Flood Potential Outlook
Issued by NWS State College, PA

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Winter/Spring Flood Potential Outlook
National Weather Service State College PA
1150 PM EST Wed Feb 14 2018

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK ISSUED FEBRUARY 14 2018...

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 February 15th 2018 through Thursday
March 1st, 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 above average.

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

Recent precipitation...Variable. The Precipitation within the State
College Forecast area during the last 30 days (January 15-February
13) was variable across the region. Above normal/ normal across most
portions with below normal/normal through far southeast and far
southwest.

Snow conditions...Below average/Average. The most significant snow
across the northern half of central Pennsylvania with 3 to 10 inches
of snowpack while snow water equivalent values are 1.0 to 1.5
inches. Isolated locations in higher elevations could have somewhat
higher values.  Areas southward have 1 to 4 inches of snow depth
with water equivalent values of less than an inch.

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.
While river ice is being observed, a warmer than normal weather
pattern is possible for much of the next two weeks. Little if any
new river ice is expected to form during the next two weeks. Given
trends, it also seems unlikely that temperatures will get cold
enough for any substantial river ice to reform for the rest of this
winter.

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

Stream flow conditions...Average/Above average. With the recent
rains water levels are flowing near normal to above normal stream
flow conditions.

Real time water data is available from the United State Geological
Survey by visiting http://water.usgs.gov .

Soil moisture conditions...Normal/Below normal. The long term Palmer
Drought Severity Index is used to infer deep soil moisture
conditions. The February 10th, 2018 chart found at
www.cpc.ncep.noaa.gov/products/analysis_monitoring/
regional_monitoring/palmer.gif suggests deep soils across much of
central Pennsylvania are near normal to slightly above normal with
areas along the Susquehanna have seen unusual moist spells.  The
most recent version (Feb 8, 2018) of the US Drought Monitor chart
does show eastern portions of the area experiencing abnormally dry
conditions (http://droughtmonitor.unl.edu).

GROUND WATER...Normal.  Monitoring wells are mostly normal with one
station below normal across the southeast portion of the region.

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 near average storage for this time
of year...as are most flood control reservoirs.

Future weather conditions...An active weather pattern seems likely
to continue for the next two weeks. Numerous weather systems seem
likely to pass near/through the region and each has the appearance of
being able to produce at least moderate precipitation across
portions of the region. Some heavy rainfall seems possible during
this next two-week period. In additions, a very mild period with
temperatures trending slightly above average will cause snowmelt
where snow still exists. The combination of frequent periods of
moderate to heavy rain, and snowmelt could produce some river
flooding.

Please visit http://www.cpc/ncep.noaa.gov 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 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 February 15 to March 1 2018: The regional
flood potential is above average for the next couple of weeks.

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

The next flood potential outlook will be issued on Thursday March
1st.

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

$$

Ceru



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