Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 290817
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
417 AM EDT Thu Jun 29 2017

.SYNOPSIS...
Clouds will thicken this morning, as a warm front approaches from
the west. This warm front will bring some showers to to areas mainly
north of Albany today. As the warm front pushes northeast across our
area tonight, showers and thunderstorms are expected, some with
heavy rainfall for northern parts of the area. Then, a very warm and
humid air mass will be in place for Friday into the weekend, with
additional showers and thunderstorms each day, especially in the
afternoon and evening hours. Some of the storms could be strong to
severe and produce heavy rainfall.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 400 AM EDT, Mid and high level clouds have already increased
across the region early this morning, ahead of a warm front
approaching from the Great Lakes. Dry conditions still occurring
across the entire area at this hour, although showers are starting
to encroach from western/central NY. The showers will move in as the
warm front impinges, mainly across the Adirondacks, upper Hudson
Valley and northern parts of southern VT this morning into the
afternoon. Not really seeing any instability noted in the models
through the day, so will not mention any thunder yet. Temperatures
will be cool where showers occur across northern areas, with mainly
mid to upper 60s for highs, but from around I-90 and the Capital
District southward, temps should reach the upper 70s to lower 80s
with some breaks of sunshine expected.

Additional showers and some thunderstorms will move in from the west
this evening, again mainly for areas north of the Capital District,
associated with the nose of a strengthening southwest flow aloft.
Surface-based instability will be lacking, but models indicating
elevated instability will be present so will mention chance of
thunder. PWATs will start to surge as the surface warm front
advances into our region, so will mention locally heavy rainfall
north of the Capital District. There is a Marginal Risk of Severe
storms north and west of Albany this evening, but it is questionable
whether strong winds aloft would be able to mix to the ground due to
a possible low-level inversion in place. Will mention the threat in
the HWO, but this appears to be a limited/conditional threat based
on a strengthening wind flow aloft, and uncertainty of mixing. It
will be warmer and more humid tonight than recent nights, with lows
in the 60s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
On Friday, our area looks to be firmly entrenched in an increasingly
warm and humid air mass, as the warm front lifts well north. The
flow aloft will be southwesterly and neutral, although models have
been hinting at a diffuse surface boundary lurking across the area.
This boundary along with differential heating/terrain will trigger
scattered to numerous showers and thunderstorms, especially during
the afternoon and evening hours. Will mention highest pops west of
the Hudson Valley, where the boundary looks to set up. There is a
Slight Risk of severe thunderstorms for the western/southern
Adirondacks due to increasing instability and moisture. Models
showing a maximum of SBCAPE in this area around 1500-2000 J/Kg with
0-6 km shear increasing to around 30 kt. Main threat looks to be
damaging wind in the warm/moist air mass, although some large hail
cannot be ruled out in the stronger updrafts since mid level lapse
rates look marginal around 6 to 6.5 C/Km. Farther southeast across
much of the rest of the area, the severe threat is more muddled due
to slightly lower instability and weaker shear. Still, Gusty winds
and locally heavy rainfall will be possible across much of the area.
Temperatures will soar into the mid to upper 80s for most valley
locations, with dewpoints increasing to around 65-70 making it feel
quite muggy.

Showers and thunderstorms could linger well into Friday evening,
with an air mass supportive of maintaining convection with humid
and relatively unstable conditions (for night time). Will mention
gradually decreasing pops after midnight, with the severe threat
also finally decreasing by the early morning hours.

Not much change in the air mass for Saturday, with perhaps a better
chance for more widespread convection developing due to a better
forcing. Models continue to indicate a pre-frontal trough moving
into the region during the day on Saturday, which will lead to
convective initiation. The degree of cloud cover is uncertain early
in the day, although not much sunshine will be needed to allow for
moderate levels of instability to build with the most/humid air mass
in place. SBCAPE could reach as high as 1500-2500 J/Kg, with 0-6 km
shear around 25-30 kt, which would be sufficient for organized
storms. Again mid level lapse rates while not overly impressive, are
forecast to be steeper than some recent events this season with a
very warm and humid air mass in place around 6 to 6.5 C/Km. As of
now, the entire area is in a Marginal Risk for severe storms, which
seems reasonable for a Day 3 outlook. If confidence increases, then
a greater threat may develop. Also, locally heavy rainfall will be
possible again with some flooding of urban/poor drainage areas. It
will be another warm and humid day, with temps and humidity levels
similar to Friday.

Showers and thunderstorms could linger well into Saturday night
(maybe even more so compared to Friday night), with a supportive air
mass along with the surface boundary moving through. Strong to
severe storms and heavy rainfall threat could persist through the
evening, then decreasing after midnight.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The extended forecast opens with a cold front moving across eastern
NY and western New England.  There is pretty good agreement with the
medium range guidance that this front will be making steady progress
across the region in the late morning into the early afternoon.
Instability is not expected to be large at this point, but SBCAPES
could be around 500 J/kg with sfc dewpts still in the 60s for the
better part of the region.  A chance of showers with a slight chance
of thunderstorms was kept in the forecast with highs near normal
with upper 70s to lower 80s in the valley areas and NW CT with a few
mid-80s in the mid-Hudson Valley, and upper 60s to mid 70s over the
mtns.  Sunday night some slightly drier air infiltrates the region
with the weak cold advection in the wake of the front. Lows temps
fall back into the mid 50s to mid 60s across the region.

Monday-Monday night...The frontal boundary may stall across PA and
Nrn NJ. The long-wave trough will remain over southeast Canada and
the Northeast.  A short-wave swinging through the upper-level trough
may focus isolated to scattered showers across the region.  The day
should not be a washout with high temps similar to Sunday with
seasonal normals in the 70s to lower to mid 80s across most of the
forecast area.  High pressure will be building in south of James Bay
with fair, cool and dry conditions for the night time period with
lows in the 50s to around 60F.

Independence Day into Wednesday...The 00Z GFS and Canadian GGEM are
mainly dry during this time frame with high pressure building in
over the region.  The 00Z ECMWF has one more short-wave moving
across the region Independence Day with a slight chance of showers
and thunderstorms.  A superblend of the guidance was in favor of
higher chance pops.  We kept the pops at slight chc at best in the
gridded forecasts.  The WPC guidance favors the Canadian anticyclone
building into southwestern Quebec by early WED with fair and dry
weather continuing into the mid-week.  A frontal boundary remains
stalled across PA and the Ohio Valley.  Some of the GEFS members
have low pressure moving along the boundary Independence Day to WED
with a slight chc of showers.  We kept the pops at slight chc in the
grids, but again this day may likely end of dry. The 00Z ECMWF has
high pressure settling right over the forecast area on WED.  Highs
will generally be in the upper 70s to lower 80s across the valleys,
and upper 60s to mid 70s over the higher terrain,  and lows will be
in the 50s to lower 60s. Humidity levels should be reasonable and
not oppressive for early July with sfc dewpts in the 50s to lower
60s.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
High pressure continues to move off the Mid Atlantic Coast this
morning, as a warm front continues to approach from the lower
Great Lakes Region and the Ohio Valley. The warm front will
focus some showers and isolated to scattered thunderstorms late
this afternoon into this evening.

VFR conditions are expected until about 20Z for
KGFL/KALB/KPSF/KPOU with increasing mid and high clouds through
the morning hours and into the early afternoon. Some showers
may move into KGFL by 20Z with MVFR vsbys and cigs in the 3.5-6
kft AGL range.  Some showers and possibly isolated to scattered
thunderstorms may reached KALB/KPSF btwn 23Z/THU-00Z/FRI.
PROB30 groups were used from 00Z-04Z for these two sites, as
well as KGFL. KPOU will likely continue VFR into Thursday
evening with mid-level cigs around 12 kft AGL.

The winds will be light from the south to southeast at 4 kts or
less this morning. They will increase from the south at 7-13 KTS
with some gusts in 18-22 KT range at KALB/KPSF in the late
morning and through the afternoon.

Outlook...

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

&&

.FIRE WEATHER...
Clouds will thicken this morning, as a warm front approaches from
the west. This warm front will bring some showers to to areas mainly
north of Albany today. As the warm front pushes northeast across our
area tonight, showers and thunderstorms are expected, some with
heavy rainfall for northern parts of the area. Then, a very warm and
humid air mass will be in place for Friday into the weekend, with
additional showers and thunderstorms each day, especially in the
afternoon and evening hours. Some of the storms could be strong to
severe and produce heavy rainfall.

Minimum relative humidity values today will range from around 45
percent across the southern part of the area to 65 percent north. RH
will increase to maximum values of 90 to 100 percent tonight.
Minimum RH values on Friday will range from around 50 percent across
the southern part of the area to 70 percent north.

Winds today will be southerly around 10 to 15 mph. Winds will remain
southerly tonight at 5 to 15 mph. Winds on Friday will shift to the
southwest around 10 to 15 mph.

&&

.HYDROLOGY...
Showers are expected today, mainly for areas north of I-90 and the
Capital District, ahead of a warm front approaching from the west.

As this front moves through the area this evening and tonight,
showers and thunderstorms may produce locally heavy rainfall for the
western Mohawk Valley, Adirondacks and Lake George and Glens Falls
area. This rainfall may cause minor flooding of urban, low lying and
poor drainage areas.

Additional showers and thunderstorms are possible Friday and
Saturday as well, especially during the afternoon and evening hours.
With a warm and humid air mass in place, any thunderstorm will be
capable of producing locally heavy rainfall once again. Some showers
or t-storms may be possible on Sunday as well, although the cold
front will be pushing through. It looks like mainly drier weather
will build in for early next week, although a few showers cannot be
ruled out.

By the end of the weekend, the heaviest rainfall looks to be across
areas north and west of Albany, where basin average amounts look to
be at least one to two inches of rainfall, with less rainfall south
and east. However, thunderstorms may result in locally higher totals
in some spots throughout the HSA.

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...Frugis/JPV
NEAR TERM...JPV
SHORT TERM...JPV
LONG TERM...Wasula
AVIATION...Wasula
FIRE WEATHER...Frugis/JPV
HYDROLOGY...Frugis/JPV


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