Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 280829
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
429 AM EDT Wed Jun 28 2017

.SYNOPSIS...
An upper level disturbance will bring an isolated shower or
thunderstorm mainly north of the Capital Region today, as high
pressure will be ridging in from the Mid Atlantic Region with mainly
fair and dry weather.  Clouds will increase tonight, as a warm front
will approach from the Ohio Valley and Great Lakes Region. The warm
front will bring showers and a chance of thunderstorm back in the
region Thursday into Thursday night.  A humid and unsettled air mass
will keep the threat of showers and thunderstorms going Friday into
weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 429 AM EDT...A mid and upper level trough remains over NY
and New England this morning with a sfc anticyclone attempting
to ridge in at the sfc from WV/VA. Some patchy/areas of fog will
linger until shortly after daybreak this morning especially in
the Upper Hudson Valley, Lake George Region and portions of
western New England due to clear/mostly clear conditions, light
to calm winds, and recently wet ground from the showers and
thunderstorms yesterday. It will be a cool start to the day with
40s to mid 50s across the region with variable cloudiness.

An impressive mid level cold pool will still be across the forecast
area in the late morning into the early afternoon with H500
temps of -20C to -22C. A weak mid-level disturbance in the NW
flow on the back side of the upper trough axis may focus mainly
isolated showers/thunderstorms north of the Capital Region
today. The SBCAPES/MUCAPES are mainly less than 500 J/kg on the
NAM/GFS, but mid-level lapse rates remain steep at around 7C/km.
We did keep the isolated threat in for the western Mohawk
Valley/northern Berkshires too for the instability showers.

Max temps today will still run below normal by about 5 degrees.
H850 temps will still be about 1 to 2 standard deviations below
normal based on the 00Z GEFS.  Decent mixing coupled with west
to northwest winds of 10 to 15 mph and some gusts 20-25 mph
will allow highs to reach the mid and upper 70s in many of the
valley areas, and across the hills, with 60s to lower 70s over
the mountains. Humidity levels will be very comfortable for late
June with sfc dewpts in the 40s to lower 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Tonight...High pressure moves off the Mid Atlantic Coast. Low
pressure will be approaching from the Upper Midwest and the
western Great Lakes Region. The mid level flow becomes flatter,
as a sfc warm front begins to lift north/northeast from the OH
Valley and the lower Great Lakes Region. Temps will cool off
early with clear/mostly clear conditions and light/calm winds,
but mid and high clouds will quickly increase from the
south/southwest after midnight. A few showers may graze the
western Adirondacks towards sunrise with the leading edge of the
warm advection pcpn, otherwise it will stay dry most of the
night-time period with lows in the 50s with a few upper 40s
across the southern Adirondacks/eastern Catskills.

Thu-Thu night...The mid-level flow becomes zonal, as a warm
front will be lifting north across most of the forecast area
during this time frame. Humidity levels will be on the increase
with sfc dewpts rising into the upper 50s to lower 60s late in
the day. The latest NAM/GFS/CAN GGEM/ECMWF are converging with
the strongest synoptic forcing due to the isentropic lift/warm
advection will be north of the Mohawk River Valley/Capital
Region during the day. The locations with the most persistent
showers and a slight chc of thunderstorms would be the southern
Adirondacks/Lake George Region/southern VT. Further south only a
slight to low chc of showers was kept in the Capital
Region/Berkshires/Northern Catskills and the Mohawk Valley. It
may stay dry the better part of the day further south. Several
disturbances will be moving along the warm front with the most
pronounced sfc wave moving east of Georgian Bay 00Z/FRI.

The better chance of showers and thunderstorms with some
elevated instability and a W/SW low-level jet of 35-40 kts will
be Thu night in the warm sector. The model guidance varies with
the potential placement of showers/thunderstorms, but a short-
wave and a sfc trough in the flat mid-level flow may kick off a
few rounds of showers and thunderstorms. The Showalter
stability indices lower to 0 to -3C with MUCAPES of 200-800
J/kg on the NAM. The higher values are north and west of the
Capital Region. PWATS surge back to 1.25-1.75" in the sticky air
mass. Some locally heavy rainfall is possible THU night
especially from the Mohawk Valley north and east. SPC continues
a Marginal Risk for a small portion of the forecast area
including the Mohawk Valley, southern Adirondacks and the Lake
George corridor. This may be due to the potential clusters of
convection or an MCS late THU into THU night, if they
materialize.

Highs will be in the upper 60s to mid 70s from the Mohawk
Valley north and east, with upper 70s to lower and even a few
mid 80s from the Capital Region south and east. Lows Thu night
will be in the 60s.

Fri-Fri Night...The forecast area gets into a much more humid
and unstable air mass to close the week. H850 temps rise to the
+16C to almost +18C range on the GFS. PWATS from the latest GEFS
increase to 1 to 2 standard deviations above normal. In the
zonal flow aloft a sfc trough or diffuse boundary may focus some
afternoon strong thunderstorms, as SBCAPES increase to
1000-2000 J/kg. The 0-6 km bulk or deep layer shear is only
25-30 kts, so some multi-cells or multi-cell lines may form.
Chance and likely pops were placed in the grids for FRI with
this potential boundary focusing convection. The showers and
thunderstorms will persist into the night time period. Highs
will be in the mid 70s to lower 80s over the mountains. Mid and
upper 80s will be common across many of the lower elevations and
hill towns. Warm and muggy lows are expected Friday night with
widespread 60s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The period starts out on Saturday with a very warm and humid air
mass entrenched across our region. A surface cyclone is forecast to
track eastward through eastern Ontario, with GFS/ECMWF both
indicating a noticeably slower trend compared to yesterday`s model
runs. Plenty of moisture will be in place, with GEFS continuing to
forecast anomalously high PWATs of +1 to +2 STDEV. Still expecting a
pre-frontal trough to trigger convection as early as late morning or
early afternoon, especially from the Capital District westward.
SBCAPE could reach 1500-2500 J/Kg, especially given sufficient
heating during the early part of the day. Deep layer shear looks to
be relatively weak, so will have to watch for pulse storms with
potential wet downbursts. Also locally heavy rainfall will be likely
with thunderstorms given the abundant deep moisture that will be in
place. Temperatures may reach the mid to upper 80s in valleys, which
combined with dewpoints near 70 will result in heat indices in the
lower to mid 90s.

The likelihood for showers and thunderstorms will continue into
Saturday night, as the surface cyclone moves into NW Quebec, while
the system`s cold front approaches from central NY. Thunderstorms
could linger through the evening, before instability starts to wane.
There will be continued chances for showers and thunderstorms on
Sunday, as the aforementioned cold front pushes eastward across the
region. Most of the activity should be during the morning/afternoon
hours, as guidance indicating the front will be east of the area by
evening. Humidity levels will start to lower behind the cold front,
with temperatures remaining slightly above normal.

Monday looks to feature mostly dry conditions, although an isolated
shower or thunderstorm cannot be ruled out, as a potential weak
short wave trough moves across the area in the weakly cyclonic flow
regime. High pressure then is expected to build in next Monday night
into the 4th of July with seasonable temperatures and comfortable
humidity levels. A frontal boundary may start to creep towards the
region towards the evening on the 4th of July, so will mention
slight chance pops at this time.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
A batch of broken mid level clouds is moving across much of the
area, which will tend to limit fog development. However, KPSF
has already seen thick fog formation occur and is socked in
with LIFR conditions. Thinking this will continue through the
rest of the night, with improvement after sunrise. Clouds may
tend to move east of the region just before sunrise, which is
when KGFL will have the best chance of seeing some fog. Will
mention a TEMPO for IFR fog between 08Z-11Z. Otherwise, some fog
in the vicinity of KALB is possible along the Mohawk River, but
not expected to move over the terminal. Skies are clearer
towards KPOU, so occasional MVFR vsby will be possible in BR
just before sunrise.

From around 12Z onward, VFR conditions are expected with just
few-sct cumulus and high level cirrus clouds around today. An
isolated shower will be possible near KGFL, but chances too
remote to include in the TAF at this time.

Winds will be variable less than 5 kt initially early this
morning, becoming westerly and increasing to around 8-12 kt by
late this morning. Some gusts near 20 kt will occur at
KALB/KPSF, especially this afternoon.

Outlook...

Thursday Night: High Operational Impact. Likely SHRA...TSRA.
Friday: High Operational Impact. Likely SHRA...TSRA.
Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday: High Operational Impact. Definite SHRA...TSRA.
Saturday Night: High Operational Impact. Likely SHRA...TSRA.
Sunday: Moderate Operational Impact. Chance of SHRA...TSRA.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: Low Operational Impact. Slight Chance of SHRA.

&&

.FIRE WEATHER...
An upper level disturbance will bring an isolated shower or
thunderstorm mainly north of the Capital Region today, as high
pressure will be ridging in from the Mid Atlantic Region with mainly
fair and dry weather. A warm front will approach from the Ohio
Valley and Great Lakes Region tonight. The warm front will
bring showers and a chance of thunderstorm back in the region
Thursday into Thursday night. A humid and unsettled air mass
will keep the threat of showers and thunderstorms going Friday
into weekend.

The RH values will lower to 30 to 50 percent this afternoon, and
then recover to 75 to 100 percent tonight. The RH values will
lower to 35 to 60 percent Thursday afternoon.

The winds will increase from the west to northwest at 10 to 15
mph with some gusts to 20-25 mph today. The winds will be come
light to calm tonight, and then increase from the south to
southeast at 5 to 15 mph on Thursday.

&&

.HYDROLOGY...
No widespread hydrological problems are anticipated over the
next several days on the main stem rivers.

A brief period of mainly dry weather is expected today into
tonight with ridging briefly building in from the south.
Isolated showers or thunderstorms may produce a tenth of an inch
of rain or so over the southern Adirondacks, Lake George
Region, and southern Vermont today.

An active weather pattern sets up Thursday into the weekend
with showers and thunderstorms possible with increasing humidity
levels each day. Rainfall amounts will vary based on where any
convection occurs. The most widespread potential rainfall is
expected Thursday and Saturday. Rainfall amounts Thursday into
Thursday night may range from a quarter of an inch to an inch
with some locally higher amounts in thunderstorms. The higher
totals right now may be across the northern basins of the HSA.

Numerous showers and scattered thunderstorms are possible on
Friday with basin average rainfall of a quarter of an inch to a
half an inch with locally higher amounts. A more widespread
rainfall in terms of shower and thunderstorm coverage is
expected on Saturday. The heavy rainfall may cause some poor
drainage flooding and ponding of water in low lying areas
heading into the weekend.

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...KL/Wasula
NEAR TERM...Wasula
SHORT TERM...Wasula
LONG TERM...JPV
AVIATION...JPV
FIRE WEATHER...KL/Wasula
HYDROLOGY...KL/Wasula


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