Monday, November 24, 2014

Red Pill or Blue Pill?


Red Pill or Blue Pill?
(Sorry Ravens fans, no Purple Pill this time...)

WINTER STORM WATCHES POSTED FOR MID-ATLANTIC & NORTHEAST
(Click on link above to see latest watches and your local NWS office)




MARYLAND: NEAR 70 DEGREES MONDAY, 5 OR MORE INCHES WEDNESDAY?!?

3:55 PM 11/24 UPDATED: Scenario A & B Map Below

  • Special FREE teleconference briefing available Tuesday late AM and early PM to ask our forecasters your questions about the storm. Send us a message to winter(at) footsforecast.org to register for the call. Indicate what weather information about this event would aid your decision-making. 
  • Four (4) time slots will be available, pick any of them at your convenience.
  • For companies or organizations, denote one representative who can report back to your group. A briefing package will be sent Tuesday AM with call-in details.


OVERVIEW (By Forecaster Mike Natoli) Regardless of heavy rain or snow, we all are likely to see a disruptive storm moving up the East coast at the very least. 
  • We have refined our ideas to two scenarios depending on surface temperatures. Temperatures will be marginal, near or slightly above freezing, which will initially make snow accumulation difficult. However, as computer models have been projecting for the past 24 hours, high snow fall rates may overcome warm surfaces and create a surprise situation Wednesday afternoon.
  • We remain cautious on this storm, because a slight shift of precip arrival or type over just 2 hours on Wednesday morning will impact the entire day's forecast. If we decide we need to make a snow accumulation forecast, that will be issued either later tonight or Tuesday morning. Until then we have narrowed the potential outcomes to TWO SCENARIOS, outlined in the next section.




SCENARIO A (50%) THE RED PILL. It's the January 26, 2011 "snow monsoon" all over again,only this time on the worst possible day of the year.
  • This scenario would occur if we end up with colder air entrenched and a weaker flow of warm air off the Atlantic. The I-95 Corridor may start out as rain, then transition to snow Wednesday late morning. This could bring accumulating snow to the big cities on the busiest travel day of the year.
  • A burst of heavy snow and low visibility in several hours ending Wednesday evening could bring holiday travel to a grinding halt.
SCENARIO B (50%) THE BLUE PILL. We start Wednesday with heavy rain through the morning, then mix with snow by the mid-afternoon, and all snow by the evening. 
  • A brief period of heavy snow may have trouble sticking in the I-95 corridor, but will still make for some slick conditions and low visibility. Travel will certainly be disrupted, but it won’t be the disaster we’d see if Scenario A plays out.
  • The heavy rain will snarl traffic as well. Those inland can expect to see heavy snow, possibly accumulating over 4”. The metropolitan areas and major cities see light accumulation, enough to look pretty for a pre-holiday glint, but shouldn't adversely impact travel.
DATA UPDATE: We want to re-emphasize for those who may not have seen our previous posts. Not since January 2011 have we seen such a high intensity-short duration projection for heavy snow. Below is a live-link to the GFS liquid forecast for BWI Airport as a representative location in the Mid-Atlantic. Many others show the same, for DC, Philly, Harrisburg, Roanoke, you name it. 
  • Even the afternoon of February 4, 2010 started generally light to moderate. The map below shows over 0.50" of liquid falling at BWI airport in just 6 hours. That's 1"per hour -- for 6 hours. It's not a guarantee, only a projection, for now.




    Forecasters M. Natoli, R. Foot and the WSC Team

    18 comments:

    Patricia said...

    I have read the sentence over and I think it is confusing. Scenario B

    First dot last sentence
    Travel will certainly be disrupted, but it won’t be the disaster we’d see if scenario B plays out.

    I think you mean is scenario A plays out, but then again, maybe not.

    ravensbbr said...

    No purple option..dangit. :-P

    kyleZ said...

    WASHINGTON-FREDERICK MD-CARROLL-NORTHERN BALTIMORE-HARFORD-
    AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-
    NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-LOUDOUN-
    NORTHERN FAUQUIER-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-HARDY-
    INCLUDING THE CITIES OF...HAGERSTOWN...FREDERICK...WESTMINSTER...
    STAUNTON...WAYNESBORO...HARRISONBURG...WINCHESTER...FRONT ROYAL...
    CHARLOTTESVILLE...WASHINGTON...LEESBURG...WARRENTON...
    MARTINSBURG...CHARLES TOWN...MOOREFIELD
    306 PM EST MON NOV 24 2014

    ...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY MORNING THROUGH
    WEDNESDAY AFTERNOON...

    THE NATIONAL WEATHER SERVICE IN BALTIMORE MD/WASHINGTON HAS
    ISSUED A WINTER STORM WATCH...WHICH IS IN EFFECT FROM WEDNESDAY
    MORNING THROUGH WEDNESDAY AFTERNOON.

    * PRECIPITATION TYPE...SNOW.

    * ACCUMULATIONS...POTENTIAL FOR FIVE INCHES OR MORE.

    * TIMING...WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON.

    * TEMPERATURES...UPPER 20S TO LOWER 30S ABOVE 1000 FEET. LOWER TO
    MIDDLE 30S BELOW 1000 FEET.

    * WINDS...BECOMING NORTHWEST 10 TO 15 MPH WITH GUSTS AROUND 20
    MPH.

    * IMPACTS...ROADS MAY BECOME SNOW COVERED AND SLIPPERY...INCLUDING
    INTERSTATES 81...70...83...66 AND 64. THIS MAY HAVE A
    SIGNIFICANT IMPACT ON HOLIDAY TRAVEL PLANS FOR WEDNESDAY. HEAVY
    AMOUNTS OF WET SNOW MAY CAUSE DOWNED TREES THAT LEAD TO AN
    ENHANCED THREAT FOR POWER OUTAGES.

    PRECAUTIONARY/PREPAREDNESS ACTIONS...

    A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
    SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
    CONTINUE TO MONITOR THE LATEST FORECASTS.

    Westsidehideaway said...

    Here we go. The Westside on Bmore has the snow salt boxes out and ready. Expecting scenario B, hoping for Scenario A. Go Ravens.

    NeedaSnowday said...

    Thanks for heads up Kyle... Am sure it will get extended, right!?

    Westside in the house!!
    Put out an APB for Julee....bird report makes this complete!

    Am pretty anxious about the game... Wish Andy could predict that as well...

    GO RAVENS!!!!!!

    kyleZ said...

    Should be interesting to say the least not expecting much in southern Harford county but time will tell Andys area looks to get good dumping though.

    Mike Cheuvront said...

    What say you Andy?

    BioPat said...

    Andy must be getting extra work completed and stocking up on the manwich in preparation for the snow. I imagine he'll be posting in the next few hours.
    I'm picking up my turkey tomorrow and celebrating our 25th anniversary with a nice dinner out and will be most thankful the storm will not be arriving until Wednesday.

    Andy, Southern York County Pa said...

    This storm is going to surprise. This is a very dynamic system as it is a southern stream coastal. It is plenty juicy, and tonight's Euro will be telling. Often as we are closer in time models pick up on the dynamics of the system and begin to handle meso scale banding and snow deformation zones which can exponentially enhance totals much better.

    Safe to say that the initial warmth at the surface and any mixing will limit initial accumulations near the immediate bay and typical urban heat island zones.

    Once this thing is cranking and the surface has cooled it is apt to pile up fast. What I will look for over the next 24 hours from the models is how and if they pick up on mesoscale features, and the deformation zone. Areas that are impacted can really cash in fast from any enhancement. These features will be on the table once the storm is cranking and the surface has cooled for urban accumulation.

    I view this as a 6-10 inch threat for immediate Baltimore metro, with an 8-12 inch zone for the hillbillies to the north.

    The most important thing is that the word is out that double digit snow totals are possible in the entire metro and snow over 6 inches seems probable.

    The NWS may expand the watches south depending on tonight's runs.

    They want to have more confidence in thermal profiles before they do anything. At this point in time one thing is clear that the ground and air truth Wednesday afternoon will be heavy snow everywhere with high impact on visibility and travel. This will be heavy wet snow and the roads will be a mess.

    I will be staying off them Wednesday.

    Foot's Forecast said...

    Thanks BioPat. You were right-- it was And we fixed it.

    A special plug for our colleague at CrunchDaddy Popcorn. Yes, it is the official popcorn of Foot's Forecast!

    It would be a proud day for us if a few nice people here would consider the innovative and excellent popcorn made by a fellow Maryland small business owner! Thanks so much everyone.

    kyleZ said...

    Hope this verifies Andy would be awesome to see.

    ravensbbr said...

    Can't wait to turn the Deere loose on this mess on T-Day morning. Beats watching the stupid parades...

    Westsidehideaway said...

    Hmmm. Andy, I want snow but this does not feel that severe. But we shall see. Meantime I got the Ravens to worry over.

    Butch Dynomite said...

    Go ravens!....maybe county will call it early. Let me sqeak out early Wed before changeover. we typically have pretty low attendance before holiday. Not confident that my street will get plowed early enough Thursday if it does pile up.

    Amy said...

    You really feel that accumulation is a possibility? I'm skeptical, but love being proven wrong. I'm hedging my bets towards the "visibility sucking / but no serious accumulation" type snow fall. Glad I'm going no where Wednesday but to pick up my catered thanksgiving meal. Might move the pick up time earlier than 2....

    Butch Dynomite said...

    I sure don't know ... I count on the others for insight. I agree with you -wetter, lower accumulations. But I tell ya if someone sneezes on 95 between New York and Petersburg Wed it will be a long night.

    Andy, Southern York County Pa said...

    Amy,

    Based on all reliable guidance accumulation is not a possibility, but a high probability. If the euro comes in more juicy you will see Winter Storm Watches expand further south.

    Andy, Southern York County Pa said...

    European model is colder and snowier. All other guidance has been snowier. The gfs is not as bullish but it has a poorer record with southern stream systems.