FXAK68 PAFC 312200

AFDAFC



AREA FORECAST DISCUSSION 

SOUTH CENTRAL AND SOUTHWEST ALASKA

200 PM AKDT SAT JUL 31 2010



.MODEL DISCUSSION...

THE MODELS ARE CONSISTENT ON THE LARGE SCALE FEATURES THROUGH

TUESDAY. MODEL SOLUTIONS DIVERGE SIGNIFICANTLY AFTER TUESDAY. THE

PRIMARY DIFFERENCE IS IN WITH THE HANDLING OF THE UPPER LOW IN

BRISTOL BAY. THE ECMWF AND GFS CONTINUE TO HAVE MAJOR RUN TO RUN

CONSISTENCY ISSUES. YESTERDAY/S 12Z ECMWF AND TODAY/S 12Z GFS RUNS

MOVE THE LOW NORTH ALONG THE BERING SEA COAST. THE 00Z ECMWF AND 00Z

GFS SOLUTIONS CONVERGED FORECASTING MORE PROGRESSIVE PATTERN MOVING

THE RIDGE EAST AND BRINGING THE UPPER LOW ACROSS SOUTH CENTRAL. THE

12Z SOLUTIONS DIVERGE AGAIN WITH THE GFS MOVING THE LOW NORTH ALONG

THE BERING COAST AND THE ECMWF MOVING THE LOW INTO THE NORTHERN GULF

OF ALASKA.  THERE IS A HING OF CONVERGENCE AS THE 12Z GFS FLATTENS

THE SOUTH CENTRAL RIDGE AND BRINGS WEST SOUTHWESTERLY FLOW OVER

SOUTHERN ALASKA.  CONFIDENCE IS INCREASING BUT IS STILL LOW BEYOND

MIDWEEK.



.ANALYSIS AND UPPER LEVELS...

RADAR AND SATELLITE SHOW THE MAIN FRONTAL BAND OF RAIN HAS PUSHED

NORTH AND EAST OF COOK INLET THIS MORNING AND INTO THE SUSITNA VALLEY

AND OVER THE EASTERN NORTH GULF COAST AND PRINCE WILLIAM SOUND. A

WEAKER BAND OF SHOWERS IS MOVING OVER THE KENAI LATE THIS MORNING.  

SHOWERS ARE ROTATING THROUGH THE KUSKOKWIM VALLEY WITH ISOLATED

SHOWERS ACROSS BRISTOL BAY CLOSER TO THE SURFACE AND UPPER LOW

CENTERS. THE ANCHOR UPPER LOW IS CENTERED JUST WEST OF UNALASKA WITH

A STRONG TROUGH EXTENDING OVER THE SUSITNA VALLEY. THIS LOW

CENTER IS BRINGING SHOWERS TO MUCH OF THE CENTRAL AND EASTERN

ALEUTIANS AS WELL AS THE PRIBILOF ISLANDS TODAY. A HIGH

AMPLITUDE RIDGE IS IN PLACE OVER THE WESTERN BERING WITH LOW CLOUDS

AND FOG IN PLACE ACROSS THE WESTERN BERING UNDERNEATH AND EAST OF

THIS RIDGE.



.SHORT TERM FORECAST...

.SOUTH CENTRAL...STEADY RAIN IS TAPERING OFF FROM THE SOUTH AND WEST

TODAY ACROSS THE AREA WITH SCATTERED SHOWERS REMAINING IN THE WAKE.

THE UPPER LEVEL TROUGH AXIS IS FORECAST TO STALL OVER SOUTHERN ALASKA

WHICH MEANS CLOUDS AND SHOWERS WILL PERSIST OVER THE REGION INTO

MONDAY. 

 

.SOUTHWEST MAINLAND...AS WITH SOUTH CENTRAL ALASKA THE COMBINATION OF

SOUTHERLY MID LEVEL FLOW AND AN UPPER LEVEL TROUGH WILL RESULT IN

SCATTERED SHOWERS ACROSS MUCH OF THE REGION THROUGH MONDAY.



.ALEUTIANS...THE MAIN UPPER LOW CENTER OVER THE SOUTH CENTRAL BERING

WILL PERSIST INTO EARLY NEXT WEEK MEANING WIDESPREAD SHOWER ACTIVITY

FOR THE CENTRAL AND EASTERN ALEUTIANS AND THE PRIBILOFS. MODELS ARE

HINTING AT A FRONT THAT WILL MOVE INTO THE WESTERN BERING AND

ALEUTIANS BY MONDAY BRINGING RAIN AND BREEZY SOUTHWEST WINDS.





.LONG TERM FORECAST...A RIDGE OVER THE EASTERN HALF OF THE STATE AND

AN UPPER LOW OVER THE ALASKA PENINSULA WILL MAINTAIN SOUTH TO

SOUTHWESTERLY FLOW FOR THE SOUTHERN MAINLAND WHICH WILL KEEP

SOUTHWEST AND SOUTH CENTRAL ALASKA CLOUDY AND MOIST. THE WARMEST

TEMPERATURES NEXT WEEK WILL BE IN THE COPPER RIVER BASIN WHERE THE

UPPER LEVEL RIDGING SHOULD ALLOW FOR HIGHS TO PUSH TO NEAR 80 ON

TUESDAY. THE CURRENT THINKING IS THAT THE UPPER LOW - OR AT LEAST A

PIECE OF IT - WILL MOVE ACROSS SOUTH CENTRAL BY MIDWEEK BRINGING A

CHANCE FOR MORE RAIN. THIS LOW WILL BE KICKED OUT OF THE BERING BY A

LARGER LOW THAT SETTLES INTO THE NORTHERN BERING BY THE END OF NEXT

WEEK. THIS SHOULD ALSO BE A WET PATTERN FOR SOUTHWEST ALASKA AND MUCH

OF THE BERING. WITH THE SUBTROPICAL HIGH FAR NORTH THE STORM TRACK IS

OVER THE BERING WHICH MEANS CONTINUED ACTIVE AND GENERALLY UNSETTLED

WEATHER FOR THE SOUTHERN HALF OF THE STATE INTO NEXT WEEKEND. AS

MENTIONED IN THE MODEL DISCUSSION CONFIDENCE IN THE FORECAST AFTER

TUESDAY IS LOW GIVEN THE SIGNIFICANT DIFFERENCES BETWEEN THE MODELS

AND RUN TO RUN INCONSISTENCY IN THE INDIVIDUAL MODELS. 





.AER/ALU...WATCH/WARNING SUMMARY

PUBLIC...NONE

MARINE...NONE

FIRE WEATHER...NONE



RHH JUL 10