Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 181751
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
151 PM EDT Fri Aug 18 2017

.SYNOPSIS...
Scattered showers and muggy conditions will continue into tonight
ahead of a cold front. Behind this front, most of Saturday
looks fair and breezy before a second cold front crosses the
area Saturday night with a chance for showers and thunderstorms.
Fair weather and seasonable temperatures are forecast for
Sunday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 118 PM EDT...Main band of showers extends from the
northeastern Catskills northeast across the Capital District
and into the lake George Saratoga Region, southern Vermont and
the Berkshires. Most rainfall totals so far have been less than
a quarter of an inch. Temperatures range from the mid 60s in
the higher terrain of southern Vermont to the upper 70s in the
mid Hudson Valley. Clearing has developed in far northern,
central and western New York. Additional showers and
thunderstorms are expected to develop in areas of sunshine and
move eastward, so the threat for showers and thunderstorms
continues into the evening.

High temperatures today remain tricky, again as dewpoints climb
and some areas may see some glimpses of sun, it seems western
areas and southern areas have the best chances to get to or just
above 80. Clouds and showers will likely result in highs in the
70s in many other areas.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
Lingering showers and thunderstorms this evening will exit east
but since the primary cold front lags behind, continued steady
boundary layer flow and low level moisture over our region could
support considerable clouds and isolated to scattered showers
into the late night tonight.

Trailing strong upper energy tracks through the region Saturday
and the boundary layer thermal gradient associated with the low
level cold front also tracks though. There should be at least
some periods of sun as mid and upper level moisture exits, while
low level moisture lingers until the cold front tracks through.

The upper jet is fairly strong for this time of year also. Surface
based instability is expected to be limited but midlevel lapse
rates are forecasted to steepen considerably. West low level
flow does not suggest much convergence but the low level
temperature and dew point boundary could provide enough forcing
to support some isolated to scattered shower and thunderstorm
activity during the afternoon and evening. Highs Saturday in the
80s but mid to upper 70s higher terrain.

Dry weather returns Sunday but even with cooler boundary layer
temperatures west to northwest boundary layer flow and
considerable sunshine, highs Sunday should be in the 80s again
with mid 70s higher terrain. Sunday night is expected to be
mainly clear with lows in the 50s to around 60.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The long term portion of the forecast starts out with fair weather
and summer-like warmth, as a ridge of high pressure moves across the
region and off the mid Atlantic coast. Relatively high mid level
heights and subsidence should allow daytime highs to reach the mid
80s in valleys Monday, with upper 70s/lower 80s across higher
terrain, followed by 85-90 for valleys, and 80-85 across higher
elevations Tuesday. An approaching cold front could spark some
showers/thunderstorms late Tuesday afternoon, mainly across the
western Adirondacks. Overnight lows Monday night should mainly be in
the lower/mid 60s, except for some 50s across higher terrain.

For Tuesday night-Wednesday, a cold front is expected to approach
from the northwest. Both 00Z/18 deterministic global models and
ensembles suggest that a wave develops along the incoming front,
somewhere across the eastern Great Lakes or western NYS, before
strengthening and moving northeast into southern Quebec. The biggest
uncertainty at this time is how quickly and how much the low
strengthens. This also impacts frontal timing across the region,
with the general consensus of a late night/early morning frontal
passage. This would tend to decrease the overall threat for severe
weather. However, a slower frontal passage for sometime later
Wednesday would increase this potential, as mid tropospheric winds
would be quite strong, combined with better instability for the
afternoon hours. For now, have sided with consensus with best
chances for showers/thunderstorms late Tuesday night into Wed
morning, then decreasing chances Wednesday afternoon, but again,
changes to frontal timing are possible over the next few days as
upper level features and their evolution become better resolved. It
should be warm/humid Tue night ahead of the front, with lows mainly
in the 60s, then highs Wednesday mainly in the 70s to around 80 for
valleys, and 60s to lower 70s across higher terrain.

Wednesday night-Thursday, assuming the aforementioned cold front
does not slow down, high pressure is expected to build in from
southern Canada and the Great Lakes region with cooler and less
humid conditions. There could be a few showers across mainly higher
elevations of the southern Adirondacks/southern VT due to lingering
cold air aloft and some mid/upper level cyclonic flow. Expect lows
Wed night in the 50s, with some 40s possible for higher elevations;
highs Thursday mainly in the 70s for lower elevations, and 60s
across higher terrain.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Showers continue across the forecast area this afternoon ahead
of an upper-level disturbance. There is a moist tropical airmass
in place, so the showers will contain periods of heavy
downpours. TEMPO groups for IFR visibility have been added to
account for the elements of heavy rainfall. An isolated
thunderstorm cannot be ruled out, but thus far, activity has
been sporadic and so TS was not included in the TAFs. Coverage
of showers will begin to decrease from northwest to southeast
this evening, but pockets of rainfall could persist until around
midnight.

During the overnight period, indications are that a low-level
stratus deck will form late. These clouds may be accompanied by
reduced visibility. There is a window for some clearing late
this evening and early tonight. If this occurs, then fog would
become more of an issue. Greatest potential for clearing and
dense fog development appears to be at KGFL. Conditions improve
a few hours after sunrise on Saturday with conditions becoming
VFR as a slightly drier airmass builds in.

Winds this afternoon will be from the south at around 5 to 10
kt, except stronger with some gusts to around 20 kt at KALB.
Winds tonight will become light and variable, increasing to
around 5 kt out of the west Saturday morning.

Outlook...

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: No Operational Impact. Slight Chance of SHRA...TSRA.
Tuesday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Wednesday: Moderate Operational Impact. Likely SHRA...TSRA.

&&

.FIRE WEATHER...
A warm front will move across the region through this morning
as a trailing weak cold front crosses the area this afternoon
and evening. Showers along with some thunderstorms will
accompany these fronts. A reinforcing cold front will track
through Saturday with some isolated showers and thunderstorms.
Conditions will improve later in the weekend with fair weather
and seasonable temperatures for Sunday.

Showers and thunderstorms are likely today and will decrease to
isolated to scattered coverage tonight. Dryer weather is
expected Saturday with just isolated to scattered afternoon and
evening showers and thunderstorms. RH values will be near 100
percent at night. RH values will be 50 to 60 percent Saturday
afternoon.

Winds will be south at 15 mph or less through tonight when winds
shift to west. Winds will be west at 15 mph or less Saturday.

&&

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

Although flash flooding is not anticipated due to the expected
steady east movement of the showers and thunderstorms, some
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 see
some minor rises, but no river flooding is expected with this
rainfall.

Total rainfall amounts through tonight 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.

Other isolated to scattered thunderstorms are possible Saturday
along a reinforcing cold front. Less humid air will start to
work its way into the region after the cold front tracks
through. Drier weather is expected 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...NAS
NEAR TERM...SND
SHORT TERM...NAS
LONG TERM...KL
AVIATION...Thompson
FIRE WEATHER...NAS
HYDROLOGY...NAS
EQUIPMENT...



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