Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 260522
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
122 AM EDT Fri May 26 2017

.SYNOPSIS...
Showers this afternoon will diminish from south to north. A break in
the precipitation this afternoon into the evening may allow for some
gusty winds to impact portions of the Taconics, Berkshires and
southern Vermont this afternoon. Then a coastal storm takes shape
tonight with additional periods of rain expected overnight into early
Friday. The holiday weekend starts off mainly dry and seasonable
before the threat for showers and possibly a few thunderstorms
returns late Sunday into Monday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 100 AM EDT...Coastal low was taking shape as
rain/convection was expanding just to the south and east of
Albany. Deformation and Trowal was evolving as this should move
across most of the region the next couple of hours. HRRR
suggests a bit more potential for thunder, especially along the
western periphery of the rain shield overnight. Grids/Forecast
are generally in excellent shape with minor tweaks per
observations and radar analysis.

The upper low center will reorient itself and become located
just south of Long Island by 06Z. Deformation in the northwest
quadrant of the low and a trowal signature in the 700-500 mb
theta-e fields is likely to result in an uptick in precipitation
coverage, especially after midnight and along and east of the
Hudson Valley where categorical PoPs remain in place. Kept
isolated thunder in the forecast as showalter values go slightly
negative. With plenty of cloud cover in place, lows tonight in
the upper 40s to low 50s will be slightly above seasonal
normals.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY NIGHT/...
The upper circulation slowly moves into the Gulf of Maine on
Friday. This should result in a diminishing trend in the
precipitation, but with cyclonic flow persisting still expect
plenty of clouds and at least the possibility for a few showers
much of the day. With the cloud cover in place, high temps are
expected to run around 10F below seasonal normals, with the
possible exception of the far south which stands the best chance
to briefly break out of the overcast later in the day.

Very weak ridging at the surface and aloft attempts to build
into the region Friday night, which may result in at least a
partial clearing trend. Lows near normal.

Saturday into Saturday night, quasi-zonal to slightly
northwesterly upper flow with weak high pressure at the surface
argue for a mainly dry period. However, the subsidence signal is
not strong, and the NWP suite amplifies the flow a bit with a
positively-tilted shortwave toward 00Z Friday. A few light
showers are not out of the question toward southern portions of
the forecast area, so have slight chance PoPs creeping into the
Catskills/Mid-Hudson Valley Saturday evening and expanding into
the Berkshires/NW CT Saturday night. Will have to watch to see
if a more amplified/wetter trend continues, but for now still
think this period will be mainly dry. Partial sunshine will
allow temps to return to near seasonable normals.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Upper cut off expected to track slowly across southern Canada just
north of the Great Lakes through the period.  There could be a
period of dry weather Sunday until the upper energy gets closer to
our region but the onset of scattered showers and isolated
thunderstorms should begin by midday and coverage will increase
toward evening.  The clouds and approaching rain will keep highs in
the upper 60s to lower 70s.

On Monday, warm advection ahead of a slowly advancing cold front
will support more clouds and increasing coverage of showers and
scattered thunderstorms. Even with the clouds and showers, warming
boundary layer temperatures will support highs Monday in the upper
60s to lower 70s. Boundary layer flow is expected to be west
southwest, which could limit the coverage a bit but we will see as
we get closer.

Sources of guidance show little pieces of upper energy tracking
through our region through the southern periphery of the upper cut
off Tuesday through Thursday.  The first phase of the cold front
tracks through later Tuesday and there may be a period of less
coverage of clouds and showers during the morning Tuesday allowing
temperatures to reach the mid to upper 70s but mid 60s to around 70
northern areas.  Better coverage of showers and thunderstorms is
expected Tuesday afternoon and night but again, west to southwest
boundary layer flow may limit coverage a bit.

Boundary layer temperatures cool steadily Wednesday and Thursday as
temperatures aloft cool a bit more rapidly proximate to the upper
low. The proximity to pieces of upper energy tracking through the
southern periphery of the upper low and the cold air aloft should
support scattered showers each day, especially each afternoon with
the daytime heating and instability.

Highs Wednesday in the upper 60s to lower 70s with some mid 70s
southern areas and lower to mid 60s northern areas.  Highs Thursday
in the uper 60s to lower 70s but around 60 to lower 60s northern
areas.ay afternoon/evening with some surface based instability,
decent mid-level thermodynamics and kinematic fields. However,
there is a chance that cool, stable air remains across at least
portions of the region, as the warm front may get hung up,
especially if an offshore surface wave develops as pronounced as
some guidance suggests. Chance for thunderstorms will depend
greatly on if and when the warm front moves through the region.
GFS/ECMWF are hinting at another secondary front moving through
the region on Tuesday with a chance for showers and
thunderstorms yet again. Temperatures are tricky for Monday,
again highly dependent on if the warm front clears the region.
For now, have leaned on the cooler side of guidance, with 60s
for most higher elevations, and lower 70s in valleys, but should
the warm front move through, temperatures across portions of
the region could be at least 5-10 degrees warmer. Overnight lows
mainly in the 50s. Tuesday highs should reach the mid/upper 70s
for lower elevations, and 65-70 across higher terrain.

Wednesday/Thursday, it appears that upper level cyclonic flow and
possible embedded upper level impulses may keep at least scattered
showers/isolated thunderstorms across portions of the region, with
greatest chances north of I-90. Some small hail/gusty winds could
occur with any convection given cold air aloft and a fairly strong
mid/upper level wind field. Highs should be in the mid 60s to lower
70s, although may be cooler Thursday behind a reinforcing cold
front. Lows should range from the mid 40s across higher terrain, to
the lower/mid 50s in valley areas.

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
Low pressure near the NYC area will move northeast to Long
Island Sound and southern New England overnight, and then will
move slowly east of New England Friday.

Rain in the KALB, KPSF and KGFL areas will continue through
tonight with mainly MVFR ceilings and visibilities but some
brief periods of IFR in heavier rain and even some VFR possible
in lulls in the rain. Rain may slowly decrease in coverage and
intensity Friday but ceilings and visibilities should continue
to be predominantly MVFR.

Winds aloft have weakened so there should not be any wind shear.
Generally north to east winds at 10 Kt or less overnight but
gusts over 15 Kt this evening at KPSF. Winds becoming north to
northwest Friday at 10 Kt or less.

Outlook...

Friday Night: Low Operational Impact. Slight Chance of SHRA.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Slight Chance of SHRA.
Sunday Night: High Operational Impact. Likely SHRA.
Memorial Day: Moderate Operational Impact. Chance of SHRA...TSRA.
Monday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Tuesday: Moderate Operational Impact. Scattered SHRA...TSRA.

&&

.FIRE WEATHER...
Showers tonight into early Friday will become less widespread
during the afternoon, but still expect a cloudy, cool, and damp
day. Slightly warmer and drier Saturday with light northwesterly
winds. A few showers are possible Sunday with more widespread
activity occurring Sunday night into early Memorial Day.

&&

.HYDROLOGY...
Radar estimates suggest a tenth to around a half inch of
rainfall has occurred today as of mid-afternoon. After a lull
into this evening, a developing system off the coast will
likely bring more rainfall to the region, with up to another
half inch possible. Locally higher amounts could occur along
eastern-facing slopes of the higher terrain. Storm total amounts
should range from around a half into to an inch. While river
flooding is not expected, the Hudson River at Poughkeepsie will
briefly approach flood stage around 06Z tonight.

Showers should taper off through the day on Friday, with only
light amounts expected. The next potential for widespread
rainfall is expected Sunday night into Memorial Day.

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.

&&

.EQUIPMENT...
The ASOS in Glens Falls at the Floyd Bennett Memorial Airport
will experience outages until communications are fully
restored.

&&

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

&&

$$
SYNOPSIS...Thompson
NEAR TERM...BGM/NAS/Thompson
SHORT TERM...Thompson
LONG TERM...NAS
AVIATION...BGM/NAS
FIRE WEATHER...Thompson
HYDROLOGY...Thompson
EQUIPMENT...ALY Staff



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