• MESO: Heavy rain - Maine

    From Weather Alert@454:1/105 to All on Tue Apr 19 14:22:00 2022
    AWUS01 KWNH 191310
    FFGMPD
    MEZ000-192300-

    Mesoscale Precipitation Discussion 0125
    NWS Weather Prediction Center College Park MD
    909 AM EDT Tue Apr 19 2022

    Areas affected...Downeast Maine...

    Concerning...Heavy rainfall

    Valid 191315Z - 192300Z

    SUMMARY...Very strong Atmospheric River and moisture flux to
    support .5-.75"/hr rates and 2-3" totals to near but probably not
    exceed FFG values in the region.

    DISCUSSION...GOES-E WV depicts a very strong, deepening cyclone
    over New England with strong WCB signature and solid mid to
    low-level drying east of the band. Additionally, there is a
    well-defined break at/just east of the surface cyclone where the
    mid to upper level flow starts to break eastward denoting solid
    diffluence through the mid to upper levels for continued surface
    low level deepening and strengthening of flow. Warm front extend
    eastward from this intersection, south of which there is very weak
    but consistent instability. MUCAPE values of 100-250 J/kg were
    analyzed along/just east of the advancing cold front and GLM was
    starting to detect some lightning with the weak developing
    convection. It is these weakening showers/thunderstorms that will
    be capable of embedded .5-.75"/hr totals. This alone is not
    likely to induced flash flooding, but add to longer term totals
    that could become more problematic. Current timing appears to
    track well with 15-16z time frame and centering near/along Bar
    Harbor.

    Very strong cool conveyor belt continues to crank 25+ kt surface
    winds along ahead of the warm conveyor belt which is supporting
    80-90kt 85H winds and helping to drive overall deep layer moisture
    values (TPW) to 1.25" near the ME coast with narrowing 1.5" values
    as far north as 41/42N. This is driving IVT values well over 1200
    kg/m/s which is indicative of very strong moisture flux transport.
    This will provide a broad area of ascent over the warm front
    across Downeast ME through the late morning. An additional
    shortwave/jet impulse will round northward, slightly delaying the
    eastward progression of the cold front allowing for increased
    duration of moderate rainfall rates of .25-.33"/hr until
    mid-afternoon and early evening, perhaps localized .5"/hr totals
    where frictional convergence along/near the coast is maximized but
    this will be transient but more likely further west near the
    developing triple-point. This will bring 3hr totals near but
    probably below FFG values within the area of concern that range
    from 1.5-3" from Lincoln county to Washington county. Given the
    warm front will be slowed/stopped by the coastal friction and the
    greatest pressure/height-falls starting to lift north and
    north-northwest, slow eastward progression of the
    triple-point/cold front should yield broad 2"+ totals and isolated
    3" maxima in this axis through 21z, this would be closer/slightly
    below FFG values that very low end urban/hydrophobic ground
    conditions flooding is possible pushing to riverine flooding,
    particularly if onshore limits outwash/backup of rivers. As such,
    will leave the tag as Heavy Rainfall.

    Gallina

    ATTN...WFO...CAR...GYX...

    ATTN...RFC...NERFC...NWC...

    LAT...LON 45466732 45146681 44656695 44086801 43796861
    43746905 43916939 44386971 44876926 45306817

    $$
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