Small Craft Advisory 166, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
630 AM ADT FRI MAR 16 2007

.SYNOPSIS...
.SHORT RANGE...A LARGE UPPER LEVEL LOW REMAIN OVER THE GULF. OLD
SURFACE LOW HAS DUMBBELLED SW OVERNIGHT AS A SHORTWAVE OVER THE
NORTH PACIFIC DEVELOPED. MODERATE SW JET STREAM WITH LONG FETCH
OF MOISTURE PUSHED AS FAR NORTH AS SOUTHERN PANHANDLE THIS
MORNING AND IS EXPECTED TO MOVE OFFF TO THE EAST TONIGHT. SECOND
WESTERLY JET MAX WILL CUT ACROSS SOUTHERN AREAS TONIGHT. ARCTIC
BOUNDARY GENERALLY STATIONARY TODAY ALONG A PASI-FFIA2 LINE. COLD
FRONT MOVING ACROSS AREA FROM WEST WILL RE-ENFORCE COLD AIR
ALREADY IN PLACE AND PUSH BOUNDARY SOUTH OF FORECAST AREA
TONIGHT.

RADAR SHOWS STEADY LIGHT PRECIPITATION HAS SPREAD ACROSS SOUTHERN
TWO THIRDS OF PANHANDLE THIS MORNING WITH VELOCITY DATA SHOWING A
SHARP SHEAR LAYER AND SHALLOW OVERRUNNING AT PASI. THIS IS
EXPECTED TO INCREASE DURING THE DAY AS MID LEVELS VEER IN MID
LEVELS AND SURFACE WINDS BACK. WILL PROBABLY SEE MAX TEMPERATURES
EARLY TODAY WITH CAA AND WEB BULB COOLING LOWERING TEMPS THIS
AFTERNOON AND EVENING. PRECIP WILL CONTINUE TO SPREAD NORTH INTO
PAYA -PAGY BY LATE MORNING AS UPPER LEVEL DEFORMATION ZONE
DEVELOPS. EXPECT ALL SNOW ACROSS NORTHERN HALF TODAY WITH A MIX
OF RAIN AND SNOW ACROSS SOUTHERN HALF THROUGH THE AFTERNOON GOING
TO ALL SNOW SHOWERS TONIGHT.

SNOWFALL AMOUNTS EXPECTED TO AVERAGE IN 8 TO 12 INCH RANGE
THROUGH TONIGHT FOR ZONES 20 25 AND COULD GO HIGHER FOR ZONES 21
AND 22  WITH EARLIER START TIME AND FOR ZONE 19 WITH A NOON
SATURDAY ENDING TIME. PAGN ON THE CUSP AND HAVE CONTINUED SNOW
ADVISORY TODAY WHILE SNOW ADVISORY FOR PAPG HAS BEEN CANCELLED
DURING THE DAY.

BY TONIGHT WE WILL SEE PRECIPITATION TRANSITION TO WIDESPREAD
SNOW SHOWERS. COASTAL AND SOUTH CENTRAL SEE TO BE HARDEST HIT BY
SNOW SHOWERS TONIGHT AND HAVE POSTED ANOTHER SNOW ADVISORY
TONIGHT FOR 3 TO 5 INCHES. SOUTHERN ZONES WILL ALSO GO TO SNOW
SHOWERS TONIGHT BUT AMOUNTS CLOSER TO 1 TO 3 INCHES.

OVER DO NOT EXPECT A LOT OF WIND WITH THIS SYSTEM. HAVE SMCR
NORTH WINDS IN CHANNELED AREAS THIS MORNING THAT IS FORECAST TO
DROP OFF THROUGH AFTERNOON AND AN NE SMCR ACROSS THE NORTHERN
GULF THAT GO TO NW TONIGHT. COULD SEE BREEZY CONDITIONS IN
WESTERLY ALONG COAST LATER TONIGHT AND SATURDAY OTHERWISE WINDS
LIGHT TO VARIABLE 15 MPH.

.LONG RANGE...STILL LOOKS LIKE A PATTERN CHANGE WILL OCCUR NEXT
WEEK...AS PERSISTENT BLOCKY RIDGE OVER THE BERING SEA FINALLY IS
FORCED OUT TO THE WNW INTO ERN RUSSIA BY MON. TROF OVER THE GULF
WILL LIKELY LIFT OUT BY TUE AS A MORE POTENT TROF PROGRESSES
ACROSS THE PAC DURING THE EARLY PART OF THE WEEK. THIS SHOULD
EVENTUALLY WARM UP THE AREA...AND RAIN MAY BECOME THE PREDOMINANT
PRECIP TYPE BY THE END OF NEXT WEEK ESPECIALLY S OF THE PAJN-PAEL
CORRIDOR.

LOOKS LIKE NEXT MAIN SYSTEM WILL MOVE INTO THE FAR SE GULF OR
JUST S OF THERE SUN NIGHT OR MON. UPPER TROF WITH THIS ONE TAKES
ON A FAIRLY PRONOUNCED NEGATIVE TILT...AND THERE IS SOME QUESTION
WHETHER THE SHORTWAVES PHASE OVER THE GULF ALLOWING PRECIP TO
BUILD BACK FURTHER W AND N THAN CURRENTLY SHOWN IN FCST.
BASICALLY STUCK WITH 00Z GFS ON THIS ONE WHICH KEPT PRECIP
LIMITED TO SRN HALF...BUT KEPT IN CHANCE POPS FOR THE N.

AFTER A PERIOD OF SHOWERY WX TUE...LOOKS LIKE ANOTHER LOW WILL
MOVE IN...THIS TIME FURTHER N INTO THE GULF WED. AGAIN...WENT
WITH GFS ON THIS...WITH ECMWF JUST A TAD WEAKER ON THE LOW.
PRECIP THREAT GOES BACK TO LIKELY ALL AREAS WED WITH THIS SYSTEM.
THIS SHOULD BRING MILDER AIR IN WITH IT...SO MORE IN THE WAY OF
RAIN FOR THE CENTRAL AND SRN AREAS IS LIKELY. GFS HINTS THAT
ANOTHER LOW WILL MOVE IN FOR THU WITH ECMWF ALSO SHOWING A WAVE
ON THE MAIN FRONTAL ZONE OVER THE ERN GULF...SO KEPT THINGS ON
THE WET SIDE FOR THU ALSO.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WSW AKZ 019>22, 025 THROUGH 6 AM SATURDAY (NOON ZONE 19)
         SNOW ADVISORY 24 UNTIL 6 AM SATURDAY
         SNOW ADVISORY AKZ023 AND 026 6 PM FRI TO 6 AM SAT
MARINE...SMCR PKZ011-032 AND 041-052

MM/RWT