Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 231734
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
134 PM EDT Fri Jun 23 2017

.SYNOPSIS...
Warm and humid weather is in store today into tonight along
with periodic showers and thunderstorms, some of which could
produce locally heavy rainfall. Saturday will see a drying trend
behind a cold frontal passage. Seasonable temperatures on Sunday
with perhaps a few showers or a thunderstorm over northern
portions of the forecast area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 120 PM EDT, isolated to scattered showers, some containing
locally heavy downpours, continue to develop across the region,
with greatest coverage mainly near and north of the I-90
corridor. Thus far, no CG lightning strikes detected.
Temperatures have already reached the mid 80s in many valley
areas, with mid 70s to lower 80s elsewhere.

The 12Z/KALY sounding indicated quite a strong mid level cap
just above H500, and overall cloud tops thus far seem to be
remaining below 25000 FT. With the -20C isotherm around this
level, limited ice within clouds likely has contributed to lack
of lightning discharges thus far. However, warm/efficient rain
processes will likely lead to locally very heavy downpours in
any showers that occur. In addition, latest SPC mesoanalysis
suggests mixed layer CAPES are (thus far) mainly 500-750 J/kg
across the region.

Overall upper level forcing seems weak this afternoon, with
mainly low level forcing in the form of broad low level
convergence and some differential heating boundaries being the
main trigger for afternoon convection. With weakening mid level
lapse rates and increasing clouds across the region, along with
fairly weak deep layer forcing, it may be tough for parcels to
break the cap in place. Thus, mainly showers with heavy
downpours for this afternoon, with perhaps a couple of stronger
embedded thunderstorms developing later this afternoon. If any
taller convective elements develop and/or congeal into multi-
cell clusters, strong wind gusts will be possible given fairly
strong 0-6 km bulk shear of 35-40 KT.

High temperatures should reach the mid/upper 80s for most valley
areas, with lower 80s across most higher elevations, except for
mainly 75-80 across higher elevations of the western Adirondacks
where due to more persistent cloud cover, and more limited
heating due to morning rainfall occurred.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
Forcing for ascent increases tonight with slightly better upper
height falls approaching along with the surface cold front. PWAT
values remain high with some moisture pooling along the front -
GFS and NAM depicting 2-2.25 inches around 03Z. Severe weather
threat would seem to wane with the loss of diurnally generated
instability, but heavy rainfall will still be a threat given the
increase in forcing and the moist atmosphere. Still, not enough
signal to go with a flash flood watch, but will continue to
mention heavy rainfall potential in the HWO. Coverage of showers
and storms will decrease late from northwest to southeast behind
the cold front. A very mild night in store especially from the
Capital District southward.

Some showers and thunderstorms may linger into Saturday morning
especially across portions of the Catskills, Mid-Hudson Valley,
and NW CT as the front will still be passing through those
areas. A drying trend will occur with PWATs dropping to below
0.75 by 18Z, and dewpoints falling into the 50s to lower 60s.
Highs will be near seasonal normals. A mainly clear to partly
cloudy and dry night is in store Saturday night.

Sunday, a rather strong shortwave trough will approach the
forecast area, rotating through the longwave trough that sets
up over much of the eastern US. This forcing could be enough to
touch off a few showers despite the dry airmass. Forecast
soundings show some shallow instability, so could hear a rumble
of thunder or two. Best chance for showers is north of I-90.
Another disturbance could generate a few showers at night as
well, though coverage should be somewhat limited with the lack
of the diurnal contribution to instability. Low temps will be
cooler than recent days, likely a bit below seasonal normals.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A mean longwave mid and upper level trough will be over the
eastern CONUS for early in the week. Guidance is in general
agreement the trough sharpens as a short wave moves about the
base of the trough Tuesday and it becomes neutrally tilted as
it exits and moves off the coast by mid week. As a result our
weather will be unsettled. Do have the mention of thunder during
the afternoon into the evening hours as instability develops
with the heating of the day. The better chances for storms
are expected on Tuesday. Temperatures are expected to run
5 to about 10 degrees below normal with highs generally from
the lower 60s to upper 70s Monday and Tuesday with lows in
upper 40s to mid 50s.

Models indicates some ridging should begin to build in Wednesday.
However, it should be brief as the flow flattens as short waves
approach and pass to our north Thursday. The longwave pattern
is expected to amplify again as a trough develops over the
Northern Plains into the Great Lakes region. Temperatures are
should moderate back to near normal by Thursday.

&&

.AVIATION /17Z FRIDAY THROUGH TUESDAY/...
A warm front has lifted north of the TAF sites as of early
afternoon. Isolated to scattered showers, and perhaps a couple
of thunderstorms, will develop within the warm and moist air
mass in place through late afternoon. Outside of any
showers/storms, mainly VFR conditions are expected. Reductions
to MVFR/IFR will be possible under cores of heavier
showers/storms.

As a cold front approaches from the west tonight, the chances
for showers and thunderstorms will increase. The most widespread
showers/thunderstorms are expected to be mainly after 03Z-
05Z/Sat.

Showers/thunderstorms should gradually taper off between roughly
06Z-10Z from northwest to southeast, although some showers may
linger until 12Z-14Z/Sat at KPSF and KPOU where the front will
pass through later. Again, areas of MVFR/IFR will be possible,
mainly for VSBYS, in heavier showers/storms.

Mainly VFR conditions are expected after any showers taper off
Saturday morning.

Winds will be from the south to southwest at 8-12 KT this
afternoon, with some gusts of 20-25 KT possible. Winds will
remain south to southwest tonight at 5-10 KT, then shift into
the west to northwest at similar speeds between 09Z-13Z/Sat as
the cold front moves through. W/NW winds may occasionally gust
up to 20-25 KT toward 18Z/Sat.

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

Outlook...

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

&&

.FIRE WEATHER...
Warmer and more humid conditions will return today, along with
increasing chances for showers and thunderstorms, some of which
may produce locally heavy rainfall. The showers and
thunderstorms should continue tonight, before gradually
tapering off Saturday as a cold front moves through and south of
the region. Another upper level disturbance could trigger a
passing shower or thunderstorm Sunday.

Minimum RH values today will be around 60 to 70 percent. A drier
airmass will allow RH values to drop to 40 to 50 percent on
Saturday.

Winds today will be south to southwest and increase to around
10 to 15 mph, with gusts up to 25 mph possible. Winds Saturday
will be from the west at 10 to mph kt with gusts to 25 mph.

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

&&

.HYDROLOGY...
Showers and thunderstorms will become more widespread today into
tonight as a frontal system gradually moves across the area. It
will become more humid, so there is the potential for locally
heavy rainfall today into tonight. Some urban/poor drainage
flooding and isolated flash flooding will be possible with
thunderstorms. Basin average rainfall forecast to be around a
half to three quarters of an inch, but locally higher amounts
will occur in thunderstorms. Showers and thunderstorms with
locally heavy downpours may linger into Saturday morning from
the Capital Region and points south and east.

Mainly dry weather then expected for Saturday afternoon with
isolated to scattered showers and thunderstorms possible 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...
KGFL airport observation has been intermittently missing again
as technicians continue to troubleshoot. We will continue to
monitor and update this statement as needed.

&&

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

&&

$$
SYNOPSIS...Thompson
NEAR TERM...KL/Thompson
SHORT TERM...Thompson
LONG TERM...IAA
AVIATION...IAA/KL
FIRE WEATHER...KL/Thompson
HYDROLOGY...KL/Thompson
EQUIPMENT...


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