Heavy Snow in Alaska, November 4, 2005

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST THU NOV 3 2005

.SYNOPSIS...
.SHORT RANGE...A 987 MB LOW CENTERED OVER THE QUEEN CHARLOTTE
ISLANDS WILL CONTINUE TO WEAKEN AND MOVE NORTHEAST INTO BRITISH
COLUMBIA THIS AFTERNOON. MEANWHILE A DIFFUSE VERTICALLY STACKED
LOW OVER THE NORTH CENTRAL GULF WILL WEAKEN THROUGH TONIGHT. THIS
LOW WILL DRIFT NORTHWARD TONIGHT BEFORE MERGING WITH A WEAK UPPER
LOW DROPPING SOUTH FROM THE CENTRAL ALASKA INTERIOR. THE RESULTING
UPPER LOW WILL EMERGE OVER THE NORTHERN GULF AS A 991 MB SURFACE
LOW.  THE LOW IS EXPECTED TO WEAKEN AND AS IT TRACKS SLOWLY
SOUTHEAST SATURDAY MORNING.

THE 987 MB LOW TRACKING NORTHEASTWARD ACROSS OF THE QUEEN CHARLOTTE
ISLANDS HAS SPREAD A BAND OF STEADY PRECIP ACROSS ZONES 28 AND 29.
HEAVIER RAINFALL AMOUNTS OVERNIGHT WAS ENOUGH TO ALLOW UNMIXED SNOW
TO DEVELOP IN PAKT THIS MORNING.  WHILE UNMIXED RAINFALL HAS
RESUMED THIS MORNING...HEAVIER RAINFALL AND DOWNWARD MOTION WILL
KEEP THE POTENTIAL OF SNOW AND RAIN IN THE PICTURE TODAY.  CURRENT
FORECAST OF 1 TO 4 INCHES FOR INTERIOR PORTIONS OF ZONE 29 TODAY
REMAINS ON TRACK WITH MODELS INDICATING DECENT QPF AMOUNTS.

CURRENT SATELLITE IMAGES SHOW NUMEROUS BANDS OF CONVECTIVE SHOWERS
DEVELOPING IN BANDS IN THE WESTERN GULF WHERE A COLD INTERIOR
AIRMASS IS SPREADING SOUTH OVER WARMER GULF WATERS.  THESE BANDS
ARE WRAPING AROUND THE LOW IN THE NORTHERN GULF KEEPING PERSISTENT
SHOWERS ACROSS THE EASTERN GULF COAST AND THE PANHANDLE FOR THE
NEXT FEW DAYS.  MORE NORTHWESTER FLOW IN ZONE 19 CONTINUES TO KEEP
TEMPS BELOW FREEZING WITH MAINLY SNOW SHOWERS...EVEN NEAR SEA
LEVEL. ELSEWHERE HEAVIER RAIN SHOWERS ARE LIKELY TO ALLOW WITH
BRIEF PERIODS OF SNOW TO MIX WITH THE RAIN ACROSS THE
PANHANDLE...HOWEVER NO ACCUMULATIONS ARE ANTICIPATED WITH THE
PREDOMINATE PRECIPITATION TYPE BEING RAIN.  COOLER AIR ADVECTING
INTO THE NORTHERN PANHANDLE OVERNIGHT WILL BRING A MORE CONSISTANT
MIX OF RAIN AND SNOW SHOWERS. AGAIN ANY ACCUMULATION IS EXPECTED TO
BE LESS THAN AN INCH.  FORECAST PERISTENCE FOR FRIDAY IS THE BEST
BET WITH CONDITIONS REMAINING SIMILAR TO THE LAST FEW DAYS.

WINDS NEAR THE LOW IN THE NORTHEASTERN GULF IS CAUSING SMALL CRAFT
WINDS IN THE NORTHERN OUTSIDES...CROSS SOUND...AND ICY STRAIT.
WINDS WILL DIMINISH THIS AFTERNOON AS THE LOW SLOWLY WEAKENS AND
DRIFTS NORTH...HOWEVER SEAS...MEANING 8 FEET OR GREATER WILL KEEP
SMALL CRAFTS IN THE OUTSIDES THROUGH TONIGHT.

.LONG RANGE... THERE WONT BE MUCH CHANGE IN THE EXTENDED FCST THIS
AFTERNOON. HI POPS AND AT OR BELOW AVE TEMPS IS THE MAIN MESSAGE.
HOWEVER... MODEL SOLUTIONS VARY CONSIDERABLY AND CONFIDENCE IS ESPECIALLY
LOW IN THE MON-TUE TIME FRAME.

THE BIG PICTURE HAS COLD AIR LEAKING SOUTHWARD OVER THE WEEKEND AND A
SHORT WAVE ARRIVING MON-TUE WITH SNOW LIKELY FOR MANY AREAS FROM ROUGHLY
CROSS SOUND-JUNEAU LINE NORTHWARD...MIXED RAIN SNOW CENTRAL PANHANDLE...
AND RAIN SOUTHERN ZONES. THE FORECAST PROBLEM THE NEXT FEW DAYS WILL BE
ADDING DETAILS TO DAYS 4-7 REGARDING THE TIMING OF THE PRECIP AND THE
LOCATION OF THE RAIN/SNOW LINE.

EURO AND NCEP MODELS HAVE MAJOR DISCREPENCIES EARLY IN THE EXTENDED RANGE
STARTING ABOUT 48HRS. ENSEMBLE DIFFERENCES GROW STEADILY IN TIME. THE
COLD AIR IN THE AK INTERIOR NOW GREADUALLY SAGS S AND EAST IN TIME AS A
RIDGE BUILDS OVER THE NORTHERN BERING. BY EARLY NEXT WEEK A WAVY
NORTHERLY FLOW FROM OFF THE POLE WIGGLES THROUGH THE INTERIOR TO THE
NORTHERN GULF. THIS WOULD FAVOR AMPLIFYING THE PATTERN AND CAUSING
CYCLOGENESIS OVER THE NORTHERN GULF. IF FLOW TRAJECTORY OVER THE WATER
ENDS UP BEING BRIEF AND DYNAMICS IN SHORT WAVE WIGGLING SOUTHWARD HOLD
TOGETHER THEN SEVERAL INCHES OF SNOW WILL BE PREVELENT ACROSS THE
NORTHERN PANHANDLE ABOUT MON. IF THE TROF DIGS OFFSHORE SE AK MAY SEE
MORE OF A W-SW ONSHORE FLOW AND LESS WIDESPREAD SNOW. NCEP IS LEANING
TOWARD TOWARD EURO MODELS AND AN AMPLIFYING UPPER AIR PATTERN.  TA

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...NONE
MARINE...SCA 21 22 41 42 43 51 52  KJH/JT