Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 250603
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
203 AM EDT Tue Apr 25 2017

.SYNOPSIS...
Soggy and damp weather will be on the increase late tonight into
Tuesday morning as coastal low moves up the east coast. A widespread
rainfall will occur across the area lingering into Wednesday.  Then
a cold front is forecast to approach toward the end of this week
with additional chances for wet weather.

&&

.NEAR TERM /THROUGH TODAY/...
As of 130 am, a few light echoes showing up on KENX radar, but
diminishing with northward extent as the approaching system
encounters the very dry airmass in place. Steadier batch of rain
approaching Long Island will also weaken as it approaches the
ALY CWA, but it will at least chip away at the dry airmass and
possibly result in a few showers by 10-12Z across our southern
tier of counties. Have tweaked PoPs downward a bit tonight to
reflect the slow moistening process of the antecedent dry
airmass. Opaque cloud cover roughly from the Capital District
south at press time will continue to expand northward the rest
of the night. Temps will likely become fairly steady with the
thickening cloud cover. Have tweaked low temps up a few degrees
south of Schoharie-Capital District-Southern VT.

Prev Disc...
As of 740 PM EDT, some light showers have begun moving into Long
Island this evening ahead of the main batch of precip moving up
the Mid-Atlantic coastline. We can expect light showers across
perhaps Ulster, Dutchess and Litchfield counties later this
evening into the overnight. The GOES-16 low level water vapor
imagery currently shows dry air over most of the area. However,
this will dry air will gradually be overcome as the better low
level moisture, currently over NC/VA and NJ, will works its way
northward overnight. In terms of the forecast, not much change
was needed. Just freshened up the hourly temps, sky cover, and
pops to reflect most recent trends. Sent updates to NDFD and web
servers.

As of 300 PM EDT, Satellite imagery reveals mostly sunny skies
from around the Capital District northward this afternoon, with
high and mid level clouds moving across areas south of Albany,
especially Ulster, Dutchess and Litchfield counties. Still a
rather mild afternoon, with temperatures in the 60s to lower
70s. Low levels are still quite dry, with dewpoints in the 30s
and 40s.

Clouds will gradually increase from south to north this evening
into the overnight hours, as a vertically stacked low pressure
system slowly tracks north along the Carolina coast. Even though
there are echoes on the radar as far north as the lower Hudson
Valley already, rainfall is not reaching the ground as the low
levels are very dry. Observations indicate the closest rainfall
reaching the surface is across southeast PA, so it will take
several hours to saturate the column. Therefore, will only
mention chance pops spreading from south to north from around
midnight to sunrise Tuesday, with likely pops shortly after
sunrise.

Much of Tuesday will feature periods of rain, mainly light in
intensity across our region. The heavier rain expected where the
best forcing and upper level diffluence will be, positioned
across Long Island and central/east New England with a
persistent southeast fetch off the Atlantic. Still, it will be a
cloudy, damp and cool day across eastern New York and western
New England. After a few mild days, temperatures will only reach
the upper 40s to mid 50s. Easterly winds will increase as well,
with gusts between 30-40 mph developing in favored areas of the
southern Greens, northern Berkshires and northern Taconics.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
Nearly vertically stacked low continues to track northward along the
east coast of the CONUS as southeast flow of magnitudes 40-50kts
advect higher moisture into most of the region.  There will likely
be some enhancements into the northwest hills of CT and Catskills
where additional rainfall totals will likely be enhanced.
Furthermore, with these wind magnitudes, portions of the Taconics,
Berkshires and southern Greens may experience some wind channeling
for slightly higher magnitudes at the surface.  Either way, not
expecting any headlines at this time with respect to winds or rain.
Overnight lows will be chilly with mainly 40s throughout the region.

Wednesday, this coastal low while initially slow moving will begin
to track northeast and increase in forward speed through the day
where the best lift and deformation/TROWAL will be primarily along
and east of the Hudson River.  Additional rainfall amounts appear to
be light at this time as please refer to the hydrology portion of
this discussion for further details.  A rather cloudy and damp day
remains in the forecast as we will shade closer to the cooler side
of the MOS guidance.

Wednesday night, due to the aforementioned faster timing of this low
will also speed up the ending time of the PoPs/Wx with drying
conditions from west to east through the evening hours.  However,
low level moisture will be tough to dissipate per the point
soundings from available guidance.  With that said, due to the
cooler highs expected earlier in the day, we will favor the cooler
side for overnight lows with upper 40s across the terrain to lower
50s for valley locations.

Thursday, could be a rather mild day as the coastal low tracks
further northeast away from the region as a narrow short wave ridge
axis slides across.  Main question will be cloud coverage as some
stratus may linger below the subsidence inversion, mainly across
western New England.  For now, best chance for late April sunshine
will be along and western of the Hudson as low level southerly flow
increases.  The NAM is the mildest with H850 temperatures near +20C
with the other available guidance about 5 degrees cooler as we will
favor the ensemble blend with mainly 70s and cooler mid-upr 60s for
western New England.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
This will be an active weather period with temperatures well above
normal...and a chance of showers and thunderstorms each day.  A cold
front will be at our doorstep toward Friday morning. This front
will become quasi-stationary just south of our forecast zones
for the balance of the period. The proximity of this frontal
boundary to our zones should keep enough instability in place to
warrant at least occasional rumbles of thunder. Some days will
be cloudier than others...but relative humidities will be on the
rise.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
A coastal low along the Carolina coast will gradually move up
the coast through the TAF period reaching the DELMARVA by
06Z/Wednesday. The air mass in place across the region is very
dry as evident by the ALY 00Z/Monday upper air sounding. It will
take time for the atmosphere to moisten before the rain develops
and spreads across the local area. Clouds will thicken and lower
overnight with MVFR expected by around sunrise at KPOU as a steady
light rain occurs then spreads northward. IFR conditions are
expected develop at KPOU by late afternoon and at KALB and KPSF
in the early evening then they will persist.

Light northeast winds overnight into Tuesday morning. Northeast
to east winds will increase in speed and become gusty for the
afternoon into the evening with gusts of 16-22 knots expected
with the strongest winds at KPSF.

Outlook...

Tuesday Night: High Operational Impact. Likely SHRA...RA.
Wednesday: Moderate Operational Impact. Chance of SHRA.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.
Saturday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Clouds with periods of rain developing through the mid week period
to further reduce fire weather related concerns.

Clouds increase tonight along with chances of rain developing from
south to north overnight and through Tuesday.  As the coastal low
tracks along the eastern seaboard, the soggy weather is expected to
linger through Wednesday.  This will keep relative humidities up to
between 70 and 90 percent tonight, and be around 70 percent through
Tuesday.  Percentages increases Tuesday night at or above 80
percent.

Light and variable winds becoming northeast to east winds will
continue tonight. The flow will become more easterly Tuesday with
wind speeds increasing to 10 to 15 mph.

&&

.HYDROLOGY...
Chances for rain will be on the increase late tonight into Tuesday
morning as coastal low moves up the east coast. A widespread
rainfall will occur across the area lingering into Wednesday. QPF
amounts are anticipated to range from about a third of an inch to
around an inch across the forecast area from northwest to southeast
tonight through Wednesday. A brief break in the wet weather is
expected Thursday before cold front approaches and moves through
Thursday night into Friday bringing chances for showers and
thunderstorms to the area.  Minimal river responses are expected at
this time.

For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...BGM
NEAR TERM...Thompson/JPV/JVM
SHORT TERM...BGM
LONG TERM...ELH
AVIATION...IAA
FIRE WEATHER...IAA/BGM
HYDROLOGY...IAA/BGM


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