Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
930 PM EDT Tuesday Aug 19 2014
high pressure will loosen its grip across the region as our weather
will turn unsettled for the later half of this week. A slow moving
and weak low pressure system will begin to impact our region
Wednesday with clouds and the chance for showers. The best chances
for wet weather will be along and west of the Hudson River
valley...especially across the western Adirondacks...western and
central Mohawk Valley and Catskills.
Near term /until 6 am Wednesday morning/...
as of 930 PM EDT...high clouds have worked into the area. IFR
11.9u-3.9u indicated that some patches of stratus have formed as
well across central New York into northern PA.
Dewpoints have been rising a little...and will do so overnight. Even
with only a partly cloudy sky...we believe overnight temperatures
needed to be raised a couple of degrees and therefore we did that
with this update.
Otherwise...only minor tweaking of the hourly grids including the
Overnight lows will generally range from 50 north and well east of
the capital region...to the middle and upper 50s over the remainder of
the area. It should remain completely dry.
Short term /6 am Wednesday morning through Friday/...
most of the short term period of weather will be under increasing
cloud cover...higher surface dewpoints and the raising the
probabilities for showers. The 12z model suite and ensembles are a
little higher with the overall quantitative precipitation forecast field along and west of the
Hudson River as precipitable waters climb 1-2 Standard deviations above normal.
The culprit was the upper low seen in the water vapor loop over the
u.P. Of Michigan. As this low tracks further east...the upper ridge over
northeast Canada strengthens. This will result in a squeeze between
this upper low and the surface ridge reattempting to build
As the case leading into this forecast...the best moisture
transport and isentropic lift remain along or west of the Hudson
River. As low level southerly flow increases through
Thursday...favorable upslope conditions for the Catskills and
dacks may experience enhance rainfall. We will place these areas
into likely probability of precipitation beginning later Wednesday and continuing into all
of Thursday. Quantitative precipitation forecast amounts could approach one inch but flood
concerns are low at this time per coordination with nerfc.
As for thunderstorm potential...while lapse rates are not too
conducive...the h850 Li/S /Aka showalter index/ drop to or just
below 0c over most of eastern New York. This will warrant the
continuation with the slight chance for thunderstorms.
As for temperatures through the period...MOS guidance is rather
close with average highs into the middle-upper 70s and some lower 80s
in the middle Hudson Valley...and overnight lows generally well into
the 50s and lower 60s.
Long term /Friday night through Tuesday/...
model guidance suggests that our area might be sandwiched between a
cutoff low to our south and east...and upper latitude middle level
ridge to our north throughout the extended period. This scenario
might keep our area dry with only some clouds from time to time. The
Canadian model does bring some showers into our region Saturday
night into Sunday but is really not supported by the latest European
and GFS extended model guidance.
We have followed wpc/S thinking and have kept our area rainfree
Saturday night through Tuesday. Temperatures look to be
seasonable...with highs 75-80 in the valleys...70-75 higher terrain
each day. Overnight lows looks to be mainly in the 50s...upper 50s
locally in the capital region.
Aviation /02z Wednesday through Sunday/...
no aviation weather related problem through much of the evening.
However...some patchy IFR mist (2sm br) might form at kgfl starting
around 04z. We have included a tempo for that to happen.
The crossover temperatures look to slowly increase into the lower
and possibly middle 50s overnight while a mainly clear sky could allow
temperatures to fall a little below these threshold at kgfl and
kpsf. We have gone with prevailing IFR mist (2sm br) at kgfl after
06z and after 08z at kpsf.
At the other two sites...kpou and kalb probably no real fog
issues...since overnight lows at those will generally be in the
upper 50s. Also...some stratus might form around kpou...probably
remaining just above the MVFR/VFR threshold.
At kalb...we placed mifg in the taf to reflect the possibility of
some fog...but likely not going to MVFR or certainly IFR.
After any possible low clouds/fog burn off between
11z-13z/Wed...expect VFR conditions once again...with scattered-broken clouds
with bases generally between 4000-6000 feet above ground level into the afternoon.
Showers will encroach the taf sites from northwest to southeast...so placed vcsh
in the tafs...starting at 17z at kgfl/18z kalb/19z kpsf and 21z
kpou. At this point showers on Wednesday afternoon appear unlikely
to drop conditions to MVFR or IFR.
The surface wind will be light or calm tonight...becoming S-southeast
5-10kts on Wednesday.
Wednesday nt - Thursday nt: moderate operational impact. Chance of rain showers.
Friday-Sun: no operational impact. No sig weather.
another dry night as high pressure remains in control. The
weather will turn unsettled for the middle of the week as a slow
moving and weak low pressure system impacts the region. The best
chances for storms will be to the west of the Hudson River
valley...especially across the western Adirondacks...and western
and central Mohawk Valley Wednesday afternoon and night.
Relative humidity values will recover toward 90 and near 100 percent
tonight. Minimum values Wednesday afternoon will be mainly in the
no Hydro problems are expected on the main Stem rivers at this time.
The weather will turn unsettled for the middle of the week as a
slow moving and weak low pressure system impacts the region. The
high 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. Model quantitative precipitation forecast has
increase with up to one inch basin average west of the Hudson
River. Due to low river levels at the present time...most of this
rain should remain within river banks.
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.