Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
649 am EDT Monday Jul 6 2015
weak high pressure builds offshore today. A warm front approaches
from the southwest tonight...then moves into the tri-state on
Tuesday. A cold front approaches from the west Tuesday
night...then tracks across the area Wednesday into Wednesday
night. The front stalls just to the south on Thursday as a weak
wave of low pressure moves along it. High pressure builds late
week and into next weekend.
Near term /until 6 PM this evening/...
a deep layered ridge has its axis slowly cross the area today.
Associated subsidence should be sufficient to keep things dry.
However an isolated shower or sprinkle cannot be completely ruled
out over far west/SW zones this afternoon.
Latest satellite trends suggest that middle and high clouds will
continue to build over the region today.
For highs today a blend of mixing down from 975-875 hpa per BUFKIT
soundings...ecs/met/mav guidance...and NAM 2-meter temperatures
was used. Highs should be near to slightly below normal.
Short term /6 PM this evening through 6 PM Tuesday/...
as deep layered ridge continues to slide offshore...should
moisten low levels sufficiently to warrant slight chance to
slight chance probability of precipitation over mainly the northwest 1/2 of the County Warning Area late tonight
in response to weak low level warm advection. For lows tonight...a
blend of mav/ecs/met guidance and NAM 2-meter temperatures was
used...with values forecast to be around 5 degrees above normal.
Forcing ahead of 700-500 hpa shortwave that moves into the region
late Tuesday warrants likely probability of precipitation over the northwest 1/3 of the County Warning Area and
chance probability of precipitation elsewhere.
Noting forecast convective available potential energy generally of 1000-1500 j/kg - slightly lower
over east Long Island/far southeast CT...showalters forecast to be mainly 0
to 2 indicating low level instability as well warrants a chance of
thunder as well. However with bulk 0-6 km shear of only 20-25
knots...risk of strong to severe storms is fairly low but cannot 100
percent be ruled out.
For highs Tuesday used a blend of ecs/met/mav guidance...with NAM
2-meter temperatures and a mix down from 975 to 900 hpa per BUFKIT
soundings. Highs should be a few degrees above normal.
Long term /Tuesday night through Sunday/...
a trough of low pressure lifts to the north Tuesday night and
Wednesday as surface cold front approaches from the west. This front
will be nearly parallel to upper steering flow...so it will be slow
to move through on Wednesday. Model timing is similar with frontal
Any leftover showers/thunderstorms Tuesday night depart or weaken. MOS temperatures
are close...and seasonably warm readings are expected.
The cold front remains over the area late Wednesday...and probably
clears the eastern zones by midnight. Will maintain high chance
coverage for now...with scattered showers/thunderstorms Wednesday. Heavy
rain is possible with this slow moving activity...with precipitable water over 2
inches along the front. The concern for heavy rain and training of
cells could lead to at least minor urban/small stream flooding.
Most model solutions forecast the front to settle to the south
Thursday...with some timing differences noted with a wave of low
pressure riding along it. Believe the low passes to the south by
Thursday or Thursday night...with weak high pressure building in
Will maintain low chances for showers Thursday into Friday...with a
dry forecast thereafter...or until possibly later Sunday as next
Temperatures should average right around normal levels through the period.
Blended forecast database with new gridded MOS and wpc guidance.
Aviation /12z Monday through Friday/...
weak high pressure will remain over the area today. A warm front
will approach from the southwest tonight.
VFR. Some patchy fog is possible across outlying terminals overnight
with MVFR visibilities.
Wind will be generally light from the south to southwest to light
and variable inland. Southeast-S sea breezes 8-10 knots develop at the
terminals Monday afternoon at all but kswf.
New York metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts
can be found at:
http:/www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: no unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: localized IFR ceilings to the east at kfok
should have no terminal impact.
Outlook for 06z Tuesday through Friday...
late tonight...MVFR or lower conditions possible late via low
clouds...patchy fog and scattered showers.
Tuesday...chance of thunderstorms with MVFR or lower conditions at times...
especially from NYC metropolitan north/west.
Tuesday night...MVFR/IFR conds likely in fog.
Wednesday...chance of thunderstorms with MVFR or lower conditions at times.
Thu-Fri...chance of showers with MVFR or lower conditions
a relaxed pressure gradient over the region will keep winds 10 knots
or less through Tuesday...with the exception of 10-15 knots winds
with occasional gusts to 20 knots in the New York bight region Tuesday
afternoon due to the sea breeze. Seas will remain below Small Craft Advisory
levels through Tuesday as well.
Patchy fog could impact the waters late tonight and Tuesday
morning...bring visibilities to 1 to 3 nm...and possibly below 1
nm at times.
Southerly flow persists ahead of a slow moving cold front Tuesday
night and Wednesday. Then as the front passes nearby and
stalls...winds should lighten as they shift to the northwest briefly.
With a weak pressure gradient in place...the winds may shift back
around to the S/SW Thursday.
As a wave of low pressure moves along the front later Thursday and
Thursday night...relatively light winds may become
variable...depending on the exact track of this low. Overall...sub
Small Craft Advisory conditions are anticipated for the middle to late week period.
Ocean sea forecasts were based on forecast database and new wave
watch output...which seemed quite reasonable. Wind climatology was
the basis for sea/wave forecast for the non ocean waters surrounding
generally around 1/4 inch or less of rain is expected late
tonight and Tuesday. With highest amounts generally west of the
Hudson River. However...with precipitable waters forecast to be
between 1.75-2 inches...there is the potential for locally heavy
rainfall with any stronger convection. Localized minor flooding
of urban and poor drainage areas would be possible if this were to
Heavy downpours with slow moving showers/thunderstorms are possible
Wednesday into Wednesday evening. As such...at least localized urban
and poor drainage flooding...with a low chance of flash
flooding...is a possibility Wednesday. Will continue to highlight
this in the severe weather potential statement from Fairfield and Nassau counties on
long term...precipitable water