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fxus61 kaly 221745 
afdaly

Area forecast discussion
National Weather Service Albany New York
145 PM EDT sun Oct 22 2017

Synopsis...
surface high pressure will move slowly east of the mid
Atlantic coast and New England this afternoon. The surface high
will continue to provide above normal temperatures and partly to
mostly sunny skies. A slow moving cold front and increasing moisture
will bring a period of unsettled weather late Monday night into the
mid week.

&&

Near term /through tonight/...
as of 120 PM EDT, another batch of cirrus clouds continues to
be drifting over the majority of the forecast area especially
from the Mid-Hudson valley/eastern Catskills northward. The
latest rap guidance has a weak vort Max rolling over the h500
ridge axis. Temps have warmed into the 60s to lower 70s. The 12z
kaly sounding had a strong radiative inversion, and it is
taking a while to mix through it. A southerly breeze has picked
up and readings close to 75f still look possible in the capital
region or in the 70-75f range. We tweaked Max temps down
slightly. Overall, Max temps above normal by 15-20 degrees in
the lower to mid 70s /some upper 70s in the Mid-Hudson valley/
in the valleys and over the hills this PM, and mid 60s to around
70f for the mtns with partly to mostly sunny conditions through
the cirrus, as the sfc anticyclone is slowly moving east of the
mid Atlantic coast. Southerly winds in the Hudson River valley
may increase to 10-15 mph with a few gusts to 20 mph.

Tonight...
those aforementioned southerly winds will eventually tap into
Atlantic moisture per moisture transport vectors and some lower
stratus may quickly advect northward from the capital region and
points southward. So some increase in cloud coverage as
temperatures overnight should range within several degrees of
50f. Some patchy fog was added to the forecast in the Hudson
River valley, and along and near the western New England higher
terrain.

&&

Short term /Monday through Monday night/...
Monday...the NCEP model suite along with international guidance show
an increase of mainly low level clouds with a tightening low-
level pressure gradient between the offshore anticyclone and low
pressure moving into the central and eastern Great Lakes by
late in the day. Low-level moisture will increase further, and
some lower stratus and possibly some light showers/drizzle will
move into locations from the capital district south during the
day (terrain will likely be the first to experience). A weak
short-wave impulse embedded in the deep southerly flow will
focus the light showers, mainly in the afternoon). Highs will
be still mild in the 60s to lower 70s.

Monday night...some timing differences with respect to the
upstream cold front approaching as the European model (ecmwf) is now the fastest
with shower potential quickly increasing. The NAM/GFS/ggem are
in better agreement with a bit slower arrival time. We will
follow along this lead which is in excellent agreement with the
previous forecast. Low level jet magnitudes increase toward
50kts as will moisture transport and higher pops. Could be quite
a bit of drizzle developing overnight as ample mixing within the
boundary layer seen in the BUFKIT profiles along with high
mixing ratios. As dewpoints climb well into the 50s and even
some lower 60s, it will be a rather warm and somewhat muggy
night.

&&

Long term /Tuesday through Saturday/...
active weather expected to start the extended period...

A sharply digging upper level trough will be strengthening over the
Ohio Valley on Tuesday, allowing a strong southerly flow across our
area at all levels of the troposphere, as upper level ridging shifts
downstream of the region. At the surface, strong low pressure will
be moving from the Great Lakes towards Ontario and Quebec, with an
occluded/cold front heading towards our area for later on Tuesday.

A strong low-level jet will be in place ahead of this system, with
850 hpa winds of 50 to 60 kts. Based off the latest 00z gefs, the
meridional wind (v-wind) anomaly looks to exceed 3 Standard for Tuesday,
along with a precipitable water anomaly of around 2-3 Standard above normal as well.
Ahead of the approaching front, we are expecting showers to become
more widespread in coverage through the day, along with gusty
southerly winds. Will continue to mention in the severe weather potential statement about winds
possibly reaching advisory criteria. The best chance for this to
occur looks to be just along/ahead of the approaching frontal
boundary, as models suggest the strong sfc forcing should allow for
a narrow cold frontal rainband to develop, with a line of heavy
showers. Could be some thunder as well, as surface cape values
could be up to 300 j/kg according to the latest 00z GFS. Even
without thunder, some strong winds aloft may mix down within the
heaviest rain showers. The models still show some subtle
differences in timing but the frontal passage looks to occur
somewhere between Tuesday afternoon and Tuesday evening. It still
looks pretty mild ahead of the front, with highs well into the 60s
or low 70s and dewpoints in the 60s, which is very high for late
October.

As the frontal boundary heads towards western New England, it may
start to slow down and possibly even stall, as a wave of low
pressure starts to develop along the boundary across the mid-
Atlantic and rides up the front, as the upper level trough becomes
negatively tilted. This could prolong rain for eastern areas for all
of Tuesday night and even into Wednesday. As a result, rainfall
amounts look to be higher than previously forecasted due to longer
duration of rain, as we have leaned closer to wpc and the
operational 00z GFS/ECMWF. We have generally forecasted 1 to 2
inches of rain across eastern New York with 2 to 3 inches for
western New England. Although these amounts are close to the
operational models, they are still higher than most members of the
00z gefs, so some refinement is still possible, as it will
ultimately depend exactly on where the front stalls. Even with these
higher amounts, widespread river flooding isn't expected due to
recent dry weather and lower flows, but minor flooding of urban,
poor drainage and low lying areas is certainly possible, especially
during the periods of heaviest rainfall and in areas where leaves
and other debris block drainage.

Due to the uncertainty with the exact timing and placement of the
front, have gone with generally just chance pops for Wednesday into
Thursday, with the highest chances across eastern areas, due to the
nearby boundary and passing surface wave. Even western areas will
still see some showers, as the cyclonic flow could still allow for
some passing showers, along with plenty of clouds. The core of the
upper level trough should be over the area on Thursday, so temps
will finally be noticeably cooler and closer to seasonal normals on
Thursday, with most areas only reaching into the 50s.

Dry weather should finally return for Friday into Saturday, as
surface high pressure returns to the area, as upper level heights
start to build once again. Temps should be back above normal once
again, especially by Saturday, as valley highs reach into the mid
60s. Another system, similar to one coming Tuesday, looks to impact
the region at some point Sunday into early next week, with much
colder air behind that front for the end of the month.

&&

Aviation /18z Sunday through Friday/...
with high pressure remaining nearby today, VFR conditions are
expected to continue for all sites with light southerly winds.
Just few-sct passing cirrus clouds are expected throughout the
afternoon and evening.

Winds will decrease for this evening with the loss of daytime
heating and winds should become very light or calm once again
for tonight. Although it looks mainly VFR for much of the
overnight hours with some additional passing high cirrus,
cannot rule out some mist/fog for late tonight at kgfl thanks to
the good radiational cooling once again. Also, thanks to the
persistent southerly flow, some low stratus may advect northward
from the coastal areas and impact kpou/kpsf towards 09z-10z
with MVFR conditions.

As the next low pressure system approaches the region tomorrow,
clouds and low level moisture will begin increasing from the
south, with potential MVFR ceilings at kpou/kpsf after 12z.

Outlook...

Monday night: moderate operational impact. Breezy chance of rain showers...dz.
Tuesday: high operational impact. Breezy definite rain showers...tsra.
Tuesday night: high operational impact. Definite rain showers...tsra.
Wednesday: moderate operational impact. Chance of rain showers.
Wednesday night: moderate operational impact. Chance of rain showers.
Thursday: moderate operational impact. Chance of rain showers.
Thursday night: low operational impact. Slight chance of rain showers.
Friday: no operational impact. No sig weather.

&&

Fire weather...
high pressure will drift eastward this afternoon as it
continues to influence our fair and dry weather with above
normal temperatures across the region. Clouds begin to increase
late tonight into Monday. A slow moving cold front impacts the
area late Monday night through Tuesday night with periods of
showers and windy conditions.

The relative humidity values will lower to 25 to 40 percent this afternoon. An
excellent recovery is expected by Monday morning with Max relative humidity
values in the 90 to 100 percent range.

Winds will be light to calm this morning, and then will be
south to southwest at 5 to 10 mph today with a few higher gusts
this afternoon. Expect southerly winds of 10 mph or less Sunday
night.

The next widespread soaking rainfall will be Monday night into
Tuesday night.

&&

Hydrology...
no precipitation is expected prior to Monday with high pressure
in control, as river flows will remain at normal to below
normal levels.

The next chance of widespread rainfall arrives Monday night
into Tuesday night associated with a cold front. Rainfall
amounts may range from three quarters of an inch to two inches
or so from this system. Some locally heavy rainfall is
possible. The heaviest totals may be along or east of the Hudson
River valley across western New England. Some ponding of water
on roadways is possible as well as clogged drains from fallen
leaves.

Another round of wet weather is possible later in the week, but
there remains quite a bit of uncertainty with evolution and
track of the system and the quantitative precipitation forecast with it. For now, light amounts
of additional rainfall are expected for most of the region with
the higher additional totals of an inch or so over western New
England Wed-Wed night. Overall, a trend to drier weather is
expected Friday into Saturday.

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.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...bgm/wasula
near term...bgm/jvm/wasula

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