Albany, NY WFO Forecast Discussion

Forecast Discussion for ALY NWS Office
000
FXUS61 KALY 170520
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
120 AM EDT Tue Jul 17 2018

.SYNOPSIS...
Widespread storms are expected Tuesday as a cold front approaches
and moves across the region. Any storms will be capable of very
heavy downpours. A cooler and less humid airmass will be ushered
in with the passage of the front with fair weather expected for
the remainder of the work week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 115 AM EDT, area of rain with embedded thunder continues
to track into the western/central Mohawk Valley and southwest
Adirondacks. Expect this area of rain/thunderstorms to persist
for another 2-3 hours, expanding into or just N/W of Saratoga
and Glens Falls. Overall trends have been decreasing in
intensity, and expect this to continue to slowly weaken during
this time.

Some additional showers/thunderstorms may form on an outflow
boundary, which currently is moving east through the
east/central Mohawk Valley into Schoharie Co. If any additional
convection develops along this, it could affect the immediate
Capital Region or points just N and W.

Also, upstream showers/thunderstorms may redevelop across the
southwest Adirondacks and Mohawk Valley through daybreak, with
locally heavy rain possible.

Elsewhere, little if any shower activity was noted across the SE
Catskills, mid Hudson Valley east through western MA and NW CT,
and expect most of these areas to remain dry through daybreak,
outside of perhaps an isolated shower/thunderstorm.

Patchy fog will be possible, with muggy conditions prevailing.
Lows mainly ranging from the mid 60s to lower/mid 70s, warmest
from the immediate Capital Region and valley areas south and
east.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
Widespread storms and needed rainfall Tuesday as a cold front
approaches and crosses the region. There are still some concerns
about the magnitude of the threat, however the better chances
for severe storms are expected to the east of the Hudson River
Valley of New York and across western New England where greater
instability is expected especially during the afternoon into
the early evening hours. In collaboration the Storm Prediction
Center, a Slight Risk was added to their Day 2 Outlook and it
may need to be expanded. Otherwise a marginal risk remains in
place for the most of the rest of the forecast area. Mid level
flow and shear will be increasing ahead of the front and
sharpening trough Tuesday and with such a humid airmass in place
storms are expected to be numerous. The timing of the front is
critical to the severe threat as it occur during the peak
heating of the day and the amount of cold cover/sunshine will
impact instability/CAPE.

Very heavy downpours will occur as precipitable water values
will be about 2 inches ahead of the front. With rainfall rates
expected to exceed an inch an hour the may threat will be for
flooding in urban areas especially low lying and poor drainage
locations. A flash flood watch was NOT issued since antecedent
conditions are dry, the storms will be moving and training is
not expected. However, isolated flash flooding can not be ruled
out.

With the passage of the cold front a cooler and drier airmass
will be ushered and fair weather as ridging builds in. Temperatures
are expected to drop to seasonable level Tuesday night with dew
points dropping into the 40s. Wednesday during the day and at
night comfortable and seasonable temperatures are expected.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
High pressure and very pleasant conditions will finish out the work
week as upper level ridging from the Great Lakes builds into the
Northeast. With eastern NY and western New England on the eastern
half of the ridge Thursday and 700mb RH showing a very dry air mass
spilling over top of it, expect much lower dew points in the 50s,
seasonable temperatures in the upper 70s to low 80s and plenty of
sunshine. Clear skies overnight should enable another cool night
in the 50s.

Friday stays very nice stays very pleasant with Canadian high
pressure maintaining control and moving into New England. During
this period, we will be closely monitoring a strengthening upper
level low and large scale trough over the Midwest/western Great
Lakes region. Most of the latest guidance suggests it cuts off up to
500mb by 12z Friday allowing the ridge downstream over the Northeast
to amplify. As the ridge axis crosses eastward through eastern
NY/western New England by 18z Friday, we should see southwesterly
return flow aloft leading to increased 850mb isotherms around 14C to
16C. Thus, expect warmer high temperatures in the mid - upper 80s
but dew points should remain comfortable in the 50s.

On Saturday the large scale cut off low slowly progresses eastward
into the Great Lakes with most of the latest model suite showing it
sharpening and digging into the TN Valley. This would again amplify
the ridge downstream that is now over New England and the western
Atlantic with the surface high building up to around 1025mb. South-
southeasterly flow increases aloft as the pressure gradient tightens
between the approaching cut low and off shore ridge. With
potentially more of a marine influence airmass reaching into our mid-
Hudson Valley and NW CT areas, high temperatures could be a bit
cooler here and lowered high temperatures to only around 80 here in
the latest update. Expecting warmer highs in the mid 80s furthering
north into the Greater Capital District and Lake George/Saratoga
area. Dew points should also be a bit higher approaching 60F.

Despite increasing warm air advection through the day Saturday, the
strengthening high pressure should suppress any precipitation south
of our region so maintained a dry forecast outside of just some
slight chance POPs in the Catskills/extreme western Mohawk Valley to
line up with neighboring offices. During the Saturday night period,
some of the global models (mainly the ECMWF and CMC) show our trough
digging into the Southeast U.S, becoming a bit negatively titled
with a secondary low developing off the Carolina coast. Gradually
increased POPS to low end chance in the mid-Hudson Valley, Catskills
and western Mohawk Valley Saturday night but still think southern VT
and areas from the Greater Capital District northward stay mainly
dry under the high pressure influence. Only increased POPs to slight
chance there.

The Sunday - Monday period will then feature the greatest potential
for areas of showers and perhaps even some thunderstorms (once in
the warm sector) as our cut off low and potential secondary coastal
low slowly progress northward into the Northeast. There are still
uncertainties with how long high pressure maintain control of our
region and suppresses precipitation to our south into Sunday.
Therefore, held off the widespread high end chance POPs until the
Sunday night - Monday period when we could be in the warm sector.
It`s worth noting that the battle between high pressure over the
western Atlantic/Northeast and the approaching low may lead to a
decent mid-level jet with some global models showing 850mb winds
strengthening up to 35-45kts. This would lead to an increased fetch
of moisture from the tropics and thus increase the heavy rain
potential. Stay tuned to future updates as we continue to iron out
the details on this system.

Temperatures on Sunday look to be a few degrees cooler than normal
due to cloud coverage and southeasterly flow ushering in a marine
influenced air mass. Highs likely remain in the mid - upper 70s with
maybe a few reaching 80F. Dew points however will be rising into the
60s so it should feel muggy. Monday we should be in the warm sector
with highs a bit higher in the low 80s and still humid.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
A shortwave trough and associated surface cold front are heading
towards the region.  Latest mosaic radar imagery shows bands of
showers and embedded thunderstorms extending towards the region from
western and central New York.  Brief reductions to MVFR/IFR
conditions (mainly due to visibility) are possible at KGFL/KALB as
these showers/t-storms move across the northern half of the area for
the late night hours. KPOU may be far enough south/east to see any
impact from these showers, but will include a TEMPO for KPSF in case
it brushes there or if other showers develop along outflow
boundaries from this activity.  Otherwise, it will remain VFR with a
bkn high clouds in place and a light south to southeast flow for
the rest of the overnight hours.

During the day on Tuesday, the storm`s cold front will allow for one
or two bands of convection that will move across the area from west
to east.  These showers and thunderstorms will impact the region
mainly during the afternoon hours (perhaps lingering into the early
evening at KPOU).  Within any shower or t-storm, visibility may be
reduced to IFR levels, with MVFR cigs. There is also the possibility
of gusty westerly winds within any thunderstorm as well.  Outside of
showers or t-storms, it looks VFR with bkn cigs around 4-6 kft and
southerly winds will be around 5-10 kts throughout the day.

Behind the front, winds will switch to the w-nw for Tuesday evening
into Tuesday night.  Clouds should clear out for most areas,
although KPOU may see some lingering mid level clouds through the
evening hours.

Outlook...

Tuesday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Wednesday: No Operational Impact. NO SIG WX.
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.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.

&&

.FIRE WEATHER...
Widespread storms are expected Tuesday as a cold front approaches
and moves across the region. Any storms will be capable of very
heavy downpours. A cooler and less humid airmass will be ushered
in with the passage of the front.

&&

.HYDROLOGY...
Widespread showers and thunderstorms are expected Tuesday as a
cold front approaches and moves across the region. Storms will
be capable of very heavy downpours which may lead to some urban
low lying and poor drainage flooding. Isolated flash flooding is
possible as rainfall rates could easily exceed one inch per hour.
Basin-average rainfall amounts of up to around an inch are
expected, which should be enough to cause some rises on area
rivers.

Mainly dry weather is then expected for Wednesday through
Friday. Showers and thunderstorms may return for next weekend
as a low pressure system approaches.

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...IAA
NEAR TERM...IAA/Frugis/KL
SHORT TERM...IAA
LONG TERM...Speciale
AVIATION...Frugis
FIRE WEATHER...IAA
HYDROLOGY...IAA

NWS ALY Office Area Forecast Discussion