Saturday, March 13, 2010


1:15 PM SATURDAY 3.13.2010  Many areas as shown above in the current US observed precip map have already seen .5-1.5" with another 1-2" occuring today. These amounts may push many streams, creeks, and rivers to near or above flood stage. Some areas in VA , WV and MD are already seeing some flooding. As of late last evening, NWS Flash Flood Guidance was  1.0" in 12 hrs over the northern part of MD and northern PA. We are monitoring data to see if these amounts will verify. ~ Forecaster Brisko

8:00 AM SATURDAY 3.13.2010 
SYNOPSIS: On this 17 year anniversary of the March 13, 1993 Superstorm (ABC news video archive); much of the eastern U.S. is being lashed by a slow-moving coastal "maelstrom" that more resembles a tropical depression. Throughout today, winds nearing 35 mph and rainfall up to 2 inches is expected across West Virginia, Virginia, Maryland and Delaware. Extensive inland flood warnings are in effect across these areas as well as central and western Pennsylvania. Coastal flooding is occuring along the Carolina coasts, the Chesapeake Bay, DelMarVa and the New Jersey Coast. In addition, much of New Jersey, eastern Pennsylvania and southern New England will bear the full brunt of onshore flow with total rainfall amounts to exceed 4 inches by Sunday. You can monitor details of observed precipitation, river flood status and stage potential at NOAA's Advanced Hydrologic Prediction Service or the Middle Atlantic River Forecast Center (MARFC)

Collaborators: Zak Brisko, Daniel Ross, Winterman, PasadenaMatt, Jason, Mr. Foot

RAINFALL: Initial concerns of amounts reaching 4 inches in Maryland have shifted northeast to New Jersey and eastern Pennsylvania. As shown on this 48 hour projection by the MARFC, total storm rainfall is still expected to range near 2 inches for many areas, but appears to be far less than first anticipated.

WINDS/COASTAL FLOODING: A long duration easterly fetch enhanced by a tightening pressure gradient between the coastal Low and surface High to the north will bring winds above 35 mph for the eastern DelMarVa and New Jersey. Areas west of the Bay and in Pennsylvania should see winds gusting to 35 mph, but sustained at roughly 25 mph. Tides both on the western Bay and along marine coasts appear 2-3 feet above normal.

RIVER FLOODING In dynamic and irregular systems such as this, rainfall amounts can vary widely. Urban flash flooding occurs very quickly, with stream channels often rising by several feet within minutes. Larger rivers of course take longer to reach flood stage, and usually well after the storm has moved on. Continue monitoring the latest river levels at your local Advanced Hydrologic Prediction Service sites.

10:45 PM FRIDAY 3.12.2010  During this dangerous and widespread spring rainstorm, please heed this advice from the National Weather Service: Turn Around Don't Drown.

SITE UPDATE: The URL will remain Once this rain event has ended, we plan to make the primary public site, however anyone attempting to visit  .org will automatically be redirected to .us.

A complicated, multi-pronged area low pressure of low pressure is crawling through the Tennessee Valley. On deck for Saturday is a developing easterly fetch laden with moisture, combining with the upper level influence of short waves rotating around a low in the southern Plains. Add to this the regular daytime heating effect, and areas of the Southeast and Mid-Atlantic may see brief torrential downpours from "popcorn" variety thunderstormss. A second set of strong to severe storms from a secondary coastal low will produce conditions similar to a weak tropical storm. Winds by Saturday may reach 35 mph, with rainfall amounts in central Virginia across central Maryland and into the DelMarVa exceeding 4 inches. Up to 4 inches likely from the WV panhandle through southern PA to New York City. Source: Middle Atlantic River Forecast Center Precipitation Maps.

Our forecasters are also closely monitoring any potential for development of tornados in the Severe Storm Zone, including the Carolinas, southern Georgia and Florida. Links to NWS advisories and warnings are included or posted on this page as needed.

Significant river and urban flash flooding possible in all areas denoted on the Middle Atlantic River Forecast Center (MARFC) map shown. Areas where significant flooding is possible or likely extend from portions of West Virginia into Central VA, much of MD, southern and eastern PA, all of DE and NJ and into southern New York.

Potomac: Point of Rocks, MD | Paw Paw, MD
Mid-Atlantic: RFC Hydrometeorological Discussion
HPC: 12-36 Hour Short Range | QPF Discussion |
MAPS: Watches & Warnings | 48-hour MD-VA precip | HPC Day 1-3

FRIDAY: Rainfall across the Mid-Atlantic may average 0.50 inches by noon, with localized amounts near 0.75 inches. Areas north of Pennsylvania will receive similar bands of moderate to heavy rain arrving in brief squalls by Friday evening.

FRIDAY PM INTO SATURDAY: A brief lull may occur from Friday mid-day to early evening before another round of tropical moisture is activated by upper level shortwave energy. In this second batch, torrential downpours are possible on Saturday, producing an additional 2.0 inches, with many areas exceeding 3.0 inches before daybreak Sunday.

ADDITIONAL UPDATES in progress. Despite the recent site domain name changes, please know your Forecast Team is in constant monitoring of this developing long duration rain event.

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