Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
324 am EDT Sat Jul 26 2014
high pressure along the Atlantic Seaboard will drift out to sea
today...with a return southwest flow of increasing moisture for
the weekend. Our weather will turn unsettled with bouts of showers
and thunderstorms from late tonight into Monday. A weak frontal
system will cross the region tonight and Sunday morning...with a
stronger cold front and low pressure system expected to move
through Sunday night and Monday. Midweek will bring below normal
temperatures as a large Canadian high pressure system settles into
the Great Plains and builds east.
Near term /through tonight/...
for today expect mainly dry conditions with a south to
southwesterly flow developing across the forecast area as high pressure slides
off the eastern Seaboard. There will be a tendency for middle and
high clouds to increase especially late in the day...but it should
remain dry. Expect highs in the middle 70s to middle 80s with south to
southwest winds at 5 to 10 miles per hour.
For tonight...short wave energy will start to move eastward
across the Great Lakes overnight. A pre-frontal trough
accompanying the energy aloft tonight...will provide low level
focus so will mention high chance to likely probability of precipitation with scattered to
numerous showers and thunderstorms. The storms overnight are not
expected to be severe. Expect overnight lows in the upper 50s to
middle 60s with winds light and variable.
Short term /Sunday through Tuesday night/...
a large 500hpa cutoff over qb will dominate this period as a
series of short waves wrap around its base...culminating with a
powerful short WV Monday...that carves out a full latitude 500hpa trough
over the eastern Continental U.S....more reminiscent of Oct than late July.
Sunday morning a weak warm front will be along the New York/new eng border to a
weak surface low in the St Lawrence. While a weak cold front front trails from
low into east PA. At 500hpa a short WV is over fca. Between 15-18utc
these systems exit fca along with their associated -shra. This leaves a
warm humid air mass with dew point in 60s across fca...and mix of clouds
and sun for the rest of the day. This is certainly a recipe for
During the afternoon convective available potential energy build to 1000-1800 j/kg on GFS...1000-2500
j/kg on NAM. 700-500hpa lapse rates incg to 7c in NAM...but only
5.5 on GFS. 0-6 km bulk shear increasing to 25kt (nam) to 35kts
All guidance shows a bias toward the southeast prtns of fca for highest convective available potential energy/lapse/shear
rates. GFS model soundings indicate little to no capping by afternoon...but
the NAM shows cap around 650hpa...but with sufficient sun this will
be overcome late in the day. So if the sun comes out...this cape
will be tapped in scattered severe thunderstorms...particularly southeast.
Is what isn't as pronounced as pvs runs is the presence of upper
dynamics. The NAM/GFS/Gem all have one short WV exiting fca in late
morning...and a second mvng into EPA/New Jersey during the evening...with the
bulk of this energy staying S of fca...or in S periphery of fca.
Given this scenario best chances for severe thunderstorms is southeast prtns of
fca. Elsewhere marginal for severe storms...but could still be a
concern...but it will be isolated pulse type and not particularly
organized. Storm Prediction Center has outlooked most of fca excpt far north for day 2.
Otherwise a warm humid day with highs in the upper 70s to middle 80s
south. Sun nt this short WV over EPA/New Jersey lifts NE into fca...as
500hpa trough sharpens in response to strong jet maximum and its associated
vorticity mvng into east Great Lakes. In response surface cyclone ensues over east
Great Lakes and tracks NE by Monday Morning. Sun nt -shra/tsms will increasing in
coverage across fca becoming widespread by morning. A much stronger cold front
in the St. Lawrence Valley will be drawn into this deepening cyclone.
On Monday morning this cold front is from rut to New York i88 Corridor. North of it precipitation
will evolve into an Anna front rain/shra...while along it and to
its S & east...wm sector cape values of 1000-1700 j/kg will continue
to allow embedded thunderstorms to form ahead and near the cold front. This cold front
will slowly drag east through the area Monday with -shra/thunderstorms likely.
To its north temperatures will remain in the 70s...reaching the 80s to its S
and east Monday.
Monday night the 500hpa short waves & surface low will race NE into
qb...carving a full latitude trough over the east Continental U.S.. this drags the
cold front to the coast...and -shra will dim as cooler air filters in
on brisk north winds.
Tuesday morning surface high pressure over Great Plains mvs east. Cold front
slides out to sea...scattered -shra end. With 500hpa trough axis still
west of fca...much of fca will remain in dry slot Tuesday and Tuesday nt
as cooler air mass filters into fca. Temperatures will be 5-10 degree below
normals with highs upper 60s to upper 70s. Tuesday nt will see lows
middle 40s to middle 50s under mainly clear skies.
Long term /Wednesday through Friday/...
period begins with unusually strong 500hpa cutoff over qb and
tailing trough over most of east Continental U.S.. over time the cut off lifts NE
in westerlies over north Canada....and a piece of energy breaks off
and retrogrades SW to miss valley by end of period as Bermuda high
pressure ridge back builds toward east Seaboard. While the models suite
is fairly in agrement...there is some spread in solutions.
Fca remains largely on east side of the 500hpa trough as it retreats
north...and for the most part remains in the dry slot associated with this
feature in the GFS. The European model (ecmwf) keeps the cut off closer and
further S...and several passing short waves combined with diurnal
heating produce isolated to scattered -shra mainly west and over hir terrain.
The only other feature of note..is as period ends GFS has Bermuda
high backing into East Coast...along with a coastal type front may
result in increasing S flow...dew point and threat of thunderstorms Sat afternoon S tier.
Hpcs overnight package reflects pvs European model (ecmwf) and current GFS. It will
be a period of pc conds...and temperatures 3-5 degree below normal with warm
days and cool nights. Isolated -shra cant be ruled out...particularly
over hir terrain...but for the most part it will be a dry comfortable
Aviation /07z Saturday through Wednesday/...
surface high will continue to shift offshore overnight with a return
southwest flow developing today. Mainly VFR conditions are expected
through the end of the taf period ending at 06z sun. The exception
will be some fog at kpsf and kgfl late in the overnight period
resulting in MVFR/IFR conds. Otherwise it be mainly clear overnight with
few-scattered cumulus developing Saturday. Expect batches of cirrus to
stream overhead with middle level clouds moving in late in the
afternoon into the evening.
Light to calm winds overnight becoming south to southwest today at 5
to 10 knots...then becoming light and variable again this evening.
Sunday night: moderate operational impact. Chance of rain showers...tsra.
Monday: high operational impact. Likely rain showers...tsra.
Monday night: moderate operational impact. Chance of rain showers.
Tuesday: moderate operational impact. Chance of rain showers.
Tuesday night: no operational impact. No sig weather.
Wednesday: no operational impact. No sig weather.
Wednesday night: no operational impact. No sig weather.
Thursday: slight chance of rain showers.
high pressure will slide offshore tonight...setting up a return
southwest flow with increasing clouds and humidity into the weekend.
Our weather will turn unsettled with bouts of showers and
thunderstorms from late Saturday through the rest of the weekend. A
weak frontal boundary will cross the region Saturday night and early
Sunday...with a stronger cold front and low pressure system expected
to move through Sunday night through Monday. Midweek will bring
below normal temperatures.
Relative humidity values will increase to 85 to 100 percent
tonight...the drop to minimum values of between 40 and 45 percent
Saturday afternoon. Relative humidity values will increase to around 90 to 100
percent Saturday night.
Winds tonight will be light and variable. Winds will become
south-southwest around 10 miles per hour on Saturday...becoming southerly
around 5 knots Saturday night.
dry weather will persist through Saturday morning or afternoon.
Showers and scattered thunderstorms will become likely Saturday
night through Sunday night. Some of the showers and thunderstorms
could produce locally heavy rainfall...especially on Sunday...which
may result in minor flooding of urban areas...poor drainage
locations and low lying area.
Additional scattered showers and thunderstorms will be possible
through middle week...as an upper level trough settles in over the
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.