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000
FXUS61 KALY 171054
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
654 AM EDT Fri Aug 17 2018

.SYNOPSIS...
A series of disturbances ahead of a cold front will bring rounds
of showers and thunderstorms today into tonight, some of which
could result in locally heavy rainfall and gusty winds. The cold
front will move through on Saturday along with continued showers
over portions of the area, but a drying trend from north to
south will take place. Some lingering showers are possible for
southern areas Sunday, but to the north it will be dry and not
as warm.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 630 am, leading edge of a batch of rainfall on the nose
of a strong low- level jet is now roughly from Oswego to
Binghamton and moving northeast. This activity is expected to
move into the Mohawk Valley and southern Adirondacks over the
next hour or so. Farther south, the LLJ is weaker, but showers
will become increasingly possible with time this morning. In
the wake of this LLJ-forced activity, will likely have a good
deal of clouds around, and perhaps some lingering showers into
around the noon hour. The question then becomes if enough
instability can be realized to generate strong convection in the
afternoon and evening hours. Low-level winds remain rather
strong with H850 winds of 25-35 kt in the afternoon and evening
hours. So despite somewhat marginal deep-layer shear of 25-30
kt, the magnitude of low-level winds suggests rotating storms
are possible. HREF mean suggests SBCAPE values of 1500-2500 J/kg
are possible in pockets by the mid-afternoon given high
boundary layer moisture and despite meager midlevel lapse rates.
A forcing mechanism is somewhat unclear, but it appears there
may be one or more low- amplitude midlevel disturbances ejecting
ahead of the positively tilted trough over the lower Great
Lakes. Will have to watch for a prefrontal trough and
differential heating boundaries to trigger convection as well.
Overall, still a lot of uncertainties with respect to severe
weather potential. Main hazards would be damaging winds and
perhaps a tornado or two, and cannot rule out large hail should
any supercellular structures develop. Though there should be
strong enough flow to keep storm motions relatively fast, there
is potential for training given the deep southwesterly flow
parallel to the slowly approaching cold front, so locally heavy
rainfall will be a threat as well. PWAT values are forecast to
be in the vicinity of 2 inches once again.

Tonight, the positively tilted trough eases its way eastward, so
enough dynamical forcing may exist for showers and a few
thunderstorms to continue. The surface cold front will approach
northern zones overnight as well as it impinges upon the moist
airmass. Locally heavy rainfall potential will continue
overnight although severe weather threat should diminish with
the loss of diurnal heating.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Forcing for ascent from the slowly approaching cold front,
augmented by vorticity maxima associated with the shearing
positively tilted trough will likely keep some showers around
Saturday, especially during the morning and possibly into the
afternoon for areas south of the Capital District. There is
still some uncertainty with how strong the forcing will be, with
the NAM indicating weaker frontal convergence and less shower
activity, while the GFS/ECMWF show more widespread activity. A
couple of thunderstorms cannot be ruled out, especially over
southern zones where some diurnal heating could generate some
instability ahead of the front. Temps are somewhat uncertain and
will depend on the degree of cloud cover and shower coverage,
but it appears they will be near normal.

Saturday night into Sunday night, model consensus still supports
the cold front finally clearing the area, keeping us under cool
easterly to northeasterly flow. However, there has been a trend
in some of the GEFS members and especially the 00Z ECMWF to
linger the front just south of our area and develop a wave of
low pressure upon it, opening the door for continued showers
through the weekend. At this point, have introduced chance PoPs
for our souther tier of counties. Future forecasts will have to
determine whether this northward trend continues. Regardless,
cooler than normal temperatures are favored for highs Sunday.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
For Monday and Monday night, mainly fair weather is expected as
surface high pressure ridges in from southeast Canada and an upper
level ridge approaches from the Great Lakes and Ohio Valley. Highs
on Monday mainly in the 70s, with lows Monday night in the 50s to
lower 60s.

Tuesday is expected to start out fair as high pressure crests over
New England. However, strong low pressure will be moving through the
Great Lakes. Some rain showers or thunderstorms may reach western
areas around Sunset. Highs Tuesday in the 70s to around 80. Low
pressure moving through eastern Canada will drag a cold front
through the area Tuesday night. Expect showers and Thunderstorms.
Lows Tuesday night mainly in the 60s with some 50s southwest
Adirondacks.

For Wednesday, a secondary cold front may trigger a few isolated
showers and storms in the afternoon and evening. High pressure will
ridge in Wednesday night from the Ohio valley bringing fair
conditions. Highs Wednesday in the 70s to around 80. Lows Wednesday
night in the 50s to around 60.

High pressure will continue to bring fair and seasonable weather on
Thursday and Thursday night. Highs Thursday in the 70s with lows
Thursday night in the 50s to around 60

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
LIFR in fog at KPSF this morning. Elsewhere VFR.

Area of rain showers over central NY will move east this morning
bringing rain showers to the TAF sites. Another round of showers and
thunderstorms, some of which could be strong to severe are possible
between 17Z/FRI to 06Z/SAT. Periods of rain may saturate the
atmosphere by Saturday morning and bring low clouds and fog to
the TAf sites.

Conditions in terms of cigs will likely be VFR/high MVFR in
rain showers this morning. Later TAF amendments will have to
pinpoint the timing for the thunderstorms.

The winds will increase from the south to southeast at 5-10 kts
in the late morning. Winds shift to south southwest in the
afternoon at 10 to 15kts. Winds KALB due to funneling up the
Hudson River Valley could be a little breezier with southerly
winds of 10-12 kts with a few gusts approaching 20 kts in the
afternoon.

Outlook...

Saturday: Moderate Operational Impact. Chance of SHRA.
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: Moderate Operational Impact. Chance of SHRA...TSRA.
Tuesday Night: High Operational Impact. Likely SHRA...TSRA.
Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.

&&

.FIRE WEATHER...
A wet period is expected through at least tonight, keeping fire
weather concerns to a minimum. Showers will likely linger into
at least Saturday morning before a drying trend occurs from
south to north. Some showers may linger into Sunday for
southern areas, but to the north, a dry northeast flow will set
up along with temperatures slightly below normal.

&&

.HYDROLOGY...
Another period of wet weather is in store through at least
tonight as a series of midlevel disturbances interact with a
moist airmass. Showers and thunderstorms will become likely this
afternoon. Though there should be strong enough flow to keep
storm motions relatively fast, there is potential for training
given the deep southwesterly flow parallel to the slowly
approaching cold front, so locally heavy rainfall will be a
threat as well. PWAT values are forecast to be in the vicinity
of 2 inches once again. Urban and poor drainage flooding is
possible along with isolated flash flooding. The Mohawk Valley
and Catskills along with portions of western New England have
seen 150-300% of normal precipitation over the last week, so
they may be particularly prone to flooding. Meanwhile, the
latest Drought Monitor indicates the southern Adirondacks are
experiencing moderate drought conditions.

Additional showers and thunderstorms will continue tonight with
a continued threat for locally heavy rainfall and possible
flooding if additional storms impact areas that saw rainfall
during the day. Deep-layer moisture will be on the decrease on
Saturday so, while showers and a few thunderstorms may linger,
they are not expected to be particularly heavy.

Although flooding of small streams and creeks is possible,
flooding on main stem rivers is not expected.

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...Thompson
NEAR TERM...Thompson
SHORT TERM...Thompson
LONG TERM...SND
AVIATION...SND
FIRE WEATHER...Thompson
HYDROLOGY...Thompson