199  
FGAK78 PACR 222026  
ESFAK  
 
HYDROLOGIC OUTLOOK  
NWS ALASKA PACIFIC RIVER FORECAST CENTER  
ANCHORAGE AK  
1 PM AKDT WED APR 22 2020  
   
.SPRING BREAKUP OUTLOOK FOR ALASKA
 
 
BREAKUP UPDATE: THE FORTY MILE RIVER UPSTREAM OF THE TAYLOR HIGHWAY  
HAS BROKEN UP AS WELL AS THE KUSKOKWIM RIVER NEAR NIKOLAI. THE TOZITNA  
RIVER HAS BROKEN UP WITH AN ICE JAM FORMING AND RELEASING. THE ANIAK  
RIVER IS REPORTED TO HAVE BROKEN UP DYNAMICALY AND IS MOSTLY OPEN AT  
THE CONFLUENCE WITH THE KUSKOKWIM. ICE IS BEGINNING TO LIFT ON THE  
KUSKOKWIM, YUKON AND KOYUKUK RIVERS.  
 
THE 2020 ALASKA SPRING BREAKUP FLOOD POTENTIAL IS FORECAST TO BE  
GENERALLY ABOVE AVERAGE SOUTH OF THE BROOKS RANGE AND AVERAGE FLOOD  
POTENTIAL FOR THE NORTH SLOPE. THE FLOOD POTENTIAL FORECAST IS BASED ON  
OBSERVED SNOWPACK, ICE THICKNESS REPORTS, AND LONG-RANGE TEMPERATURE  
FORECASTS AND FOCUSES ON THE KUSKOKWIM, TANANA , YUKON, KOYUKUK,  
COPPER, AND NORTH SLOPE RIVERS. RECENT OBSERVED AND FORECAST  
TEMPERATURES SUGGEST A GENERALLY EARLIER THAN NORMAL, MORE DYNAMIC  
TYPE BREAKUP FOR LOCATIONS STATEWIDE.  
 
TIMING OF BREAKUP STATEWIDE IS EXPECTED TO BE SEVERAL DAYS EARLIER  
THAN NORMAL. BREAKUP ALONG THE YUKON RIVER UPSTREAM OF FAIRBANKS  
IS EXPECTED TO BE 1 TO 3 DAYS EARLIER THAN MEDIAN DATES; GENERALLY 3 DAYS  
EARLIER AT LOCATIONS DOWNSTREAM FROM FAIRBANKS TO ANVIK; AND 3 TO 5 DAYS  
EARLIER AT LOCATIONS DOWNSTREAM FROM ANVIK TO THE MOUTH. BREAKUP ALONG THE  
KUSKOKWIM RIVER AT NIKOLIA DOWNSTREAM TO TULUKSAK ARE EXPECTED TO BE 1  
TO 2 DAYS EARLIER THAN MEDIAN DATES AND 2 TO 5 DAYS EARLIER DOWNSTREAM  
FROM TULUKSAK TO THE MOUTH.  
 
TEMPERATURES - STATEWIDE, TEMPERATURES OVER THE PAST FEW WEEKS GENERALLY  
HAVE BEEN NORMAL TO BELOW NORMAL. HOWEVER, TEMPERATURES OVER THE NEXT  
SEVERAL WEEKS ARE EXPECTED TO BE NORMAL IN AREAS NORTH OF THE BROOKS  
RANGE AND ABOVE NORMAL FOR THE REMAINING PARTS OF THE STATE. STATEWIDE,  
TEMPERATURES FOR APRIL AND MAY ARE EXPECTED TO BE ABOVE NORMAL.  
 
ICE - THE APRIL 1ST ICE THICKNESS DATA INDICATE THAT ICE THICKNESS IS NEAR  
NORMAL ACROSS THE STATE. A FEW MEASUREMENTS ACROSS INTERIOR ALASKA  
RANGED FROM 32 INCHES AT GALENA, WHICH IS 82% OF AVERAGE; 33 INCHES  
AT NENANA, WHICH IS 80% OF AVERAGE; 48 INCHES AT EAGLE, WHICH IS  
117% OF AVERAGE.  
 
SNOW - APRIL 1ST SNOWPACK BY THE NATURAL RESOURCES CONSERVATION SERVICE  
(NRCS) INDICATES GREATER THAN NORMAL SNOWPACK ACROSS INTERIOR ALASKA  
RANGING FROM 117% IN THE CENTRAL YUKON BASIN TO 197% OF AVERAGE IN  
THE KUSKOKWIM BASIN. THE YUKON GOVERNMENT IS ALSO REPORTING GREATER  
THAN NORMAL SNOWPACK ACROSS THE UPPER YUKON RIVER BASIN IN CANADA.  
THE SNOWPACK IS NEAR NORMAL ALONG THE NORTH SLOPE AND BELOW NORMAL ALONG  
THE GULF COAST AND THROUGHOUT SOUTHEAST ALASKA.  
 
CLIMATE OUTLOOK:  
 
APRIL AND MAY WEATHER IS THE MOST IMPORTANT FACTOR DETERMINING THE SEVERITY  
OF RIVER ICE BREAKUP. DYNAMIC BREAKUPS HAVE A HIGH POTENTIAL FOR ICE JAM  
FLOODING AND TYPICALLY REQUIRE COOLER THAN AVERAGE TEMPERATURES DURING MARCH  
AND INTO THE FIRST FEW WEEKS OF APRIL FOLLOWED BY AN ABRUPT TRANSITION TO  
WARMER THAN NORMAL TEMPERATURES IN LATE APRIL TO EARLY MAY. THERMAL BREAKUPS  
HAVE A LOW POTENTIAL FOR ICE JAM FLOODING AS RIVER ICE GENERALLY ROTS IN PLACE.  
 
THE CLIMATE OUTLOOK FOR SPRING 2020 SUGGESTS A MORE DYNAMIC TYPE BREAKUP THIS  
YEAR. OBSERVED TEMPERATURES IN MARCH THRU THE FIRST WEEK OF APRIL WERE GENERALLY  
BELOW NORMAL TO NORMAL. THE SECOND AND THIRD WEEKS OF APRIL WERE GENERALLY  
WARMER THAN NORMAL. TEMPERATURE FORECASTS FOR THE LAST WEEK IN APRIL  
INDICATE NEAR NORMAL TEMPERATURES STATEWIDE WITH EQUAL CHANCES FOR ABOVE AND  
BELOW NORMAL FOR EARLY MAY. THE MID-MARCH 3-MONTH CLIMATE OUTLOOK  
INDICATES INCREASED CHANCES OF ABOVE AVERAGE TEMPERATURES THROUGHOUT ALASKA.  
 
FURTHER INFORMATION CAN BE FOUND AT THE FOLLOWING WEB SITES:  
WEATHER-  
HTTPS://WWW.WEATHER.GOV/APRFC/AGAK78PACR  
 
SNOW-  
HTTPS://WWW.WEATHER.GOV/APRFC/NRCS_AK_SWE  
HTTPS://WWW.WEATHER.GOV/APRFC/SNOW_DEPTH  
HTTPS://WWW.WCC.NRCS.USDA.GOV/SNOW/  
 
ICE THICKNESS-  
HTTPS://WWW.WEATHER.GOV/APRFC/ICETHICKNESS  
 
CLIMATE PREDICTION-  
HTTP://WWW.CPC.NCEP.NOAA.GOV/  
 
RIVER ICE BREAKUP FLOOD THREAT:  
 
THE TWO GENERALIZED TYPES OF RIVER ICE BREAKUP ARE DYNAMIC (MECHANICAL)  
AND THERMAL. A DYNAMIC BREAKUP MOVES FROM THE HEADWATERS OF A RIVER  
DOWNSTREAM IN A SOMEWHAT LINEAR FASHION. ICE JAM FLOODING OCCURS MORE OFTEN  
DURING A DYNAMIC TYPE BREAKUP THAN A THERMAL TYPE. A THERMAL TYPE BREAKUP  
RESULTS IN THE RIVER ICE ROTTING IN PLACE PRIMARILY DUE TO GRADUAL TO RAPID  
WARM UPS AND LITTLE SNOWMELT RUNOFF. THERMAL TYPE BREAKUPS USUALLY RESULT  
IN FEWER ICE JAMS AND LESS CHANCE OF FLOODING.  
 
STATEWIDE, BREAKUP THIS YEAR IS EXPECTED TO LEAN GENERALLY TO THE DYNAMIC  
TYPE. TEMPERATURES STATEWIDE OVER THE PAST FEW WEEKS GENERALLY HAVE BEEN  
NORMAL TO BELOW NORMAL. HOWEVER, TEMPERATURES OVER THE NEXT SEVERAL WEEKS  
ARE EXPECTED TO BE NORMAL IN AREAS NORTH OF THE BROOKS RANGE WITH ABOVE  
NORMAL TEMPERATURES FOR THE REMAINING PARTS OF THE STATE. TEMPERATURES  
STATEWIDE FOR APRIL AND MAY ARE EXPECTED TO BE ABOVE NORMAL. SOUTH OF  
THE BROOKS RANGE, THE EXPECTED MORE DYNAMIC TYPE BREAKUP, ABOVE NORMAL  
TEMPERATURES, AND ABOVE AVERAGE SNOWPACK HAS INCREASED THE POTENTIAL FOR  
FLOODING THIS YEAR TO ABOVE AVERAGE, WHILE FLOODING POTENTIAL NORTH OF THE  
BROOKS RANGE IS EXPECTED TO BE AVERAGE.  
 
THE FOLLOWING TABLE GIVES AN ESTIMATION OF FLOOD POTENTIAL FOR  
VARIOUS LOCATIONS AROUND THE STATE AND BASIN RUNOFF VOLUMES.  
---------------------------------------------------------------------  
SNOWMELT RUNOFF VOLUME...EXPECTED WATER VOLUME FROM SNOWMELT DURING  
THE MELT SEASON.  
 
FLOOD POTENTIAL...THE LIKELIHOOD OF FLOODING FROM SNOWMELT AND/OR  
ICE JAMS. THIS IS INITIALLY CALCULATED BASED ON THE FLOOD  
FREQUENCY FOR THE 2000 TO 2019 HISTORICAL RECORD AND ADJUSTED  
TO REFLECT CURRENT CONDITIONS.  
 
* MEDIAN BREAKUP DATES ARE FOR THE PERIOD 1980 THROUGH 2019 AND ARE  
CALCULATED FOR LOCATIONS WITH AT LEAST 5 YEARS OF DATA.  
** ACTUAL BREAKUP DATE FOR THIS YEAR  
---------------------------------------------------------------------  
 
SNOWMELT FLOOD MEDIAN NO. OF FORECAST  
RIVER - REACH RUNOFF POTENTIAL BREAKUP YEARS BREAKUP  
VOLUME DATE* USED DATE  
------------- ---------- --------- ------- ------ --------  
SOUTHEAST PANHANDLE ABOVE  
 
KENAI RIVER AVERAGE LOW OPEN TO SKILAK LAKE  
 
ANCHOR RIVER BELOW LOW MOSTLY OPEN  
 
MATANUSKA RIVER ABOVE AVERAGE LOW  
 
SUSITNA RIVER ABOVE AVERAGE  
GOLD CREEK MOD  
SUNSHINE LOW-MOD 05/02 31 04/26-05/02  
 
YENTNA RIVER ABOVE AVERAGE  
LAKE CREEK LOW-MOD 04/30 29 04/27-05/03  
 
SKWENTNA RIVER ABOVE AVERAGE  
SKWENTNA LOW-MOD 04/29 25 04/23-04/29  
 
COPPER RIVER BASIN AVERAGE  
GAKONA RVR @ HWY LOW 04/29 32 04/23-04/29  
GULKANA RVR @ HWY LOW 04/29 30 04/23-04/29  
 
CHENA RIVER ABOVE AVERAGE  
CHENA LAKES PROJECT MOD  
FAIRBANKS LOW 04/25 27 OPEN  
 
TANANA RIVER ABOVE AVERAGE  
CHISANA @ NORTHWAY LOW-MOD 04/26 27 04/17-04/23  
SALCHA LOW-MOD  
FAIRBANKS LOW-MOD 04/28 19 04/26-04/02  
NENANA LOW-MOD 04/29 40 04/24-04/30  
MANLEY LOW-MOD 05/02 29 04/26-05/02  
 
KUSKOKWIM RIVER ABOVE AVERAGE  
NIKOLAI LOW-MOD 04/22 34 **04/21  
MCGRATH MOD 05/04 40 04/30-05/06  
STONY RIVER LOW-MOD 05/01 32 04/27-05/03  
SLEETMUTE MOD 05/01 31 04/27-05/03  
RED DEVIL MOD 05/03 34 04/28-05/04  
CROOKED CREEK MOD 05/03 34 04/29-05/05  
ANIAK MOD 05/04 37 04/29-05/05  
KALSKAG LOW-MOD 05/04 31 04/30-05/06  
TULUKSAK LOW-MOD 05/06 28 05/01-05/07  
AKIAK LOW-MOD 05/08 34 05/01-05/07  
KWETHLUK MOD 05/03 8 04/30-05/06  
BETHEL LOW-MOD 05/09 40 05/01-05/07  
NAPAKIAK LOW-MOD 05/10 25 05/03-05/09  
 
YUKON RIVER (UPPER) ABOVE AVERAGE  
DAWSON, YT LOW-MOD 05/03 40 04/29-05/05  
EAGLE MOD 05/03 40 04/28-05/04  
CIRCLE MOD-HIGH 05/07 36 05/02-05/08  
FORT YUKON MOD 05/10 36 05/04-05/10  
BEAVER LOW-MOD 05/09 24 05/04-05/10  
STEVENS VILLAGE LOW-MOD 05/10 23 05/05-05/11  
RAMPART LOW-MOD 05/10 25 05/04-05/10  
 
YUKON RIVER (MIDDLE) ABOVE AVERAGE  
TANANA LOW-MOD 05/07 35 05/01-05/07  
RUBY LOW-MOD 05/08 34 05/02-05/08  
GALENA MOD 05/10 39 05/04-05/10  
KOYUKUK MOD 05/08 14 05/04-05/10  
NULATO MOD 05/10 23 05/04-05/10  
KALTAG LOW-MOD 05/11 34 05/05-05/11  
ANVIK LOW-MOD 05/13 32 05/07-05/13  
 
YUKON RIVER (LOWER) ABOVE AVERAGE  
HOLY CROSS LOW-MOD 05/14 33 05/06-05/12  
RUSSIAN MISSION LOW-MOD 05/14 34 05/06-05/12  
MARSHALL MOD 05/14 28 05/06-05/12  
PILOT STATION LOW-MOD 05/13 23 05/07-05/13  
MOUNTAIN VILLAGE LOW-MOD 05/15 33 05/08-05/14  
ALAKANUK/EMMONAK MOD 05/20 32 05/12-05-18  
 
KOYUKUK RIVER ABOVE AVERAGE  
BETTLES LOW-MOD 05/09 38 05/01-05/07  
ALLAKAKET LOW-MOD 05/09 33 05/03-05/09  
HUGHES MOD 05/10 33 05/03-05/09  
 
SEWARD PENINSULA ABOVE AVERAGE  
BUCKLAND MOD 05/15 30 05/09-05/15  
 
KOBUK RIVER ABOVE AVERAGE  
KOBUK MOD 05/13 36 05/07-05/13  
SHUNGNAK LOW-MOD 05/16 29 05/10-05/16  
AMBLER LOW-MOD 05/16 35 05/10-05/16  
 
NOATAK RIVER ABOVE AVERAGE  
NOATAK LOW-MOD 05/13 23 05/17-05/19  
 
BROOKS RANGE - NORTH AVERAGE  
COLVILLE @ UMIAT LOW-MOD 05/24 19 05/16-05/22  
COLVILLE @ COLVILLE LOW-MOD 06/02 22 06/26-06/01  
 
SAGAVANIRKTOK RIVER AVERAGE  
DALTON HWY LOW-MOD  
 
FOR MORE DETAIL AND TO SEE A FLOOD POTENTIAL MAP, REFER TO OUR WEBSITE  
AT HTTPS://WWW.WEATHER.GOV/APRFC/FLOODPOTENTIAL  
 
THE NEXT SPRING BREAKUP OUTLOOK IS SCHEDULED AT 2PM AKDT FRIDAY APRIL 24TH, 2020  
 

 
BCJ  
 
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