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Get ready L.I.!!

Discussion in 'Weather' started by linycctitan, Dec 10, 2007.

  1. linycctitan

    linycctitan Senior Member
    Messages: 588

    This was just in from the NWS Forecast Center @ Upton, LI, NY as of 10:32pm tonight. I know it's a bit too early to get excited but purplebou:redbounce:bluebouncxysport

    Long term /Thursday through Monday/...
    there is a potential for two systems to impact the local area
    during this time.

    Outside of the latest 12z run of the GFS forecast model...most models
    including the NAM and the European model (ecmwf) show a flatter wave developing
    which would move further S and allow cold air damming to occur SW
    from a high pressure system over New England. With an upper level split flow
    in place...the entire tri state area could experience a
    significant winter weather event Thursday into Thursday evening. The highest quantitative precipitation forecast
    would range from 0.4 to 0.8 inches...with the highest amounts
    occurring from NYC east and S. There is a potential for a 4 to 6 inch
    snowfall...with sleet and some rain holding amounts down. Stay tuned.

    Regarding the development of a strong coastal low for this
    weekend...there is a high degree of uncertainty...as a deepening
    upper level trough approaches the region. Precipitation amounts from
    this system could be in the 1 to 2 inch range. Stay tuned.
  2. linycctitan

    linycctitan Senior Member
    Messages: 588

    Looks like another wait & see!!

    Area forecast discussion
    National Weather Service Upton New York
    539 am EST Tuesday Dec 11 2007

    high pressure builds in from the west this morning...then slides
    offshore this afternoon. A cold front will cross the tri-state
    tonight and Wednesday morning. High pressure builds in from the
    Great Lakes behind the front into Thursday...then gradually lifts
    northeast. Meanwhile...a storm system will move across the Middle
    Atlantic States Thursday...then pass to the south of Long Island
    Thursday night. High pressure then builds over the Great Lakes
    into Friday night...and then into southeastern Canada into
    Saturday night. Meanwhile...another storm system will move
    northeast through the southeastern states Saturday night...then
    move northeast near the coast Sunday and Sunday night. Another
    high then builds in on Monday.


    Near term /until 6 PM this evening/...
    region will be dominated by a high transiting across the region.
    Associated subsidence inversion will make for slow clearing of
    any clouds underneath it this morning (especially across southern
    portions)...then clouds and showers ahead of next system build in
    this afternoon from west to east. Cloud cover will act to keep
    temperatures quite a bit cooler than the would be under full
    sun...noting 850 temperatures of up to 8c (subsidence inversion
    associated with crossing high will also limit mixing as well).
    Still will end up around normal (consistent with a mav/FWC/met blend).


    Short term /6 PM this evening through Thursday night/...
    with cold front not moving through until well after midnight
    (followed sref/GFS blend for timing)...and strong (35-45kt) low level
    southerly flow...will likely see rising temperatures
    tonight...with the 12 hour low for tonight actually occurring
    during the evening hours (hence the low for tonight being forecast
    at or just below the high for today)...would not be surprised if
    some locations in NE New Jersey/NYC metropolitan end up with readings into the l-M
    50s. Fortunately will be warm enough at all levels for only
    rainfall with showers ahead of the front tonight...do have
    categorical probability of precipitation consistent with sref probability of > .01 inches of

    Highs for Wednesday more than likely will occur in the morning
    with falling temperatures during the afternoon.

    High pressure building in from the Great Lakes will supply the
    necessary low level cold air for the next system of interest
    Thursday and Thursday night. NAM is quite a bit slower than any
    other model or ensemble mean in its timing of the system...the
    GFS/CMC global and European model (ecmwf) are the fastest...the UKMET and gfes mean
    are in between the two...with the sref in between the middle group
    and the fast group. Opted for the sref solution for timing...and a
    blend of NAM/GFS for thermal structure with the upcoming system.

    With sufficient cold air...all precipitation should start as snow
    as it develops from SW to NE Thursday. As warmer air builds in
    aloft (with secondary low tracking to the north/west)...will see
    sleet mixing in...and depending on how much warmer air comes in
    off the water (expected east-northeast track and isallobaric flow could limit
    this) could see precipitation mix with/change to rain across Long
    Island/NYC metropolitan as well. With low expected to track near the
    40/70 Bench Mark could see an all snow event across the far
    northern tier...but more than likely all areas will see some sleet
    mixed in...if not a turn over to all sleet (once again potential
    for mixing in rain over Long Island...but only across the heat
    island and southern Long Island do I feel fairly confident the
    precipitation will change to all rain for a time Thursday
    afternoon/evening...before cooler air returns Thursday night as
    the low pulls out...working the transition back towards frozen
    precipitation. While some algorithms do spit out some freezing
    rain...for now feel threat is minimal...as it appears lowest
    levels will either support rain or frozen precipitation...but not
    have a real shallow layer of below freezing temperatures near the
    surface for any substantial period of time (except for maybe over
    interior portions of NE nj). Precipitation should come to an end from west
    to east late Thursday night.

    Potential continues for a significant winter storm...especially
    across interior locations Thursday and Thursday night...having 30
    percent confidence that warning criteria (6 inches of snow) could
    be met across interior areas...will address in the hazardous weather


    Long term /Friday through Monday/...
    18 and 00z runs of GFS and 00z gfes and European model (ecmwf) argue for more cold
    air to be in place ahead of coastal storm for Saturday night and
    Sunday...with gfes mean furthest southeast with low track (tacking it
    completely south and east of long island). Adjusted temperatures
    downward in the extended and increased probability of precipitation Saturday night and
    Sunday in collaboration with surrounding offices. See potential
    for significant amounts of quantitative precipitation forecast and wind...p-type will be very much
    dependant on storm track.