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Area forecast discussion
National Weather Service Albany New York
807 PM EDT Tue Aug 20 2019

after a dry evening, clouds, scattered showers and thunderstorms
will approach our area from the southwest later tonight. Warm muggy
conditions, along with showers and thunderstorms are forecast for
Wednesday, with some storms possibly becoming severe. Some
additional rain showers are possible on Thursday as a cold front
slowly crosses the area. Fair and cool weather is forecast for
Friday into the weekend.


Near term /until 6 am Wednesday morning/...
as of 8:07 PM, fair weather continues across eastern New York
and New England. Just some high clouds bisecting the area.
Temperatures range from the 60s across the higher terrain to the
low 80s in the capital district. Winds are light and variable.
Expect fair weather to continue through midnight.

a warm front separating dew points in the upper 60s in southern
PA from dew points in the mid to upper 50s in central New York will
begin to lift northward toward the area later tonight, spreading
some clouds northeast across our area. Scattered showers and
thunderstorms may develop after midnight, especially southwest
of Albany. These storms will remain elevated with no severe risk
overnight. The increasing clouds will keep the fog threat down
overnight, especially south and west of Albany. Low temperatures
tonight will be mainly in the 60s with 50s southern Adirondacks.


Short term /6 am Wednesday morning through Thursday night/...
the weather will become active Wednesday into Wednesday night as
a cold front and associated mid-to-upper level short wave
approaches our area from the west. Wednesday morning will start
with scattered showers and maybe a few thunderstorms in
association with a warm front lifting north across the area. Dew
points will rise substantially with the passage of this front,
returning to the mid 60s to near 70 by midday Wednesday. A pre-
frontal surface trough will likely develop over central New York
during the day Wednesday ahead of a cold front moving east from
the Great Lakes. The trough will become the focus for
thunderstorm development by early afternoon. Increasing low-
level moisture will allow for MLCAPE to rise through the
morning. The amount of MLCAPE available to fuel the convection
on Wednesday afternoon will depend partially on how much
cloudiness in association with scattered early morning showers
manages to linger across the area. Sref plumes indicate most
likely MLCAPE values of 1000 to 2000 j/kg during the afternoon
Wednesday and this would certainly be sufficient for a round of
strong to severe storms given increasing mid-level flow and
shear associated with the approaching mid-level trough with deep
layer shear increasing to 30 to 35 kts during the afternoon.

The cams are strongly suggesting organized convection
in the form of short lines of storms Wednesday afternoon. Some
discrete storms are also likely and they will be rotating given
the moderately strong deep-layer shear and confirmed by cam
forecasts of enhanced updraft helicity. Strong winds will likely
be the primary threat with storms Wednesday afternoon, but
large hail associated with discrete supercells is also possible.
Model soundings are also showing 0-1 km shear values to 30 kts
with 0-1 km helicity well over 100 S-1. Based on this, it would
seem possible that a few tornadoes could also occur over the
northeast Continental U.S. Where storms can interact with enhanced low-
level shear associated with boundaries left over from previous
or ongoing convection. Based on all of the above the Storm Prediction Center has put
our entire area in a slight risk for severe storms Wednesday.

Storms will be moving east of the area Wednesday night, followed
by a more quiet pattern for the rest of the week with much lower
humidity. A few isolated showers may occur Thursday with the
passage of a mid-level cold pool, but low-levels will be drying
out which should keep shower activity to a minimum. High
temperatures Thursday will range from the 70s over higher
terrain to near 80 in the Hudson Valley.


Long term /Friday through Tuesday/...
a mainly dry and seasonable weekend is anticipated as a positively
tilted upper level trough moves through the area and Canadian high
pressure takes control through early next weekend. Northerly flow
should keep temperatures a few degrees below normal and keep
humidity levels low through the weekend. High temperatures generally
should be pleasant in the 70s with overnight lows in the 50s before
temperatures gradually warm heading into early next week, rising
back towards normal around 80. The potential for rain increases
towards the middle of next week as the next system approaches from
the Midwest. Read on for details.

Our cold front from Thursday should be just south of forecast area
on Friday, around NYC/southern New England but the guidance still
shows potential for a shortwave to ride along the boundary Friday
morning. Should this happen, the southern areas of the Mid-Hudson
valley and northwest CT could see some showers, mainly Friday morning. For
now kept a dry forecast to be in line with the neighboring wfos but
we will monitor trends and adjusts pops upwards, if necessary.

Otherwise, our positively tilted trough will progress southward from
Canada into the northeast Friday into Saturday. The base of the
trough looks to feature a 500mb shortwave with an associated cold
pool which guidance suggests moves right over through eastern New York and
western New England during the day on Saturday. Since 700mb moisture
on most members of the latest guidance is very dry, the models are
not producing quantitative precipitation forecast. However, we will monitor trends as the cold pool
aloft could generate a few scattered diurnally driven showers. For
now we maintained a dry forecast which is in line with the
neighbors. Temperatures under the northerly flow should fall a
degrees shy of normal for late August and stay in the low to mid 70s
with low humidity. The higher terrain in the Adirondacks, Catskills
and greens could even stay in the upper 60s. Overnight lows should
turn chilly in the 50s (40s higher terrain) as clear skies and calm
winds lead to good radiational cooling.

The GFS and CMC-New Hampshire show heights rising on Sunday as strong upper
level ridging and an expansive/rather strong ~1025hpa surface high
from southern Canada kicks our shortwave out to sea. The European model (ecmwf)
continues to linger the shortwave over New England but this seems to
be the outlier. Expecting mainly sunny skies on Sunday under the
strong surface high pressure with temperatures slightly warmer than
Saturday in the mid - upper 70s. Again, cool temperatures overnight
in the 50s expected once again Sunday night.

High pressure stays in control Monday with similar temperatures
anticipated. The next chance for precipitation along with an
increase in temperatures and humidity looks to arrive in the middle
of the week. The latest 12z guidance still shows discrepancies in
timing and intensity of precipitation so continued to only show
slight chance probability of precipitation for the Monday night and Tuesday period.


Aviation /00z Wednesday through Sunday/...
VFR conditions will prevail across all taf sites through
midnight tonight (21/04z) as high pressure slides off the New
England coast.

As a warm front slowly progresses northward tonight, clouds increase
from south to north after 04z/21. There is potential for
showers and storms at all taf sites towards morning which is
covered with a prob30 group from 09z/21 to 12z/21. In addition,
any taf site that experiences precipitation could easily see
MVFR or even a period of IFR conditions due to low clouds
and/or fog. For now, we allowed the reduced ceilings and
visibility in the prob30 group to illustrate this potential.

MVFR ceilings may linger into the morning hours, especially at sites
that experiences rain overnight.

Ceilings may improve/break towards 17z/18z which is why however,
additional showers and an increased threat for thunderstorms,
some severe with potential for damaging winds, are expected
during the afternoon.

Winds should stay southerly and under 5kt overnight before
becoming south-southwesterly after sunrise and increasing to
5-15 kt. Strong gusty winds are possible in and around


Wednesday: high operational impact. Likely rain showers...tsra.
Wednesday night: moderate operational impact. Chance of rain showers...tsra.
Thursday: low operational impact. Slight chance of rain showers.
Thursday night: low operational impact. Slight chance of rain showers.
Friday: low operational impact. Breezy no sig weather.
Friday night: no operational impact. No sig weather.
Saturday: no operational impact. No sig weather.


Fire weather...
dry, warm weather will continue this evening, then clouds and
scattered showers and thunderstorms will develop late tonight as
a warm front approaches the area. Showers and thunderstorms will
become more likely during the day Wednesday and especially
Wednesday afternoon as a cold front approaches from the west. Relative humidity
values Wednesday afternoon will fall to 55 to 65 percent. A
drier and milder airmass returns Thursday into the weekend,
allowing for good drying conditions. Relative humidity values Thursday will
fall to 45 to 55 percent. Winds will be generally 10 kts or
less, except briefly higher near thunderstorms Wednesday.


an anomalously moist airmass will spread back into the region
tonight into Wednesday with precipitable water values increasing to 1.50-2.00
inches. Numerous showers and thunderstorms are expected to
develop in the moist airmass Wednesday as moderate instability
develops, and any storm will be capable of heavy rainfall.
Though a strong wind field will result in fast moving storms,
there is potential for repeated rounds of storms which will lead
to the threat of urban/poor drainage flooding and possible
isolated flash flooding.

Mainly dry weather is expected Thursday into the weekend.

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...
New York...none.


near term...snd/mse
short term...mse

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