Small Craft Advisory 997, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKST SUN DEC 14 2008

.ANALYSIS AND UPPER LEVELS...
HIGH AMPLITUDE RIDGE IN PLACE OVER THE GULF OF ALASKA AND MOST OF THE
EASTERN INTERIOR OF THE STATE. A SHORT WAVE TROUGH WITH A STRONG
FRONTAL BOUNDARY IS MOVING ACROSS THE CENTRAL AND EASTERN BERING SEA.
A LONG WAVE UPPER LEVEL TROUGH IS LOCATED OVER EASTERN SIBERIA WHERE
AN ARCTIC AIRMASS IS BUILDING. AT THE SURFACE...A 1058 MB HIGH
PRESSURE IS CENTERED OVER THE CENTRAL YUKON TERRITORY WITH CLEAR
SKIES DOMINATING SOUTH CENTRAL ALASKA. HIGH CLOUDS ASSOCIATED WITH
THE APPROACHING FRONTAL BOUNDARY CAN BE FOUND OVER MUCH OF THE
SOUTHWEST INTERIOR AND ANOTHER SURFACE HIGH PRESSURE AT 1031 MB IS
CENTERED ON THE BACK SIDE OF THE FRONT OVER THE CENTRAL ALEUTIANS.

.MODEL DISCUSSION...
A SIMILAR THEME AS THE PREVIOUS SEVERAL MODEL DISCUSSIONS...GOOD
AGREEMENT AND CONSISTENCY THROUGH MONDAY NIGHT LEADS TO HIGH FORECAST
CONFIDENCE. ON TUESDAY OUT WEST...THE MODELS ARE STILL HAVING A
DIFFICULT TIME WITH THE DEVELOPMENT OF A NORTH PACIFIC LOW AND HOW IT
WILL INTERACT WITH THE STRONG AREA OF HIGH PRESSURE OVER MAINLAND
ALASKA. THE NAM...EC...AND UKMET ALL INITIALIZE VERY POORLY WHEN
LOOKING AT THE LAYER HUMIDITY AND COMPARING TO THE WATER VAPOR
SATELLITE IMAGERY. THE GFS IS THE BEST OF THE BUNCH AND HAS SHOWN
SOME IMPROVED CONSISTENCY RECENTLY IN ITS HANDLING OF THE DEVELOPING
SYSTEM. WILL TREND SOME OF THE MID RANGE FORECAST TO THE GFS BUT
OVERALL...NOT MAKING MANY CHANGES BEYOND TUESDAY. WILL LET THE
EVENING FORECASTERS LOOK AND SEE IF THERE IS ANY IMPROVEMENT IN THE
CONTINUITY.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
CLEAR SKIES AND FAIR TEMPERATURES...FOR MID DECEMBER...ARE DOMINATING
SOUTH CENTRAL ALASKA. THE EXCEPTION CONTINUES TO BE THE ANCHORAGE
BOWL WHERE LOW LEVEL STRATUS AND DENSE FOG REFUSE TO MIX OUT. A DENSE
FOG ADVISORY HAS BEEN ISSUED THROUGH MONDAY MORNING WHEN THE AFFECTS
OF THE UPPER TROUGH SHOULD FINALLY MIX UP THE BOUNDARY LAYER AND HELP
ERODE THE FOG. THE UPPER TROUGH WILL SHEAR APART AS IT CROSSES THE
ALASKA RANGE AND INTO SOUTHCENTRAL. PRECIPITATION WILL BE LIMITED TO
SHOWER ACTIVITY ALONG THE RANGE AND A CHANCE OF SNOW OVER KODIAK.
OTHERWISE...SKIES WILL QUICKLY CLEAR ON THE BACKSIDE AS AN UPPER
LEVEL RIDGE REGAINS CONTROL OF THE AREA. IN ANCHORAGE...FOG AND
STRATUS WILL LIKELY RETURN TUESDAY NIGHT.

SOUTHWEST ALASKA...
SNOW WILL SPREAD INLAND ALONG THE KUSKOKWIM DELTA TONIGHT.
SOUTHEASTERLY WINDS AHEAD OF THE FRONT ARE GUSTING TO 50 MPH FROM THE
WESTERN CAPES UP TO THE DELTA. SNOW WILL DIMINISH QUICKLY AS IT
SPREADS INLAND WITH ONLY AN INCH OR TWO EXPECTED OVER THE KUSKOKWIM
VALLEY TONIGHT THROUGH MONDAY MORNING. HIGH PRESSURE BUILDS MONDAY
WITH CLEAR SKIES AND NEAR AVERAGE TEMPERATURES EXPECTED THROUGH
TUESDAY. TUESDAY IS WHEN DISCREPANCIES IN THE MODELS ARISE AND
CONFIDENCE DECREASES. AT THIS POINT...EXPECTED WARM ADVECTION TO MOVE
NORTHWARD SPREADING RAIN AND SNOW ALONG THE COAST WHILE THE INTERIOR
REMAINS COLD AND DRY. PRECIPITATION SPREADS FURTHER INLAND WEDNESDAY
AS SOUTHWESTERLY FLOW AT ALL LEVELS HELPS PUSH THE MOISTURE TOWARD
THE LOWER KUSKOKWIM VALLEY. TEMPERATURES WILL BE ABOVE AVERAGE UNTIL
THE NEXT PUNCH OF ARCTIC AIR FROM SIBERIA INVADES THE AREA LATER IN
THE WEEK.

BERING SEA/ALEUTIANS...
A FRONTAL BOUNDARY IS NOW LOCATED ALONG A NORTH-SOUTH LINE FROM THE
PRIBILOF ISLANDS TO JUST WEST OF UNALASKA. ST PAUL ISLAND
TRANSITIONED TO SNOW QUICKLY ON THE BACK SIDE OF THE FRONT...SO
ANTICIPATING SIMILAR TRANSITION ALONG THE EASTERN ALEUTIANS AND
ALASKA PENINSULA LATER THIS EVENING. GUSTY NORTHWEST WINDS ARE
ACCOMPANYING THE FROPA. AGAIN...THIS FRONT WILL QUICKLY WEAKEN AS IT
MOVES EAST...SHIFTING OUR FOCUS OVER THE WESTERN ALEUTIANS WHERE A
STORM FORCE FRONT IS DEVELOPING TONIGHT BUT WILL SUFFER A SIMILAR
FATE AS THE PREVIOUS FRONT AS IT ENCOUNTERS THE LONG WAVE UPPER LEVEL
RIDGE OVER THE MAINLAND. IT WILL QUICKLY WEAKEN BEFORE IT MAKES IT TO
THE CENTRAL ALEUTIANS BRINGING ONLY SMALL CRAFT WINDS TO THE EASTERN
BERING SEA ON TUESDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...150 155 160 165 170 172 175 180 185.
         STORM WARNING...176.
FIRE WEATHER...NONE.

AB DEC 08