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Area forecast discussion 
National Weather Service Albany New York
1053 PM EDT Wednesday Oct 1 2014

Synopsis...
clouds will dominate with chances for showers lingering and patchy
drizzle occurring across areas mainly east of of the Hudson River
valley. This is the result of an area of low pressure at surface
passing well to our south...in combination with a low in the upper
levels of the atmosphere moving over the region. Clouds will give
way to breaks of sunshine as the day progresses Thursday as high
pressure builds in from the north. The high will dominate our
weather into Friday night. A strong low pressure pressure and its
associated cold front will approach Saturday bringing widespread
chances for showers to the area.

&&

Near term /until 6 am Thursday morning/...
the region in under the influence of a surface low passing well to
our south and an upper level level low moving over the region.
This is resulting lots of clouds and low level moisture along with
some showers and patchy drizzle for areas mainly to the east of
the Hudson River valley. The upper low will be slow to move off the
east. Have adjusted probability of precipitation to account for current activity (showers
and drizzle).

Lows mainly in the lower to middle 50s with 40s across the higher
terrain. Patchy fog will form and be the most dense is areas where
the cloud cover is least northwest portion of the forecast area
due to more radiational cooling.

&&

Short term /6 am Thursday morning through Saturday/...
in the wake of the cutoff low pressure area...high pressure will
build back into the region from eastern Canada...not only at the
surface but aloft. Even so...scouring out the clouds will be
challenge given an rather strong subsidence inversion and lowering
sun angle. The clouds will likely hang much of the day to the south
and east of Albany...with more breaks of sunshine to the northwest
of the capital region.

Thursday should be completely dry. High temperatures will be based
on the slow dissipation of clouds...thereby leaning with the cooler
side of guidance. This will still translate to highs 65-70...pretty
close to normal for the time of year...and slightly warmer than
today.

Thursday night...by this time...we assume most of the clouds will be
scoured out. With high pressure building in at all levels of the
atmosphere it will be calm night and presumably mostly clear. This
would set the stage for fog...perhaps areas of fog in the
valleys...and even patchy fog across the higher terrain. This is how
we will play it out in our forecast and grids. The surface wind (and
wind aloft) looked too light for the formation of stratus...but that
is always possible as well.

Once the fog forms...radiational cooling would slow down...or even
go the other way by a point or two...due to the latent heat release
due to condensation. We figure on lows in the middle to upper
40s...with some lower 40s in the normally cooler places.

Friday looks nice once we loose the fog and any low clouds...which
in some valleys...might not happen until midday. Once again high
temperatures will be tricky to forecast. Did lower some high
temperatures a category based on the latest MOS trends. By
afternoon...a south to southeast breeze 5-15 miles per hour will help the cause
to mix the column a little better. With a good deal of midday and
afternoon sunshine...we are forecasting high temperatures within a
few degrees of 70...higher in the valleys...a tad lower over the
higher terrain...especially to the east of the capital region.

Friday night...a southerly breeze and increasing clouds should
mitigate the formation of fog...at least in most places. For
now...no mention of fog in the grids. Went on the higher side of
guidance regarding low temperatures...especially right in the
capital region. We forecast low temperatures from the upper 40s
across the higher terrain...to 50-55 most other areas...mildest in
the capital region.

The southerly breeze will be ahead of a strong developing middle
latitude trough which will also feature a strong surface low
pressure area working across the Great Lakes and a cold front
extending south from it. The low pressure will pass to our north and
whip the cold front through the County Warning Area late Saturday.
Unlike many disturbances of late...this front will have ample Gulf
of Mexico moisture to work with (pushing precipitable waters to over 1.5
inches)...and strong forcing. The upper level trough looks will
become negatively tilted. These factors will should all add up to a
soaking rainfall for the entire region. We did slow the arrival of
showers a little Friday overnight (lowering probability of precipitation a little) but
Saturday looks quite wet...especially midday and early
afternoon...as a line of showers...possibly including a rumble or
two of thunder moves on through. The wind field does not look
especially strong...but there should be some pretty gusty winds up
to 25-30 miles per hour just ahead of the cold front...especially if we were to
reap any convection. While this wind would not produce any
damage...it would be enough in combination with the rain...to pull
many leaves off the trees.

With the clouds and showers...high temperatures on Saturday will be
held to the 60s...despite warm h850 temperatures up to +13c.

&&

Long term /Saturday night through Wednesday/...
our entire region will be experiencing periods of unsettled weather
on and off throughout the extended period. Temperatures will start
below average as we go through the second half of the weekend but
will modify to near normal values as we go into middle of next week.

Saturday night through Sunday...a noticeable cold front will make
its way through the region as a negative tilted upper level trough
digs into the middle Atlantic behind the front with the apex into the
Delaware-Maryland-Virginia peninsula by Saturday evening. Latest 01/12z guidance and
probabilistic models do have the progression of the upper level
trough moving through at different times...however both show
enhancement of precipitation along the front as upper level dynamics
behind the cold front will help produce sufficient ascent throughout
the atmosphere for some locally enhanced quantitative precipitation forecast totals. The frontal
system will exit the region Sunday morning with the latest 12z data
showing t850 and t925 temperatures ranging between 1c and 4c. This
will make temperatures on Sunday well below normal with high temperatures
ranging from the middle 50s to lower 60s across the region.

Sunday night through Wednesday...an upper level low centered near
western Ontario with a broad area of influence reaching the lower 48
will begin to retrograde northward toward Hudson Bay as we head
toward the middle of the week. Our region will be on the east side
of this broad upper level low pressure system. This will shift winds
from a westerly to southerly direction ushering in warmer
temperatures back into the region. This southerly flow will also
steer weak surface low pressure impulses through the region where
isolated to scattered showers will be possible as we go from Sunday
night through Wednesday. Differences in impulse intensities and
timing exist between the 12z models at this time. High temperatures
will modify well into the 60s as we go into the middle of next week.

&&

Aviation /03z Thursday through Monday/...
with a surface low passing well to our south and an upper level
level low moving over the region have lots of clouds and low
level moisture in place. Some showers and drizzle will linger
into the overnight hours with chances decreasing late.

Clouds heights will lower tonight with fog developing...widespread
MVFR conditions expected to dominate. However...IFR conditions are
expected at kpsf for a good chunk of the overnight. Gradually
improvement on Thursday with VFR developing during the afternoon
as the upper level moves off to the east and ridging builds in.

Light to calm winds overnight with a light north-NE flow shifting to
east-southeast as the day progresses Thursday.

Outlook...

Thursday night-Fri: no operational impact. No sig weather.
Friday night: moderate operational impact. Chance of rain showers.
Sat: high operational impact. Likely rain showers.
Sat night: moderate operational impact. Chance of rain showers.
Sun-Mon: no operational impact. No sig weather.

&&

Fire weather...
most areas did not receive much if any rainfall today. The only
exception was some areas in Vermont/the Berkshires and Connecticut
received around a quarter of an inch or more of rainfall.

Relative humidity values will approach 100 percent overnight and drop only to
around 50 percent by Thursday afternoon. There should be some
sunshine...mainly north and west of the capital region by Thursday
afternoon...with little or no sunshine southeast of Albany.

The wind will be calm or light from the north or northeast through
Thursday.

A full recovery expected again Thursday night.

Friday will have more sunshine and a south to southeasterly breeze
kicking up to 10-15 miles per hour afternoon. Relative humidity values will drop into the 40s.

Friday night...clouds will increase again and relative humidity values will recover
to between 75-90 persistent. A southerly breeze might
persist...limiting the formation of dew.

A soaking rain looks likely on Saturday with most areas expected to
receive a quarter inch or better.

Cooler...mainly drier weather returns Sunday.

&&

Hydrology...
a nearby upper level low will allow for some light rain showers
today into tonight...mainly for eastern and southern parts of the
region through this evening. Basin average rainfall will be two
tenths of an inch or less...and this looks to have little effect on
area rivers and streams...which have been running quite low lately
due to a lack of recent rainfall.

It will dry Thursday and Friday.

A more widespread rainfall is expected with the passage of a cold
front on Saturday. Most areas look to see at least a half inch of
rain with this system. This rainfall will not cause any hydrologic
issues...and will be beneficial to the region.

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...iaa/hwjiv
near term...iaa/hwjiv
short term...hwjiv
long term...lfm
aviation...iaa
fire weather...hwjiv
hydrology...hwjiv

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