Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 300507
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
107 AM EDT Tue May 30 2017

.SYNOPSIS...
More clouds and showers are likely Tuesday and Wednesday, with
thunderstorms also possible as additional upper level
disturbances move through the region. A dry day is finally in
store Thursday. Temperatures will remain near to below normal.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1 AM EDT, widespread low clouds/stratus envelops the
entire region, and based on latest IR satellite imagery, do not
anticipate this to change through daybreak. There could be some
patchy drizzle developing through daybreak, and across higher
terrain, some fog as well.

Temperatures should only fall a couple of degrees in most areas
from current levels, with mainly lower/mid 50s, except perhaps
some mid/upper 40s across the highest terrain of the
Adirondacks, as well as the southern Green Mtns and Berkshires.

Tuesday, another shortwave is expected to approach in the
afternoon/evening. Models suggest some destabilization across
central/western NYS in the afternoon, with perhaps some
instability developing across the western Mohawk Valley/Adirondacks
and eastern Catskills/Schoharie Valley if a few breaks in the
clouds develop. There will be increasing 0-6 km bulk shear
potentially exceeding 50 kt, esp across the southern Adirondacks
and Mohawk Valley by later in the day, so if some convection
migrates into western areas, some gusty winds may occur. In
addition, MLMUCAPES reach 500-1000 J/KG acrs this region Tuesday
afternoon. Latest SPC Day 2 Outlooks has the region in a
Marginal Risk for severe wind gusts with convection late Tuesday
afternoon/evening, but remains highly conditional on how much
destabilization, from any breaks in the clouds that develop,
late in the day. Current forecast highs are in the upper 50s to
upper 60s.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
Tuesday night, remnant convection may still be ongoing across
the region through midnight, especially from the Capital Region
and points N and W. Convective trends should weaken through the
night, esp S and E of the Capital Region where a deeper stable
marine layer may reside. So, gradually decreasing chances for
showers/storms through the night, with lows mainly in the upper
40s to mid 50s.

The flow pattern will be dictated by a nearly-stationary upper
low over northern Ontario. Upper trough axis extending southward
from the low will swing through on Wednesday, resulting in the
likelihood of another batch of diurnally-enhanced showers and
thunderstorms. Potential for severe weather is intriguing with
fast midlevel flow resulting in deep-layer shear values around
50 kt. The limiting factor will again be instability. However,
there does appear to be a window for partial clearing Wednesday
morning (depending on the departure of any Tuesday night
activity) which would boost surface-based instability values.
Midlevel lapse rates are progged to be solid at around 6.5-7
C/km as 500 mb temps drop to near -20C. Model surface dewpoints
from the GFS/NAM in the upper 50s to low 60s may be a bit
overdone, but even with MOS values in the mid-50s combined with
highs in the 70s in the valleys, could still generate AOA 500
J/kg MLCAPE. Combined with deep-layer shear values, this could
be enough for organized convection. Low wet bulb zero heights
around 7500 feet suggest hail will be a threat with any
organized convection, along with gusty winds. Given uncertainty
with instability, SPC day 3 marginal risk looks good for now.

Wednesday night into Thursday, midlevel flow will become more
northwesterly in the wake of the trough passage as the Ontario
upper low elongates in a west-east fashion. Subsidence spreading
across the area looks to finally result in a dry day Thursday,
although somewhat cooler than normal with 850 mb temps dropping
to around 3C. Clouds may increase somewhat late Thursday night
ahead of the next system.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The very active pattern continues into early June as a large upper
level trough influences the Northeast for the end of the work week
into the first weekend of the month bringing is multiple
precipitation threats and cooler temperatures.

We start the extended period with a cold front dropping out of
southern Canada into the Northeast on Friday. While uncertainties
exist with the front`s arrival time, have put the highest POPS in
for the daytime Friday and lingered low chance POPS into the
evening, especially for south/eastern zones. With WAA out ahead of
the front bringing 850mb isotherms up to 8C - 11C, high temperatures
Friday should reach into the mid 70s for southern areas. Further
north/west highs may only reach mid 60s where the front should
arrive earlier in the day. Included slight chance thunder with the
frontal passage as well given the southwesterly flow out ahead of
the front.

This front looks to stall on Saturday with the Euro and Canadian
showing it stalling in the NYC/coastal CT area and a cooler air mass
associated with Canadian high pressure building in behind it. The
GFS is the outlier with its solution showing the front stalling much
further north and west well into our CWA. Have edited the forecast
to be in line with the EURO/Canadian solution. The cooler Canadian
air mass will lead to below normal temperatures for the first
weekend of June with highs in the upper 60s/low 70s Saturday and
even cooler Sunday with most places struggling to rise out of the
60s. There is decent packing of the isobars due to the stalled
boundary in close proximity to incoming high pressure so breezy
conditions can be expected as well.

Uncertainty exist with the precipitation threat for Saturday as most
of the guidance shows a disturbance riding along the stalled
boundary. Just how far north the boundary stalls will determine
which areas receive showers in our CWA, if any. Have left chance
POPS for now with highest POPS for southern spots to keep in line
with the Canadian/Euro consensus. The uncertainty continues into
Sunday, unfortunately, as the Canadian shows the front sliding well
to our south and thus a dry forecast while the Euro shows a
disturbance from the Ohio Valley moving northward into our region.
Left slight chance POPs in for now but it is a low confidence
forecast. Increased POPS heading into Monday as a potentially potent
disturbance from the Midwest should move eastward into the
Northeast. There is uncertainty on timing of precipitation as the
Canadian shows the upper level shortwave cutting off rapidly in the
Midwest and thus a slower arrival time while the Euro shows a weaker
shortwave that moves in quicker. Given the time of year, have leaned
closer to the EURO`s solution of a weaker system and thus only have
chance POPS.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Abundant low level moisture will persist through daybreak, with
MVFR Cigs, except at KPSF, where IFR is expected. There could be
a few dips into IFR at other TAF sites as well after 08Z/Tue.

Also, some showers may develop toward 12Z, esp at KALB and KGFL.

For Tuesday, expect mainly MVFR Cigs to continue through the
day. Several waves of showers and possibly embedded
thunderstorms are expected to translate east/northeast, and
affect KGFL/KALB and possibly KPSF between late morning and
early evening. Some gusty winds could occur in any stronger
thunderstorms.

For Tuesday night, after any showers/thunderstorms taper off in
the evening, expect mainly MVFR/IFR conditions, mainly for
Cigs.

South to southeast winds through daybreak should average between
5-10 KT, then increase to 8-12 KT by early Tuesday afternoon.
Some stronger gusts, possibly to 20-25+ KT, could occur at KALB
in the afternoon. South to southeast winds should average 5-10
KT Tuesday night.

Winds may be much stronger, and variable in direction in and
near any thunderstorms.

Outlook...

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

&&

.FIRE WEATHER...
A series of upper level disturbances will continue to impact the
region, with showers and thunderstorms likely Tuesday and
Wednesday. Rainfall is not in the forecast for Thursday, but
temperatures will be a bit cooler than normal with RH values
bottoming out mainly in the 40s. Westerly winds gusting to near
20 mph may help to dry things out somewhat.

&&

.HYDROLOGY...
Steady rainfall continues to exit east, with reports and radar
estimates suggesting 0.25" to up to 1.00" has fallen, with
heaviest amounts over Herkimer County. Additional periods of
showers and thunderstorms are likely late tonight into Tuesday.
Rainfall totals are generally expected to remain at a half inch
or below, but locally a half inch to an inch is possible over
the Mohawk Valley and Western Adirondacks. Showers and
thunderstorms are likely yet again on Wednesday, with an
additional 0.25-0.75" expected. Widespread flooding is not
expected, although some minor urban, small stream, and poor
drainage flooding cannot be ruled out especially if storms
train over the same area.

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 at the Pittsfield Municipal Airport, MA continues to
experience outages with hourly METARS occasionally or
continuously missing. This will persist until communications are
fully restored.

&&

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

&&

$$
SYNOPSIS...IAA/KL/Thompson
NEAR TERM...IAA/KL/11
SHORT TERM...Thompson
LONG TERM...Speciale
AVIATION...IAA/KL
FIRE WEATHER...Thompson
HYDROLOGY...Thompson
EQUIPMENT...



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