931 FGUS71 KBUF 181449 ESFBUF NYC003-009-011-013-029-037-045-049-051-055-063-069-073-075-117- 121-251500- Winter/Spring Flood Potential Outlook National Weather Service Buffalo NY 1049 AM EDT Thu Mar 18 2021 ...BELOW NORMAL FLOOD RISK FOR WESTERN NEW YORK THROUGH APRIL 1ST... ...NEAR NORMAL FLOOD RISK FOR THE BLACK RIVER BASIN THROUGH APRIL 1ST... This is the sixth flood potential outlook of the 2021 season. Flood outlooks will be issued every two weeks into early spring to summarize basin conditions and to assess the potential for flooding. The outlooks are based on current and forecast hydrometeorological conditions. This includes snow cover and water equivalent, creek and river levels and the amount of ice on them, along with the expected conditions during the next two weeks. ...CURRENT CONDITIONS SUMMARY... Warm weather between March 8th and 12th melted a significant portion of the snowpack. For basins south of Lake Ontario, there is hardly any snow pack in place with snow water equivalent (SWE) values negligible. The warm up also flushed out all of the river and creek ice in these basins. As a result, temperatures will be somewhat irrelevant for these basins since the snow is all gone. Snow still remains in the Black River Basin, but most of the snowpack is confined to higher terrain on the Tug Hill and the Western Adirondacks. The warm weather melted most of the snow pack across lower elevations, but the snow was so deep across higher terrain that significant SWE values remain across a little less than half of the basin. This limited snow coverage limits the potential quick run-off. SWE values in the Black River basin are below normal for this date, averaging only around 80 percent of the normal value. There also may be limited river and creek ice in place, however this has weakened considerably due to higher sun angles and warmer weather so it will be less likely to cause ice jams. The following is a summary of the conditions by basin as of Thursday morning, March 18th: ...BUFFALO AREA CREEKS / LAKE ERIE BASIN... .SNOW COVER..........None, except patches up to 2 inches. .WATER EQUIVALENT....None, except highly localized up an inch. .CREEK FLOWS.........Below normal. .CREEK ICE...........None. .GROUND FROST........Less than 3 inches. .GROUND STATE........Frozen in spots otherwise saturated. ...GENESEE RIVER BASIN / FINGER LAKES / ROCHESTER AREA... .SNOW COVER..........None. .WATER EQUIVALENT....None. .CREEK FLOWS.........Near normal. .CREEK ICE...........None. .GROUND FROST........Less than 3 inches. .GROUND STATE........Frozen in spots otherwise saturated. ...ALLEGHENY RIVER BASIN... .SNOW COVER..........None. .WATER EQUIVALENT....None. .CREEK FLOWS.........Near normal. .CREEK ICE...........None. .GROUND FROST........Less than 3 inches. .GROUND STATE........Frozen in spots otherwise saturated. ...BLACK RIVER BASINS / TUG HILL... .SNOW COVER..........None, increasing to 1 to 2 feet on the Tug Hill and Adirondacks. .WATER EQUIVALENT....None, increasing to 3 to 7 inches on the Tug Hill and Adirondacks. .RIVER/CREEK FLOWS...Near normal. .RIVER/CREEK ICE.....Patchy ice in spots, some thick chunks but is weakened from higher sun angle and warmer weather. .GROUND FROST........Less than 6 inches. .GROUND STATE........Mainly frozen. ...TEMPERATURE AND PRECIPITATION OUTLOOK... Low pressure passing by to the south will bring some rain or wet snow to the area today, with the greatest amounts of precipitation falling across the Western Southern Tier into portions of the Allegheny and Genesee River basins. Precipitation amounts will be modest, averaging a quarter to a half inch across the Western Southern Tier to less than a quarter inch north of this. High pressure will build across the region on Friday, kicking off a long stretch of dry weather which will last through Tuesday next week. Little, if any, precipitation is expected during this time. Meanwhile, Friday will start off on the cool side with a warming trend during the period. By early next week high temperatures will be in the 50s across the Black River basin, with highs in the 50s and 60s elsewhere. After this, there will be a series of storm systems which pass close to our area. The pattern aloft will favor systems passing by to the west, which would generally maintain warm weather and would more likely produce rain instead of snow. Forecast confidence lowers with time, but in general the most concerning timeframe is March 25th - 29th when range model guidance suggests the potential for a significant rain producing system somewhere in the region. Even so, the overall risk of heavy rainfall in our area is limited with the chance of rainfall amounts exceeding 2 inches less than 25 percent. The latest Climate Prediction Center (CPC) 8 to 14 Day Outlook strongly favors above normal temperatures and it also favors above normal precipitation. ...FLOOD POTENTIAL OUTLOOK... Through April 1st, the risk for flooding is below normal for the Buffalo Creeks, and the Allegheny and Genesee River basins and near normal for the Black River basin. The flood risk for all basins is low through March 24th. This is because there will be an extended period with dry weather during most of this time. However, the warmer weather will continue to melt off snow pack in the Black River basin which will result in high but within bank flows heading into late next week. Warm weather is expected to continue later into the outlook period. This will not be a factor for most basins where the snow pack will be all gone. However, there still will be some snow and and potentially run-off from melting in the Black River basin. This will make the basin somewhat vulnerable to flooding, especially if there is a significant rain producing system during this time. Snow pack is below normal, but given that a warm and fairly wet pattern is expected the overall flood risk for the Black River basin is near normal. The flood risk will largely depend on how much rain falls during the period with little doubt that it will be a warm pattern. It's difficult to completely rule out an unusually strong rain producing system late in the outlook period so even though the flood risk is below normal for other basins it is still non-zero. Always be sure to monitor the latest forecast. $$ Apffel