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Flood Potential Outlook
Issued by NWS
Issued by NWS
000
FGAK78 PACR 092157
ESFAK
AKZALL-102200-
HYDROLOGIC OUTLOOK
NWS ALASKA PACIFIC RIVER FORECAST CENTER ANCHORAGE AK
200 PM ADT THU MAY 09 2013
...SPRING BREAKUP OUTLOOK FOR ALASKA...
THE SPRING BREAKUP FLOOD POTENTIAL THROUGHOUT ALASKA IS CURRENTLY
RATED AS MODERATE FOR MOST OF THE STATE. THIS FORECAST IS BASED ON
OBSERVED SNOWPACK... ICE THICKNESS REPORTS AND LONG RANGE TEMPERATURE
FORECASTS.
SHORT TERM FLOOD OUTLOOK-
OVER THE NEXT 2-3 DAYS AIR TEMPERATURES ARE GOING TO BE NEAR NORMAL IN
THE YUKON BASIN IN CANADA...UPPER TANANA BASIN AND ACROSS SOUTHCENTRAL
ALASKA. THE MAGNITUDE OF THE TEMPERATURE INCREASE AND ITS LENGTH OF TIME
ARE LESS SIGNIFICANT THAN FORECASTS FROM A COUPLE OF DAYS AGO INDICATED.
HOWEVER SNOWMELT RUNOFF RATES WILL INCREASE BY THIS COMING WEEKEND. THE
INCREASED SNOW MELT AND SUBSEQUENT RUNOFF WILL LIKELY INITIATE BREAKUP
ON THE UPPER YUKON, TANANA, AND SUSITNA RIVER TRIBUTARIES BY EARLY NEXT
WEEK. CONDITIONS ARE STILL FAVORABLE FOR A DYNAMIC BREAKUP WHERE GREATER
CHANCES FOR SIGNIFICANT ICE JAMS EXIST ALONG WITH BETTER CHANCES THAT
FLOODING MIGHT BE MORE SEVERE THAN NORMAL.
ICE - MAY 1ST ICE THICKNESS MEASUREMENTS ARE AVAILABLE FOR A LIMITED
NUMBER OF SITES IN ALASKA. THEY INDICATE THAT ICE THICKNESS IS GENERALLY
BETWEEN 100 AND 150 PERCENT OF NORMAL. ACCUMULATED FREEZING DEGREE DAYS
ARE ABOVE NORMAL FOR MOST OF MAINLAND ALASKA WITH THE HIGHEST
PERCENTAGES OVER THE SOUTHWEST... KODIAK ISLAND AND SOUTHEAST ALASKA.
SNOW - AN ANALYSIS OF THE MAY 1 SNOWPACK BY THE NATURAL RESOURCES
CONSERVATION SERVICE (NRCS) INDICATES A MUCH ABOVE NORMAL SNOWPACK OVER
MUCH OF THE STATE. SIGNIFICANT APRIL SNOW INCREASED THE SNOWPACK ACROSS
THE STATE WHICH IS HIGHLY UNUSUAL. THE MAY 1 SNOW PACK IS 150% - 250% OF
NORMAL ACROSS MOST OF INTERIOR ALASKA WITH ONLY THE KOYUKUK RIVER BASIN
HAVING LESS RELATIVE SNOW WITH 70-90% OF NORMAL. SOUTHCENTRAL ALASKA AND
THE COPPER RIVER BASIN ALL HAVE BETWEEN 100-150% OF NORMAL. SOUTHEAST
ALASKA SNOWPACK IS ESTIMATED TO BE GREATER THAN 150% OF NORMAL. LASTLY
THE UPPER YUKON BASIN IN CANADA AS OF MAY 1 WAS BETWEEN 120-150% OF
NORMAL. THERE IS ENOUGH SNOW ANYWHERE ACROSS THE STATE TO PRODUCE
SIGNIFICANT SNOWMELT RUNOFF PEAKS AND POTENTIAL FLOODING IF SUBJECTED TO
A RAPID WARMING PATTERN.
FOR MORE DETAILS ON THE SNOWPACK.. PLEASE REFER TO THE VARIOUS SNOW
GRAPH OPTIONS AT THE APRFC WEB SITE AT HTTP://APRFC.ARH.NOAA.GOV
OR ON THE NRCS WEB SITE AT
HTTP://WWW.AK.NRCS.USDA.GOV/SNOW/DATA/CURRENT.HTML
WEATHER - APRIL TEMPERATURES WERE WELL BELOW NORMAL OVER ALMOST ALL OF
ALASKA WITH SIGNIFICANTLY BELOW NORMAL TEMPERATURES OVER THE INTERIOR.
BELOW NORMAL TEMPERATURES CONTINUED TO OCCUR DURING THE FIRST SEVERAL
DAYS OF MAY ACROSS MAINLAND ALASKA. A RELATIVELY SHARP INCREASE IN
TEMPERATURES ARE EXPECTED OVER SOUTHCENTRAL AND INTERIOR ALASKA DURING
THE NEXT 2-3 DAYS. THE MOST IMPORTANT FACTOR DETERMINING THE SEVERITY OF
BREAKUP REMAINS THE WEATHER DURING THE NEXT 2-3 WEEKS. DYNAMIC BREAKUPS
WITH A HIGH POTENTIAL OF ICE JAM FLOODING TYPICALLY REQUIRE AN ABRUPT
TRANSITION TO WARM SUMMER-LIKE TEMPERATURES SOMETIME IN MAY. CURRENTLY
WEATHER MODELS ARE INDICATING AN ABRUPT TRANSITION TO NEAR NORMAL OR
SLIGHTLY ABOVE NORMAL TEMPERATURES OVER THE EASTERN INTERIOR AND SOUTH
CENTRAL ALASKA BY THE END OF THE WEEK. LONG RANGE FORECASTS FOR THE 6
TO 14 DAY PERIOD INDICATE COOLER THAN NORMAL TEMPERATURES FOR THE WEST
HALF OF ALASKA AND THE NORTH SLOPE WITH NORMAL TEMPERAATURES ELSEWHERE.
AREAS OF SOUTHCENTRAL ALASKA THAT RECEIVED SIGNIFICANT RAINFALL LAST
FALL LIKELY HAVE HIGHER THAN NORMAL GROUNDWATER LEVELS. THESE AREAS
ARE MORE SUSCEPTIBLE TO MINOR FLOODING AND DRAINAGE ISSUES IN THE
EVENT OF A RAPID WARMUP.
FOR MORE INFORMATION ON THE OUTLOOKS FOR THIS SPRING PLEASE REFER TO
THE CLIMATE PREDICTION CENTER WEB SITE AT
HTTP://WWW.CPC.NCEP.NOAA.GOV/INDEX.PHP
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 1970 THROUGH 2012 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 ABOVE
KENAI RIVER ABOVE
ANCHOR RIVER ABOVE 04/16 10
MATANUSKA RIVER ABOVE 04/30 8
SUSITNA RIVER ABOVE
GOLD CREEK LOW-MOD 05/03 9
SUNSHINE LOW-MOD 05/02 28 5/11-5/15
YENTNA RIVER AVERAGE
LAKE CREEK LOW-MOD 05/01 22 5/11-5/16
SKWENTNA RIVER AVERAGE
SKWENTNA LOW-MOD 05/03 19 5/12-5/16
COPPER RIVER BASIN AVERAGE
GAKONA RVR @ HWY LOW 05/02 25 5/10-5/15
GULKANA RVR @ HWY LOW 05/01 29 5/10-5/15
CHENA RIVER ABOVE
CHENA LAKES PROJECT LOW
FAIRBANKS LOW 04/28 26 5/11-5/16
TANANA RIVER ABOVE
NORTHWAY LOW 04/21 31 5/08**
SALCHA MODERATE
FAIRBANKS LOW 04/29 14 5/12-5/16
NENANA LOW-MOD 05/04 39 5/13-5/17
MANLEY LOW-MOD 05/01 23 5/14-5/18
KUSKOKWIM RIVER AVERAGE
NIKOLAI LOW 04/24 30 5/10-5/15
MCGRATH MODERATE 05/07 39 5/16-5/21
STONY RIVER LOW 05/05 25 5/16-5/21
SLEETMUTE MODERATE 05/05 24 5/17-5/22
RED DEVIL MODERATE 05/06 27 5/17-5/22
CROOKED CREEK MODERATE 05/07 27 5/18-5/23
ANIAK MODERATE 05/08 34 5/18-5/23
KALSKAG LOW-MOD 05/08 24 5/19-5/24
TULUKSAK LOW-MOD 05/10 21 5/20-5/25
AKIAK LOW-MOD 05/10 27 5/20-5/25
KWETHLUK MODERATE
BETHEL LOW-MOD 05/12 42 5/22-5/27
NAPAKIAK LOW-MOD 05/13 19 5/23-5/28
YUKON RIVER (UPPER) ABOVE
DAWSON, YT 05/06 43 5/13-5/18
EAGLE MODERATE 05/05 35 5/14-5/18
CIRCLE MODERATE 05/09 31 5/15-5/20
FORT YUKON LOW-MOD 05/10 30 5/15-5/20
BEAVER LOW 05/11 18 5/16-5/21
STEVENS VILLAGE LOW 05/12 18 5/17-5/22
RAMPART LOW 05/12 18 5/18-5/23
YUKON RIVER (MIDDLE) ABOVE
TANANA LOW-MOD 05/10 28 5/19-5/24
RUBY LOW 05/11 29 5/19-5/24
GALENA MODERATE 05/13 29 5/20-5/25
KOYUKUK MODERATE
NULATO MODERATE 05/12 17 5/20-5/26
KALTAG LOW 05/14 37 5/21-5/26
ANVIK LOW 05/16 26 5/22-5/27
YUKON RIVER (LOWER) ABOVE
HOLY CROSS LOW 05/16 26 5/23-5/28
RUSSIAN MISSION LOW 05/15 28 5/23-5/28
MARSHALL MODERATE 05/15 22 5/24-5/29
PILOT STATION LOW 05/17 16 5/24-5/29
MOUNTAIN VILLAGE LOW 05/19 26 5/25-5/30
ALAKANUK/EMMONAK MODERATE 05/23 28 5/26-5/31
KOYUKUK RIVER AVERAGE
BETTLES LOW 05/09 31 5/20-5/25
ALLAKAKET LOW 05/10 26 5/21-5/26
HUGHES MODERATE 05/10 32 5/21-5/26
SEWARD PENINSULA BELOW
BUCKLAND RIVER BELOW
BUCKLAND MODERATE 05/18 23 5/23-5/28
KOBUK RIVER BELOW
KOBUK MODERATE 05/16 33 5/23-5/29
SHUNGNAK LOW 05/18 23 5/24-5/30
AMBLER LOW 05/18 30 5/24-5/30
NOATAK RIVER BELOW
NOATAK LOW 05/20 18 5/25-5/30
BROOKS RANGE - NORTH AVERAGE
COLVILLE @ UMIAT LOW 05/24 13 5/30-6/03
COLVILLE @ COLVILLE LOW-MOD 06/01 16 6/01-6/07
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 FRIDAY MAY 10.
$$
JHC
- National Weather Service
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- Bismarck, ND 58504
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- Page last modified: May 1st, 2013 15:32 UTC