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fxus61 kaly 202309 
afdaly

Area forecast discussion
National Weather Service Albany New York
709 PM EDT Fri Oct 20 2017

Synopsis...
high pressure will build in over the mid Atlantic region and
the northeast tonight into Saturday. The high will shift off
the New England coast to close the weekend, as temperatures will
be above normal into next week. Unsettled weather returns late
Monday through Tuesday with a cold front.

&&

Near term /until 6 am Saturday morning/...
as of 709 PM EDT...high pressure continues to ridge in from the
Piedmont region and the mid Atlantic states early this evening.
The strong subsidence associated with the sfc anticyclone will
allow for clear conditions to continue most of the night. Clear
skies and the winds becoming light to calm especially in the
valley areas should allow for radiational cooling. Low and mid-
level warm advection does begin in the early to mid morning
hours. Temps should cool off in the dry and radiational cooling
environment with light boundary layer winds.

Lows will range from the mid 30s to lower 40s across the
forecast area. The colder spots will be in the sheltered valleys
and across the southern Adirondacks.

&&

Short term /6 am Saturday morning through Monday/...
Saturday...a pleasant late October weekend will begin with the
ridge at the sfc and aloft building in from near and just east
of the mid Atlantic region. Mid and upper level heights rise.
The 500 hpa heights based on the latest 12z gefs are 1 to 2
Standard deviations/Standard devs/ above normal. 850 hpa temps are
also 1 to 2 Standard devs above normal. This has been a common trend
this October. The actual h850 temps warm advect into the +12c to
+14c range over the County Warning Area. Strong subsidence from the anticyclone
will continue to yield mostly sunny/sunny conditions and dry
weather. A blend of the mav/met MOS guidance yields highs in the
70-75f range in the valleys and over some of the hills with mid
and upper 60s over the mountains. The winds will be light and
variable in direction. These temps continue to be 10 to 15
degrees above normal.

Saturday night...the low and mid level warm advection continues
with the 500 hpa ridge axis setting up right over the New York and New
England border. This high amplitude ridge dominates over the
East Coast with a closed anticyclone centered just east of the
Carolinas. A cold front slowly is shifting east of the Central
Plains with a neutral-tilted mid and upper trough moving over
the plains. Another dry and seasonably cool night is expected
with perhaps some high clouds drifting in overnight. Lows will
generally be in the 40s with a few upper 30s in the CT River
Valley and southern Vermont.

Sunday-Sunday night...fair and tranquil weather continues, as
the ridge holds strong over the northeast and East Coast. The
12z gefs continues to have h850 temp anomalies of 1 to 2
Standard deviations above normal. Low-level southerly flow
begins in the sfc and boundary layer. The record high for Albany
for Sunday Oct 22 is 86f set in 1979. The normal high is 57f.
We are not expecting any records. We are expecting Max temps to
be about 15-20 degrees above normal. Highs will be in the mid
and upper 70s in the valley areas...and mid 60s to lower 70s
over the elevated terrain. This blocking ridge continues into
Sunday night. The southerly flow may allow for some stratus and
patchy mist to form. We have added the patchy fog to the grids.
Lows will be milder in the mid 40s to lower 50s.

Monday...the mid and upper level ridge based on the latest
European model (ecmwf)/GFS keeps this day dry, as it slowly weakens and
retrogrades downstream. The Canadian ggem has some light
drizzle or showers impacting some of the region. Some stratus
and mist is possible in the morning, but should burn off in the
afternoon. The cold front stalls west of the region with a
cutoff low near the lower MS River Valley. A more progressive
northern stream trough will be moving across the northern
plains/upper MS River Valley and upper Midwest, which will
interact with the cutoff later in the week and bring some wet
and potentially windy weather to region Tuesday into the mid-week.
Overall, a slight chc of showers was placed in the extreme
northwestern zones late in the day, but mild and mainly dry
weather will persist on Mon. Highs still in the 60s to lower 70s
with a bit more clouds than sun anticipated.

&&

Long term /Monday night through Friday/...
the period starts out Monday night with our region under the
influence of a strengthening southerly flow ahead of a frontal
boundary slowly approaching from the south and west. The first
half of the night looks mainly dry, with increasing chances for
showers during the latter half of the night as moisture
increases and the front gets closer. It will be unseasonably
mild with the moist southerly flow, with low temps mainly in the
mid to upper 50s.

By Tuesday, the upper level pattern across the eastern half of
the Continental U.S. Becomes quite amplified, with a phasing upper level
trough developing across the Midwest and upper Great Lakes.
Ahead of the trough, a mild meridional southerly flow along the
East Coast will continue to result in unseasonably warm
temperatures along with a surge of deep moisture. Forecast precipitable water
anomalies from the gefs indicating around +1 to +3 stdev by
Tuesday evening. Models such as the European model (ecmwf) and GFS show
considerable strengthening of southerly 850 mb winds Tuesday
afternoon into the evening. So it will be a warm and fairly
humid day ahead of the main cold front, which is expected to be
tracking eastward across western/central New York through Tuesday
afternoon. Models have different solutions regarding the
position of the main surface wave associated with the deepening
upper trough. However, the majority of solutions indicate the
cyclone to track well north and west of our region. Therefore,
we are anticipating the cold front to push through in the
Tuesday evening/night time frame.

The main impacts associated with the cold front are expected to
be a line of low-topped convection (or narrow cold frontal
rainband), as we typically experience with cold fronts impinging
on an anomalously warm/moist air mass in a high shear/Low Cape
environment. There will likely be a period of heavy rainfall
associated with the ncfrb and gusty winds. Will have to watch
for the potential for strong to perhaps some damaging winds.
Models now indicating the front to be fairly progressive, so
while some heavy rainfall is possible, flooding is not
anticipated.

Rain should end by Wednesday morning, as a short wave ridge
builds in behind the departing front. The air mass behind the
cold front is somewhat cooler but not significantly colder, so
temperatures will still be above normal. Low confidence forecast
then shaping up for the Thursday/Friday time frame. Ridging
looks to develop across much of the Ohio Valley and Great Lakes,
however coastal cyclogenesis is possible over New England as a
piece of the remnant upper trough potentially interacts with a
baroclinic zone along the coast. The European model (ecmwf) is most aggressive
with this solution, while the GFS is not depicting coastal
development. Will mention low chance pops for now until forecast
confidence increases.

&&

Aviation /23z Friday through Wednesday/...
a ridge of high pressure at the surface and aloft will remain
in place through the 24 hour taf period ending 00z Sunday. This
will result in clear skies and light/variable winds. Dry air
mass in place should preclude any fog formation tonight into
Saturday morning, so VFR conditions are expected to prevail.

Outlook...

Saturday night: no operational impact. No sig weather.
Sunday: no operational impact. No sig weather.
Sunday night: no operational impact. Patchy fog.
Monday: no operational impact. No sig weather.
Monday night: moderate operational impact. Chance of rain showers.
Tuesday: high operational impact. Breezy definite rain showers.
Tuesday night: high operational impact. Breezy likely...ra.
Wednesday: low operational impact. Slight chance of rain showers.

&&

Fire weather...
an area of high pressure will build in tonight into the
tomorrow from the mid Atlantic region and then shift offshore
on Sunday resulting in continued dry and mild conditions.

Relative humidity values will increase to 70 to 100 percent over most of the
region tonight, and then lower 25 to 40 percent tomorrow
afternoon, and then recover to 70 to 100 percent for most of
the region Sunday morning.

Northwest or north winds at 10 to 15 mph late this afternoon
will become light to calm tonight. The winds be variable in
direction at 10 mph or less tomorrow afternoon, and will once
again become light to calm Saturday night.

&&

Hydrology...
no precipitation is expected through the weekend into most of
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 an inch and
a half from this system. Some locally heavy rainfall is
possible.

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 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...wasula
near term...jpv/wasula
short term...wasula

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