255  
FXAK69 PAFG 202232  
AFDAFG  
 
NORTHERN ALASKA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE FAIRBANKS AK  
232 PM AKDT WED SEP 20 2017  
   
DISCUSSION
 
 
MODELS...SOLUTIONS VERY SIMILAR IN THE NEAR TERM WITH HEIGHT  
DIFFERENCES OF ONLY 1-2 HPA FOR THE MAJOR FEATURES. MODELS  
HEIGHTS DIVERGE A BIT WITH TIME TO 2-5 HPA, BUT POSITIONS OF THE  
FEATURES REMAIN QUITE SIMILAR UNTIL FRIDAY AFTERNOON WHEN THEY  
START DIVERGING. THE SURFACE SOLUTIONS INITIALIZED WELL AGAINST  
THE 20/18Z ANALYSIS WITH ONLY MINOR PRESSURE DIFFERENCES. FOR THE  
SHORT TERM WILL UTILIZE A EQUAL BLEND FOR MOST ELEMENTS WITH A  
LEAN TOWARD THE NAM PRECIPITATION SOLUTION. PRECIPITATION TYPE  
CONTINUES TO BE A CHALLENGE, AND WILL BE UNTIL WINTER FULLY SETS  
IN NEXT MONTH.  
 
ALOFT AT 500 HPA...MAIN LONGWAVE TROUGH CONTINUES TO WORK ITS WAY  
EAST, BUT WILL STALL AND LIE FROM HIGH IN THE CANADIAN ARCHIPELAGO  
SOUTHWEST OVER NORTON BAY, AND SOUTH OVER THE CENTRAL ALEUTIANS  
INTO FRIDAY. THE TROUGH THEN SLIDES JUST A BIT EAST TO LIE FROM  
THE CANADIAN ARCHIPELAGO OVER DEMARCATION POINT TO BRISTOL BAY BY  
SATURDAY MORNING. A SHORTWAVE SOUTH OF THE ALASKA RANGE IS MOVING  
EAST THIS AFTERNOON, AND WILL MOVE OVER THE YUKON TERRITORY  
TONIGHT. A 547 DAM LOW WILL DEVELOP OVER THE BERING STRAIT THIS  
AFTERNOON AND MOVE INTO THE LONGWAVE TROUGH AS IT MOVES OVER  
NORTON BAY TONIGHT AND HEIGHTS FALL TO 540 DAM. RIDGING SOUTH OF  
THE MAINLAND WILL PUSH NORTH TO THE ALASKA RANGE AFTER THE  
SHORTWAVE MOVES INTO THE YUKON TERRITORY TONIGHT, AND OVER THE  
SOUTHEAST INTERIOR BY THURSDAY MORNING. A RIDGE AXIS THAT LIES  
OVER THE WESTERN ALASKA PENINSULA WILL ROTATE NORTHEAST THURSDAY  
PUSHING 552 DAM HEIGHTS NORTHWEST OVER FAIRBANKS AND FORT YUKON,  
THEN ROTATES OVER THE YUKON TERRITORY BY SATURDAY MORNING. RIDGING  
OVER SIBERIA WILL BUILD EAST OVER THE CHUKCHI SEA AND SOUTHWEST  
ARCTIC TONIGHT, AND BY THURSDAY AFTERNOON RIDGING WILL EXTEND FROM  
OVER WRANGEL ISLAND EAST TO 150W, AND BY FRIDAY AFTERNOON TO  
140W. AT 850 HPA...ZERO ISOTHERM LIES FROM FT MCPHERSON YT TO  
DELTA JUNCTION TO WASILLA TO NUNIVAK ISLAND, AND WILL PUSH BACK TO  
THE NORTH TONIGHT TO LIE FROM DAWSON YT TO LIVENGOOD TO ANVIK TO  
THE PRIBILOF ISLANDS BY THURSDAY AFTERNOON, AND CONTINUES TO SLIDE  
SLOWLY BACK TO THE NORTH THROUGH FRIDAY.  
 
SURFACE...A DECAYING FRONT LIES FROM FT MCPHERSON YT OVER THE  
UPPER YUKON FLATS TO A WEAKENING 1018 MB LOW NEAR GALENA, THEN  
SOUTHWEST TO A 987 MB LOW SOUTH OF ADAK. BY THURSDAY EVENING THE  
FRONT WILL BASICALLY DISSIPATE AND LEESIDE TROUGHING WILL DEVELOP  
NORTH OF THE ALASKA RANGE WITH A 1009 MB LOW DEVELOPING NEAR  
KANTISHNA. WEAK RIDGING OVER THE ALASKA RANGE WILL PULL BACK TO  
THE SOUTH. RIDGING BUILDING EAST ACROSS THE ARCTIC COAST WILL  
CONTINUE TO BUILD WITH A 1028 MB LOW NORTH OF DEADHORSE MOVING TO  
200 NM NORTH OF DEMARCATION POINT AS IT BUILDS TO 1031 MB, AND A  
1017 MB HIGH OVER THE GULF OF ANADYR SLIDING TO THE SOUTHWEST  
OVER THE NORTHERN BERING SEA BY THURSDAY AFTERNOON. THE RIDGING  
OVER THE ARCTIC COAST WILL HOLD IN PLACE INTO FRIDAY WITH A 1026  
MB HIGH DEVELOPING 150 NM NORTH OF POINT BARROW FRIDAY MORNING AND  
REMAINING STATIONARY INTO SATURDAY MORNING BEFORE IT MOVES EAST  
TO THE BEAUFORT SEA. INVERTED TROUGH OVER THE WEST COAST EXTENDS  
NORTH OVER KOTZEBUE SOUND, AND WILL REMAIN STATIONARY AS THE LOW  
SOUTH OF THE ALEUTIANS MOVES TO BRISTOL BAY BY FRIDAY MORNING AND  
A BROAD AREA OF LOW PRESSURE PUSHES OVER MAINLAND ALASKA. LEESIDE  
TROUGHING WILL ENHANCE THE PRESSURE GRADIENT ACROSS THE ALASKA  
RANGE, SO STRONG GUSTY WINDS STARTING LATE THURSDAY NIGHT TO  
SATURDAY MORNING IN ALASKA RANGE PASSES.  
 
ARCTIC COAST AND BROOKS RANGE...THE TALE OF TWO ARCTIC COASTS  
TODAY WITH THE HIGH SETTING UP JUST OFFSHORE OF BARROW. TO THE  
EAST EXPECT LOW CLOUDS, SOME LIGHT RAIN OR SNOW AND PATCHY FOG  
WITH THE ONSHORE FLOW. WINDS WILL BE NORTH TO EAST AT 10 TO 20 MPH  
EAST OF THE HIGH. TO THE WEST SOME CLOUDS, BUT PERIODS OF  
CLEARING SKIES WITH WINDS EAST TO SOUTH AT 5 TO 15 MPH. OVER THE  
BROOKS RANGE AND PLAINS EXPECT CLOUDY SKIES WITH A MIX OF WEATHER  
IN THE PLAINS AND MAINLY LIGHT SNOW IN THE CENTRAL AND EASTERN  
BROOKS RANGE. NO SIGNIFICANT SNOWFALL IS EXPECTED. WINDS WILL BE  
NORTHEAST TO EAST AT 5 TO 15 MPH. TEMPERATURES WARMING INTO THE  
MID TO UPPER 30S DURING THE DAY, AND IN THE 20S AT NIGHT.  
 
WEST COAST AND WESTERN INTERIOR...A MIX OF CLOUDS WILL RANGE FROM  
MOSTLY CLEAR AT TIMES NORTH OF THE SEWARD PENINSULA TO CLOUDY IN  
THE LOWER YUKON DELTA. SOME LIGHT RAIN IN THE MIDDLE YUKON  
ASSOCIATED WITH THE INVERTED TROUGH OVER THE WEST COAST WILL  
SLOWLY DISSIPATE TONIGHT. SOME LIGHT RAIN MOVING THE UPPER  
KUSKOKWIM VALLEY EARLY FRIDAY AS THE LOW MOVES INTO BRISTOL BAY  
AND A WEATHER FRONT PUSHES BACK TO THE NORTH. LIGHT RAIN SOUTH AND  
EAST OF GOLOVIN FRIDAY. WINDS NORTH TO EAST FOR MOST AREAS AT 5 TO  
20 MPH WITH THE STRONGEST WINDS NEAR THE BERING STRAIT.  
TEMPERATURES STEADY WITH LOWS IN THE 30S, AND HIGHS IN THE 40S.  
 
CENTRAL AND EASTERN INTERIOR...LIGHT RAIN MOVING THROUGH THE AREA  
WILL BE ENDING IN THE FAIRBANKS AREA AS IT MOVES NORTHEAST INTO  
THE EASTERN INTERIOR. SOME CLEARING BEHIND THE SYSTEM WILL BRING  
COOLING TEMPERATURES AND FOG ALONG THE RIVERS AND LAKES THURSDAY  
MORNING THAT MAY IMPACT VISIBILITY DURING THE MORNING HOURS.  
RAINFALL AMOUNTS WILL BE LESS THAN 0.25 INCH WITH THIS SYSTEM. THE  
NEXT SYSTEM IN LINE WILL BRING INCREASING CLOUDS THURSDAY  
AFTERNOON, BUT WITH LEESIDE TROUGH SETTING UP AND DOWNSLOPE/GAP  
WINDS DEVELOPING PRECIPITATION WILL BE LIMITED TO AREAS NORTH AND  
WEST OF FAIRBANKS. PERIODS OF SNOW IN DENALI NP TONIGHT AND  
THURSDAY WITH UP TO 2 INCHES OF ACCUMULATION IN THE PASSES ALONG  
THE PARK ROAD. MUCH HEAVIER AMOUNTS POSSIBLE AT HIGHER ELEVATIONS.  
ALSO A CHANCE OF SNOW ALONG THE PARKS AND RICHARDSON HIGHWAYS,  
BUT EXPECT IT TO MELT AS IT FALLS WITH ROAD TEMPERATURES STILL  
ABOVE FREEZING. SNOW ON THE STEESE HIGHWAY SUMMITS THIS EVENING,  
BUT NO SIGNIFICANT ACCUMULATION EXPECTED. LIGHT WINDS WILL BE  
VARIABLE, BUT MAINLY FROM THE NORTHWEST.  
 

 
 
COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE.  
 

 
   
HYDROLOGY
 
RIVERS RUNNING HIGH, BUT SLOWLY FALLING. RIVERS WILL  
REMAIN HIGH THROUGH THE WEEK.  
 

 
   
AFG WATCHES/WARNINGS/ADVISORIES
 
 
SMALL CRAFT ADVISORY FOR PKZ210.  
 

 
 

 
 
SDB SEP 17  
 
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