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Information on MARFC Hydrologic Ensemble Forecast Service (HEFS)
In late 2017, the Middle Atlantic River Forecast Center (MARFC) began issuing experimental short term ensemble hydrologic forecast products from the new NWS Hydrologic Ensemble Forecast Service (HEFS). The above “POTENTIAL RIVER LEVELS” is a product of that experimental short term ensemble hydrologic forecast
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Hazardous Weather Outlook
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 505 AM EST Sat Jan 19 2019 MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-201015- Washington-Frederick MD-Carroll-Northern Baltimore- Extreme Western Allegany-Central and Eastern Allegany- Northwest Montgomery-Central and Southeast Montgomery- Northwest Howard-Central and Southeast Howard-Northwest Harford- Augusta-Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke- Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper- Northern Fauquier-Southern Fauquier-Western Highland- Eastern Highland-Western Loudoun-Eastern Loudoun- Northern Virginia Blue Ridge-Central Virginia Blue Ridge- Hampshire-Morgan-Berkeley-Jefferson-Hardy-Western Grant- Eastern Grant-Western Mineral-Eastern Mineral-Western Pendleton- Eastern Pendleton- 505 AM EST Sat Jan 19 2019 This Hazardous Weather Outlook is for eastern West Virginia, northern and central Virginia, and central and western Maryland with the exception of Garrett County. .DAY ONE...Today and Tonight A Winter Storm Warning is in effect for much of northern and western Maryland, eastern West Virginia and the northern Shenandoah Valley of Virginia Saturday into Saturday night. Significant icing with some snow and sleet is expected. Further south, Winter Weather Advisories are in effect Saturday into Saturday night for lesser amounts of snow and ice across the southern Shenandoah Valley, Blue Ridge, and northwest suburbs of Washington. .DAYS TWO THROUGH SEVEN...Sunday through Friday Gusty winds may cause localized wind damage Sunday afternoon into Monday. Bitterly cold wind chills are expected Sunday night into Monday morning. Wind chills will be below zero across much of the area and may approach 20 below zero over the mountains. The combination of moderate to heavy rain, along with snowmelt and ice melt, has the potential to produce flooding during the second half of the upcoming week. .SPOTTER INFORMATION STATEMENT... Please relay significant weather reports to the National Weather Service. $$
High-impact winter storm affects the region over the weekend
A strong storm system will move from the Southern Plains to the Tennessee Valley Saturday morning, and subsequently to just south of Pittsburgh, PA Saturday night. The storm will likely redevelop near the I-95 corridor between Philadelphia and New York City late Saturday night, and will continue to near Boston Sunday morning. Heavy interior snows are expected from this system, and heavy rain for areas mainly SE of the I-95 corridor. In between will likely see snow to start, then changing to sleet and freezing rain, and in some areas significant icing, before changing to rain in some of those areas.
As the system pulls away Sunday morning, ALL areas will change to snow at least briefly from NW to SE as cold air rushes in on the back side of the system, and ALL areas will experience a flash freeze Sunday afternoon and evening. It will also become increasingly windy Sunday afternoon through Monday.
Impacts and Timing:
Impacts will be high for ALL areas, regardless of dominant precipitation type. Expect heavy snow for areas along and NW of I-95 in PA/NJ to break out Saturday afternoon, which will continue as heavy snow north, and begin to change to sleet, then freezing rain from south to north on Saturday evening and overnight. Far northern areas will remain all snow or a mix of sleet and snow. Southern areas that started as snow/mix will transition to plain rain for a time later Saturday night and marginal areas in the middle may remain below freezing and experience extensive icing issues. Heavy rain and flooding concerns will present themselves closer to the I-95 corridor and all points SE. Northern and central areas will end as snow at least briefly before ending as the cold air rushes in and a flash freeze will occur in ALL areas on Sunday afternoon and evening. Windy conditions will develop behind this system accompanying the cold air advection, with wind gusts over 40mph expected from Sunday afternoon through the overnight, and much of Monday. Very cold temperatures Sunday and Monday nights will be in the single digits, and in some places, below zero with dangerous wind chills Sunday night and Monday.
Expect impacts to include, but not limited to:
- Heavy snow in northern regions that will make travel nearly impassable.
- Heavy icing expected in central areas that start as a thump of heavy snow, then transitions to rain
- Power outages are expected to be higher than usual with the combination of heavy snow, heavy rain, freezing rain, and windy conditions Sunday afternoon through Monday, especially in the “red zone” on the ice map below
- Thunderstorms will be possible in southern NJ and DE mainly when the low pressure moves by late Saturday night and early Sunday morning
- Flash freeze will occur behind this system, and all wet roads, slush, and standing water will freeze rapidly Sunday afternoon and evening. Black ice will be a travel hazard since wet roadways will not be able to be treated in advance where rain is occurring or has occurred.
- High wind gusts expected to be over 40mph at times region wide from Sunday afternoon through Monday
Timing is generalized, but expect precipitation to move in generally from west to east during the course of Saturday afternoon from west to east. Precipitation will end from west to east from Sunday early to late morning, and likely as brief snow for central and northern areas.
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#StormMode Only Updated DURING “Weather Events“
Official National Weather Service Middle Atlantic River Forecast Center
When the river is rising … ACTION STAGE
When the river is rising … ACTION STAGE the river overflows the lowest natural riverbank and reaches “first trailer RIMS” in River Bend Park. ACTION STAGE is estimated (John Kolsun) at 20.51 feet OBSERVED at Dam Number Five.
at River Bend Park
When the river is rising … FULL BANK at River Bend Park (estimated John Kolsun) at 19.51 feet AT DAM NUMBER FIVE. Above 19.51 feet @ Dam 5 a rise in water surface will cause the river to overflow the lowest natural riverbank somewhere in the corresponding reach.