Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Albany New York
118 PM EDT Monday Aug 3 2015

Synopsis...
a cold front will move into the region this evening and move to
the coast by morning. It may trigger strong to severe thunderstorms
late this afternoon and evening. An upper level disturbance will
linger over Quebec through much of the week...bringing cooler air
into our region...and triggering scattered showers during the
afternoon and evening Tuesday and Wednesday...mainly north of i90
and over the higher terrain.

&&

Near term /through tonight/...
some severe thunderstorms are possible this afternoon into
tonight...

As of 930 am EDT...most of the cin is mixed out...a fine line/pre
frontal trough is from slk-bgm and appears it will be the focus of
convective development this afternoon. Ahead of it skies have been
sunny...dew point are in the lower 60s and temperatures are in the 80s with a
few more hours of diurnal heating to go. At 500hpa the first
short WV rotating around the base of the large qb/ont cut off is
in the east Great Lakes and mvng slowly east with the best dynamics north or north of
fca.

Mu cape values are now in the vicinity of 1000-1500 j/kg...middle level
lapse rates are around 6.5c. Scattered thunderstorms will form along this line
during the afternoon hours...which will be come strong and some may be
severe.

This scattered-broken line of storms will progress in bowing segments
across the region during the afternoon and evening. See latest Storm Prediction Center disc. Pre-
frontal trough will reach svt-ridge by evening...and drift east as
activity dim and atmos stablizes. Overnight this boundary will
shift east as the main cold front mves into the east Great Lakes...and then to
coast by daybreak.

With cyclonic 500hpa flow across the region and cooling at 500hpaclouds
will increase north toward daybreak. Minds will remain in the 60s.

&&

Short term /Tuesday through Wednesday night/...
Tuesday...the cold front will be near western New England by
daybreak. The surface dewpt boundary will still be progressing east
across eastern New York. The NAM is advertising alot of instability for Tuesday
with a deeply sheared environment. The GFS has less again...but
there is a small area of high instability from the the Mass Pike
south and east into northwest CT. Storm Prediction Center does have Litchfield city clipped by
the marginal risk. Middle level lapse rates will be around 6.5c/km
with another short-wave rotating around the upper level low. Will
have to monitor for some strong storms with gusty winds and small
hail /no enhanced wording yet/...especially from the capital
district south and east. Low- level cold advection will be ongoing
during the late morning into the PM. Downsloping effects off the
eastern Catskills/eastern dacks may allow maximum temperatures to get into the middle
and u80s in the Hudson River valley/capital region. Expect m70s to
l80s in most other locations...except over the southern dacks/southern
greens where some u60s to l70s are possible in the cold advection
regime...as h850 temperatures lower to +10c to +16c from northwest to southeast over
the forecast area by the late PM. A slight to low chance of thunderstorms
will continue until sunset.

Tuesday night...with the loss of the diurnal heating the scattered
showers and thunderstorms will diminish quickly. The isolated-scattered
showers may linger the longest over the southern dacks. Lows will
generally be in the middle 50s to around 60f with some u40s to l50s
over the southern dacks/southern greens. Humidity levels will be quite
comfortable.

Wednesday-Wednesday night...the forecast area will still be under the influence of
the upper level low centered over S-central Quebec. In the cyclonic
flow another piece of short-wave energy will swing across upstate
New York and New England. The best chance of isolated-scattered showers due to the
cyclonic vorticity advection will be north and west of the
capital region. H500 temperatures will be around -15c to -18c from aly
north and west. The h500 heights are about 2-3 Standard devs below
normal based on the latest gefs for Wednesday. H850 temperatures will be 1-2
Standard devs below normal. Highs on Wednesday will be in the m60s to l70s
over the mountains...and middle and u70s in the valleys...with a few 80f
readings near kpou. Clearing skies and light to calm winds will
allow for cool night for the first week of Aug...with high
pressure building in. Lows will range from the u40s to m50s over
the forecast area.

&&

Long term /Thursday through Sunday/...
below normal temperatures expected with highs mainly in the 70s.

Guidance is in general agreement that a cold front should stall to our
south late in the week somewhere across the middle Atlantic region. The exact
location is very much in question at this time. Guidance is also in
general agreement that a large upper level low will move north of the
Canadian Maritimes late in the week leaving the Great Lakes region and
northeast under a longwave trough though the weekend.

The differences in the models are on how they handle short wave energy
moving through the longwave trough and its impacts the position of the
stalled boundary and the strengthen of an area of low pressure that is
expected to form and move eastward along the boundary. Guidance have not
been showing any consistency. At this time...the operational run of the GFS
keeps the boundary...low and precipitation shield to our south while the
European model (ecmwf) brings a soaking rainfall to the area late Thursday night and Friday
to mainly to areas south of Interstate 90.

Have favored guidance from the weather prediction center to maintain
forecast consistency and have chance probability of precipitation for areas south of I-90 late
Thursday night and Friday. As for the weekend...have mainly slight chances
probability of precipitation since the timing of additional short waves in highly uncertain.

&&

Aviation /18z Monday through Saturday/...
a period of showers and thunderstorms is expected to impact the
taf sites as a cold front approaches the region late this afternoon
and evening. Conditions will be favorable for the possibility for
some strong to severe thunderstorms.

VFR conditions are expected well into the afternoon hours with
conditions lowering to MVFR with the convection late this afternoon
and evening. IFR conditions will be possible but have not been include
in the tafs at this time. Have addressed the threat of the storms with
a prob30 group including thunderstorms. Fog is expected to develop late
tonight as the cloud cover decreases and winds lighten up.

At kalb...southerly winds will continue and are expected to become gusty.
At the other taf sites...a south to south-southwest wind will develop
which will become gusty ahead of the cold front during the day. A lighter
southerly flow is expected in the wake of the storms as we head into the
overnight hours.

Outlook...
Tuesday night-Thu: no operational impact. No sig weather.
Thursday night-Fri: low operational impact. Slight chance of rain showers.

&&

Fire weather...
a cold front will approach from the eastern Great Lakes
region today with a chance of showers and thunderstorms. The cold
front will be east of the region Tuesday morning...but an upper
level disturbance will continue the threat for scattered showers
and thunderstorms Tuesday afternoon...as cooler and drier air will
arrive for Wednesday.

The relative humidity values will lower to 40 to 60 percent this afternoon...and
increase to 75 to 100 percent tonight. The relative humidity values will lower to
35 to 55 percent Tuesday afternoon.

The winds will be from the south to southwest at 10 to 20 miles per hour
today...and south to southwest at 5 to 15 miles per hour tonight. The winds
will be form the west to northwest at 10 to 20 miles per hour on Tuesday with
the front moving across the region.

&&

Hydrology...
mainly dry weather is expected this morning with showers and
thunderstorms expected this afternoon and evening as a cold front
approaches and crosses the region. The storms will be capable of
producing locally heavy downpours as precipitable waters rise up to around 1.5
inches ahead of the boundary. The heavy rainfall could lead to
some minor flooding in poor drainage and low lying areas. Also
some sharp within bank rises would be expected on streams...creeks
and some small rivers.

Isolated to scattered showers and thunderstorms are expected on
Tuesday especially during the afternoon as the upper level trough
axis approaches and passes over the region. Rainfall amounts may
range from a tenth to a third of an inch with locally higher
amounts.

A trend towards drier weather will occur on Wednesday...and
continue until Friday morning.

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...Snyder
near term...Snyder/wasula
short term...wasula
long term...iaa
aviation...iaa
fire weather...bgm/wasula
hydrology...bgm/wasula

National Weather Service Glossary of Abbreviations