February 8-9, 2013 Nor’easter Forecast

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By Stephen Gode on February 8, 2013, 1:03am Last modified: February 8, 2013, 6:34am

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An water vapor image from the Geostationary Operational Environmental Satellite (GOES) on February 8th, 2013 at 5:15 UTC (12:15 am EST).

Connecticut forecast for the Nor’easter:

Major winter storm is on its way!  The development of the main low pressure area is occurring now near the Carolinas, which is moving northeasterly! Two vorticity maximums from two shortwaves will phase for relatively strong cyclogenesis just enough to the south and east of Connecticut to give a swath of heavy snowfall. Vorticity is the measure of rotation of air along the horizontal plane. Phasing is when two low pressure areas combine into one (typically) intensifying low pressure area. Strong cyclogenesis is the rapid development of a cyclone (low pressure area). The storm may have a chance to undergo bombogenesis during the period of Friday morning to Saturday morning. Bombogenesis means a drop in surface barometric pressure by 24 or more millibars in a 24-hour period in the center of a mid-latitude cyclone. During the storm, the banana high pressure area (and initial cold air damming) to our north should lock in enough cold air and amble moisture overspreading from the south will give Connecticut potentially an all snow event.

NOAA 500 mb analysis heights/temperature valid 00z (7 pm EST) Fri. February 8,2013:

College of DuPage Analysis valid Fri 8 Feb 2013 6z (1 am EST) HPC fronts valid 4z (11 pm EST February 7, 2013): 
College of DuPage shows decent 3 hour pressure falls already up to 6 mb near coastal North Carolina. Analysis valid Friday February 8, 2013 6z (1 am EST):

Timing: Light snow may break out early Friday morning across the state. Rapidly deteriorating conditions may start about noon. Worst of the conditions will be expected in the afternoon into Friday night. Snow will start to taper off in the early morning hours on Saturday and the snow could end by noon.

Precipitation and Snowfall: Expect about 10-20 inches of snow statewide. The storm is expected to be an all snow event, but there is a chance of some mixed precipitation. Mesoscale snowbands will setup across all areas of the state, but where the most intense and nearly stationary snowbands develop can be where potentially much higher totals could occur. The higher totals could occur more likely in northeastern parts of Connecticut where banding may tend to setup more and colder air in the hills could have higher snow ratios. Under the most intense snowbands, there will be snow rates of 1-3+ inches per hour. Lower amounts could be experienced near the shore where mixing could occur at times, especially portions of Southwest Coastal Connecticut (if late development of the storm) and in areas where the snow stays generally lighter (in between or away from snowbands for an extended period/s of time). If there is any mixing, the best chance for any other types of precipitation is rain. Depending on temperature profiles, there is always a chance of freezing rain and sleet. Total liquid equivalent should range about 1-2+ inches.

Thundersnow Possibility: During the height of the storm this Friday night, thundersnow could occur in the vicinity of the most intense snowbands, because of strong upward motion (convective nature of the mesoscale snowbands).

Temperatures: Lows will be in teens (interior, especially more likely in the hills) and twenties both Thursday night and Friday night. High temperatures on Friday will be in the low to mid thirties. High temperatures on Saturday will generally be in the twenties. Wind chill values Friday night may at times fall below zero, especially in the hills of Connecticut (more likely northeast portions of the state).

Winds:  Winds will generally be sustained at about 15 to 35 mph with gusts 40-50+ mph. Winds will be stronger in eastern Connecticut, especially near the shore and with higher elevation where the air may experience less friction. There can be scattered power outages, especially at the shore due to the affects of the forecasted strong winds and wet snow (higher water content snow).

Visibility: During the height of the storm this Friday night, there will be near whiteout to blizzard condition at times (near zero visibility) across the state, especially in eastern Connecticut. There is a Blizzard Warning in effect across the entire state issued by the National Weather Service (NWS). A Blizzard Warning means severe winter weather conditions are expected or occurring. Falling and blowing snow with strong winds and poor visibilities are likely. This will lead to whiteout conditions and make travel extremely dangerous. Do not travel. If you must travel, then have a winter survival kit (ready.gov) with you. If you get stranded, then stay with your vehicle. Some areas may not experience a true blizzard. Some areas may not reach the criteria for a blizzard. To be a blizzard (another detailed definition), a snow storm needs to have sustained winds or frequent wind gusts of at least 35 mph with blowing and drifting snow and to reduce (tends to be accompanied by heavy snow falling) visibility of a quarter mile or less for at least three consecutive hours. Drifts are expected to reach a few to several feet.

Seas: Minor to moderate coastal flooding is expected, especially in western parts of Connecticut from the persistent northeasterly fetch Friday night. Significant beach erosion is also possible. Tidal departures are expected to be up to about 3-5 feet above astronomical tides, especially at the Southwest shore of Connecticut. Waves could approach 10 feet over the eastern most waters of Long Island Sound.

This storm may track a bit further offshore due to the possibility of late phasing and it could be more progressive. Also, there can be periods of persistent mixing from a layer of warm air overspreading the state, especially near the shoreline. So, most of Connecticut could escape the brunt (stronger winds/heavier snow), but it is not likely. Forecasts can change easily. But expect what a lot of forecasts say at this point. Prepare for the worst and hope for the best! 

Check back to WXedge for additional updates. 

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Stephen Gode

Town: North Haven, CT  

Reporting for WXedge since September 2012.

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