOFT PASSES NORTHEAST INTO
WESTERN CANADA. THUS THE HEAVY RAIN ACROSS THE CENTRAL PANHANDLE
SHOULD LIFT FARTHER NORTHWESTWARD QUICKLY ACROSS THE GLACIER
BAY/LYNN CANAL REGION TO STALL OVER YAKUTAT AND ELFIN COVE FOR
THURSDAY. AT THIS POINT, THURSDAY RAINFALL TOTALS AMOUNT TO AROUND
1 INCH OVER YAKUTAT, AND A QUARTER TO THREE QUARTERS OF AN INCH
ACROSS THE NORTHERN PANHANDLE. AS A RIDGE OF HIGH PRESSURE PUMPS
WARM AIR AND INCREASINGLY STABLE CONDITIONS, SOUTHERN PANHANDLE
TEMPERATURES SHOULD CLIMB INTO THE LOWER TO MIDDLE 60S, LIKE LAST
WEEK, THREATENING RECORDS.

BY THURSDAY NIGHT THE NORTH PACIFIC TROUGH ORIGINALLY RESPONSIBLE
FOR THE WET WEATHER ACROSS THE NORTHEAST GULF LIFTS NORTH AND
BEGINS TO BE SHUNTED NORTHEAST AS IT IS STEERED NORTHEAST BY JET
ENERGY ALOFT. THEREFORE CHANCES OF RAIN SPREAD EAST AND SOUTH
THURSDAY NIGHT. ONSHORE FLOW COUPLED WITH COOLER 850 TEMPERATURES
BRING IN WEAKLY UNSTABLE AIR BY LATE FRIDAY. HOWEVER, DRIER MID-
LEVEL FLOW WILL MEAN RAIN AMOUNTS WILL BE ON THE LIGHTER SIDE.

AS A NEW SYSTEM BOLTS EASTWARD SOUTH OF THE ALEUTIAN CHAIN
FRIDAY, A RIDGE WILL MOVE INTO THE PANHANDLE FROM THE GULF AND
HELP DRY THIS WEEKEND'S WEATHER. WET WEATHER LOOKS POISED TO
RETURN TO SOUTHEAST ALASKA EARLY NEXT WEEK.

WINDS WERE BOOSTED THROUGH THE CENTRAL INNER PASSAGES AS THE FRONT
LIFTS NORTHWARD, SO THAT STEPHENS PASSAGE AND NORTHERN CHATHAM
EXPERIENCE SMALL CRAFT WINDS THURSDAY. IN ADDITION, WINDS WERE
INCREASED THROUGH SUMNER AND FREDERICK TO 30 KT THURSDAY MORNING.
MODELS ARE STILL HAVING A DIFFICULT TIME WITH THE TRACK OF THE
SURFACE LOW ADVANCING NORTHWARD ON THURSDAY/THURSDAY NIGHT.
THEREFORE WINDS OVER THE GULF AS WELL AS THE PANHANDLE MAY NEED TO
BE ADJUSTED AT THIS LATE JUNCTURE. CONTINUED DISPARITY OF
SOLUTIONS FAILED TO LEAD US INTO MAKING MUCH MORE THAN CHANGES FOR
LOCAL EFFECTS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM THIS EVENING THROUGH LATE TONIGHT FOR AKZ027.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-033>036-041>043-051.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052-053.
&&

GARNER/JWA

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