Flood Potential Outlook
Issued by NWS Binghamton, NY

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483 FGUS71 KBGM 151717 ESFBGM NYC007-015-017-023-025-053-065-067-077-097-099-101-105-107-109- 123-PAC015-069-079-103-115-127-131-171730- Winter/Spring Flood Potential Outlook National Weather Service Binghamton NY 117 PM EDT Thu Mar 15 2018 ...AVERAGE RIVER FLOOD POTENTIAL THROUGH MARCH 29th... This is the sixth in a series of regularly scheduled hydrologic outlooks issued during the Winter and Spring season. This outlook is designed to provide a generalized assessment of river flood potential (not flash flooding) across Central New York and Northeast Pennsylvania for the next two weeks...March 15th to March 29th. ...SUMMARY... .Antecedent conditions in the majority of our basins would suggest a higher than average risk of river flooding for the next two weeks. However, medium and long range weather forecasts suggest gradual warming trends and a limited chance for heavy precipitation. The flood favorable conditions in place would thus be mitigated by a gradual melting of the snow pack and no heavy rainfall. The overall flood potential is therefore considered about average for late March. ...CURRENT CONDITIONS... .PRECIPITATION: Above average. The first two weeks of March have seen 1 to 3 inches of precipitation across the basins. Over the past 30 days, precipitation departures ranged from 125 to 200% of normal. .SNOW COVER AND WATER EQUIVALENT: Above Average. Several coastal storms, and lake effect events, have re-established a deep snow cover across many of the basins. The deepest snow cover existed across the headwaters of the Susquehanna and Upper Delaware basins where snow depths ranged from 8 to 18 inches. Up to 2 feet of snow was in place over the highest peaks in the Catskills, the Tully-Heighburgs and the southern Tug Hill. Elsewhere, snow cover ranged from 2 to 12 inches with the lowest totals in the Chemung and Finger Lakes area. The liquid equivalent of the snowpack was about 1 to 3 inches with locally higher amounts approaching 6 inches in the deep snow areas. .RIVER ICE COVER: Normal. The river ice season has passed. All main river channels were clear of any significant ice cover. .STREAMFLOW: Above normal. Streamflow, averaged over the past 28 days, was above normal at a majority of the stream gauge locations when compared to the long term history of each gauge. Some streams from the northern Chemung across the Finger Lakes were running at normal levels. .SOILS AND GROUNDWATER: Above normal. The Palmer Drought Severity Index, along with other multi-model soil moisture indicators, showed wetter than average deep soil conditions throughout the basins. Groundwater levels were generally normal to above normal. .RESERVOIR AND LAKE LEVELS...Variable. NYC Reservoirs were slightly above the long term median pool height. The Finger Lakes levels were generally normal, while Lake Wallenpaupack in NEPA was above its March target pool height. ...FORECAST OUTLOOK... .FUTURE WEATHER CONDITIONS: The 6 to 14 day outlook calls for colder than normal temperatures and slightly above average precipitation. Several other computer forecast simulations suggested generally normal precipitation, and little to no significant storms in the period. The exception being another possible coastal storm during the March 20-21 time frame, which right now is looking to be a cold-side event with mainly snow, or mixed precipitation. .LONG RANGE RIVER MODELING AND PROBABILITY FORECASTS: The ensemble of river forecast systems indicated a lower than average risk of flooding during the next 1-2 weeks. An analysis of flooding, using current hydrologic conditions compared to historical flows, suggested the majority of basins have a lower than average chance of flooding, although basins in the Upper Susquehanna and Delaware headwaters were exhibiting a higher than historical average chance of minor to moderate flooding through early April. ...IN CONCLUSION... This outlook estimates the potential for river and lake flooding based on a current overview of hydro-meteorological factors which contribute to flooding. It is important to note that significant flooding does not occur from snow melt alone. Rainfall, how much and in how short a period of time, is the most important factor in determining the severity of flooding. Specific forecasts of heavy rainfall and flash flooding are not included in this outlook. The next Winter/Spring Flood Outlook will be issued by this office in two weeks, on March 29th 2018. If conditions change in the interim: Flood Watches, Warnings or Advisories will be issued as necessary. $$ JAB

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