Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
200 am EDT Thursday Aug 21 2014
a slow moving weak low pressure system over the Great Lakes region
will impact the forecast area with showers and possibly a stray
thunderstorm as it drifts eastward overnight into Thursday night.
The low will track off the coast Friday. Moisture and a few stray
showers will linger Friday as cooler air filters in. This weekend...
high pressure will build over the eastern United States at all
levels of the atmosphere...with increasing sunshine...and warming
Near term /until 6 am this morning/...
as of 100 am...have expanded the area of likely probability of precipitation overnight to
reflect current radar trends. Have also expanded the area with
chance probability of precipitation further to the east. Otherwise no other changes made to
the current forecast.
Overnight lows will be milder than past nights...generally in the
Short term /6 am this morning through Saturday/...
a conveyor belt of showers and perhaps embedded thunderstorms will
move through on Thursday with the best forcing looking to be from
the capital region northward. Rain could be briefly heavy at
times...but right now not enough signals to add enhanced wording
the grids. We went with categorical probability of precipitation early in the Adirondacks
(orographics will likely assist with ascent there)...likely probability of precipitation
most other areas...except chance probability of precipitation well south of Albany where the
forcing and precipitable waters looks lower.
We are not necessarily expected a complete washout on Thursday...but
it will be damp and gray with the threat of showers just about any
Due to the canopy of clouds...we expect temperatures to only top in
the 70s...but it will be humid. If we were to get more breaks of
sunshine...instability (which we expect to be limited) would
increase. For now...just a chance of mainly non-severe
thunderstorms...(wind fields are fairly weak) but again more
sunshine could mean taller thunder.
Thursday night...the actual occlude front will cross the
region...keeping the likelihood of showers and possibly
thunderstorms around (lower chances again south). Temperatures will
cool a little more by daybreak Friday...ranging from the upper 50s
northwest...to middle 60s southeast.
Friday...the upper low opens and moves to our east.
However...initially there will be very little subsidence behind the
low so lots of clouds and a few additional showers and or pockets of
drizzle will likely linger...mainly across the higher terrain. For
this day...carried low probability of precipitation (30) for elevations 1000 feet or
higher...slight probability of precipitation (20) for valley areas.
Due to the clouds...and cold air advection...leaned with the (but
not all the way) the cooler met guidance. We look for highs only
within a few degrees of 70 on Friday...with most of the higher
terrain remaining in the 60s all day long.
Friday night...subsidence improves but we will likely get under an
inversion which could keep clouds and perhaps a little patchy around
at least into the evening. We have no mention of drizzle right now
but it is certainly possible. Lows Friday night dip back mainly into
the 50s...lower to middle 50s north and west of Albany...upper 50s from
By Saturday...ridging aloft looks to build southward over the region
and looks to scour at least some of the clouds away. A stray
afternoon pop up shower cannot be entirely ruled out but from this
Vantage Point...the threat of a shower on Saturday looks too low to
include in the grids for now.
Sunshine should help warm the column up a little. H850 temperatures
look to be around +12c which with normal mixing...would yield
surface temperatures in the middle to upper 70s.
Long term /Saturday night through Wednesday/...
through the extended period...tranquil weather will dominate the
forecast. A baroclinic boundary will continue to drift south of the
Delaware-Maryland-Virginia peninsula as we go into Saturday. An upper level ridge will
continue to build into the region with a more dominant presence as
we go into early next week. The orientation axis of the upper level
ridge SW to NE right over our area will provide continual tranquil
weather over the region. Upper level jet dynamics also favors large
scale surface divergence as our region will be in the left entrance
region of an 80-90 knots jet as supported by the latest 20/12z model
and probabilistic data. Our next chance of precipitation will be
past the end of the extended period with a frontal boundary which
will be updated accordingly as time gets closer to middle next week.
Winds will be light and variable under the high pressure and will
shift more to a southwesterly flow as the apex of the upper level
ridge will slowly slide east of our region as we go early next week
ahead of our next weather system. Temperatures will be around
average to slightly above average as we work toward the middle of
next week with highs ranging from the middle 70s to lower 80s.
Aviation /06z Thursday through Monday/...
low pressure and its associated frontal boundary will impact the
eastern New York and western New England taf sites the next 24 hours with
periods of showers and perhaps some isolated thunderstorms.
A mixture of VFR/MVFR conditions continue this morning at
kalb/kgfl/kpou/kpsf. The MVFR conditions are mainly from kalb-kpsf
northward where a few bands of showers continue to persist ahead
of the surface low and frontal boundary. The closed upper level low
over the central and eastern Great Lakes region will keep the showers
going much of the morning. Other showers will move into kpou between
09z-12z with lowering ceilings/visibilities to MVFR levels. Widespread MVFR
conditions are expected in the late morning into the early PM.
Some improvement to VFR ceilings/visibilities is expected from kalb south and
east in the early PM...but showers will move back in between 21z-00z
based on the latest NAM/hrrr. Some isolated thunderstorms are
possible...but the probs are still below 50 percent...so we will
let later taf issuances address the thunderstorm possibilities.
The winds will light and variable this morning...and then increase
from the southeast to south at 5-8 kts. Expect light to calm winds
Thursday night-friday: moderate operational impact. Chance of
Friday night-monday: no operational impact. No sig weather.
scattered showers this evening will become more numerous as we head
into Thursday. Showers will be numerous through the day
Thursday...except scattered south of Albany. We assigned a "wet
flag" to all the nfdrs except stonykill. Average basin rainfall is
expected to over a quarter of an inch in most areas. There could be
some thunderstorms as well containing localized downpours.
Scattered to numerous showers will persist Thursday night. It will
remain mostly cloudy and damp for Friday with a few lingering
By Saturday we should return to dry weather which could linger into
early next week.
Relative humidity values will be elevated the next could of days...generally over
60 percent...sometimes close to 100 percent. Afternoon relative humidity values
should return to more normal levels by Saturday...closer to 50
The wind will variable to south 5-10 miles per hour on Thursday...shifting to
the north or northwest 5-10 miles per hour on Friday.
no Hydro problems are expected on the main Stem rivers at this time.
The weather will turn unsettled for Thursday and Thursday night as a
slow moving and weak low pressure system impacts the region bringing
precipitable water air of around 1.5 inches. The highest quantitative precipitation forecast amounts will occur to
the west of the Hudson River valley...especially across the western
Adirondacks...and western and central Mohawk Valley including the
Catskills. Up to an inch of rainfall is possible Wednesday afternoon
through Thursday night mainly north and west of Albany. Due to low
river levels and fairly dry soil conditions...there will be little
if any impact on area streams and rivers.
However...any shower or thunderstorm through early this evening will
be slow moving and could produce localized rainfall amounts well
over an inch. This could result in significant ponding of water on
roadways and areas of poor drainage.
There could be some additional showers on Friday but these should be
lighter as the precipitable water values will drop back down closer to an inch.
Dry weather returns by 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.