Wildfire in Alaska, June 1 to 7, 2003

NORTH ALASKA FORECAST DISCUSSION
230 PM ADT SAT MAY 31 2003

AT THE SURFACE...BROAD HIGH PRESSURE COVERS THE ARCTIC AND BEAUFORT
SEA COAST WITH A THERMAL TROUGH DEEPENING ON THE NORTH SIDE OF THE
ALASKA RANGE AND DIPPING SOUTHWESTWARD ALONG THE LOWER YUKON VALLEY
AND KUSKOKWIM DELTA. A VERTICALLY-STACKED 996 MB LOW SITS OVER THE
GULF OF ALASKA WITH WEAKENING OCCLUSION EXTENDING EASTWARD ACROSS THE
SOUTHEAST PANHANDLE...WITH A 990 MB LOW NEAR SHEMYA IN THE SOUTHERN
BERING. DENSE FOG CONTINUES TO PLAGUE NORTHWEST ALASKA WITH POOR
VISIBILITIES IN STRATUS/FOG AT POINT HOPE...SHISHMAREF...TIN
CITY...AND SAINT LAWRENCE ISLAND. AN ARCTIC FRONT LIES FROM ICY CAPE
TO DEMARCATION POINT.

ALOFT...500 MB RIDGE AXIS HAS MOVED NORTH...AND IS ALONG AN OLD
CROW-SEWARD PENINSULA LINE. CIRCULATION ABOUT CLOSED 500 MB LOW OVER
THE GULF OF ALASKA SWINGING SHORTWAVE WESTWARD ACROSS THE
SOUTHWESTERN INTERIOR...AXIS ROUGHLY MCGRATH-BETTLES...WHICH LINES UP
WITH SOME HIGH CLOUDS ON THE OVERHEAD IMAGERY. A SECOND SHORTWAVE
FOLLOWS OVER THE SURFACE OCCLUSION OVER THE SOUTHEAST PANHANDLE.

MODELS...IN REASONABLE AGREEMENT ON A LIKELY STORY THROUGH MONDAY...
CLOSED LOW ALOFT NOW ENTERING THE WESTERN BERING SEA FROM THE RUSSIAN
FAR EAST WILL DIG SOUTHWARD AND MERGE WITH GULF OF ALASKA CLOSED LOW
AS RIDGE ACROSS THE STATE WEAKENS AND RETREATS INTO NORTHERN YUKON
TERRITORY AT THE END OF THE WEEKEND....AND A NEW RIDGE BUILDS
NORTHWESTWARD FROM THE EASTERN GULF OF ALASKA INTO THE SOUTHEAST
INTERIOR. LOW FLOW/NO FLOW REGIME ALOFT HANDS THE WEATHER CONTROL TO
TOPOGRAPHY AND WEAK SURFACE COVERGENCE BOUNDARIES. AVN DOES A
SOMEWHAT BETTER JOB OF MAINTAINING PERSISTENT SURFACE THERMAL TROUGHS
IN THE INTERIOR...AND GETS THE EDGE FOR THIS ROUND OF FORECASTS FOR
FEATURE PLACEMENT. ETA WILL BE USED FOR CONVECTIVE FORECASTS IN THE
INTERIOR.

NORTH SLOPE...CONTINUING TO BE SCRAPED BY SHORTWAVES SCOOTING
EASTWARD OVER NORTH SIDE OF RETREATING ZONAL RIDGE... AND IN CLEAR
AREAS PLAGUED BY ONGOING FOG AND STRATUS. AS RIDGE FULLY RETREATS BY
MONDAY... SOME SHORTWAVE ACTIVITIY ON THE CREST OF THE RIDGE WILL
ENHANCE CLOUDS AND PRODUCE SOME LIGHT MIXED PRECIPITATION GENERALLY
FROM PRUDHOE BAY EASTWARD ON MONDAY. ARCTIC MARINERS... EASTERLIES
DECREASING AND BACKING TO THE SOUTH FROM BARROW EASTWARD OVER THE
WEEKEND... AND VEERING TO THE NORTH FROM WEST OF BARROW... AND WILL
STAY SUB-ADVISORY.

WEST COAST...GRADUAL INCREASE IN CLOUDINESS AS BERING SEA TROUGH DIGS
AND DEEPENS...BUT NO PRECIPITATION FOR THE NEXT COUPLE OF DAYS.
FOG/STRATUS WITH POOR VISIBILITIES WILL CONTINUE TO BE THE FORECAST
CHALLENGE THIS ROUND. FOR MARINERS...NORTH AND NORTHWEST WINDS
DECREASING THROUGH THE PERIOD AND WILL REMAIN BELOW ADVISORY LEVELS
FOR THE NEXT COUPLE OF DAYS.

INTERIOR...THERMAL TROUGHING AND TOPOGRAPHY THE KEY PLAYERS THIS
ROUND...SHOWERS THIS EVENING WILL BE GENERALLY SOUTH AND EAST OF A
FORT YUKON TO SAINT MARYS LINE... 300 J/KG CAPES CENTERED OVER TANANA
WITH THETA-E RIDGE EXTENDING FROM EAGLE TO ANVIK. WITH HIGH CLOUD
BASES...THESE WILL GENERALLY BE PRETTY DRY. ON SUNDAY...CONVECTIVE
POTENTIAL MOVES NORTH ALONG AN ARCTIC VILLAGE TO ANVIK AXIS UNDER A
THETA-E RIDGE...300 J/KG CAPE MAXIMA BETWEEN GALENA AND TANANA...AND
NEAR THE CANADIAN BORDER EAST OF ARCTIC VILLAGE. WITH ADDITIONAL
MOISTURE AVAILABLE...WILL EXPECT SOME WETTING RAINS WITH THIS FROM
FORT YUKON TO ANVIK TO EASE DRY THUNDERSTORM THREAT. AN EXCEPTION
WILL BE THE FORTYMILE COUNTRY WHERE THE DRY THUNDERSTORM THREAT WILL
CONTINUE FOR THE REMAINDER OF THE WEEKEND. FOR FIRE WEATHER...WILL
CONTINUE CURRENT ROUND OF RED FLAG WARNINGS THROUGH TONIGHT...AND
ANTICIPATE RED FLAGS FOR ZONES 222/223/224/225/226 FOR SUNDAY DUE TO
DRY THUNDERSTORM POTENTIAL. FOR HYDROLOGY...PRECIPITABLE WATERS AT
CLIMATOLOGY WITH PRECIPITATION AMOUNTS IN QUICK SHOWERS ON THE ORDER
OF A COUPLE OF TENTHS. EXPECT LITTLE FLASH FLOOD TROUBLE WITH THESE
DUE TO DRY SOILS. SURFACE RIDGE PENETRATING NORTHWESTWARD INTO THE
EASTERN ALASKA RANGE ON MONDAY WITH THERMAL TROUGH NORTH OF THE HILLS
WILL PRODUCE AUGMENTED GAP LOW THROUGH PASSES...BUT WINDS FORECAST TO
REMAIN BELOW WARNING THRESHOLDS FOR RIGHT NOW.

MEDIUM RANGE...SHOWING SOME DISAGREEMENT BY MIDWEEK...BUT ALL
MAINTAIN TROUGH OVER THE WEST COAST AND WESTERN INTERIOR...AND BUILD
RIDGE IN SOME FORM NORTHWARD UP THE CANADIAN BORDER. MRF/AVN KEEP
VERY MERIDIONAL PATTERN...WHILE ECMWF BROADENS THE TROUGH INTO AN
EASTWARD LOBE OVER THE GULF OF ALASKA...AND ROCKS THE CANADIAN RIDGE
TO THE NEGATIVE. PATTERN SUGGESTS GENERALLY CLOUDY CONDITIONS FOR
WEST COAST AND WESTERN INTERIOR...GENERAL OFFSHORE FLOW FOR THE
BEAUFORT SEA COAST...AND CLEAR/DRY CONDIITONS -- POSSIBLY AGGRAVATED
BY CHINOOK FLOW -- WITH ASSOCIATED CONVECTIVE POTENTIAL FOR THE
EASTERN INTERIOR THROUGH MIDWEEK.

.AFG...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...RED FLAG WARNINGS:
   SATURDAY EVENING...ZONES 215/216/219/220/221/222/223/224/225/226
   SUNDAY...ZONES 222/223/224/225/226

TS MAY 03