Winter/Spring Flood Outlook
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Winter/Spring Flood Outlook
000
FGUS71 KCTP 120356
ESFCTP
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066-121600-

HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1056 PM EST FRI JAN 11 2008

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK 1...

INTRODUCTION.

DURING THE WINTER AND SPRING...THE NATIONAL WEATHER SERVICE ISSUES A
SERIES OF WINTER AND SPRING FLOOD POTENTIAL OUTLOOKS. THESE OUTLOOKS
ESTIMATE THE POTENTIAL FOR RIVER FLOODING (NOT FLASH FLOODING)
ACROSS CENTRAL PENNSYLVANIA BASED ON A CURRENT ASSESSMENT OF
HYDROMETEOROLOGICAL FACTORS WHICH CONTRIBUTE TO RIVER FLOODING.
ACROSS CENTRAL PENNSYLVANIA...THESE FACTORS INCLUDE RECENT
PRECIPITATION...SOIL MOISTURE...SNOW COVER AND SNOW WATER
EQUIVALENT...RIVER ICE...STREAMFLOW...FUTURE WEATHER CONDITIONS AND
OTHERS. THIS OUTLOOK DOES NOT ADDRESS THE SEVERITY OR EXTENT OF ANY
FUTURE RIVER FLOODING.

THIS OUTLOOK COVERS THE SUSQUEHANNA RIVER BASIN INCLUDING THE WEST
BRANCH...JUNIATA...AND MUCH OF THE MIDDLE AND LOWER SUSQUEHANNA
VALLEY. ALSO COVERED ARE PORTIONS OF THE UPPER AND LOWER ALLEGHENY
BASINS...INCLUDING AREAS FROM WARREN AND MCKEAN COUNTIES IN THE
NORTH...THROUGH CAMBRIA AND SOMERSET COUNTIES IN THE SOUTH.

THIS OUTLOOK IS VALID FRIDAY JANUARY 11TH THROUGH FRIDAY JANUARY
25TH 2008...AND IS PARTIALLY BASED ON THE LATEST NATIONAL WEATHER
SERVICE MEDIUM RANGE WEATHER FORECASTS WHICH SUGGEST THAT
TEMPERATURES AND PRECIPITATION WILL BE NORMAL TO BELOW NORMAL OVER
THE NEXT TWO WEEKS.

IN CENTRAL PENNSYLVANIA...HEAVY RAINFALL IS THE PRIMARY FACTOR WHICH
LEADS TO RIVER FLOODING. IT IS IMPORTANT TO NOTE THAT HEAVY RAINFALL
CAN RAPIDLY CAUSE RIVER FLOODING ANY TIME OF THE YEAR...EVEN WHEN
OVERALL RIVER FLOOD POTENTIAL IS CONSIDERED LOW OR BELOW AVERAGE.

DETAILED DISCUSSION.

CURRENT RIVER FLOOD POTENTIAL...NORMAL.
THE OVERALL POTENTIAL FOR RIVER FLOODING DURING THE NEXT TWO WEEKS
ARE CONSIDERED ABOUT AVERAGE OVER THE REGION.

CURRENT FLOODING...NONE.

RECENT PRECIPITATION...ABOVE AVERAGE.
PRECIPITATION OVER THE SUSQUEHANNA BASIN COVERED BY THE STATE
COLLEGE HYDROLOGIC SERVICE AREA (HSA) DURING THE LAST 30 DAYS WAS
GENERALLY ABOVE NORMAL. PRECIPITATION OVER MOST OF THE MAIN
STEM...WEST BRANCH AND JUNIATA BASINS WAS ABOUT 15 TO 25 PERCENT
ABOVE NORMAL.

SNOW CONDITIONS...MUCH BELOW AVERAGE.
NO HYDROLOGICALLY SIGNIFICANT SNOW EXISTS OVER THE STATE COLLEGE
HYDROLOGIC SERVICE AREA. THIS LACK OF SNOW IS WELL BELOW WHAT IS
NORMALLY EXPECTED FOR THIS TIME OF YEAR.

RIVER ICE...MUCH BELOW AVERAGE.
NO ICE EXISTS IN AREA RIVERS AND STREAMS. THIS IS WELL BELOW NORMAL
FOR THIS TIME OF YEAR.

STREAMFLOW CONDITIONS...AVERAGE TO MUCH ABOVE AVERAGE.
STREAMFLOW CONDITIONS ACROSS ALL OF THE SUSQUEHANNA BASIN AND THE
UPPER PORTIONS OF THE ALLEGHENY BASINS ARE AVERAGE TO WELL ABOVE
AVERAGE FOR THIS TIME OF YEAR. REAL TIME WATER DATA IS AVAILABLE
FROM THE UNITED STATES GEOLOGICAL SURVEY BY VISITING
HTTP://WATER.USGS.GOV ON THE INTERNET.

SOIL MOISTURE CONDITIONS...AVERAGE TO WELL ABOVE AVERAGE.
THE LATEST PALMER DROUGHT SEVERITY INDEX CHART IMPLIES THAT SOIL
MOISTURE CONDITIONS WERE UNUSUALLY MOIST...VERY MOIST OR EXTREMELY
MOIST OVER MOST OF CENTRAL PENNSYLVANIA. WETTEST CONDITIONS WERE
NOTED ACROSS PENNSYLVANIA'S NORTHERN TIER COUNTIES. SOIL MOISTURE
MONITORING CHARTS FROM NOAA'S CLIMATE PREDICTION CENTER CAN BE FOUND
AT WWW.CPC.NCEP.NOAA.GOV/SOILMST/ AND WWW.DROUGHT.GOV.

GROUND WATER...AVERAGE TO ABOVE AVERAGE.
MONITORING WELLS INDICATE THAT CURRENT GROUND WATER LEVELS ARE
GENERALLY AVERAGE TO ABOVE AVERAGE ACROSS MOST OF CENTRAL
PENNSYLVANIA. HOWEVER...SEVERAL COUNTIES STILL ARE SHOWING BELOW
AVERAGE GROUND WATER LEVELS AS A RESULT OF DRY CONDITIONS DURING
2007. CURRENT GROUND WATER CONDITIONS BASED ON A 30 DAY MOVING
AVERAGE CAN BE FOUND AT
HTTP://PA.WATER.USGS.GOV/MONITOR/GW/INDEX.HTML

RESERVOIR CONDITIONS...NEAR AVERAGE.
MOST WATER SUPPLY RESERVOIRS WITHIN CENTRAL PENNSYLVANIA ARE HOLDING
NEAR AVERAGE STORAGES FOR THIS TIME OF YEAR...AS ARE MOST FLOOD
CONTROL RESERVOIRS.

FUTURE WEATHER CONDITIONS.
GENERALLY DRY WEATHER WITH NO SIGNIFICANT PRECIPITATION EVENTS ARE
EXPECTED FOR THE NEXT WEEK ACROSS CENTRAL PENNSYLVANIA. A STORM
SYSTEM WILL DEVELOP OVER THE COASTAL ATLANTIC REGION...BUT AT THIS
TIME IT APPEARS THAT SIGNIFICANT PRECIPITATION FROM THIS SYSTEM WILL
BE EAST OF CENTRAL PENNSYLVANIA. THE 8 TO 14 DAY OUTLOOK VALID FROM
JANUARY 19 TO THE 25TH INDICATIONS BELOW NORMAL TEMPERATURES AND
PRECIPITATION CAN BE EXPECTED FOR CENTRAL PENNSYLVANIA THROUGH THE
PERIOD.

ADVANCED HYDROLOGIC PREDICTION SERVICE (AHPS)...AVERAGE.
ANOTHER TOOL USED TO ASSESS THE POTENTIAL FOR RIVER FLOODING IS THE
ADVANCED HYDROLOGIC PREDICTION SERVICE...AHPS. AHPS GENERATES
PROBABILISTIC RIVER FORECASTS BASED ON CURRENT BASIN
CONDITIONS...INCLUDING RIVER LEVELS...SOIL MOISTURE...EXTENT AND
CONDITION OF ANY SNOWPACK...ALONG WITH 50 YEARS OF HISTORIC
TEMPERATURE AND PRECIPITATION DATA. FOR THIS OUTLOOK PERIOD...AHPS
INDICATES THAT THE LIKELIHOOD OF RIVER FLOODING IS ABOUT NORMAL
COMPARED TO WHAT HAS BEEN HISTORICALLY OBSERVED DURING THIS SAME
TIME PERIOD. RIVER INFORMATION CAN BE FOUND WEATHER.GOV/AHPS

SUMMARY.
ALTHOUGH SNOW PACK AND RIVER ICE IS WELL BELOW AVERAGE...RECENT
RAINFALL AND SNOWMELT HAVE PRODUCED WET SOILS AND HIGHER THAN
NORMAL STREAM FLOWS ACROSS THE REGION. THESE TWO OFFSETTING
FACTORS LEAD TO A WINTER/SPRING FLOOD POTENTIAL OF AVERAGE AT THIS
TIME.

THE NEXT WINTER/SPRING FLOOD POTENTIAL OUTLOOK WILL BE ISSUED ON
OR ABOUT FRIDAY JANUARY 25TH 2008.

OTHER HYDROMETEOROLOGICAL INFORMATION CAN BE FOUND BY VISITING THE
STATE COLLEGE INTERNET HOMEPAGE AT WEATHER.GOV/STATECOLLEGE.

$$

SUMMARY/OVERVIEW OF FLOOD POTENTIAL JANUARY 11 - JANUARY 25 2008:

CURRENT FLOODING...NONE.
RECENT PRECIPITATION...ABOVE AVERAGE.
SNOW CONDITIONS...MUCH BELOW AVERAGE.
RIVER ICE...MUCH BELOW AVERAGE.
STREAMFLOW CONDITIONS...AVERAGE TO MUCH ABOVE AVERAGE.
SOIL MOISTURE CONDITIONS...AVERAGE TO WELL ABOVE AVERAGE.
GROUND WATER...AVERAGE TO ABOVE AVERAGE.
RESERVOIR CONDITIONS...AVERAGE.
AHPS...NORMAL.
OVERALL FLOOD POTENTIAL...NORMAL.

$$

 
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Page Last Modified: 14 January 2008 07:12:34 UTC
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