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000
FXUS61 KALY 190823
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
423 AM EDT Sun Aug 19 2018

.SYNOPSIS...
Today will be mainly dry with seasonable temperatures for much
of the area, although areas from the southern Berkshires to the
Catskills and on south will see a bit more cloud cover, cooler
temperatures, and perhaps a few showers. Calm and seasonable
weather is expected tonight into Tuesday morning. Showers and
thunderstorms associated with a strong low pressure system are
expected late Tuesday into early Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 400 am, stratus has remained widespread across most of the
forecast area, except for far northern zones where fog is
prevalent. Have removed fog from the forecast elsewhere and
adjusted temperatures upward to match current obs.

Loosely organized area of surface low pressure will be located
offshore of New Jersey today while high pressure becomes centered
over the Gaspe Peninsula of Quebec. One of the main challenges today
will be how quickly drier air can advect in on the low/midlevel
northeasterly winds to erode the existing cloud deck. Have generally
kept cloud cover around a bit longer than blended guidance. Areas
from the Berkshires to the Catskills and points south may remain
mostly cloudy for the majority of the day as some moisture at higher
levels in the atmosphere may add to the cloud cover. With weak
midlevel vorticity maxima moving through along with weak low-level
frontogenesis and the poleward exit region of a 60 kt upper jet,
could see enough forcing for ascent for a few showers in these
locales. Have gone toward the cool end of the guidance envelope for
highs here with generally upper 60s to mid-70s. Further north toward
the Capital District, Upper Hudson Valley and Mohawk Valley, a bit
more sunshine is expected to send temps into the upper 70s to near
80. This is a somewhat low confidence forecast however, and will
hinge upon the progression of the cloud cover.

Tonight, the low-level anticyclone is expected to expand into the
area, resulting in a continued diminishing trend in the cloud cover.
Low temps expected to be near to slightly cooler than normal, with
50s common and some 40s across portions of the Adirondacks.
Typically prone spots may see patchy fog.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
Expect a tranquil day Monday as we remain under the influence of the
surface high and under weak midlevel flow. Partly to mostly sunny
skies expected with near seasonable temps.

Monday night into Tuesday, a strong midlevel trough over the Upper
Midwest will deamplify a bit as it tracks eastward toward Lake Erie.
Low-level winds will turn southeasterly ahead of this feature. These
winds along with gradually increasing high clouds will likely allow
for Monday night to be a bit milder than Sunday night, but depending
on the speed of the system, we could still see good radiational
cooling conditions for at least the first part of the night.
Dynamical lift will increase Tuesday afternoon and evening ahead of
the shortwave, and a very strong southerly low-level jet (40 kt at
850 mb) translates into the region, increasing moisture transport.
Winds of this magnitude are approaching 4 standard deviations above
normal. The overall strength of the surface low, modeled by the
deterministic and ensemble guidance around 998 mb at 00Z Wed over
southeast Ontario, is 3 to 4 standard deviations below normal. So we
are certainly looking at an unseasonably strong and dynamic system
for this time of year. Model consensus favors most of the precip
associated with this system occurring after the short term period,
but some showers and possibly a thunderstorm will be possible late
in the day mainly west of the Hudson Valley.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Anomalous low pressure for late August moves up the Saint
Lawrence River Valley Tuesday night into Wednesday. Tuesday night,
strong southwesterly 850mb jet should push northeastward into our
region leading to widespread precipitation. GEFS shows 850 wind
anomaly and 850 moisture flux of 4-5 SD above normal across the
northern half of forecast area. PWATs are forecast in the 1.5 to 2
inch range across the area. Negative showalter index indicates
elevated instability so a few rumbles of thunder and some locally
heavy rainfall possible. Lows Tuesday night in the 60s.

On Wednesday, a secondary cold front will cross the area. Ahead of
the front, a line of showers and thunderstorms may develop in the
warm sector. At this time, it looks like the main threat area for
thunderstorms would be south and east of Albany, but timing the
front 3 days out is always tough. Highs Wednesday will range from
the upper 60s southern Adirondacks to low 80s mid-Hudson Valley.

By Wednesday afternoon and night, it looks to turn breezy as the
impressive surface low (which its 990-995mb MSLP 3-4 standard
deviations below normal for this time of year according to the GEFS)
moves through northern New England/southern Canada leading to a
decent pressure rise/fall couplet and isallobaric wind field.
Wind gusts of 20-30mph are forecast Wednesday afternoon/evening in
the Adirondacks, Mohawk Valley, Capital District, Southern Vermont
and northern Berkshire County. Cold advection will lead to gradually
falling temperatures Wednesday afternoon as well and we should see a
drastic drop in humidity heading into Wednesday night. Overnight
lows should be comfortable falling into the 50s, with 40s southern
Adirondacks.

Pleasant conditions remain in place Thursday and Friday as large
scale high pressure and weak ridging moves in from the Midwest.
Temperatures should be closer to normal for late August only
reaching into the upper 70s to around 80 both days. Humidity level
remains low as well thanks to the northerly flow. Lows Friday and
Saturday in the 50s.

The weak ridge axis should move into eastern New England heading
into Saturday which should lead to a southerly flow aloft.
This in turn should allow temperatures to warm up a few degrees
Saturday reaching into the low 80s in the valleys with 70s in the
hill towns.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
Easterly flow of moist air around low pressure currently south
of Long Island, coupled with an upper level low pressure system,
is causing and area of low clouds and spotty light rain. -RA
reported at KALB and KPSF along with MVFR cigs. VFR cigs at
KGFL and KPOU.

Low clouds expected to only slowly erode after sunrise on
Sunday. Cigs should rise to VFR level all TAF sites by 19/12Z.
Some dense (IFR) radiational fog is possible at KGFL if clouds
erode a little faster overnight tonight.

Winds will be north to northeast overnight at 5 to 10 kts. Winds
Sunday will turn from northeast to southeast at 5 to 10 kts.

Outlook...

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. Definite SHRA...TSRA.
Wednesday: High Operational Impact. Likely SHRA...TSRA.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
High pressure located to the northeast will keep precipitation
out of the forecast for the most part through Tuesday morning. A
few sprinkles are possible early this morning, and a few showers
are possible throughout the day today from the Berkshires to
the Catskills and points south. Temperatures here will be a bit
cooler than normal today, but seasonable elsewhere today and
everywhere on Monday. RH values will mainly fall into the 45 to
55 percent range today and Monday with a light easterly to
northeasterly wind. Showers and thunderstorms will be likely
late Tuesday into early Wednesday ahead of a strong low pressure
system.

&&

.HYDROLOGY...
A mainly dry period is expected through Tuesday morning,
although a few light showers are possible today from the
Berkshires to the Catskills and points south. This will allow
river levels to recede. Showers and thunderstorms will be likely
late Tuesday into early Wednesday ahead of a strong low pressure
system.

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