Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 171042
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
642 AM EDT Thu Aug 17 2017

.SYNOPSIS...
With high pressure nearby, dry and comfortable weather is expected
today.  It will turn more humid tonight thanks to a southerly flow
ahead of an approaching frontal system, which will bring widespread
showers and possible thunderstorms to the region for late tonight
into Friday.  The weather will be clearing out over the weekend with
temperatures close to normal.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 635 AM EDT...Surface high pressure is located over
central New York and it continues to slowly slide eastward
towards our area. IR satellite imagery shows mainly clear skies
over the area, with just a few thin passing cirrus clouds
around.

Good radiational cooling this morning has allowed for a cool
morning with some patchy fog, mainly for near/over bodies of
water. Some areas have fallen into the lower to mid 40s for lows
this morning, which is rather chilly for mid-August. Any fog
should dissipate within the next hour and with a sunny start to
the day, temps should quick rise this morning.

During the day today, high pressure will continue to move
across the area and shift southeast of the region. It will
continue to be dry today with just some passing cirrus clouds.
Mid and high level clouds will eventually thicken from west to
east by late this afternoon into this evening, as the next
system starts to approach from the Great Lakes.

Highs today will range from the mid 70s in the high terrain to
the low 80s in southern valley areas. Dewpoints will be
comfortable for August, with readings mainly in the 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
An upper level shortwave and associated surface storm will be
moving across the upper Great Lakes tonight and move towards
Ontario and Quebec for tomorrow. Although the tonight period
will start off dry across the area, clouds will be thickening
and increasing this evening and into the overnight hours.

Ahead of this system, a strong s-sw flow in the low to mid
levels will be advecting plenty of deep moisture into our
region. The southerly flow will be rather strong for August, as
both the 00Z GEFS and 03Z SREF suggests 850 hpa u-wind
anomalies of 2-4 STD above normal for around 12Z Friday. As a
result, surface dewpoints and PWATs will be rising through the
night, with most areas seeing dewpoints in the low to mid 60s by
the late night hours. With strong isentropic lift in place,
some rain showers along the storm`s warm front will be lifting
across southern and western areas by late tonight. These initial
showers will be light and spotty, but all areas have a chance
of seeing some rainfall by daybreak on Friday. Lows tonight will
only fall into the upper 50s to mid 60s for most locations.

On Friday morning, the surface warm front will continue to be
lifting across the area from southwest to northeast during the
morning hours. Models hint at some elevated instability with the
boundary moving across, so will allow for some thunder in the
morning hours.

PWATs will be continuing to rise and will reach in excess of two
inches over much of the area by Friday afternoon (about 2 to 3
STD above normal), as our area enters into the storm`s warm
sector. It still looks fairly cloudy, but a few breaks are
certainly possible, especially for southern areas. Model
soundings show some surface-based instability will be possible
and CAPE values may reach 500-1500 J/kg. This will ultimately
depend on just how many breaks of sun can occur. With strong
winds aloft, 0-6 km bulk shear values will reach 35-45 kts,
depending on the location. The 3km NAM shows some additional
showers and thunderstorms will impact the region for the
afternoon and evening hours ahead of the advancing cold front,
but doesn`t really hint at any strong organization of the
storms.

Considering the strong shear and moist environment, cannot rule
out a stray strong storm, although limited instability and poor
mid level lapse rates will keep the severe threat from being
more widespread. The main threat will likely be the heavy
rainfall. Although there`s enough flow to keep things moving
along, the very high PWATs would be capable of producing heavy
rainfall in a short period of time. Depending on where it falls,
this could lead to some minor flooding, particularly of poor
drainage and low lying areas.

High temps on Friday look to reach into the 70s. If we do get
any breaks of sunshine, temps could get into the 80s, but this
is unlikely due to expected cloud cover.

The cold (or occluded) front should be crossing through the
area on Friday night, which will end the widespread rain from
west to east. Lows will only fall into the 60s and it will
continue to be fairly muggy overnight, despite the passing
boundary, as the much drier/cooler air will remain well upstream
of the region.

On Saturday, our area will still be upstream of the advancing
upper level trough and will be situated within w-sw flow aloft.
As a result, it probably still be fairly warm and muggy. Cannot
rule out a few showers in spots (perhaps even a thunderstorm)
due to the cyclonic flow ahead of the shortwave, but these will
more scattered in coverage. Temps look to reach into the 80s for
valley areas and dewpoints still will be in the 60s.

The upper level trough will be passing over the area on Saturday
night. Still could be a shower for far northern areas, but most
spots look to stay dry with temps falling into the upper 50s to
mid 60s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
High pressure controls the weather Sunday and Monday with warm
advection occurring later Monday and through Tuesday. It looks like
the weather for eclipse Monday should be mostly sunny. Strong upper
energy develops in eastern Canada Tuesday and drops south, with an
associated cold front tracking through in the Wednesday time frame.
There could be some initial scattered shower and thunderstorm
activity Tuesday afternoon with any pre frontal surface trough. The
best chances for showers and storms would be Wednesday and Wednesday
night.

Highs Sunday in the lower 80s with 70s higher terrain, warming to
the mid to upper 80s by Tuesday ahead of the cold front. The clouds,
showers and thunderstorms Wednesday will result in highs in the
upper 70s and lower 80s but lower 70s higher terrain.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
High pressure will continue to build into the region at all
levels of the atmosphere through today. Some patchy fog is
occurring at KGFL and KPSF that should burn off by around 13Z.
VFR conditions with just scattered clouds above 3000 feet are
expected through this evening.

Clouds will lower and thicken tonight as a warm front approaches
and after 06Z some ceilings will lower to MVFR, with the best
chances for MVFR ceilings at KPOU, KGFL and KPSF. A few isolated
showers could also approach all TAF sites before daybreak Friday and
included a VCSH.

Winds light/variable to calm through mid morning. A light
southeast to southwest flow will develop by mid morning morning
and persist through the day at 6 Kt or less and could be
variable in direction through tonight.

Outlook...

Friday Night: Moderate Operational Impact. Likely SHRA...TSRA.
Saturday: Low Operational Impact. Slight Chance of SHRA...TSRA.
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: Moderate Operational Impact. Scattered SHRA...TSRA.

&&

.FIRE WEATHER...
With high pressure nearby, RH values will fall to 40 to 50
percent this afternoon with rather light winds. Southerly winds
will increase for tonight into tomorrow, but most areas should
seeing a wetting rainfall during that time. With a very moist
air mass in place, RH values will only fall to around 70
percent on Friday with southerly winds of 10 to 15 mph.

&&

.HYDROLOGY...
Dry weather is expected today into this evening, but a frontal
system will bring some showers and thunderstorms to the region
between late tonight and late Friday night. With dewpoints
reaching into the upper 60s to lower 70s and PWATs reaching
around 2 inches, locally heavy downpours will be possible.

Based on the latest model guidance, the chance for the heaviest
rainfall is on Friday afternoon and evening, just ahead of the
approaching cold front. Although flash flooding is not
anticipated due to stronger winds aloft (which should keep heavy
rainfall moving quickly), showers/thunderstorms 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 seem some minor rises, but no
river flooding is expected with this rainfall. Less humid air
will start to work its way into the region for late Friday
night. Total QPF amounts 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.

Although a lingering light rain shower or two cannot be ruled
out for Saturday, drier weather should return for 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...
Technicians will continue to work on the KENX radar Thursday and
hope to have the radar back in service in the afternoon.

&&

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

&&

$$
SYNOPSIS...Frugis
NEAR TERM...Frugis
SHORT TERM...Frugis
LONG TERM...NAS
AVIATION...NAS
FIRE WEATHER...Frugis
HYDROLOGY...Frugis
EQUIPMENT...



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