Flood Potential Outlook
Issued by NWS State College, PA

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Winter/Spring Flood Potential Outlook
National Weather Service State College PA
220 PM EDT Thu Mar 30 2017

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK ISSUED MARCH 30 2017...

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...streamflows...future weather conditions and
other. 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
south.

This outlook is valid Thursday March 30 through Thursday April 13,
2017.

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.

Two week river flood potential...The current potential for river
flooding is average.

Current flooding...None.
No flooding is occurring in the region at this time.

Recent precipitation...Variable.
Precipitation within the State College Forecast area during the last
30 days (February 28 - March 30th) is variable across the
region...with most of the region seeing slightly below average
values. A stripe of average to slightly above average precipitation
is noted from southwest to northeast across the central portion of
the area.

Snow conditions...Average.
Snow has melted across the region. There is still some snow to melt
off across the headwaters of the Susquehanna Basin in New York State.
That will melt off in the next several days.

Snow data and information sources include the NOAA/NWS Operational
Hydrologic Remote Sensing Center (www.nohrsc.noaa.gov)...the US Army
Corps of Engineers...NWS Cooperative Observers...the Community Rain,
Hail and Snow Network (COCORAHS) and others. Snow depth and basin
average water equivalent estimates can be seen at
www.erh.noaa.gov/er/marfc and www.nohrsc.noaa.gov .

River ice...Below average.
There is no river ice in the area from now going forward this season.

Follow river ice conditions at
http://erh.noaa.gov/ctp/hydro/riverice/index.php .

Stream flow conditions...Average.
Most rivers and streams are flowing near average levels given the
recent snow melt and rainfall.
Real time water data is available from the United State Geological
Survey by visiting http://water.usgs.gov .

Soil moisture conditions...Average
The latest soil moisture reports show that most of the region is
reporting near average moisture conditions. The March 25, 2017 chart
(found at www.cpc.ncep.noaa.gov/products/analysis_monitoring/
regional_monitoring/palmer.gif) suggest deep soils across the area
contain moisture that is fairly close to normal for this time of
year. The most recent version (March 27, 2017) of the US Drought
Monitor chart does show eastern portions of the area experiencing
abnormally dry to moderately dry conditions
(http://droughtmonitor.unl.edu).

Moisture monitoring charts from NOAA`s Climate Prediction Centre can
be found at:
www.cpc.ncep.noaa.gov/products/soilmst_monitoring/us/soilmst/
soilmst.shtml and www.drought.gov .

Ground Water...Variable.
Monitoring wells are all at or above normal for western areas while
southern and eastern areas of the region are below or even much
below average...corresponding to where drought conditions are being
observed.

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...Average.
Most water supply reservoirs within central Pennsylvania are holding
average storage for this time of year...as are most flood control
reservoirs.

Future weather conditions...Average
A very active weather pattern is forecast across the region for the
next several days. Most locations will receive between one and two
inches of rain by Saturday. This will produce significant stream and
river rises over the region into early next week. At this time no
flooding is forecast for the State College Forecast Area though
flooding is possible to the north and east of the area closer to the
headwaters of the Susquehanna and Delaware River basins.

Another weather system is expected during the April 4-5 time frame
that will produce additional runoff and conditions will need to be
monitored closely.

Advanced Hydrologic Prediction Service (AHPS)...Normal.
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 snow pack...along with 50 years of history
temperatures and precipitation data. For this outlook period...AHPS
indicates that the likelihood of river flooding is near average
compared to what has been observed during this same time period
across small river basins in central Pennsylvania. It is quite common
for water levels to be high this time of year and excessive rainfall
could lead to flooding. River information can be found at
water.weather.gov .

Summary of flood potential March 30 to April 13, 2017:
The flood potential for the NWS State College Hydrologic Service Area
is average for the next couple of weeks. Water levels are high right
now over parts of the area which is expected. Several storm systems
will bring rainfall to the area but at this time no excessive rain is
forecast. There will be significant rises and water levels on the
mainstem of the Susquehanna will likely crest near Action Stage
levels late this weekend or sometime next week.

Overview: Current Flooding...None.
Recent Precipitation...Variable.
Snow Conditions...Average.
River Ice...None.
Stream Flow Conditions...Average.
Soil Moisture Conditions...Average.
Ground Water...Variable.
Reservoir Conditions...Average.
AHPS...Average.
Overall Flood Potential...Average.

The next flood potential outlook will be issued on Thursday April
13th.

Other hydrometeorological information can be found by visiting the
State College Internet Homepage at http://weather.gov/ctp .

$$

CR



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