Flood Potential Outlook
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13
000
FGAK78 PACR 221832
ESFAK
AKZALL-140000-

HYDROLOGIC OUTLOOK
NWS ALASKA PACIFIC RIVER FORECAST CENTER ANCHORAGE AK
2 PM ADT TUE APRIL 22 2014

...SPRING BREAKUP OUTLOOK FOR ALASKA....

THE SPRING BREAKUP FLOOD POTENTIAL IS CURRENTLY 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.

TEMPERATURES - OVER THE NEXT FEW WEEKS TEMPERATURES ARE LIKELY TO BE NEAR OR
ABOVE NORMAL OVER THE MAINLAND. FOR APRIL... TEMPERATURES ARE EXPECTED TO BE
ABOVE NORMAL IN WESTERN AND NORTHERN ALASKA AND NEAR NORMAL OVER THE EASTERN
INTERIOR AND SOUTHEASTERN PARTS OF THE STATE. OVER THE APRIL-MAY-JUNE PERIOD
TEMPERATURES ARE EXPECTED TO BE ABOVE NORMAL STATEWIDE.

PRECIPITATION - IS NOT EXPECTED TO BE A SIGNIFICANT FACTOR IN THIS YEARS
BREAKUP PROCESS. PRECIPITATION OVER THE MAINLAND IS LIKELY TO BE NEAR NORMAL
FOR BOTH THE ONE MONTH AND FOR THE APRIL-MAY-JUNE PERIOD.

FOR MORE INFORMATION ON THE 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 INDICATE THAT ICE THICKNESS IS
VARIABLE ACROSS THE STATE... WITH LOCATIONS GENERALLY BETWEEN 48 AND 122
PERCENT OF NORMAL. MANY LOCATIONS IN THE TANANA BASIN REPORTED BELOW NORMAL
THICKNESS.  ICE THICKNESS ON THE NORTH SLOPE AND IN SOUTHCENTRAL ALASKA ARE
BELOW NORMAL... WHILE THICKNESS IN WESTERN ALASKA ARE BELOW NORMAL. ICE
THICKNESS IN LOWER YUKON LIKELY IS BELOW NORMAL... NORMAL IN MIDDLE YUKON AND
NORMAL TO ABOVE NORMAL IN THE UPPER YUKON BASIN. ACCUMULATED FREEZING DEGREE
DAYS ARE BELOW NORMAL OVER MOST OF ALASKA... EXCEPT IN SOUTHWESTERN AND
SOUTHEAST ALASKA WHERE THEY ARE ABOVE NORMAL.

SNOW - THE APRIL 1 SNOWPACK ANALYSIS SHOWS BELOW AVERAGE CONDITIONS IN WESTERN
ALASKA... ABOVE NORMAL IN NORTHERN ALASKA... NORMAL TO BELOW NORMAL IN
SOUTHEAST... NORMAL IN INTERIOR ALASKA... AND NORMAL TO ABOVE NORMAL IN THE
CANADIAN YUKON. SNOW MONITORING SITES IN THE CANADIAN YUKON ARE REPORTING
100-130% OF NORMAL. SOUTHCENTRAL AND WESTERN ALASKA ARE REPORTING BELOW NORMAL
SNOWPACK... WITH LESS THAN 50% OF NORMAL IN THE KUSKOKWIM BASIN AND THE LOWER
YUKON.

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 POSSIBILITY OF ABOVE NORMAL STATEWIDE
TEMPERATURES OVER THE NEXT 4-6 WEEKS MIGHT 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. IN A THERMAL BREAKUP...
EVEN THOUGH ICE STRENGTH DETERIORATES SIGNIFICANTLY... BREAKUP MIGHT ACTUALLY
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 IS OFTEN
INCONSISTENT UP AND DOWN THE RIVER.

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

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.

*  AVERAGE BREAKUP DATES ARE FOR THE PERIOD 1980 THROUGH 2013 AND ARE
      CALCULATED FOR LOCATIONS WITH AT LEAST 5 YEARS OF DATA.
** ACTUAL BREAKUP DATE FOR THIS YEAR
---------------------------------------------------------------------

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

KENAI RIVER

ANCHOR RIVER       BELOW AVERAGE  LOW        04/13     10    04/17**

MATANUSKA RIVER    BELOW AVERAGE             04/30      8    04/18**
SUSITNA RIVER                     LOW
  GOLD CREEK                      LOW        05/03      7  04/27-05/03
  SUNSHINE                        LOW        05/01     25  04/25-05/01

YENTNA RIVER       BELOW AVERAGE
  LAKE CREEK                      LOW        05/01     23  04/25-05/01

SKWENTNA RIVER     BELOW AVERAGE
  SKWENTNA                        LOW        05/01     19  04/25-05/01

COPPER RIVER BASIN    AVERAGE
  GAKONA RVR @ HWY              LOW-MOD      05/01     26  04/25-05/01
  GULKANA RVR @ HWY             LOW-MOD      04/30     25  04/24-04/30

CHENA RIVER           AVERAGE
  CHENA LAKES PROJECT
  FAIRBANKS                       LOW        04/26     22  04/21-04/26

TANANA RIVER          AVERAGE
  NORTHWAY                        LOW        04/26     26  04/22-04/27
  SALCHA                        LOW-MOD
  FAIRBANKS                       LOW        04/30     15  04/24-04/30
  NENANA                          LOW        05/01     31  04/25-05/01
  MANLEY                          LOW        05/04     24  04/28-05/04

KUSKOKWIM RIVER     BELOW AVERAGE
  NIKOLAI                         LOW        04/24     28    04/21**
  MCGRATH                         LOW        05/07     34  05/01-05/07
  STONY RIVER                     LOW        05/06     26  04/30-05/06
  SLEETMUTE                       LOW        05/05     25  04/29-05/05
  RED DEVIL                       LOW        05/07     28  05/01-05/07
  CROOKED CREEK                   LOW        05/07     28  05/01-05/07
  ANIAK                           LOW        05/08     31  05/02-05/08
  KALSKAG                         LOW        05/08     25  05/02-05/08
  TULUKSAK                        LOW        05/10     22  05/03-05/09
  AKIAK                           LOW        05/11     28  05/04-05/10
  KWETHLUK                      LOW-MOD
  BETHEL                          LOW        05/12     33  05/04-05/10
  NAPAKIAK                        LOW        05/14     20  05/06-05/12

YUKON RIVER (UPPER)   AVERAGE
  DAWSON, YT                                 05/05     34  04/28-05/04
  EAGLE                         LOW-MOD      05/05     32  04/20-05/04
  CIRCLE                        LOW-MOD      05/10     30  05/03-05/09
  FORT YUKON                      LOW        05/11     30  05/04-05/10
  BEAVER                          LOW        05/11     18  05/04-05/10
  STEVENS VILLAGE               LOW-MOD      05/12     17  05/05-05/11
  RAMPART                         LOW        05/12     19  05/05-05/11

YUKON RIVER (MIDDLE)  AVERAGE
  TANANA                        LOW-MOD      05/10     29  05/03-05/09
  RUBY                            LOW        05/12     28  05/05-05/11
  GALENA                        LOW-MOD      05/13     33  05/06-05/12
  KOYUKUK                       LOW-MOD      05/14      9  05/07-05/13
  NULATO                        LOW-MOD      05/13     18  05/06-05/12
  KALTAG                          LOW        05/14     28  05/07-05/13
  ANVIK                           LOW        05/17     27  05/09-05/16

YUKON RIVER (LOWER)   AVERAGE
  HOLY CROSS                      LOW        05/16     27  05/09-05/15
  RUSSIAN MISSION                 LOW        05/16     28  05/09-05/15
  MARSHALL                        LOW        05/17     22  05/10-05/16
  PILOT STATION                   LOW        05/18     17  05/11-05/17
  MOUNTAIN VILLAGE                LOW        05/19     27  05/12-05/18
  ALAKANUK/EMMONAK              LOW-MOD      05/23     29  05/16-05-22

KOYUKUK RIVER         AVERAGE
  BETTLES                         LOW        05/10     31  05/04-05/10
  ALLAKAKET                       LOW        05/11     28  05/05-05/11
  HUGHES                        LOW-MOD      05/11     27  05/05-05/11

SEWARD PENINSULA
  BUCKLAND RIVER                LOW-MOD
  BUCKLAND                      LOW-MOD      05/19     24  05/13-05/19

KOBUK RIVER
  KOBUK                         LOW-MOD      05/17     30  05/11-05/17
  SHUNGNAK                        LOW        05/18     24  05/12-05/18
  AMBLER                          LOW        05/19     30  05/13-05/19

NOATAK RIVER        ABOVE AVERAGE
  NOATAK                          LOW        05/20     19  05/14-05/20

BROOKS RANGE - NORTH  ABOVE AVERAGE
  COLVILLE @ UMIAT                LOW        05/25     15  05/19-05/25
  COLVILLE @ COLVILLE           LOW-MOD      06/01     17  05/26-06/01

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

THE NEXT SPRING BREAKUP OUTLOOK IS SCHEDULED AT 2 PM ADT WEDNESDAY APRIL 23
2014.

$$
CVB



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.