Gale Warning 471, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT TUE JUN 30 2009

.MODEL DISCUSSION...
IN THE SHORT TERM MODELS ARE IN GOOD AGREEMENT.IT APPEARED YESTERDAY
THAT THERE WAS FINALLY SOME CONSENSUS IN THE LONG TERM ON THE
PLACEMENT AND STRENGTH OF A LOW IN THE BERING SEA...BUT THE LATEST
RUN OF THE GFS ONCE AGAIN SEEMS TOO AGGRESSIVE AND HAS BEEN VERY
INCONSISTENT FROM RUN TO RUN. ON THE OTHER HAND...THE EUROPEAN HAS
BEEN MORE CONSISTENT WITH THIS FEATURE...SO ARE FAVORING THAT
SOLUTION IN THE LONG TERM.

.ANALYSIS AND UPPER LEVELS...
THE AMPLIFIED PATTERN CONTINUES ACROSS THE ENTIRE REGION. A VERY
LARGE UPPER LEVEL TROUGH IS PRESENT STRETCHING FROM EASTERN RUSSIA
ACROSS TO THE GULF OF ALASKA. EMBEDDED IN THIS OVER ALL TROUGH IS A
NEARLY VERTICALLY STACKED LOW PRESSURE CENTER IN THE WESTERN BERING.
AN UPPER LEVEL RIDGE CONTINUES TO BUILD ACROSS SOUTH CENTRAL ALASKA
AND EXTENDS INTO THE ALASKAN INTERIOR.

.SHORT TERM FORECAST...
ACROSS SOUTH CENTRAL ALASKA A THERMAL RIDGE CONTINUES TO BUILD AND IS
SLOWLY HEATING UP THE UPPER LEVELS. THUNDERSTORMS WILL BE POSSIBLE
AGAIN TODAY...AS THERE IS STILL SOME INSTABILITY...BUT WILL LIKELY BE
CONFINED TO THE MOUNTAINS. 12Z SOUNDING INDICATES VERY WEAK AND
VARIABLE WINDS ALOFT. STORMS THAT DO FORM WILL ONCE AGAIN MOVE VERY
SLOWLY...CREATING LOCALLY HEAVY RAINFALL. THUNDERSTORM CHANCES ALONG
THE MOUNTAINS WILL CONTINUE THROUGH THE SHORT TERM...AS SUBSIDENCE
FROM THE RIDGE IS NOT QUITE STRONG ENOUGH TO SUPPRESS ALL CONVECTION.

TO THE WEST A SURFACE LOW CONTINUES MOVE SLOWLY ACROSS THE WESTERN
BERING. WHILE THE SURFACE LOW IS NOT PARTICULARLY IMPRESSIVE THE
UPPER LEVEL TROUGH WILL CONTINUE TO BUILD CREATING AN AMPLIFIED
PATTERN. GUSTY WINDS AND ISOLATED SHOWERS WILL BE POSSIBLE ACROSS THE
BERING...BUT WINDS SHOULD REMAIN BELOW GALE FORCE THROUGH THURSDAY.

.LONG TERM FORECAST...
CONFIDENCE IN THE LONG TERM HAS BEEN REDUCED BY THE LATEST GFS RUN.
WILL TREND TOWARDS THE EUROPEAN SOLUTION FOR NOW BUT SERIOUS
DIFFERENCES IN THE STRENGTH AND POSITION OF A LOW MOVING INTO THE
BERING EXIST. AT PRESENT TIME IT APPEARS A STRONGER LOW WILL MOVE
FROM THE GULF OF ALASKA NORTH INTO THE BERING SEA. A NEARLY
STATIONARY COLD FRONT WILL SET UP NEAR BRISTOL BAY AND REMAIN THERE
THROUGH FRIDAY.

CONTRASTING THIS LOW...THE RIDGE ACROSS SOUTH CENTRAL ALASKA WILL
CONTINUE TO BUILD. THIS RIDGE SHOULD KEEP THE COLD FRONT FROM MOVING
EAST OF BRISTOL BAY...AND WILL ALSO DECREASE PRECIP CHANCES ACROSS
THE REGION. IT APPEARS THAT SOUTH CENTRAL ALASKA MAY HAVE A WARM AND
DRY FOURTH OF JULY HOLIDAY.

THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL LIKELY BE STRONG
ENOUGH TO GENERATE GALE FORCE WINDS STARTING FRIDAY. THE EXACT
STRENGTH OF THE WIND DEPENDS ON HOW THE LOW EVOLVES...AND WE WILL
CONTINUE TO MONITOR THIS SYSTEM.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...NONE
FIRE WEATHER...NONE

TARALDSEN JUN 09