Sunday, November 23, 2014

Turkey in the snow?

Turkey in the Snow?

7:30 PM EST 11/23 - UPDATED - Discussion of scenarios below. 

NOAA Snow Probabilities: Moderate (40%) chance of 4" for Northeast US

1:05 PM 11/23 (By the Kentucky & Winter Stormcast Teams) Although the Thanksgiving holiday period is finally arriving, Mother Nature shows no signs of taking time off as the potential is increasing for a significant weather event that could snarl one of the busiest travel days of the year.

THE SITUATION: Our team first identified the potential for a "White Thanksgiving" in an October 25 post, due in part to data showing a record high snow-cover for Siberia and the downstream effects that large Arctic highs would have coming across the Pole. Now in present day, numerous medium range model runs support a significant winter storm occurring on Wednesday into Thanksgiving morning near the East coast. 
  • The areas which may see notable to significant impacts from this system extend from South Carolina to the Mid-Atlantic, into the Northeast all the way to Maine. 
  • As with all storm forecasts more than 72 hours out, we expect considerable variance between forecasted data and outcomes, until shortly before the event begins.
  • The timing of this system creates additional concern for the traveling public, hence we are outlining scenarios early to help identify which pattern will prevail.

SCENARIO A: OUR GOOSE IS COOKED. An area of low pressure develops in the northern Gulf and moves along the East coast, bringing Gulf moisture while drawing in Atlantic moisture. The system would tap cold air from a snow-cover influenced surface high in western PA/NY. 

  • This track would hug the shoreline, bringing heavy rain and tidal flooding to coastal communities and heavy snow in the interior. 
  • As temperatures fall into the 30s through the Mid-Atlantic and Northeast, rain would change to snow in the major cities and continue heavy overnight, producing  a major snowfall to a majority of the Northeastern states. 
  • CNN features long lines of weary travelers stuck in airports.
The latest liquid projections by the US Global Forecast System for BWI airport show why there's much concern for Scenario A. Nearly 1.0" of liquid falling as snow would be a major problem.

SCENARIO B: BETTER LEAVE EARLY ANYWAY. The storm develops weaker and further east than in Scenario A. This would produce far less precip for the Carolinas, Mid-Atlantic and Northeast. 

  • However, colder air will be more available, as northwest flow would rush in behind the departing storm. Coastal areas would see a cold rain or wet snow that has trouble sticking until after nightfall Wednesday. 
  • The bulk of energy would affect northern states, especially New England while the Mid-Atlantic is only brushed with light accumulations. 

SCENARIO C: CANCEL THE SNOWSUIT SEARCH! Strength and influence of the Great Lakes system on Tuesday nudges any coastal Low pressure away from the eastern seaboard, in tandem with surface high pressure to the north. 

  • This would bring only brief light precipitation to coastal areas, little or no precipitation to major cities and minimal impacts on Thanksgiving travel.

Our Winter Stormcast Team will be frequently monitoring the latest changes and updating here as data becomes available. Our next update is planned for Monday where we will narrow the scenarios to 2 options and begin discussing precip and snowfall ideas.

(Report by the Kentucky Team: Forecasters Kyle Jackson, Darius Mack, and Lead Forecaster Chris Reece. Additional content by Maryland Team members Mike Natoli, Connor Meehan, Joey Krastel and Rich Foot)

Saturday, November 22, 2014

"Cutting it kinda close..."

"Cutting it kinda close, don't ya think?"
-Elastigirl in The Incredibles, 2004

6:55 PM EST 11/22 - UPDATED - Scenario Map and Storm Track Probability posted below. Text of the scenarios will be added on Sunday. By Monday we will narrow to 2 tracks, with preliminary snowfall ideas by Monday night and a snowmap by Tuesday afternoon. 

3:42 PM EST 11/22 - Early this week, we posted a report hoping that the weather would not "be a turkey" for the upcoming holiday weekend. However, the pre-winter pattern indicates Mother Nature did receive our memo from October 25*, and appears determined to deliver the first widespread White Thanksgiving to the Mid-Atlantic and Northeast since 1989. (*Hint: It's the post where we said this year, there's better chance of a White Thanksgiving than a White Christmas." 

TEAM STATEMENT: Our composite analyses of several well-known computer models suggests a potentially significant winter weather event may affect much of the East coast for the Wednesday-Thursday period. The timing of this storm could seriously disruptive the Wednesday afternoon and evening holiday travel, if present indications for that time period do not change appreciably.

(Left: Liquid forecasts from NOAA as of Saturday 11/22 show a large swath of precip to affect the East coast Wed night through Friday)

  • The system is still 4-5 days away from affecting any of us. But the untimely prospect of a serious storm arriving on the busiest travel days of the year warranted an early heads up
  • If traveling by air on Wednesday night anywhere along the East coast, it might be strategic to contact the airline now and be aware of your options if the situation deteriorates.
  • It is too early to project when and where snow will fall Wednesday. If planning to travel by vehicle, consider now alternate times or routes you could take if snow develops Wed night in your area or along your route.

TRACK: Our three-outcome graphic above depicts the likely paths, and by Sunday-Monday we can narrow this down to the one solution we expect to be most probable. We emphasize that much can change at 120 hours prior to a storm. Slight shifts can produce major differences, and with a lot of air movement and liquid in play, it warrants close attention.
The Takeaway: We understand how serious this situation would be for millions of people all across the country and around the world. In the words of our headline, this really is cutting it kinda close, in how it could completely disrupt the travel plans of everyone depending on air travel in or out of the Northeast. It's not appropriate to cancel your plans based on a 5-day forecast, but it is reasonable to contact your airline and learn your options if the situation sours quickly on Wednesday.

TEMPS: Despite an expected spike into the 50s and 60s by Tuesday, another push of Arctic air will return to the region. Some computer scenarios show a cold rain on Wednesday changing to snow before nightfall. Were the coastal low to develop as shown on Tue-Wed, it would tap a large reservoir of nearby cold air due to the recent heavy snowcover in the Great Lakes to New York state. The European model, notable for accuracy in long range calls from recent winters, shows sub 34 F temps from Virginia north by 7 PM Wednesday.
The Takeaway: Were these temps to occur during a "nor-easter" setup, the result would be wind-whipped heavy snow to hit major East coast interstates of the Northeast corridor at the absolute worst possible time: Wednesday night.

LIQUID: The NOAA Weather Prediction Center's latest liquid projections, (shown above) prepared by actual meteorologists using input from several model sources to convey what we call a "broad brush" look at what's possible. A general 0.50" to 0.75" of liquid is, at this point, the most probable outcome for the I-95 corridor. 
The Takeaway: A slight shift to the west by Wednesday would bring much heavier precipitation, and possibly, heavy snow with low visibility, to the expected high traffic volume areas of the map. 

NEXT UPDATE: Our team will keep close watch on this developing story, and post updates in the early morning and early evening, with a mid-day reassessment each day. 

Forecasters Foot, Connor Meehan, Mike Natoli, Joey Krastel (MD Team); Justin Barker and Andy Smith (VA Team)

Wednesday, November 19, 2014

Hey weather: Don't be a turkey!

UPDATED 11/22/2014 - If long range projections are on target, it appears Mother Nature got our memo from 9/25 when we anticipated that a "White Thanksgiving was more likely this year than a White Christmas." The European and US Global Forecast System model printouts, though just at the 120-hour mark, are leaning toward a more snowy result for the mid-Atlantic Wednesday night into Thanksgiving Day. With this event potentially impacting the busiest travel period of the year, we are preparing an overview of the possible hazards, timing and intensity for posting here on Sunday.

NEXT MON 11/25 AS OF WED 11/19.
11/19/2014 - We know it's coming on quickly, there's nothing anyone can do about it, and there are some who wish it would never happen.

It's not the raucous Midwest-Great Lakes storm to roar through the heartland next week... 

Rather, it is the sometimes dreaded Thanksgiving week travel and the shopping frenzy to follow -- that plunges us all headlong into a spin cycle of insanity. Toss in a "little weather" to the airline adventure and whoop! There it is: Harried parents and woesome children at long ticket counter lines... and so on.

But thanks to taxpayer-funded technology, we have access to this really cool technology from the US Department of Commerce that actually SHOWS, like, a glimpse of what things could be like next week as the holiday travel season launches forth. This way, it's not a mystery to anyone:
  • MONDAY: A vigorous storm system will develop in the southern plains and head for the Great Lakes. On east side of the storm, temperatures Mon-Tue in the Eastern U.S. will begin rebounding to seasonal levels. On the west side of the storm, as noted by the cold front above, conditions will be -- you guessed it -- STORMY! Strong winds, heavy rain and then potentially heavy snow.
  • TUESDAY: We already hear Airport Operators saying, "Can we just get that thing outta here before Wednesday?" Well try, my friends, we'll try. However, it is reasonable to expect flight delays may begin Tuesday and spread into Wednesday because of the front sweeping across the Eastern states.  Places that face potential travel disruptions may include the I-95 corridor from Richmond to New York as a series of Lows could develop and move north along the cold front. Indications point to this being more of a "wet" day than a "white" one, as temperatures should stay above freezing. We'll monitor closely of course as the day approaches. 
  • WEDNESDAY: Arrival of the dreaded big travel day. Early interpretation from NOAA's Day 7 map, while still quite distant in weather time concerns, suggests the hope of travelers may pan out: High pressure looks to reestablish behind the front in the Eastern US, stabilizing the pattern from storminess for Wed into Thanksgiving Day. 
Until then, think ahead to how you would alter your plans for travel on Wed 11/26 IF you had to, unless the weather decides to cut us a break this year and not be a turkey after all.

Forecaster Foot & the Long Range Team