Winter Storm Feb 1st and 2nd

Weather BriefingWinter Storm February 1st& 2nd, 2011
Prepared 11 AM EST –Monday January 31, 2011
Joe Miketta
NOAA’s National Weather Service
Philadelphia/Mt. Holly NJ Forecast office
Weather.gov/phi




A major winter storm is on the way for Tuesday February 1stthrough Wednesday February 2nd.
•Two phases expected with this system…mainly snow starting around midnight or so tonight lasting into Tuesday morning. Then a lull before precipitation begins again Tuesday evening.
•Primary impacts from this storm will be significant icing from freezing rain, heavy wet snow, heavy rain and coastal flooding.
•As of 11 AM Monday, a Winter Storm Watch is posted for the northern two-thirds of the NWS Mount Holly County Warning Area (CWA). Warnings/Advisories will most likely be issued later today (Monday).
•Precipitation will begin as snow throughout most of the Mount Holly CWA during the overnight hours tonight (midnight or so). Most of this precipitation will stay in the form of snow and will taper off by mid-morning. Some freezing rain could mix in at times toward morning, mainly south. The second round of precipitation will begin during the evening hours on Tuesday, beginning as snow in the north, but perhaps a snow/sleet/freezing rain mixture in the south. As warmer air moves in aloft, a changeover from frozen precipitation to plain rain is expected from the south into the Philadelphia suburbs. However, a complete change-over to plain rain is not expected over the far northern suburbs of Philadelphia, the Lehigh Valley, the southern Poconos or northern NJ north of I-195.
•Icing threat: There continues to be a high risk for significant icing (in excess of 0.25 inches) due to freezing rain. There is a moderate risk for severe icing (in excess of 0.50 inches). Chances of a catastrophic ice storm (in excess of 0.75 inches) are low, but still possible. Most likely timing for icing is late Tuesday evening into Wednesday (with the second phase). Highest risk areas for most severe icing is north and west of the I-95 Corridor. See icing slide for more details.
•Heavy snow threat: Snow will begin during the overnight hours tonight, and continue into Tuesday morning. Two to four inches is possible by the beginning of Tuesday morning’s commute (higher amounts north, lower amounts in the Philadelphia area). Additional accumulations can be expected during the second phase of the storm, especially north of Philadelphia. However, sleet/freezing rain/rain mixture will keep additional amounts down. There is a threat for 4+ inches of snow from this event (both phases), with the highest risk in east central PA into northern NJ.
•Rainfall threat: Areas which see primarily rain (south & east of the I-95 Corridor) can see rainfall amounts in excess of one inch. This will cause localized flooding problems. Flooding problems will be exacerbated in those areas which currently have considerable snow pack, as storm drains and culverts may be blocked by snow/ice.
•Coastal flooding threat: New moon occurs Wednesday, February 2nd, so regular high tides will be running high. Therefore, there is an enhanced risk of minor coastal flooding at the times of high tide.
•Maintain situational awareness by monitoring our website at: http://weather.gov/phi