FGUS61 KRHA 141904 ESGRHA Winter/Spring River Flood Potential Outlook NWS Middle Atlantic River Forecast Center (MARFC) State College, PA 2:00 pm EDT Thu, March 14, 2024 Outlook Number 24-06 - March 14, 2024 This Winter/Spring River Flood Potential Outlook is valid for the two-week period March 14 - March 28, 2024. 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 ABOVE AVERAGE EASTERN AREAS The river flood potential during the next two weeks (through March 28, 2024) is mostly average for middle to late March in the MARFC area of responsibility. Above average river flood potential exists across NJ and eastern 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 - ABOVE AVERAGE During the last 30 days (February 13, 2024 - March 13, 2024) observed precipitation across the entire MARFC area of responsibility is running above average. Observed precipitation is generally ranging from around 0.5 inches above average to around 3.5 inches above average across south-central NY, PA, NJ, DE, MD, the eastern panhandle of WV, and VA. Precipitation departure data can be seen at www.weather.gov/marfc/Precipitation_Departures. SNOW CONDITIONS - BELOW NORMAL NORTH TO NORMAL SOUTH As of this morning (March 14, 2024), 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, as well as down along the higher terrain of the Allegheny and Appalachian Mountains from west-central PA into western MD and the eastern panhandle of WV. Farther south and east, no snow coverage across most of southern to eastern PA, most of NJ, central to eastern MD, DE, and VA represents normal conditions for the middle of March. 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. A general trend of near to below average temperatures is expected for middle to late March based on the latest NWS Climate Prediction Center’s 6-10 and 8-14 day outlooks. Thus, significant river ice formation is not expected during this period. STREAMFLOW CONDITIONS - ABOVE NORMAL The latest data from the United States Geological Survey (USGS) indicates current streamflow conditions within the MARFC region are generally above normal across southern NY, PA, DE, MD, the eastern panhandle of WV, and VA. A higher concentration of above normal streamflows exists across NJ into eastern PA. For current streamflow conditions, please visit waterdata.usgs.gov/nwis/rt. SOIL MOISTURE CONDITIONS - ABOVE TO MUCH ABOVE AVERAGE Soil moisture is running above to much above average across the entire Mid-Atlantic region. Moist to extremely moist soils exist across NJ, DE, much of PA, and into southern NY. Meanwhile, soil moisture conditions are also running above average farther south across MD, the eastern panhandle of WV, and VA. The long-term Palmer drought severity index is useful to estimate deep soil moisture conditions. The March 9, 2024 map (seen at www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_ monitoring/palmer.gif) suggests deep soils are moist to extremely moist across NJ, DE, much of PA, and into southern NY, with mostly above average conditions southward through MD and VA. Additional soil moisture data shows that above to much above average anomalies exist across most of the MARFC service area. 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/SLIGHTLY BELOW AVERAGE SOUTH Within the MARFC service area, real-time USGS groundwater monitoring wells indicate current groundwater levels generally range from average to above average in southern NY, most of PA, most of NJ, and DE. Groundwater wells are normal to slightly below normal across most of MD, VA, and the eastern panhandle of WV. To see groundwater levels visit waterdata.usgs.gov/nwis/gw. RESERVOIR CONDITIONS - NEAR/ABOVE AVERAGE NORTH, NEAR/SLIGHTLY 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 above average storage for this time of year. FUTURE WEATHER CONDITIONS - NEAR TO BELOW AVERAGE TEMPERATURES During the next two weeks, a few passing weather systems are expected to bring mainly light to perhaps moderate precipitation into the Mid-Atlantic region. The latest (March 13, 2024) 6 - 10 and 8 - 14 day weather outlooks issued by the NWS Climate Prediction Center indicate that below average temperatures followed by near normal temperatures are favored through the outlook period. Meanwhile, near normal precipitation is favored early, followed by above normal precipitation chances over the nine-day period March 19 - March 27, 2024. Visit www.cpc.ncep.noaa.gov/ to view the outlooks. ENSEMBLE RIVER FORECASTS - LIMITED/LOW THREAT OF RIVER FLOODING The most recent runs (March 14, 2024) 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 river flooding developing during the next 6-10 days (through the morning of March 24, 2024). Please visit www.weather.gov/erh/mmefs. Longer- term forecasts suggest no apparent increased chance for river flooding compared to normal for middle to late March. Any future river flooding will depend primarily on shorter-term weather conditions, such as the occurrence of widespread heavy rainfall. SUMMARY Precipitation departures and streamflow conditions are generally running above average for this time of year across the MARFC service area. In addition, soil moisture continues to run above to much above average across most of the region. Below normal snow conditions exist across northern parts of the MARFC service area, while no snow coverage across southern areas represents normal conditions. No significant river ice exists in the MARFC service area. Ensemble river forecast runs do not show strong signals for river flooding developing during the next 6-10 days. With these factors in mind, generally average river flood potential exists for most of the MARFC service area. However, above average river flood potential exists across NJ to eastern PA where precipitation, streamflow, and soil moisture departures are running the highest across the region. WATER SUPPLY OUTLOOK According to the latest (March 12, 2024) U.S. Drought Monitor (droughtmonitor.unl.edu), normal conditions exist across the MARFC service area. Precipitation amounts over the last 30 days have been near to above normal. Assuming a continuation of near normal precipitation over the next couple of months, few or no water supply shortages are anticipated within the MARFC region through May, 2024. 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/?REF=aymt_homepage_panel and on Twitter @nwsmarfc. The next winter/spring river flood outlook product will be issued by this office March 28, 2024.