Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 180540
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
140 AM EDT Fri Aug 18 2017

.SYNOPSIS...
A low pressure system will impact the region late tonight into
Friday night. The system`s warm front will move across the region
late tonight and Friday morning with its cold front crossing
the area during the afternoon and evening hours. Showers along
with some thunderstorms will accompany these fronts. It will
become warm and muggy tonight. Conditions will improve over the
weekend with fair weather and seasonable temperatures for Sunday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Some sprinkles are developing over the region with the better
coverage of showers and potential light measurable rain
approaching western areas. There is a surface dew point
boundary to the south that is drifting north and some of the low
level forcing associated with that feature could support
additional shower development in southern areas through
daybreak. Just some minor adjustments to the rain chances
through daybreak. No real changes to temperatures and sky cover
with the cloudiness preventing temperatures from falling much
from current readings. Lows in the 60s everywhere with rain
chances increasing everywhere through daybreak, with showers
likely in western areas.

&&

.SHORT TERM /6 AM THIS 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 /06Z FRIDAY THROUGH TUESDAY/...
Low pressure will track through the Great Lakes through daybreak
and into southeast Canada during today. A warm front associated
with the low will track northward across the region this
morning, followed by a cold frontal passage this evening.

Although VFR conditions are expected through around 08Z/Fri, low
stratus clouds currently developing across NYC area, LI and CT
are expected to expand north and west through daybreak. Expect
mainly IFR Cigs to develop between 08Z-13Z/Fri. IFR Cigs may
persist until 14Z-16Z/Fri before becoming MVFR/VFR, last at KPSF
and KGFL.

Showers are expected to increase in areal coverage between
08Z-12Z/Fri. There could be some embedded heavier showers, and
even a few thunderstorms during this time. The showers and
embedded thunderstorms may taper off from west to east between
roughly 14Z-17Z/Fri. Then, additional scattered showers and
thunderstorms are expected for Friday afternoon and evening.
Periods of IFR Cigs/Vsbys will be possible within heavier
showers/storms.

The showers/thunderstorms are expected to decrease in coverage
between 03Z-06Z/Sat. However, low Cigs are expected to redevelop
during this time, with some low MVFR/IFR conditions possible.

Winds will become southeast to south through daybreak at 5-10
KT, although may become gusty at KALB up to 15-20 KT. South to
southeast winds should continue at 8-12 KT through Friday, with
some gusts of 15-20 KT possible. Winds will veer into the
southwest Friday night and decrease to less than 8 KT.

Low level winds shear has been included in KGFL/KPOU and KPSF
TAF sites between 08Z/Fri and 14Z/Fri, as surface winds at these
sites remain from the southeast to south at less than 8 KT,
while winds around 2000 FT AGL increase from the south to
southwest at 30-40 KT.

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

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...IAA/Frugis/JVM
NEAR TERM...NAS
SHORT TERM...Frugis/JVM
LONG TERM...Cebulko
AVIATION...IAA/KL
FIRE WEATHER...Frugis/JVM
HYDROLOGY...Frugis/JVM
EQUIPMENT...


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