768  
FXAK68 PAFC 261712  
AFDAFC  
 
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE ANCHORAGE AK  
912 AM AKDT FRI MAY 26 2017  
   
ANALYSIS AND UPPER LEVELS
 
 
A BROAD UPPER LEVEL TROUGH REMAINS OVER THE MAJORITY OF THE AOR,  
WITH SOME RIDGING BUILDING OVER THE FAR WESTERN BERING, AND  
ANOTHER RIDGE AHEAD OF THE TROUGH OVER THE PACIFIC NORTHWEST. THE  
TROUGH REMAINS EVIDENT ON IR SATELLITE IMAGERY, WITH THE CLEARING  
LINE TRANSITING FURTHER EAST OVER THE YAKUTAT AREA. A FEW  
LINGERING SHOWERS CONTINUE TO TAPPER OFF OVER SOME OF THE  
MOUNTAINS ALONG THE NORTHERN GULF COAST, ALASKA RANGE, AND  
TALKEETNA MOUNTAINS. FURTHER WEST, A SURFACE LOW JUST SOUTH OF  
COLD BAY CONTINUES TO BRING SOME RAIN AND GUSTY WINDS TO THE  
ALASKA PENINSULA.  
 

 
   
MODEL DISCUSSION
 
 
OVERALL MODEL GUIDANCE SEEMS TO BE IN GOOD SYNOPTIC AGREEMENT  
WITH EACH OTHER. LARGER DIFFERENCES START TO OCCUR AS WE MOVE  
INTO THE WEEKEND, AND WATCH THE EVOLUTION OF A STRONG WAVE MOVING  
OUT OF THE BERING. AMERICAN MODELS SEEMS TO BE CHARGING THE WAY  
WITH REGARDS TO THIS FEATURE, BOTH FASTER AND DEEPER THAN THE  
CANADIAN AND EUROPEAN SOLUTIONS. BY SUNDAY AFTERNOON, MODEL SPREAD  
INCREASES BOTH AT THE UPPER AND LOWER LEVELS OF THE ATMOSPHERE,  
DECREASING OVERALL CONFIDENCE AS WE GO INTO THE HOLIDAY WEEKEND  
AND INTO NEXT WEEK.  
 

 
   
AVIATION
 
 
PANC...GUSTY SOUTHERLY WINDS WILL CONTINUE THROUGH THIS AFTERNOON  
AND EVENING. SOME SHOWERS ARE POSSIBLE AGAIN THIS AFTERNOON AND  
EVENING AS WELL, BUT VFR CONDITIONS SHOULD PREVAIL.  
 

 
   
SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)
 
 
CLOUDS AND SHOWERS WILL BE ON THE INCREASE YET AGAIN TODAY AS A  
WEAK SHORT- WAVE MOVES UP FROM THE GULF. HOWEVER, THE FLOW WILL BE  
DIFFERENT THAN YESTERDAY, WITH SOUTHERLY FLOW THIS MORNING  
BACKING TOWARD THE SOUTHEAST IN THE AFTERNOON. THE AREAS MOST  
LIKELY TO SEE SHOWERS WILL BE FROM WESTERN PRINCE WILLIAM SOUND  
ACROSS THE KENAI PENINSULA TO THE WESTERN SUSITNA VALLEY, WITH  
ISOLATED TO SCATTERED SHOWERS ACROSS THE REMAINDER OF THE REGION.  
ALSO, UPPER LEVEL TEMPERATURES WILL GRADUALLY WARM SO THE  
ATMOSPHERE WILL NOT BE AS UNSTABLE AS FRIDAY, THOUGH STILL  
UNSTABLE ENOUGH TO PRODUCE SOME LOCALLY HEAVY RAINFALL.  
 
ATTENTION WILL THEN SHIFT TO A LOW PRESSURE SYSTEM SOUTH OF THE  
ALASKA PENINSULA. AN UPPER LEVEL SHORT-WAVE DROPPING SOUTHEASTWARD  
ACROSS THE EASTERN BERING SEA TODAY WILL RE-INVIGORATE THIS LOW  
AS IT CONTINUES SOUTH OF THE ALASKA PENINSULA TONIGHT, AMPLIFYING  
THE FLOW. THIS WILL SPREAD RAIN NORTHWARD FROM KODIAK ISLAND TO  
THE NORTH GULF COAST TONIGHT THROUGH SATURDAY. FLOW WILL SHIFT  
SOLIDLY TO SOUTHEAST LEADING TO DOWNSLOPE DRYING IN THE LEE OF THE  
KENAI AND CHUGACH MOUNTAINS. THUS, THE BULK OF RAIN WILL BE  
CONFINED TO THE COAST ALONG WITH UPSLOPE AREAS ALONG THE WEST SIDE  
OF COOK INLET AND THE SUSITNA VALLEY. EVEN IF IT STAYS DRY INLAND  
CLOUD COVER WILL BE FAIRLY EXTENSIVE, SO TEMPERATURES WILL REMAIN  
ON THE COOL SIDE.  
 
LOOKING TO SUNDAY, THE UPPER TROUGH WILL EVOLVE INTO A CLOSED LOW  
AND LIFT NORTHWARD INTO SOUTHWEST ALASKA. DEPENDING ON THE EXACT  
TRACK (AND DIRECTION OF FLOW OVER SOUTHCENTRAL), THERE IS  
POTENTIAL FOR RAIN TO SPREAD INLAND.  
 

 
   
SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)
 
 
SOUTHWEST ALASKA WILL REMAIN IN A GENERALLY TROUGHY PATTERN FOR  
THE NEXT SEVERAL DAYS BRINGING A CONTINUATION OF THE PRESENT COOL  
SHOWERY WEATHER PATTERN. WHILE THE TROUGH THAT MOVED THROUGH  
YESTERDAY IS NOW CLEAR OF THE AREA ALLOWING SHOWERS TO WEAKEN  
SOMEWHAT AND BECOME LESS FREQUENT, A SURFACE LOW SOUTH OF THE  
ALASKA PENINSULA AND TRACKING EAST WILL SPREAD ADDITIONAL MOISTURE  
NORTH INTO SOUTHWEST ALASKA. SHOWERS WILL REINTENSIFY AND  
INCREASE IN COVERAGE THIS AFTERNOON AND EVENING AS SOLAR HEATING  
AIDS INSTABILITY. A TROUGH ASSOCIATED WITH THE SURFACE LOW WILL  
ROTATE ACROSS BRISTOL BAY THIS EVENING AND EXTEND NORTH INTO  
SOUTHWEST ALASKA WHERE IT WILL REMAIN STALLED TONIGHT THROUGH  
SATURDAY. THE SURFACE LOW WILL BEGIN DRIFTING SLOWLY NORTH  
SATURDAY NIGHT TO MOVE INTO SOUTHWEST ALASKA ON SUNDAY.  
 

 
   
SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)
 
 
THE SURFACE LOW CURRENTLY SOUTH OF THE WESTERN TIP OF THE ALASKA  
PENINSULA WILL CONTINUE EAST THEN STALL OVER THE SOUTHWESTERN  
GULF. A FLAT RIDGE BRINGING LOW STRATUS AND PATCHY FOG WILL  
PROGRESS FROM THE WESTERN ALEUTIANS/BERING EAST TO THE CENTRAL  
ALEUTIAN/BERING TONIGHT AND TO THE EASTERN ALEUTIANS AMPLIFYING  
NORTHWEST ACROSS THE PRIBILOF ISLANDS SATURDAY AND SATURDAY NIGHT.  
THE NEXT FRONTAL SYSTEM WILL REACH THE WESTERN ALEUTIANS LATE AND  
CONTINUE EAST TO THE CENTRAL ALEUTIANS SATURDAY NIGHT WHERE IT  
WILL STALL THROUGH SUNDAY.  
 

 
   
LONG TERM FORECAST (DAYS 3 THROUGH 7)
 
 
THE EXTENDED FORECAST BEGINS ON MONDAY WITH THE CUT OFF LOW THAT  
IS POISED TO DEVELOP NEAR KODIAK ISLAND THIS WEEKEND LIFTING  
NORTHWARD THROUGH WESTERN ALASKA. THIS WILL OCCUR AS PART OF AN  
AMPLIFICATION OF THE LARGE SCALE PATTERN OVER THE COURSE OF THE  
NEXT WEEK, WITH A SPRAWLING LONGWAVE TROUGH ENCOMPASSING THE  
BERING SEA AND WESTERN MAINLAND AS A STOUT RIDGE BUILDS OVER  
WESTERN CANADA. FORECAST CONFIDENCE REMAINS LOWER THAN NORMAL AS  
MODELS CONTINUE TO DIVERGE ON THE SMALLER SCALE DETAILS, BUT THIS  
SYNOPTIC PATTERN WILL GENERALLY RESULT IN CONTINUED CLOUDY AND  
SHOWERY CONDITIONS ACROSS THE SOUTHERN MAINLAND AS BROAD ONSHORE  
FLOW REMAINS FOCUSED ALONG THE GULF COAST BETWEEN THE LARGE SCALE  
FEATURES. BENIGN SHOWERY CONDITIONS CAN ALSO BE EXPECTED OVER MUCH  
OF THE BERING BENEATH THE UPPER TROUGH. TEMPERATURES WILL  
GRADUALLY CLIMB BACK TO AROUND NORMAL THROUGH THE WEEK AS THE CUT  
OFF LOW DEPARTS INTO THE ARCTIC AT THE BEGINNING OF THE WEEK AND  
SCOURS OUT WHAT REMAINS OF THE COLDER AIR ALOFT.  
 

 
 
   
AFC WATCHES/WARNINGS/ADVISORIES
 
 
PUBLIC...NONE.  
MARINE...NONE.  
FIRE WEATHER...NONE.  
 

 
 

 
 
SYNOPSIS AND MODEL DISCUSSION...TP  
SOUTHCENTRAL ALASKA...SEB  
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR  
LONG TERM...CB  
 
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