River Summary
Issued by NWS

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SRAK48 PACR 052350
RVAAK
AKZALL-292200-

ALASKA SPRING BREAKUP SUMMARY
NWS ALASKA PACIFIC RIVER FORECAST CENTER ANCHORAGE AK
2 PM ADT TUE MAY 5 2015

...SPRING BREAKUP SUMMARY FOR ALASKA....

FLOOD WARNING/WATCHES:
NONE

AREAS OF CONCERN - LOCATIONS IN THE STATE THAT WILL BE WATCHED CLOSELY INCLUDE
THE UPPER YUKON RIVER FROM EAGLE DOWNSTREAM TO FORT YUKON... KOBUK ON THE KOBUK
RIVER... BUCKLAND ON THE BUCKLAND RIVER... KALSKAG ON THE KUSKOKWIM RIVER
BECAUSE OF THE JUMBLED ICE FROM THE FALL BREAKUP... AND THE DALTON HIGHWAY NEAR
MILE 400 WHERE THE SAGAVANIRKTOK RIVER HAS BEEN OUT OF BANK NEAR DEADHORSE.
BREAKUP FLOODING IS POSSIBLE IN OTHER AREAS AS WELL... BUT THE COMBINATION OF
SNOWPACK... ICE THICKNESS... AND SUSCEPTIBILITY TO FLOODING CAUSE THESE
LOCATIONS TO BE THE MOST LIKELY TO SEE FLOODING THIS SEASON.

THE SPRING BREAKUP FLOOD POTENTIAL IS RATED AS LOW TO LOW-MODERATE STATEWIDE.
THIS FORECAST IS BASED ON OBSERVED SNOWPACK AND ICE THICKNESS REPORTS AND
MEDIUM TO LONG RANGE TEMPERATURE AND PRECIPITATION FORECASTS. CURRENTLY BREAKUP
AT MOST LOCATIONS IS EXPECTED TO BE A FEW DAYS EARLIER THAN NORMAL. ALTHOUGH
FLOOD POTENTIAL IS RATED AS LOW... FLOODING CAN STILL OCCUR IF ICE JAMS FORM
DOWNSTREAM OF A VILLAGE.

TEMPERATURES - THIS BREAKUP HAS BEEN CHARACTERIZED BY ABOVE NOMRAL
TEMPERATURES.  THE LONG RANGE OUTLOOK FOR MAY INDICATES ABOVE NORMAL
TEMPERATURES WITH THE GREATEST DEPARTURE FROM NORMAL OVER THE SOUTHERN PORTION
OF ALASKA...BUT STILL A 20% CHANCE OF ABOVE NORMAL TEMPERATURES IN THE NORTHERN
PORTION OF THE STATE.

PRECIPITATION - PRECIPITATION IS NOT EXPECTED TO BE A SIGNIFICANT FACTOR IN
THIS YEAR`S BREAKUP PROCESS.

FOR MORE INFORMATION ON THE TEMPERATURE AND PRECIPITATION OUTLOOKS PLEASE REFER
TO THE CLIMATE PREDICTION CENTER WEB SITE AT HTTP://WWW.CPC.NCEP.NOAA.GOV/

ICE - APRIL ICE THICKNESS DATA ARE AVAILABLE FOR A LIMITED NUMBER OF OBSERVING
SITES IN ALASKA.  APRIL 1ST MEASUREMENTS INDICATED THAT ICE THICKNESS WAS
VARIABLE ACROSS THE STATE... WITH LOCATIONS GENERALLY BETWEEN 60 AND 133
PERCENT OF NORMAL. MANY LOCATIONS IN THE TANANA BASIN REPORTED BELOW NORMAL
THICKNESS.  ICE THICKNESS IN SOUTHWESTERN... SOUTHCENTRAL... WESTERN... AND
INTERIOR ALASKA WAS BELOW NORMAL. ICE THICKNESS LIKELY IS BELOW NORMAL IN
THE LOWER YUKON... NORMAL IN THE MIDDLE YUKON AND NORMAL TO ABOVE NORMAL IN THE
UPPER YUKON BASIN. ACCUMULATED FREEZING DEGREE DAYS ARE WELL BELOW NORMAL
OVER MOST OF ALASKA.

SNOW - THE APRIL 1ST SNOWPACK ANALYSIS SHOWED WELL BELOW AVERAGE CONDITIONS IN
WESTERN AND SOUTHCENTRAL ALASKA WITH LESS THAN 50% OF NORMAL IN THE KUSKOKWIM
BASIN AND THE LOWER YUKON. THE FAIRBANKS AREA UP TO THE BROOKS RANGE WAS NEAR
NORMAL WHILE NORMAL TO ABOVE NORMAL SNOWPACK WAS OBSERVED IN MOST OF THE
CANADIAN YUKON. WARMER THAN NORMAL APRIL TEMPERATURES HAVE CAUSED THE SNOWPACK
AROUND THE STATE TO RIPEN AND BEGIN TO MELT.  MAY 1 SNOWPACK WILL BE AVAILABLE
DURING THE SECOND WEEK OF MAY.

FOR WEATHER... ICE AND SNOW CONDITIONS... PLEASE REFER TO
HTTP://WWW.APRFC.ARH.NOAA.GOV/FCST.PHP?PRODUCT=AGAK78PACR AND FOR VARIOUS SNOW
GRAPH OPTIONS... REFER TO THE APRFC WEB SITE AT HTTP://APRFC.ARH.NOAA.GOV OR
THE NRCS WEB SITE AT HTTP://WWW.AK.NRCS.USDA.GOV/SNOW/DATA/CURRENT.HTML

BREAKUP: NORMALLY SPRING BREAKUP IS DYNAMIC AND MOVES FROM THE HEADWATERS OF A
RIVER DOWNSTREAM IN A LINEAR FASHION. THE COMBINATION OF LOW SNOWFALL IN
WESTERN ALASKA COMBINED WITH THE WARM MARCH AND APRIL TEMPERATURES ALONG WITH
THE FORECAST OF ABOVE NORMAL STATEWIDE TEMPERATURES OVER THE NEXT 4 WEEKS WILL
LIKELY RESULT IN A THERMAL BREAKUP FOR RIVERS IN SOUTHCENTRAL AND SOUTHWEST
ALASKA. A THERMAL BREAKUP OCCURS WHEN THERE IS NOT ENOUGH SNOWMELT TO PUSH ICE
DOWNSTREAM AND TEMPERATURES GENERALLY WARM UP SLOWLY. IN A THERMAL BREAKUP...
EVEN THOUGH ICE STRENGTH DETERIORATES SIGNIFICANTLY... BREAKUP CAN OCCUR LATER
THAN NORMAL. ALSO... NO COHERENT BREAKUP FRONT DEVELOPS IN THIS SCENARIO... AND
MULTIPLE LOCATIONS MAY BEGIN TO SEE ICE MOVEMENT SIMULTANEOUSLY. ICE JAM
FLOODING FROM A THERMAL BREAKUP IS RARELY SERIOUS... BUT STILL POSSIBLE. TIMING
OF BREAKUP DURING A THERMAL BREAKUP MIGHT RANGE FROM SEVERAL DAYS EARLIER TO
SEVERAL DAYS LATER THAN  NORMAL... AND CAN BE INCONSISTENT UP AND DOWN THE
RIVER.

THE OUTLOOK FOR SIGNIFICANT PRECIPITATION IS LOW AND UNLIKELY TO INFLUENCE
BREAKUP THIS YEAR. EVEN WITH THIN ICE AND LOW SNOWPACK... A FASTER THAN
EXPECTED RISE IN TEMPERATURES OR A SIGNIFICANT RAIN EVENT COULD PRODUCE RAPID
MELT AND HIGHER THAN EXPECTED FLOWS... RESULTING IN ICE JAMS FORMING
AND INCREASED RISK OF FLOODING.

BREAKUP IS EXPECTED TO BE THERMAL IN SOUTHERN... SOUTHWESTERN... WESTERN ...
AND INTERIOR AREAS OF THE STATE... WITH THERMAL TO DYNAMIC BREAKUP IN
NORTHEASTERN AREAS... SPECIFICALLY IN THE UPPER YUKON AREA... AND DYNAMIC  ON
THE NORTH SLOPE. FLOOD POTENTIAL FROM ICE JAMS WILL BE LOW FOR MOST OF  THE
STATE.



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THE FOLLOWING TABLE GIVES ESTIMATES FOR FLOOD POTENTIAL... BASIN RUNOFF
VOLUMES... AVERAGE BREAKUP DATES (1980-2014)... AND AN INITIAL RANGE FOR SPRING

BREAKUP ESTIMATES FOR VARIOUS LOCATIONS AND BASINS THROUGHOUT THE STATE.

---------------------------------------------------------------------
SNOWMELT RUNOFF VOLUME...EXPECTED WATER VOLUME FROM SNOWMELT DURING
                         THE MELT SEASON.

FLOOD POTENTIAL...THE LIKELIHOOD OF FLOODING FROM SNOWMELT AND/OR
                  ICE JAMS.

*  AVERAGE BREAKUP DATES ARE FOR THE PERIOD 1980 THROUGH 2014 AND ARE
      CALCULATED FOR LOCATIONS WITH AT LEAST 5 YEARS OF DATA.
---------------------------------------------------------------------

                      SNOWMELT   FLOOD      AVERAGE  NO. OF  FORECAST
RIVER - REACH         RUNOFF     POTENTIAL  BREAKUP  YEARS   BREAKUP
                      VOLUME                DATE *   RECORD  DATE
-------------         ---------- ---------  -------  ------  --------
SOUTHEAST PANHANDLE    BELOW

KENAI RIVER            BELOW

ANCHOR RIVER           BELOW                 04/14     11

MATANUSKA RIVER        BELOW                 04/30      8      OUT**

SUSITNA RIVER          BELOW
GOLD CREEK                          LOW      05/03      7     04/29**
SUNSHINE                            LOW      05/03     26     04/30**

YENTNA RIVER           BELOW
LAKE CREEK                          LOW      05/02     24     04/28**

SKWENTNA RIVER         BELOW
SKWENTNA                            LOW      05/01     20     04/27**

COPPER RIVER BASIN    AVERAGE
GAKONA RVR @ HWY                    LOW      05/02     28
GULKANA RVR @ HWY                   LOW      05/01     27

CHENA RIVER           AVERAGE
CHENA LAKES PROJECT                 LOW
FAIRBANKS                           LOW      04/26     23     04/24**

TANANA RIVER          AVERAGE
NORTHWAY                            LOW      04/26     26     04/22**
SALCHA                              LOW                       04/28**
FAIRBANKS                           LOW      04/30     15     04/30**
NENANA                              LOW      05/01     32     04/24**
MANLEY                              LOW      05/04     25     05/01**

KUSKOKWIM RIVER        BELOW
NIKOLAI                             LOW      04/24     29     04/15**
MCGRATH                             LOW      05/07     35     04/30**
STONY RIVER                         LOW      05/06     27     04/30**
SLEETMUTE                           LOW      05/06     26     04/30**
RED DEVIL                           LOW      05/07     29     04/30**
CROOKED CREEK                       LOW      05/07     29     04/29**
ANIAK                               LOW      05/08     32   05/03-05/06
KALSKAG                             LOW      05/08     26   05/03-05/06
TULUKSAK                            LOW      05/10     23   05/03-05/08
AKIAK                               LOW      05/11     28   05/03-05/09
KWETHLUK                            LOW
BETHEL                              LOW      05/12     34     05/04**
NAPAKIAK                            LOW      05/14     20   05/04-05/11

YUKON RIVER (UPPER)   AVERAGE
DAWSON, YT                          LOW      05/05     34     05/04**
EAGLE                               LOW      05/05     34   05/04-05/07
CIRCLE                            LOW-MOD    05/10     31   05/06-05/09
FORT YUKON                          LOW      05/11     31   05/07-05/11
BEAVER                              LOW      05/11     19   05/07-05/11
STEVENS VILLAGE                     LOW      05/12     18   05/08-05/12
RAMPART                             LOW      05/12     20   05/08-05/12

YUKON RIVER (MIDDLE)   BELOW
TANANA                              LOW      05/10     30   05/05-05/08
RUBY                                LOW      05/12     29   05/06-05/09
GALENA                              LOW      05/13     34   05/06-05/10
KOYUKUK                             LOW      05/13     10   05/06-05/11
NULATO                              LOW      05/13     19   05/06-05/11
KALTAG                              LOW      05/14     29   05/07-05/12
ANVIK                               LOW      05/17     28   05/08-05/13

YUKON RIVER (LOWER)    BELOW
HOLY CROSS                          LOW      05/16     28   05/08-05/12
RUSSIAN MISSION                     LOW      05/16     29   05/08-05/12
MARSHALL                            LOW      05/16     23   05/08-05/12
PILOT STATION                       LOW      05/17     18   05/09-05/13
MOUNTAIN VILLAGE                    LOW      05/19     28   05/10-05/15
ALAKANUK/EMMONAK                    LOW      05/23     29   05/13-05/19

KOYUKUK RIVER         AVERAGE
BETTLES                             LOW      05/10     33   05/06-05/08
ALLAKAKET                           LOW      05/11     29   05/07-05/09
HUGHES                              LOW      05/11     28   05/07-05/10

SEWARD PENINSULA       BELOW

BUCKLAND RIVER         BELOW
BUCKLAND                          LOW-MOD    05/18     25   05/13-5/19

KOBUK RIVER            BELOW
KOBUK                             LOW-MOD    05/17     31   05/05-05/11
SHUNGNAK                            LOW      05/18     25   05/06-05/12
AMBLER                              LOW      05/19     31   05/07-05/13

NOATAK RIVER          AVERAGE
NOATAK                              LOW      05/20     20   05/17-05/23

BROOKS RANGE - NORTH  AVERAGE
COLVILLE @ UMIAT                    LOW      05/24     16   05/21-05/27
COLVILLE @ COLVILLE                 LOW      06/02     18   05/30-06/05
SAGAVANIRKTOK NR PRUDHOE            HIGH*    05/25     19   05/21-05/29

*NWS HAS NO RECORD OF ICE JAM RELATED FLOODS FOR THE SAGVANIRKTOK. CONSIDERING
CURRENT FLOODING CONDITIONS CAUSED BY AUFEIS... A HIGH FLOOD POTENTIAL EXISTS
FOR MORE FLOODING DURING THE SNOWMELT AND RIVER ICE BREAKUP PROCESS.

FOR MORE DETAIL AND TO SEE A FLOOD POTENTIAL MAP REFER TO OUR WEB
SITE AT HTTP://APRFC.ARH.NOAA.GOV.

THE NEXT BREAKUP SUMMARY WILL BE ISSUED BY 4PM ON WEDNESDAY MAY 6, 2015.

$$
CVB




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