Area Forecast Discussion
Issued by NWS Albany, NY

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902
FXUS61 KALY 161409
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1009 AM EDT Wed Aug 16 2017

.SYNOPSIS...
High pressure building in from the Great Lakes will bring fair and
less humid weather today. This high will continue to allow for
dry and comfortable weather tonight into tomorrow. More humid
conditions will return for late in the week, as southerly winds
increase ahead of low pressure moving into the Great Lakes.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 1009 AM EDT...Cold air advection across the area is
causing areas of clouds especially over the higher terrain.
Temperatures range from the 60s in the hill towns to the 70s in
the valleys. Winds are from a northerly direction. 8AM upper
air sounding shows a strong subsidence inversion over the area.
Strato cumulus will grow into cumulus later today with suns
heating. Sounding suggests cloud bases around 5000ft msl and
cloud tops around 10000ft msl.

Through the day today, sky cover should be mostly to partly
sunny. Temps will vary from north to south across the area.
While areas in the Adirondacks will only reach the low to mid
70s, parts of the mid-Hudson Valley and NW CT should reach the
mid 80s, as the cooler/drier air will be slow to make its way
fully into the region.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Surface high pressure will pass over the region tonight and
slowly slide southeast of the area for tomorrow. As a result, it
looks mainly clear and comfortable for tonight, with lows in the
50s for most areas. There could be some patchy fog for valley
areas once again. Temps on Thursday should reach around 80 for
valley areas, but dewpoints will only be in the 50s, along with
plenty of sunshine.

Some clouds will start to increase on Thursday evening, as the
next storm system starts to approach from the Great Lakes. A
developing southerly wind will allow moisture to return to the
region, with dewpoints increasing back into the 60s.

As a warm front starts to approach, western and southern areas
may see a chance for some light rain showers for late Thursday
night, but the better chance is probably on Friday. With the
increasing clouds/chance for precip, temps will only fall into
the upper 50s to mid 60s for lows.

During the day Friday, showers and possible thunderstorms are
expected, as surface warm front lifts across the area and the
cold front starts to approach. Although the best upper level
dynamics will remain north/west of the area, enough forcing will
be in place, as the surface cold front will be crossing during
the late evening hours. The best chance for seeing thunderstorms
will be during the afternoon/evening hours, although how
widespread thunder will be will depend on how much instability
is in place. Model guidance suggests there could be 500-1000
J/kg of CAPE, but this assumes temps reach the upper 70s and
dewpoints reach the upper 60s. If cloud cover is more extensive,
then instability may be more limited. 0-6 km bulk shear is
around 35-40 kts, although strong/severe storms will probably
not be a widespread issue due to the limited amounts of
instability. Still, cannot totally rule out a rogue strong
storm, but it appears fairly isolated. The main issue may be
heavy rainfall, as PWAT values will be around 2 inches and any
shower/t-storm may produce very heavy rainfall within a short
period of time. There should be enough flow to keep things
moving, so flash flooding probably won`t be a concern, but
urban/low lying/poor drainage flooding is certainly possible.

The storm`s cold front should be crossing at sometime Friday
evening into Friday night, as POPs should lower and skies
should be clearing out by late Friday night. Lows look to fall
into the 60s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Lingering intervals of clouds, scattered showers and isolated
thunderstorms Saturday as the cold front exits.  Highs Saturday in
the upper 70s to mid 80s but cooler in higher terrain.

Dry weather and mainly sunny Sunday and Monday, probably into
Tuesday morning as high pressure controls the weather.  The next
upper energy and cold front approaches later Tuesday and into
Wednesday. So, including increasing chances for showers and
scattered thunderstorms Tuesday afternoon.

Highs Sunday in the upper 70s to mid 80s but cooler in higher
terrain.  Some warm advection beginning Monday with highs in the mid
80s but upper 70s higher terrain. Highs Tuesday also in the mid 80s
with upper 70s in higher terrain.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
Any fog and low clouds should burn off/lift by 14Z. Once the
fog and low clouds end, VFR conditions will prevail with just
scattered clouds above 3000 feet. There is some chance for IFR
conditions in ground fog again Thursday morning near sunrise at
KGFL and KPSF. Since low probability, left it out of TAFs for
now.

Winds northwesterly at to 8 to 10 knots by late morning/early
afternoon. Winds will trend toward calm again this evening.

Outlook...

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

&&

.FIRE WEATHER...
Dry weather is expected today and tomorrow, before a widespread
wetting rainfall looks to occur for Friday. Dew formation is
expected tonight with some patchy fog as well.

RH values will fall to the 40 to 50 percent today and tomorrow.
NW winds will be 5 to 10 mph today. Winds on Thursday will be
light and variable.

&&

.HYDROLOGY...
Dry weather is expected today and tomorrow, but a frontal
system will bring some showers and thunderstorms to the region
between Thursday night and late Friday night. With dewpoints
reaching into the upper 60s to lower 70s and PWATs reaching
around 2 inches, the chance for the heaviest rainfall be on
Friday afternoon and evening. Although flash flooding is not
anticipated due to stronger winds aloft (which should keep
heavy rainfall moving quickly), showers/thunderstorms will be
capable of producing heavy downpours within a short period of
time, which may lead to minor flooding of poor drainage, urban
and low lying areas. Main stem rivers may seem some minor rises,
but no river flooding is expected with this rainfall. Although
a lingering shower or two cannot be ruled out for Saturday,
drier weather should return on Sunday.

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 KENX radar will be down into Wednesday due to an azimuthal
gearbox and motor problems. A Radar Operations Center
technician will potentially arrive to assist the ALY tech staff
repairing and further diagnosing the radar on WED.

In addition, KGFL ASOS continues to experience intermittent
outages.

&&

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

&&

$$
SYNOPSIS...SND
NEAR TERM...SND/Frugis
SHORT TERM...Frugis
LONG TERM...NAS
AVIATION...SND
FIRE WEATHER...Frugis
HYDROLOGY...Frugis
EQUIPMENT...



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