WPC Met Watch |
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Mesoscale Precipitation Discussion: #0687 (2018) |
(Issued at 1119 PM EDT Fri Aug 17 2018
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MPD Selection |
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Mesoscale Precipitation Discussion 0687
NWS Weather Prediction Center College Park MD
1119 PM EDT Fri Aug 17 2018
Areas affected...Northeast Corridor from NYC Metro to Midcoast
Maine
Concerning...Heavy rainfall...Flash flooding possible
Valid 180318Z - 180730Z
Summary...Waves of thunderstorms will sweep across the remainder
of the Northeast Corridor through the early portion of the
overnight hours, with rain rates peaking in the 1-2 in/hr range.
This amount of heavy rain in urban areas and places that have
experienced heavy rain over the past several weeks could result in
flash flooding.
Discussion...Regional radars showe3d a ribbon of rain extending
from southern Maine into northern New Jersey, and extending as far
northwest as the Capital Region in New York. The rain was situated
in a corridor where low-level moisture transport was maximized,
with 850mb winds exceeding 30 knots and precipitable water values
exceeding 2 inches. In fact, the Albany sounding this evening
measured a 2.2 inch PW; this does not set a record, but is among
the highest values observed at that site for August, an indicator
of the anomalous nature of the moisture plume. Model analyzed PWs
are above the 99th percentile relative to the CFSR climatology.
Therefore, even moderate to heavy rain bands (as well as
thunderstorms) should be fairly efficient rainfall producers.
Widespread flash flooding and extreme rainfall totals appear less
likely given the fast forward propagation of some of the
thunderstorms. Although instantaneous rain rates should be
relatively high, they may not linger in any one area for an
extended period of time. However 1-2 in/hr rain rates are being
estimated by radars, and several waves of heavy rain could still
lead to scattered flood impacts across the region, with localized
bands of heavier rainfall and flash flooding.
Hi-res models appear to be too quick to diminish ongoing
convection and rain, and it wouldn't be surprising to see some of
the thunderstorms reach the I-95 corridor from Rhode Island into
eastern Massachusetts.
Lamers
ATTN...WFO...ALY...BOX...BTV...GYX...OKX...PHI...
ATTN...RFC...MARFC...NERFC...
LAT...LON 44346923 43786909 43326987 42737033 42037055
41077203 40467434 40847465 41637368 42927335
43557194
Last Updated: 1119 PM EDT Fri Aug 17 2018
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