Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Albany New York
121 am EDT Wednesday may 27 2015
high pressure off the eastern Seaboard will funnel warm
and humid air across the region through much of this week. Isolated
to scattered showers and thunderstorms will be possible during the
afternoon and evening hours today...as an upper level disturbance
and a surface trough move across the region. A cold front will move
through on Thursday with a brief break with dry weather for Friday.
Near term /until 6 am this morning/...
as of 121 am EDT...a very warm and humid air mass is over the
forecast area this morning with temperatures in the 60s to m70s. Variably
cloudiness continues as middle and high clouds continue to stream in
from the west/SW associated with the convection over eastern Ohio and western
PA. The short-wave associated with the upstream convection...and
its associated surface trough will be the focus for strong to possibly
severe convection later today /mainly this afternoon/. With this
update have increased temperatures a few degrees in the immediate capital
region with the clouds and srly surface flow persisting. Also backed
the probability of precipitation off later tonight based on the latest hrrr layer column
maximum reference trends. An isolated pop-up showers is possible over the northern
tier...southern dacks...Lake George region....srn Vermont. One occurred
around an hour ago. The probability of precipitation start to increase again in the later
morning as the showers and thunderstorms associated with the surface
trough and upper level disturbance approach from the W/SW.
Short term /6 am this morning through Thursday night/...
severe weather potential for most of the region on Wednesday...
The National Weather Service Storm Prediction Center has placed
most of our region within the slight risk category on Wednesday.
The combination of a very moist atmosphere with precipitable waters climbing in
excess of 1.75 inches...surface dewpoints well into the 60s...some
gradual height falls aloft and pre-frontal trough axis for
enhancing low level convergence to interact with increasing
buoyancy as sbcapes climb toward 2k j/kg...severe thunderstorm
potential is on the increase. A departing upper jet with entrance
region dynamics and shear profiles increasing to around 30kts
should result in some organization. The main question will be how
much insolation we will receive as the NCEP model suite does
suggest ample moisture...although...models do tend to
overestimate. So we will add some enhanced wording to the
forecast/grids at this time. As for temperatures...MOS guidance is
warmer on the met MOS than the mav MOS...we will favor the warmer
side of the guidance envelope.
The frontal axis is prognosticated to be over western New England during
the evening with a decrease in coverage and intensity of the
convection at that time. However...the secondary cold front and
main upper trough has yet to approach so we will keep chance probability of precipitation
in the grids overnight and into the day on Thursday. In
fact...trends in the 12z guidance are a little faster with these
features which will allow for the chance of showers to diminish
through the day Thursday. As for Thursday highs...an ensemble
approach of the h850 thermal fields suggest cold advection will be
occurring through the day with less than 10c for the dacks. We
will therefore keep temperatures between 65-70f for these areas
and keep 70s to lower 80s for the remainder of the region. Winds
will shift to the west-northwest with an increase in magnitudes as
gusts well into the 20kts are expected.
Subsidence increases quickly Thursday night with rising surface
pressures and a much drier atmospheric column advecting into the
region. The result will be clearing skies...diminishing winds and
a more comfortable night as lows dip back into the 50s for most of
Long term /Friday through Tuesday/...
above normal temperatures Friday-Sat should trend back to near...or
possibly even a bit below normal by sun-Tue...as the East Coast
upper level ridge deamplifies with the approach of shortwave energy
from southern Canada. As it deamplifies...a cold front will cross the
region sometime late Sat or early sun. This should bring showers and
thunderstorms to the region. Depending on additional shortwave
energy rounding the base of the incoming upper level trough
approaching the Great Lakes/southeast Canada...it is possible that the cold
front slows down and/or a wave develops along it and tracks south of
the region. Should this occur...showers or even a period of steady
rain could linger in the wake of the front for sun into early
Monday...especially across southern areas.
So...initially expect dry and warm conditions for Friday as upper
level heights rise once again. Humidity levels should be
moderate...so despite maximum temperatures reaching the middle/upper 80s in
portions of the Hudson River valley...apparent temperatures should mainly
remain below 90. Friday nt/Sat am should remain dry...but warm...with
min temperatures only falling into the Lower/Middle 60s for most lower
elevations...and 55-60 across higher elevations.
For Sat-Mon...the aforementioned cold front should approach from the
northwest later Sat...and slowly press south and east Sat nt into
early sun. Will indicate high chance to low likely probability of precipitation for
showers/thunderstorms for Sat afternoon and night...gradually tapering
downward from northwest to southeast on Sunday. However...given some uncertainty
on how far south and east the front reaches...and whether a wave of
low pressure develops along the boundary...will keep slight chance to
low chance for most central and southern areas into Monday. Maximum temperatures
should be rather warm Sat...with temperatures reaching 85-90 in valleys and
Lower/Middle 80s across higher elevations. Dewpoints should rise into
the lower 60s...so apparent temperatures should be fairly close to the
actual high temperatures of 85-90. Sat nt/sun am mins should fall into the
50s to lower 60s...then expect cooler maximum temperatures for sun into
Monday...with maxes mainly in the 60s to lower 70s sun...and mainly 60s
for Monday. Sun nt/Monday am mins should fall into the 40s to lower 50s.
Monday nt-Tue...still some uncertainty as to how far south the
aforementioned frontal boundary reaches. Will keep slight chance to low
chance probability of precipitation...highest across southern areas for this time period. Monday
nt/Tuesday am mins should fall into the middle 40s to lower 50s...with Tuesday
maximum temperatures reaching 70-75 for most valleys...and 65-70 across higher
Aviation /05z Wednesday through Sunday/...
high pressure anchored off the eastern Seaboard will maintain a warm
and humid southwest flow across the region through Wednesday. A weak
upper level disturbance may trigger scattered showers...and possibly
an isolated thunderstorm or two into early this evening...especially for
kpou and kpsf.
A stronger upper level disturbance will trigger showers and some
thunderstorms for Wednesday afternoon.
The best chance for showers or even a few thunderstorms this
evening will be at kpou and kpsf. There could be brief periods of
MVFR/IFR ceilings/visibilities within any heavier downpours.
After sunset...any lingering showers/thunderstorms should weaken.
Depending on how much rainfall occurs this afternoon/early
evening...there could be areas of MVFR or borderline IFR ceilings/visibilities
later tonight...with the best chance at kpsf.
On Wednesday...after any patchy low clouds/fog burn off...expect
mainly VFR conditions through 18z/Wed. Showers and thunderstorms may
develop after 18z/Wed...with increasing chances thereafter. For
now have placed -shra in tafs after 18z.
Winds will remain from the south to southwest tonight at mainly
5-10 knots. On Wednesday...winds will be south to southwest and
increase to 8-12 knots...with gusts of 15-22 knots once again by late
Winds will be stronger...and variable in direction in and near any
thunderstorms on Wednesday.
Wednesday to Wednesday night: moderate operational impact. Chance of
Thursday: moderate operational impact. Chance of rain showers...tsra.
Thursday night: low operational impact. Slight chance of rain showers.
Friday to Friday night: low operational impact. Slight chance of
Saturday: moderate operational impact. Chance of rain showers...tsra.
warm and humid with chances for showers and thunderstorms...mainly
during the afternoon into the early evening.
Minimum relative humidity values Wednesday and Thursday afternoons in the 50s.
no widespread Hydro problems expected this week...however
thunderstorms will be capable of producing heavy
downpours...mainly on Wednesday.
The U.S. Drought monitor has much of eastern New York and western
New England in the d1 category...which is considered moderate
drought at this time.
Warm and humid with chances for showers and thunderstorms...mainly
during the afternoon into the early evening. The better and more
widespread chances are expected Wednesday afternoon int0 the evening.
Precipitable water values of 1.75+ inches are expected so storms
will be capable of producing heavy downpours.
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.