Winter/Spring River Flood Potential Outlook
NWS Middle Atlantic River Forecast Center (MARFC)
State College, PA 11:59 am EST
Thu, January 19, 2023
Outlook Number 23-02 - January 19, 2023
This Winter/Spring River Flood Potential Outlook is valid for the two-week period January 19 - February 2, 2023. This outlook estimates the potential for river flooding (not flash flooding) to develop during the next two weeks across the Middle Atlantic River Forecast Center`s (MARFC) area of responsibility (Mid- Atlantic Region) based on a current assessment of hydrometeorological factors which can contribute to river flooding. Across the MARFC area, these factors include future weather conditions, recent precipitation, soil moisture, snow cover and snow water equivalent, river ice, streamflow and other factors. This outlook does not address the severity/extent of any future river flooding. Remember, in the Mid-Atlantic region, heavy rainfall is the primary factor which leads to river flooding. Heavy rainfall can rapidly cause river flooding any time of the year, even when overall river flood potential is considered to be low or below average.
TWO-WEEK RIVER FLOOD POTENTIAL - AVERAGE, EXCEPT BELOW AVERAGE NORTH
The river flood potential during the next two weeks (through February 2, 2023) is mostly average for late January to early February in the MARFC area of responsibility. However, below average conditions exist for river flooding during this timeframe across northern areas, including southern NY and northern PA. Factors which contribute to this assessment of river flood potential are discussed in some detail below. CURRENT RIVER FLOODING - NONE No river flooding is currently occurring within the MARFC service area.
RECENT PRECIPITATION - BELOW AVERAGE/AVERAGE SOUTH AND EAST, NEAR/SLIGHTLY ABOVE AVERAGE NORTH
During the last 30 days (December 20, 2022 - January 18, 2023) observed precipitation across eastern portions of the MARFC region including southeastern PA, central/southern NJ, DE, eastern MD, and eastern VA has ranged from 0.5 to 2.0 inches below average. In addition, observed precipitation across western MD, the eastern panhandle of WV, and western VA has ranged from 0.5 to 1.5 inches below average. Meanwhile, precipitation has been about average in central VA and central MD. Farther north, observed precipitation across central PA has ranged from 0.5 to 1.0 inches above average, while precipitation has been about average in northern PA and southern NY. Precipitation departure data can be seen at www.weather.gov/marfc/Precipitation_Departures.
SNOW CONDITIONS - NORMAL TO BELOW NORMAL
As of this morning (January 19, 2023), little or no snow covers the ground in the MARFC area of responsibility. Areal extent, depth, and snow water equivalents are below normal for northern areas including southern NY and northern PA but are about normal elsewhere in the Mid- Atlantic. Snow information can be found at www.weather.gov/marfc/Snow and www.nohrsc.noaa.gov.
RIVER ICE - NONE
Currently, no significant river ice exists on rivers within the MARFC service area. River ice formation is not expected during the next two weeks given that the latest NWS Climate Prediction Center`s 6-10 and 8-14 day temperature outlooks suggest warmer than normal temperatures in the near term, followed by normal to slightly below normal temperatures towards the end of January and into early February.
STREAMFLOW CONDITIONS - NORMAL/SLIGHTLY ABOVE NORMAL NORTH, NORMAL TO BELOW NORMAL SOUTH AND EAST
The latest data from the United States Geological Survey (USGS) indicates current streamflow conditions within the MARFC region are normal to slightly above normal in southern NY and across most of PA. Streamflow conditions are normal to slightly below normal from northern NJ and southeast PA southward into DE, MD, VA, and the eastern panhandle of WV. Streamflow conditions are below normal in central/southern NJ. For current streamflow conditions, please visit waterdata.usgs.gov/nwis/rt.
SOIL MOISTURE CONDITIONS - GENERALLY AVERAGE, EXCEPT SLIGHTLY ABOVE AVERAGE NORTH
Soil moisture is generally average across the Mid-Atlantic region. Soil moisture conditions may be slightly above average across portions of southern NY and central PA. Soil moisture may also be trending slightly above average in southwest VA. The long-term Palmer drought severity index is useful to estimate deep soil moisture conditions. The January 14, 2023 map (seen at www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_ monitoring/palmer.gif) suggests deep soils are somewhat moist across portions of southern NY, central PA, and southwest VA, with generally average conditions elsewhere. Additional soil moisture data confirms the mainly average to slightly moist soils across the Mid-Atlantic region. For more information, visit www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/ and then click on U.S. Monitoring.
GROUNDWATER - NEAR/ABOVE AVERAGE NORTH, NEAR/BELOW AVERAGE SOUTH
Within the MARFC service area, real-time USGS groundwater monitoring wells indicate current groundwater levels generally range from average to slightly above average in southern NY, most of PA, and northern NJ. Groundwater wells are normal to slightly below normal from southeast PA and central/southern NJ into DE, MD, VA, and the eastern panhandle of WV. To see groundwater levels visit groundwaterwatch.usgs.gov/usgsgwnetworks.asp.
RESERVOIR CONDITIONS - NEAR/ABOVE AVERAGE NORTH, NEAR/BELOW AVERAGE SOUTH
Most major reservoirs within the MARFC region are holding storages that are running mostly near average for this time of year, though some reservoirs in southern areas are slightly below average while some reservoirs in northern areas are slightly above. For example, reservoirs in the Delaware River Basin that supply NYC with water are showing near or even slightly above average storage for this time of year.
FUTURE WEATHER CONDITIONS - RELATIVELY MILD AND ACTIVE PATTERN
A somewhat active weather pattern, with a couple of storm systems bringing light to moderate precipitation, is expected through this weekend into early next week. Near to slightly above normal temperatures are also expected early in the outlook period. Looking ahead at the latest (January 18, 2023) 6 - 10 and 8 - 14 day weather outlooks issued by the NWS Climate Prediction Center, a gradual transition from slightly above normal temperatures to normal and even slightly below normal temperatures is expected by the end of the outlook period. Meanwhile, precipitation is expected to be somewhat above normal through the latter part of next week, followed by near normal precipitation toward the end of the nine-day period January 24 - February 1, 2023. Visit www.cpc.ncep.noaa.gov/ to view the outlooks.
ENSEMBLE RIVER FORECASTS - LIMITED/LOW THREAT OF RIVER FLOODING
The most recent runs (January 19, 2023) of the short-term (6-10 day) ensemble river forecasts, which take into account anticipated future weather conditions including precipitation and temperatures, show no strong signals for any river flooding developing during the next 6-10 days (through the morning of January 29, 2023). Please visit www.weather.gov/erh/mmefs. Longer-term forecasts suggest no apparent increased chance for river flooding compared to normal for late January and early February. Any future river flooding will depend primarily on shorter-term weather conditions, such as the occurrence of widespread heavy rainfall.
Average to below average conditions exist for precipitation, streamflow, and groundwater across southern and eastern areas. Meanwhile, slightly above average streamflow, precipitation, and soils are found across northern areas. Currently, there is no meaningful snow or ice within the MARFC service area. With the lack of available snow and river ice to contribute to runoff, there are no strong signals that indicate more than average chances for river flooding for the MARFC region. In fact, the lack of a snowpack or river ice across northern areas, including southern NY and northern PA, supports below average chances for river flooding for this time of year. There are currently no strong indicators for excessive heavy rainfall that could result in river flooding during the next 7 days.
WATER SUPPLY OUTLOOK
According to the latest (January 17, 2023) U.S. Drought Monitor (droughtmonitor.unl.edu), abnormally dry conditions are present across a small portion of northern NJ and also in southern NJ. A small area of abnormally dry conditions also exists in east-central VA as well as in the eastern panhandle of WV and far western MD. Elsewhere, a small area of moderate drought conditions exists in the southern Delmarva peninsula. Assuming near normal precipitation over the next few months, few or no water supply shortages are anticipated within the MARFC region through April, 2023. Please visit www.drought.gov, www.cpc.ncep.noaa.gov and www.weather.gov/marfc/WRO for additional drought and water supply information.
Please visit the NWS MARFC homepage at www.weather.gov/marfc or find us on Facebook at www.facebook.com/NWSMARFC and on Twitter @nwsmarfc.
The next winter/spring river flood outlook product will be issued by this office February 2, 2023.