Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 172015
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
415 PM EDT Thu Aug 17 2017

.SYNOPSIS...
It will turn more humid tonight thanks to a southerly flow
ahead of an approaching frontal system, which will bring
widespread showers and possible thunderstorms to the region for
late tonight into Friday. The weather will be clearing out over
the weekend with temperatures close to normal.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Latest GOES-16 imagery shows impressive low pressure system over
Wisconsin with convection across the Ohio Valley and mid/upper
level clouds expanding into western New York. Fortunately,
eastern New York has remained sunny and dry today as high
temperatures climbed into the mid 70s and low 80s. This will all
change tonight as the low pressure system tracks closer to the
area and cloud cover expands into eastern New York. Ahead of
this system, a strong south-southwest flow will advect in deep
moisture. The latest GEFS/SREF shows PWATS 2-3 S.D. above
normal, and the 850mb u-wind anomalies of 2-3 S.D. above normal
overnight tonight through tomorrow evening.

As a result, surface dewpoints and PWATs will be rising through
the night, with most areas seeing dewpoints in the low to mid
60s by the late night hours. With strong isentropic lift in
place, some rain showers along the storm`s warm front will be
lifting across southern and western areas by late tonight. These
initial showers should be light and spotty, but all areas have
a chance of seeing some rainfall by daybreak. Lows tonight will
only fall into the upper 50s to mid 60s for most locations.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
On Friday morning, the surface warm front will continue to be
lifting across the area from southwest to northeast during the
morning hours. Models hint at some elevated instability with the
boundary moving across, so will allow for some thunder in the
morning hours.

PWATs will be continuing to rise and will reach in excess of two
inches over much of the area by Friday afternoon, as our area
enters into the storm`s warm sector. It still looks fairly
cloudy, but a few breaks are certainly possible, especially for
our western and southern areas. Model soundings show some
surface- based instability will be possible and CAPE values may
reach 500-1500 J/kg. This will ultimately depend on just how
many breaks of sun can occur. With strong winds aloft, 0-6 km
bulk shear values will reach 35-45 kts, depending on the
location. The 3km NAM shows some additional showers and
thunderstorms will impact the region for the afternoon and
evening hours ahead of the advancing cold front, but doesn`t
really hint at any strong organization of the storms.

Considering the strong shear and moist environment, cannot rule
out a stray strong storm, although limited instability and poor
mid level lapse rates will keep the severe threat from being
more widespread. SPC currently has the entire forecast area in a
marginal risk for severe weather. The main threat will likely
be the heavy rainfall. Although there`s enough flow to keep
things moving along, the very high PWATs would be capable of
producing heavy rainfall in a short period of time. Depending on
where it falls, this could lead to some minor flooding,
particularly of poor drainage and low lying areas.

High temps on Friday look to reach into the 70s. If we do get
any breaks of sunshine, temps could get into the 80s, but this
is unlikely due to expected cloud cover.

The cold (or occluded) front should be crossing through the
area on Friday night, which will end the widespread rain from
west to east. Lows will only fall into the 60s and it will
continue to be fairly muggy overnight, despite the passing
boundary, as the much drier/cooler air will remain well upstream
of the region.

On Saturday, our area will still be upstream of the advancing
upper level trough and will be situated within w-sw flow aloft.
As a result, it probably still be fairly warm and muggy. Cannot
rule out a few showers in spots (perhaps even a thunderstorm)
due to the cyclonic flow ahead of the shortwave, but these will
more scattered in coverage. Temps look to reach into the 80s for
valley areas and dewpoints still will be in the 60s.

The upper level trough will be passing over the area on Saturday
night. Still could be a shower for far northern areas, but most
spots look to stay dry with temps falling into the upper 50s to
mid 60s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
There should be mostly clear conditions for viewing of the eclipse
on Monday as high pressure will be over head!

SUNDAY THROUGH TUESDAY MORNING...High pressure will be overhead the
forecast region Sunday through the first half of Tuesday. Mostly
sunny conditions will accompany the high pressure system with high
temperatures in the low 80s starting Sunday and moderating into the
upper 80s by Tuesday. Low temperatures will be warm in the 60s with
the terrain running about 5 degrees cooler.

TUESDAY AFTERNOON THROUGH THURSDAY...A sharp upper tropospheric
shortwave will provide good dynamics for cyclogenesis over the Great
Lakes Tuesday into Wednesday. There will be a chance for showers and
thunderstorms Tuesday and Wednesday afternoons. Convection will be
dependent on the timing of the frontal boundaries which is uncertain
at this point. The GFS and ECMWF both have this low rapidly
deepening to our North with a robust cold front draped to the South,
so this system may become a feature of interest as we approach mid
next week. High pressure will begin to build in overnight Wednesday
into Thursday with dry conditions returning for Thursday. Highs
Wednesday will be in the upper 70s to low 80s and cooler on Thursday
in the upper 60s to low 70s. Lows will be in the upper 50s both
nights.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR through the remainder of the afternoon hours under a canopy
of thin CI/CS and some mid level AC clouds as a warm front
approaches from southwest NY State.

Clouds will lower and thicken tonight as a warm front advances
closer and after 06Z some ceilings will lower to MVFR, with the
best chances for MVFR ceilings at KPOU, KGFL and KPSF. Some
showers are expected as we will place a PROB30 at this time.
Seems the best concentration for MVFR/IFR conditions arrives
just before sunrise. There is a potential for LLWS to develop
too as we will evaluate upstream conditions/trends including
future guidance before entering into the forecast.

Winds light/variable with a light southeast to southwest flow
through the afternoon at 6 Kt or less and could be variable in
direction through tonight.

Outlook...

Friday Night: Moderate Operational Impact. Chance of SHRA...FG...TSRA.
Saturday: Low Operational Impact. Slight Chance of 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.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. Chance of SHRA...TSRA.

&&

.FIRE WEATHER...
Southerly winds will increase for tonight into tomorrow, but
most areas should seeing a wetting rainfall during that time.
With a very moist air mass in place, RH values will only fall to
around 70 percent on Friday with southerly winds of 10 to 15
mph. Saturday will be slightly drier with RH values falling to
around 50 to 60 percent.

&&

.HYDROLOGY...
A frontal system will bring some showers and thunderstorms to
the region between late tonight and late Friday night. With
dewpoints reaching into the upper 60s to lower 70s and PWATs
reaching around 2 inches, locally heavy downpours will be
possible.

Based on the latest model guidance, the chance for the heaviest
rainfall is on Friday afternoon and evening, just ahead of the
approaching cold front. 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. Less humid air
will start to work its way into the region for late Friday
night. Total QPF amounts will be variable depending on exactly
where showers/thunderstorms track. While most areas should see
at least a half inch of rain, its possible that some point locations
may see upwards of an inch or two.

Although a lingering light rain shower or two cannot be ruled
out for Saturday, drier weather should return for Sunday into
Monday.

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...
While repairing the azimuthal gear box, radar technicians have
determined that the bull gear on KENX radar needs to be
replaced. This will require the radar to be out of service until
at least next Friday, August 25th.

&&

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

&&

$$
SYNOPSIS...Frugis/JVM
NEAR TERM...Frugis/JVM
SHORT TERM...Frugis
LONG TERM...Cebulko
AVIATION...BGM
FIRE WEATHER...Frugis
HYDROLOGY...Frugis
EQUIPMENT...



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