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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