Winter/Spring River Flood Potential Outlook
NWS Middle Atlantic River Forecast Center (MARFC)
State College, PA
2:47 pm EDT Thu, January 20, 2022
Outlook Number 22-02 - January 20, 2022
This Winter/Spring River Flood Potential Outlook is valid for the two-week period January 6 - February 3, 2022.
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
The river flood potential during the next two weeks (through February 3, 2022) is average for January into early February in the MARFC area of responsibility. 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 - NEAR AVERAGE
During the last 30 days (December 21, 2021 - January 19, 2022) observed precipitation across the MARFC region has mostly been near average plus or minus 0.5 inch. Areas ranging from 0.5 to 1 inch below average include southeastern NY, northeastern PA, and northwest VA. Areas ranging from 0.5 to 1 inch above average include south-central PA, the area around the middle and lower Chesapeake Bay region, and southeastern VA. Here in southeastern VA, amounts have been 2 inches above normal in some places. Precipitation departure data can be seen at www.weather.gov/marfc/Precipitation_Departures.
SNOW CONDITIONS - MOSTLY NEAR NORMAL
As of this morning (January 20, 2022), snow covers the ground in southern NY and areas about 20 to 40 miles west of Interstate 95. Typically for mid to late January, the snow/no snow line extends roughly along or just west of Interstate 95 from northern NJ to near DC. South of DC, the snow/no snow line typically runs roughly 50 to 75 miles west of Interstate 95. In the region from southern NY, northern PA, and the higher mountains of central PA, western MD, eastern WV panhandle, and western VA, snow depths range from 4 to 11 inches. Snow water equivalents in this area range from 1" to over 1.5" in southern NY and northern PA. For the remainder of this region, snow water equivalents are 0.5" to 1". Eastward from here, snow depths are 1 to 3 inches and snow water equivalents range from one tenth to 0.5". Snow conditions are below normal for this time of year in northern NJ and southeastern PA. Snow conditions are about normal, more or less, for most of the remainder of the MARFC region. Snow conditions are above normal in western VA. Elsewhere where patchy snow exists, water equivalent values are negligible. Snow information can be found at www.weather.gov/marfc/Snow and www.nohrsc.noaa.gov.
RIVER ICE - SOME, NOT WIDESPREAD
Currently, some river ice exists on some rivers within the MARFC service area. In southern and southeastern NY and central PA, border ice and partially frozen channels are reported on many smaller streams and rivers. A bit more widespread ice coverage is reported on larger, slower moving, calmer river locations, such as the lower Susquehanna River. Additional river ice formation is likely during the next two weeks since we are now in the coldest time of the year and the latest NWS Climate Prediction Center`s 6-10 and 8-14 day temperature outlooks both suggest colder or even much colder than normal temperatures.
STREAMFLOW CONDITIONS - NEAR OR ABOVE MEDIAN
The latest data from the United States Geological Survey (USGS) indicates current streamflow conditions within the entire MARFC region are near median for the date. The exception is a band of above median streamflow conditions that can be found along Interstate 95 from northeast NJ southward to southern VA. For current streamflow conditions please visit waterdata.usgs.gov/nwis/rt.
SOIL MOISTURE CONDITIONS - SOMEWHAT WET FAR NORTH, OTHERWISE DRY/VERY DRY
Soils are a bit moist across southern NY portions of the MARFC service area but are dry or very dry in NJ as well as southern PA southward into MD, DE, WV and VA. The long-term Palmer drought severity index is useful to estimate deep soil moisture conditions. The January 15, 2022 map (seen at www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_ monitoring/palmer.gif) suggests deep soils are moist in the north to dry in the south. Additional soil moisture data confirms the very dry soils across southern portions of the region. Visit www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/ and then click on U.S. Monitoring.
GROUNDWATER - AVERAGE TO BELOW AVERAGE
Within the MARFC service area, real-time USGS groundwater monitoring wells indicate current groundwater levels generally range from average to below average for this time of year region-wide. While some locations indicate above average levels, these areas are too few to pinpoint any particular part of the MARFC service area. To see groundwater levels visit groundwaterwatch.usgs.gov/usgsgwnetworks.asp.
RESERVOIR CONDITIONS - AVERAGE TO ABOVE AVERAGE
Most major reservoirs within the MARFC region are holding storages that are average or somewhat above average for this time of year. For example, reservoirs in the Delaware River Basin that supply NYC with water are showing average storage for this time of year.
FUTURE WEATHER CONDITIONS - COLD AND DRY
At the present time there are no strong indications of any widespread heavy rain events for the MARFC region for the next 7 days. A storm system moving across the Southeast into early this weekend is expected to remain mostly south and east of the MARFC area of responsibility but could still bring light precipitation amounts in coastal and southeastern areas. Beyond that, little or no precipitation is expected in the next week. A cold weather pattern looks likely to continue in the longer range. The latest (January 19, 2022) weather outlooks issued by the NWS Climate Prediction Center suggest that temperatures are likely to be below or even much below normal and precipitation to be below normal when averaged over the entire nine-day period January 25 - February 2, 2022. In southeastern VA, precipitation may average closer to normal. Visit www.cpc.ncep.noaa.gov/ to view the outlooks.
ENSEMBLE RIVER FORECASTS - VERY LIMITED THREAT OF RIVER FLOODING
The most recent runs (January 20, 2022) of the short-term (6-10 day) ensemble river forecasts, which take into account anticipated future weather conditions including precipitation and temperatures, show little threat of any river flooding developing during the next 6-10 days (through the morning of January 30, 2022) within the MARFC region. Widespread river flooding in January and early February is uncommon within the MARFC region, but is still possible. Please visit www.weather.gov/erh/mmefs. Longer-term forecasts suggest no apparent increased chance for river flooding compared to normal for late January or early February. Any future river flooding will depend primarily on shorter-term weather conditions, such as the occurrence of widespread heavy rainfall.
Except for southern New York and northernmost Pennsylvania, long term dryness has led to overall drier than usual conditions for soils, streamflow, and groundwater. Recent wet weather continues to nudge these conditions into a somewhat better situation, but mainly for streamflows. Colder, more seasonable weather has led to some ice formation on rivers, mainly in the north. Additional ice will likely form in the next two weeks as cold, January temperatures persist. Snow has increased significantly over the past couple of weeks, mainly as a result of a storm this past weekend. Snow is on the ground within the MARFC region west of Interstate 95. Below or even much below average temperatures are expected over the next week or two and are expected to minimize snowmelt but increase ice formation. However, snow should still gradually, slowly melt over southern sections. There are currently no strong indicators for heavy rainfall that could result in river flooding during the next 7 days. And, there are no indications of any fast snowmelt events for this region at the present time, as temperatures are likely to be below or even much below normal for the next couple of weeks.
WATER SUPPLY OUTLOOK
According to the latest (January 18, 2022) U.S. Drought Monitor (droughtmonitor.unl.edu), abnormally dry conditions are present in south-central and southeast PA, southern NJ, the northern part of the Delmarva, parts of the eastern panhandle of WV, and central and western VA. Scattered pockets of moderate drought are present in western VA. Assuming near-normal precipitation over the next few months, few or no water supply shortages are anticipated within the MARFC region through April, 2022.
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 2-3, 2022.