Winter Storm in Alaska, February 26 to 27, 2012

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
558 AM AKST SUN FEB 26 2012

.SHORT TERM...RIDGE AXIS OVER THE COASTAL WATERS WILL PUSH EAST
TODAY AND BE OUT OF SE ALASKA BY LATE TONIGHT. A FRONTAL BOUNDARY
DEVELOPING IN THE WESTERN GULF MOVES TO THE EASTERN GULF TONIGHT.
THERE IS ALSO A STATIONARY BOUNDARY EXTENDING FROM JUST OFFSHORE
PAYA TO CSP TO NEAR FIIA2. THIS BOUNDARY EXPECTED TO PUSH A BIT
TO THE NORTHEAST LATE THIS AFTERNOON AND EARLY EVENING THEN BACK
TO SOUTHWEST AND ORGANIZE LATER TONIGHT IN ADVANCE OF APPROACHING
STRONGER FRONT.

 CLOUDS WILL SPREAD ACROSS NORTHERN HALF OF SOUTHEAST ALASKA
TODAY AND ACROSS SOUTHERN HALF TONIGHT. SNOW WILL SPREAD INTO
PAYA MIDDAY AND ACROSS NORTHERN HALF BY THIS EVENING. INITIALLY
ALL PRECIP EXPECTED TO BE SNOW BUT WILL MIX WITH RAIN ALONG NE
COAST EARLY EVENING AND TURN TO ALL RAIN S OF SITKA TONIGHT.
HEAVIEST PRECIP ARRIVES LATE EVENING ALONG NE COAST AHEAD OF
FRONT. THE INCREASE IN INTENSITY PLUS BLOCKED FLOW NEAR SURFACE
WILL PUSH RAIN SNOW LINE BACK TO SW WITH AROUND 12 INCHES OF
HEAVY SNOW EXPECTED PAYA-PAHN-CSP WHERE A WSW HAS BEEN POSTED.
REMAINDER NORTH ZONES HAVE SNOW ADVISORY WITH 3-5 INCHES
EXPECTED. PRECIP JUST REACHES SOUTHERN ZONES BY MONDAY MORNING.

 WILL HAVE A LEE SIDE LOW FORM ACROSS SOUTHERN YUKON TODAY. THIS
WILL INCREASE SOUTHERLY GRADIENTS TO SMCR IN THE CANAL AND ACROSS
NORTHERN PANHANDLE THIS AFTERNOON. THIS GRADIENT DIMINISHES LATE
EVENING AS FRONT APPROACHES AND PRES BEGIN TO FALL ALONG
DEVELOPING FRONTAL WAVE IN SOUTH CENTRAL GULF. WINDS IN COASTAL
WATERS REACH GALES ON SUNDAY AND DIMINISH TO SMCR IN NORTHERN
GULF WITH REORIENTATION OF FRONT AND DEVELOPING WAVE TO SOUTH.

 GOOD MODEL AGREEMENT THROUGH THE SHORT TERM ALTHOUGH THERE ARE
VERY MINOR BUT IMPORTANT DIFFERENCES IN LOCATION OF RAIN SNOW
LINE THIS EVENING WHICH WILL HAVE AN IMPACT ON WSW. USED NAM FOR
PRES AND WIND IN GRIDS.

.LONG TERM...MODELS CONTINUE TO BE IN FAIR AGREEMENT THROUGH MOST
OF THE WEEK BUT DIFFERENCES BEGIN TO POP UP WITH A SIGNIFICANT
LOW/FRONT MOVING OVER THE GULF/PANHANDLE THURSDAY AFTERNOON
THROUGH FRI. THERE WAS NOT MUCH CHANGE FROM THE PREVIOUS FORECAST
FROM MON NIGHT THROUGH NEXT WEEKEND AND JUST MINOR CHANGES IN THE
MID RANGE. USED A BLEND OF THE EC/NAM IN THE MID RANGE WITH ABOUT
AVERAGE FORECASTER CONFIDENCE BUT LOW CONFIDENCE ON THE SNOW
AMOUNTS OVER THE NORTHERN HALF OF THE PANHANDLE ON MON.

THE FORECAST FOR MONDAY CONTINUED TO BE TRICKY WITH P-TYPE ISSUES
AS THE NORTHERN HALF OF SE AK WILL BE JUST ON THE LINE BETWEEN
RAIN AND SNOW. THE BIG QUESTION IS WIND DIRECTION AT PLACES AS IT
WILL PLAY A BIG ROLE IF THE PRECIP WILL BE RAIN/MIX OR ALL SNOW. AT
THE START OF THE LONG RANGE PERIOD A RIDGE OF HIGH PRESS OVER THE
FORECAST AREA WILL CONTINUE TO SHARPEN UP AS THE COLD FRONT/SURFACE
TROF DRIFTS INTO THE EASTERN GULF THROUGH MON. THIS WILL KEEP
STRONG SOUTH WINDS OVER THE INNER CHANNELS PRODUCING GUSTY WINDS
OVER LAND AREAS WITH MAX SMALL CRAFTS OVER THE MARINE WATERS. AS
THE FRONT WILL WEAKEN OVER THE COASTAL AREAS THROUGH MON AFTERNOON
AND THE WINDS WILL DIMINISH. GUSTS TO 40 MPH WILL BE POSSIBLE OVER
THE NORTHERN LAND AREAS WITH GUSTS TO 35 MPH OVER THE NORTHERN
INNER AREAS IN THE MORNING BUT DIMINISH IN THE AFTERNOON AND
SLOWLY BACK AROUND TO THE NORTH LATE MON NIGHT. THE STRONG GUSTS
WILL ALONG DEVELOP ALONG THE COASTAL AREAS IN THE MORNING AND THEN
SPREAD OVER THE FAR SOUTHERN AREAS IN THE LATE MORNING WITH FRONT
MOVING OVER THE AREA.

ALL THE SOUTH WINDS FROM A STRONG SOUTHERLY PRESSURE GRADIENT WILL
WARM AIR TEMPS ABOVE FREEZING BUT DEW POINTS MAY REMAIN NEAR
FREEZING. THIS SITUATION WILL PRODUCE A RAIN AND SNOW MIX OVER THE
NORTHERN HALF OF THE PANHANDLE BUT DO NOT EXPECT MUCH IN
ACCUMULATIONS WITH HIGHEST AMOUNTS OVER THE FAR NORTHERN INNER
CHANNELS BUT WILL MIX WITH RAIN THROUGH DAY EXPECT FOR THE
HIGHWAYS AS THEY MAY SEE ACCUMULATIONS OF UP 2 INCHES. THE
NORTHERN GULF COAST AREA IS ALSO A HARD FORECAST AS THE WINDS WILL
BE FROM THE SOUTHEAST IN THE MORNING BUT WITH HEAVY PRECIP THERE
WILL BE A MIX OF RAIN AND SNOW DUE TO SNOW NOT MELTING BY THE TIME
IT MAKES IT TO THE SURFACE. AS THE TROF DRIFTS EAST THE WINDS WILL
BACK AROUND TO THE NORTHEAST AND BY THE AFTERNOON THE SHOWERS WILL
BE MORE SNOW THAN RAIN BUT AGAIN WITH AIR TEMPS ABOVE FREEZING DO
NOT EXPECT MUCH ACCUMULATIONS DURING THE DAY. THE SOUTHERN AREAS
WILL REMAIN ALL RAIN THROUGH MONDAY BUT AS THE COLD FRONT MOVES
EAST OF THE AREA THEY MAY SEE SOME SNOW MIXED IN MONDAY NIGHT.
SNOW AMOUNTS OVER THE INNER CHANNELS FOR MON NIGHT WILL BE
GENERALLY LESS THAN 1 INCH IN A MIX OF RAIN AND SNOW SHOWER
BECOMING ALL SNOW OVER THE FAR NORTHERN AREAS.

FROM TUE/WED...THE PARENT SURFACE LOW WILL DRIFT SE AND STRETCH
ACROSS THE GULF. THE UPPER LEVEL TROF WILL SLOWLY DRIFT EAST AND
KEEP SHOWER LIKELY TO SCATTERED OVER THE FORECAST AREA. FOR THE
MOST PART THE P-TYPE WILL BE TRICKY BUT A MIX LOOKS GOOD FOR NOW. WINDS
WILL BE ON THE LIGHTER SIDE BUT BE FROM THE NNE WITH THE LOW OVER
THE GULF.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM AKST
     MONDAY FOR AKZ018-020-021-025.
         WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 5 AM AKST
     MONDAY FOR AKZ019-022.
         WINTER STORM WARNING FROM NOON TODAY TO 5 AM AKST MONDAY FOR
     AKZ017.
MARINE...GALE WARNING FOR PKZ043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-021-022-031>036-041-042-053.

&&

MM/ABJ