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Hydrologic Outlook

Hydrologic Outlook

Hydrologic Outlook
National Weather Service State College PA
1219 PM EST Thu Jan 18 2018



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

This outlook is valid Thursday January 18th 2018 through Thursday
February 2nd, 2018.

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...Isolated flooding from ice jams
There are several active ice jams that are producing localized
flooding across the region.

Recent precipitation...Average.
Precipitation within the State College Forecast area during the last
30 days (December 18th - January 16th) is close to average across
the region.

Snow conditions...Below average.
Snow covers the entire region, which is fairly typical for this time
of year. Snow depths range from two to 12 inches with liquid water
equivalents up to 1.5 inches in snowiest spots. This is a little
below average for this time of year.

Snow data and information sources include the NOAA/NWS Operational
Hydrologic Remote Sensing Center ( 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 and .

RIVER ICE...Above Average.
The cold weather over the last month has allowed significant river
ice formation. The rain and warm weather last week saw a break up and
some ice jam flooding. With the recent cold weather, the ice has
refrozen and remains signficant across the region.
With the recent cold snap, many rivers and streams are reporting
river ice which is generally above average in thickness for this time
of year.

Follow river ice conditions at .

Stream flow conditions...Average.
Most rivers and streams are affected by ice right now. With the
recent rains water levels are flowing close to average.

Real time water data is available from the United State Geological
Survey by visiting .

Soil moisture conditions...Below Average
The latest soil moisture reports show that the southeast half of the
area has below average soil moisture levels, while the rest of the
area is near average. This can be viewed by looking at the January
13, 2018 chart found at
regional_monitoring/palmer.gif . The most recent version (Jan 18,
2018) of the US Drought Monitor chart does show eastern portions of
the area experiencing abnormally dry to moderately dry conditions

Monitoring wells are mostly normal with a few stations below normal
across the region.

Current ground water conditions based on a 30 day moving average can
be found at .

Reservoir conditions...Below Average.
Most water supply reservoirs within central Pennsylvania are holding
below average storage for this time of are most flood
control reservoirs.

Future weather conditions...Milder and Westter
The region will be undergoing a rather significant weather pattern
change. A return to milder temperatures are expected. Initially it
will be dry, but a more active weather pattern is expected by early
next week.

Please visit
http://www.cpc/ for longer range weather outlooks.

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
for water levels to be high this time of year and excessive rainfall
could lead to flooding. River information can be found at .

Summary of flood potential January 4 to January 18 2018:
The regional flood potential is below average for the next couple of
weeks...due mostly to the low snow pack and recent dry conditions.
While river ice is substantial, water levels are quite low and it
would take a significant amount of rainfall to cause river flooding.

Overview: Current Flooding....Ice Jam Flooding.
Recent Precipitation...Average.
Snow Conditions...Below.
River Ice...Above.
Stream Flow Conditions...Average.
Soil Moisture Conditions...Average.
Ground Water...Variable.
Reservoir Conditions...Below.
Overall Flood Potential...Average.

The next flood potential outlook will be issued on Thursday March 2nd.

Other hydrometeorological information can be found by visiting the
State College Internet Homepage at .



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