Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 211403
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
1003 AM EDT Tue Aug 21 2018

.SYNOPSIS...
High pressure will drift east of Maine today, as
clouds will increase ahead of a warm front.  A low pressure system
moving into the central and eastern Great Lakes Region and its warm
front will bring showers and some scattered thunderstorms.  A cold
front moves through Wednesday morning into the early afternoon with
the scattered showers and thunderstorms ending, as it will become
breezy and less humid.  High pressure builds in from the west on
Thursday with fair weather and comfortable humidity levels heading
into the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Much of southern VT and the northern Berkshires are seeing quite
a bit of sun this morning. Clouds are steadily advancing east
across eastern NY, the southern Berkshires and NW CT. All areas
should become cloudy through this afternoon with the approach of
the next system. Based on radar and satellite trends, the
leading edge of showers will enter the western Mohawk Valley,
southern Adirondacks, Schoharie Valley and eastern Catskills
later this afternoon. Made some minor adjustments to sky cover,
rain chances and temperatures through this afternoon. Some more
details are available in the previous AFD below...

The low-level sfc pressure gradient between the departing
anticyclone and low pressure approaching from the lower Great
Lakes Region will allow south to southeast winds to increase to
10 to 20 mph with a few higher gusts. Clouds will increase,
thicken and lower. The trend based on the GFS/NAM/CMC and some
of the CAMS has been for the warm advection pcpn to hold off
until the mid to late pm for most of the forecast area. The best
chance for a few light rain showers will be west of the Hudson
River Valley. Temps will be near or slightly below normal due
to the clouds with highs in the 75-80F range in the valleys, and
upper 60s to lower 70s over the higher terrain.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Tonight...A progressive wave of low pressure will move northeast
through the central and eastern Great Lakes Region into southern
Quebec. The cyclone will deepen and intensify to 990-995 hPa by
daybreak. A low-level jet at H850 will increase from the south
to southwest at 30-40 kts transporting in Gulf moisture. PWATS
surge to 1 to 3 STD DEVS above normal based on the latest 00Z
GEFS. The better jet streak and associated upper dynamics remain
well north and west of the forecast area, but the low-level
forcing, isentropic lift on the 300K sfc ahead of the warm front
should focus some bands of showers with some embedded thunder,
as Showalter stability indices lower to 0C to -2C. In the
southwest flow, some orographic enhancement is possible over the
southwest Adirondacks and the Catskills. We kept POPs in the
high likely and categorical range overnight. It will become
humid and min temps will likely wet bulb in the 60s with 60-65F
readings over the higher terrain, and mid 60s to around 70F in
the lower elevations. Total rainfall by daybreak will be in the
tenth to half an inch range with perhaps up to an inch over the
Adirondacks, western-central Mohawk Valley, and the Schoharie
Valley and eastern Catskills, so no hydro problems expected.

Wednesday...It is still unclear whether the cold front will
catch up to the warm front for an occluded front to move
through in the morning. The latest guidance shows the forecast
area in potentially a mini-warm sector in the morning, but the
cold front will be quickly moving through eastern NY and into
western New England in the 15Z-18Z time frame. Clouds may
prevent complete destabilization, but both the NAM/GFS are
showing 1000-1500 J/kg of sfc based instability, but this is
based on sfc dewpts in the lower 70s. Instability will likely be
a tad lower in the 500-1000 J/kg range with 0-6 km effective
bulk shear increasing to 35-40+ knots. The best chance for some
stronger convective cells maybe east of the Hudson River Valley
over western New England, and the latest Day 2 from SPC does
place western New England in a Marginal Risk. The greatest
threat would be for strong gusty/isolated damaging winds. We
will highlight this threat in the HWO. The mid-level lapse rates
are relatively weak until late in the when the front clears.

Actually, the mid to late afternoon period will likely feature
breezy conditions with better mixing. A secondary cold front
slips through with dewpoints and humidity levels lowering. In
the cold advection, temps still may spike in the valleys due to
downsloping. Highs will only be in the mid 60s to around 70F
over the southern Adirondacks, southern Greens, and eastern
Catskills, with lower to mid 70s over the hills and in the
western Mohawk Valley, and upper 70s to lower 80s in the valleys
with the highest temps in the mid-Hudson Valley. West to
northwest winds will increase to 10 to 20 mph with gusts in the
25-35 mph range.

Wed night...A few instability, lake induced showers may impact
the western Adirondacks and western Mohawk Valley off Lake
Ontario with the upper level trough approaching the region. It
will be much cooler with lows in the 50s with some 40s over the
Adirondack Park and southern Greens.

Thursday...Sun will mix with instability clouds with a pleasant
late August Day, as temps will be near or slightly below normal
with 60s to lower 70s over the mtns, and mid to upper 70s over
the valleys. High pressure will be ridging in from the Midwest
as the upper level trough clears the Northeast. It will remain
breezy with northwest winds of 10-20 mph.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Dry and seasonable conditions to end the work week, lasting through
at least the first half of the weekend before unsettled weather
returns by early next week.

The long term period starts out Thursday night with surface high
pressure centered over the central Appalachians, extending northeast
into our region. This will result in clear and cool conditions, with
comfortable humidity levels. Upper level heights will rise on
Friday, as the 500 mb ridge axis moves across the region. The
surface high will shift eastward towards the coast, with a light
southwest flow developing around the high. So after a cool start,
temperatures should respond to warming aloft and abundant sunshine.

As the surface high gradually shifts eastward off the coast, it will
continue to influence our weather with continued dry conditions
through Saturday. Another day of low-level S-SW flow will result in
warmer temperatures with humidity levels starting to rise as well.
Saturday looks to be the pick of the weekend, as some unsettled
weather may arrive on Sunday. The ridge aloft is expected to flatten
out by Sunday, as some short wave energy moves in from the Great
Lakes. Still, it is unclear how much instability/forcing will be
present, so will only mention slight to low chance pops with the
better chances west of the Hudson Valley.

Additional short wave energy may move through on Monday as well, with
continued zonal flow aloft. A strong upper level ridge is expected
to build across the Ohio/Tenn Valley region, which may result in a
ring-of-fire type setup across our region depending on the position
of surface boundaries. Bottom line is that it could turn more
unsettled early next week with multiple chances for showers and
thunderstorms and continued above normal temperatures.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Stratus clouds mainly in the 3500-5000 ft AGL range this morning,
although KPOU will occasionally have MVFR cigs around 2500-3000 ft.
Expecting broken cloud cover to persist through the day with a moist
SE flow continuing.

Showers will develop later this evening into the overnight, as a low
pressure system track into the eastern Great Lakes. Some rumbles of
thunders will also be possible due to elevated instability.
Conditions will lower to MVFR with possible IFR at KPSF.

Winds will be light and variable into the early morning, then
becoming south-southeast around 5-10 kt.

Outlook...

Tuesday Night: High Operational Impact. Breezy Ocnl SHRA...TSRA.
Wednesday: High Operational Impact. Breezy Likely SHRA...CHC TSRA.
Wednesday Night to Saturday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
High pressure will drift into the Canadian Maritimes today, as
a low pressure system approaches from the Great Lakes Region. A
warm front will bring showers late this afternoon and tonight,
then a cold front will bring showers and scattered thunderstorms
Wednesday, mainly in the morning. In the wake of the cold
front, it will turn cooler and less humid with fair conditions
for the end of the week.

The RH values will only lower to 55 to 75 percent this
afternoon, and recover to around 100 percent tonight. The min RH
values will be 50 to 75 percent Wednesday afternoon.

The winds will increase from the south to southeast at 10 to 20
mph this afternoon with a few higher gusts. It will remain
breezy overnight with south to southwest winds of 10 to 15 mph,
and the winds will shift to the west to northwest at 10 to 20
mph by Wednesday afternoon with gusts in the 25 to 35 mph range.

A widespread wetting rain is likely tonight through Wednesday
morning.

&&

.HYDROLOGY...
Mainly dry weather is expected through this morning for the
Albany Hydro Service Area. River levels will continue to recede
back to seasonal levels after the rains the past few weeks.

Showers will increase late this afternoon into early Wednesday
ahead of a strong low pressure system and its warm and cold
fronts, with scattered thunderstorms possible Wednesday
morning into the early afternoon. Total QPF ranges from a
few tenths of an inch to an inch from the system, with greatest
amounts expected across portions of the southwest Adirondacks
and western Mohawk Valley region.

Some within-bank river rises are possible, but no widespread
problems are currently anticipated. Dry weather returns
Thursday into the weekend, as flows will recede again.

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


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