Blizzard in Alaska, March 25 to 26, 2009

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKDT TUE MAR 24 2009

CORRECTED FOR SPELLING ERRORS

.ANALYSIS AND UPPER LEVELS...OMEGA BLOCK IN PLACE WITH RIDGE
OVER EASTERN SIBERIA AND LARGE CLOSED LOWS OVER CHINA AND THE
ALEUTIANS/BERING SEA REGION. AN UPPER LOW OVER THE EASTERN GULF
IS EXITING THE REGION. IT DID NOT PULL ALONG THE GULF SURFACE
LOW AS EXPECTED. THIS LOW REMAINS BACK OVER THE NORTHWESTERN
GULF...NEARLY STATIONARY AT THE MOMENT. THUS...SNOW CONTINUES
IN KODIAK WHERE UP TO 20 INCHES OF SNOW FELL WITH THIS STORM.
A FEW SNOW SHOWERS ASSOCIATED WITH ARE ALSO EVIDENT ON RADAR
FROM THE KENAI PENINSULA TO BRISTOL BAY. SATELLITE IMAGERY
SHOWS THE NEXT MAJOR STORM ABOUT 700 MILES SOUTH OF DUTCH
HARBOR WITH WARM FRONT EXTENDING WELL OUT AHEAD OF THE LOW.

.MODEL DISCUSSION...MODEL SOLUTIONS ARE GROUPED TOGETHER ON THE
TRACK OF THIS NEXT MAJOR STORM AND THIS HAS BEEN QUITE CONSISTENT
FROM RUN TO RUN...SO FORECAST CONFIDENCE IS HIGH. WHERE MINOR
DIFFERENCES IN TRACK OR DEPTH EXIST WILL BE USING THE GFS/NAM
WHICH ARE NEARLY IDENTICAL.

.SHORT TERM FORECAST...THE SURFACE LOW OVER THE GULF WILL LIFT
NORTHWESTWARD AND WEAKEN AS UPPER TROUGH AXIS LIFTS NORTHWARD
ACROSS MAINLAND ALASKA DUE TO A BUILDING RIDGE AHEAD OF THE NEXT
SYSTEM. THUS...SCATTERED SNOW SHOWERS WILL PERSIST THROUGH TONIGHT
FROM THE KENAI PENINSULA AND COOK INLET ACROSS THE MOUNTAINS TO THE
KUSKOKWIM VALLEY.

THE NEXT STORM WILL PRODUCE WIDESPREAD PRECIPITATION AND WINDS AS
IT MOVES FROM THE NORTH PACIFIC TONIGHT TO THE NORTHERN GULF
THURSDAY. THERE IS BLIZZARD POTENTIAL ON THE NORTH TO WEST SIDE OF
THE LOW JUST OUT AHEAD OF THE WARM FRONT/OCCLUDED FRONT. THE EASTERN
ALEUTIANS WILL STAY FIRMLY ON THE COLD SIDE OF THE FRONT...BUT
THERE IS SOME QUESTION AS TO WHETHER THEY WILL BE CLOSE ENOUGH TO
THE FRONT TO SEE STEADY SNOWFALL OR WHETHER THEY WILL REMAIN MORE
SHOWERY. A BLIZZARD WATCH WILL BE ISSUED FOR LATE TONIGHT THROUGH
THURSDAY AFTERNOON. HEADING FARTHER EAST...THE WARM FRONT WILL
CROSS THE ALASKA PENINSULA WEDNESDAY MORNING AND THEN OCCLUDE
SHORTLY THEREAFTER. ENOUGH WARMING WILL OCCUR TO CHANGE
PRECIPITATION TO RAIN FROM SAND POINT ON UP THE PENINSULA TOWARD
KING SALMON. BACK IN COLD BAY HOWEVER...THE FRONT DOES NOT LOOK
LIKE IT WILL CROSS OVERHEAD. SO WINDS WILL MAINTAIN A NORTHERLY
COMPONENT AND PRECIPITATION WILL LIKELY REMAIN PRIMARILY SNOW.
THUS...BLOWING SNOW WILL REDUCE VISIBILITIES...BUT WITH TEMPERATURES
SOMEWHERE NEAR FREEZING DO NOT EXPECT BLIZZARD CONDITIONS. BLIZZARD
CONDITIONS DO BECOME MORE LIKELY WEDNESDAY EVENING BEHIND THE LOW
AS COLD ADVECTION KICKS IN. SINCE THERE IS STILL LOTS OF TIME TO
LOOK AT THIS WILL NOT ISSUE ANYTHING QUITE YET. FOR PORTIONS OF THE
BRISTOL BAY NORTH AND WEST OF KING SALMON LOW LEVEL FLOW WILL REMAIN
NORTHERLY AND MAINTAIN TEMPERATURES AT OR BELOW FREEZING. SOME WARM
POCKETS OF AIR MAY MOVE OVERHEAD AS THE WARM OCCLUSION REACHES THE
AREA WEDNESDAY AFTERNOON. THEREFORE...THERE COULD BE SOME ISOLATED
AREAS OF FREEZING RAIN...BUT IF IT DOES OCCUR IT SHOULD BE
INSIGNIFICANT AND SHORT-LIVED. HEADING FURTHER NORTH WHERE
PRECIPITATION WILL DEFINITELY STAY ALL SNOW...STRONG NORTHERLIES
WILL DEVELOP ALONG THE KUSKOKWIM DELTA. SINCE THEY ARE FARTHER
FROM THE LOW AND ASSOCIATED FRONTAL SYSTEM THE SNOW WILL BE LIGHT.
HOWEVER...TEMPERATURES WILL REMAIN QUITE FRIGID AND SNOW WILL BE
FAIRLY DRY...SO IT WILL NOT TAKE MUCH TO BLOW IT AROUND AND REDUCE
VISIBILITIES. THEREFORE...WILL ISSUE A BLIZZARD WATCH FOR THE
KUSKOKWIM DELTA FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT.

THE BIGGEST CONCERN AS WE HEAD TO THE GULF AND SOUTHCENTRAL IS
FLOODING ON KODIAK ISLAND. THERE IS A DEEP SNOW PACK FROM THE LATEST
GULF STORM. AS THE LOW APPROACHES KODIAK ISLAND FROM THE SOUTHWEST
ON WEDNESDAY LOTS OF WARM AIR AND MOISTURE WILL MOVE IN. ALTHOUGH
PRECIPITATION WILL START AS SNOW TONIGHT IT WILL RAPIDLY CHANGE TO
ALL RAIN BY WEDNESDAY MORNING. WITH A STRONG FRONT MOVING THROUGH
PRECIPITATION WILL BE ENHANCED BY THE TERRAIN AND EXPECT KODIAK
CITY TO GET AT LEAST AN INCH OF RAINFALL WHILE TEMPERATURES RISE
TO AROUND 40. THIS WILL CAUSE PARTIAL MELTING OF THE SNOW AND ICED
UP STORM DRAINS WILL LIKELY PREVENT WATER FROM DRAINING. WILL ISSUE
A FLOOD ADVISORY TO HIGHLIGHT THIS THREAT. WITH SUCH A POWERFUL
SYSTEM HEADED FOR THE GULF IT LOOKS LIKE A NO DOUBTER FOR MAX GALES
TO STORM FORCE WINDS ACROSS THE GULF WATERS. A BARRIER JET WILL SET
UP ALONG THE NORTH GULF GULF COAST AS THE FRONT APPROACHES WEDNESDAY
AFTERNOON INTO EVENING. WILL INCREASE FORECAST WINDS TO 55 KT...BUT
WOULD NOT BE SURPRISED TO SEE GUSTS TO 75 KT OR STRONGER THROUGH
CHANNELED AREAS ALONG THE COAST. SOUTHERLY FLOW ALOFT WILL HELP PUSH
THIS FRONT INLAND...SO ALSO EXPECT SIGNIFICANT WINDS TO MAKE IT INTO
CORDOVA...PRINCE WILLIAM SOUND...AND PORTAGE VALLEY TO TURNAGAIN ARM.
THE WINDS COULD EVEN BRIEFLY REACH WARNING CRITERIA...BUT WILL NEED
TO RE-EVALUATE THIS AS WE GET CLOSER TO THE EVENT. STRONG EASTERLY
FLOW AHEAD OF THE FRONT WILL PRODUCE DOWNSLOPE DRYING IN THE USUAL
PLACES...ALTHOUGH WITH STRONG DYNAMICS AND ABUNDANT MOISTURE THERE
MAY BE BRIEF PERIODS OF LIGHT PRECIPITATION ON THE LEE SIDE OF
MOUNTAINS. ASIDE FROM KODIAK ISLAND...THE HEAVIEST PRECIPITATION IS
EXPECTED ACROSS WESTERN PRINCE WILLIAM SOUND AND THE WEST SIDE OF
COOK INLET. SNOW COULD BE HEAVY OVER WESTERN PRINCE WILLIAM
SOUND...SO THE POTENTIAL FOR A HEAVY SNOW WARNING WILL NEED TO BE
MONITORED. NORTHERLY LOW LEVEL FLOW DOWN THE SUSITNA VALLEY WILL
KEEP MOST OF THE SNOW OVER THE EXTREME SOUTHWEST PORTION OF THE ZONE.

ALTHOUGH THERE IS SOME UNCERTAINTY IT LOOKS LIKE THE STORM WILL HEAD
TO THE CLIMATOLOGICALLY FAVORED LOCATION OF PRINCE WILLIAM SOUND
WHERE IT WILL GRADUALLY WEAKEN LATER THIS WEEK. MEANWHILE...AN UPPER
LEVEL SHORTWAVE WILL DROP DOWN ACROSS THE BERING SEA BRINGING YET
ANOTHER SHOT OF COLD AIR. THUS...A CHANCE OF SNOW SHOWERS WILL
PERSIST ACROSS THE ENTIRE FORECAST AREA INTO NEXT WEEKEND.

.LONG TERM FORECAST...
THE SIBERIAN BLOCK WILL SLOWLY RETROGRADE THROUGH THE WEEKEND
INTO EARLY NEXT WEEK. THIS WILL KEEP MAINLAND ALASKA WITHIN THE MEAN
TROUGH POSITION AND ALSO BRING THE BERING SEA PROGRESSIVELY INTO
CYCLONIC FLOW AS WELL. THE BOTTOM LINE IS UNSETTLED WEATHER FOR
SOUTHERN ALASKA AND THE BERING SEA WITH PERIODIC IMPULSES WRAPPING
AROUND THE LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 155 185.
MARINE...STORM WARNING...120 130.
         GALE WARNING...125 132 138 140 141 150 155 160 165 170 171
                        172 179 180 185.
         HEAVY FREEZING SPRAY...165 179.
FIRE WEATHER...NONE.

SEB MAR 09