Area forecast discussion
National Weather Service New York New York
138 am EDT Sat may 25 2013
Synopsis...
low pressure on a cold front just east of the local area will
deepen as it moves into the Gulf of Maine on Saturday...then
weakens Saturday night. Low pressure lifts to the Canadian
Maritimes early in the week as high pressure builds. A warm front
will approach by middle week...moving briefly to the north...then
dropping back to the south by late week.
&&
Near term /until 6 am this morning/...
forecast of occasional rain showers overnight on track based on latest
radar trends. Did lower forecast lows a tad based on latest
observation trends - with now Lower-Middle 40s expected.
Upper level trough closes off into the region overnight with
surface cold front pushing farther east of the region. Cold air
advection will continue behind the front. The boundary layer
winds increase and keep more mixing conditions in place.
&&
Short term /6 am this morning through 6 PM Sunday/...
the upper level low moves across and east of the region on
Saturday while deepening with a dip in the jet stream moving
across our region. A much cooler than normal day is in store
along with showers developing again with the diurnal instability
and cold pool aloft.
Surface low develops starts to deepen in the Gulf of Maine. Low
level jet of around 40-50 knots develops near 925 mb and with
expectation of good mixing the maximum gust potential could reach
40-45 knots. This is most pronounced with the GFS BUFKIT soundings
with NAM BUFKIT keeping it more in the 35-40 knots range. Increased
wind gusts a good 10 knots above previous forecast package and is a
few kts below criteria but there is a chance that some sites could
see gusts in the 40-45 knots range Saturday...probably middle to late
afternoon into early evening.
Also of note is the cold pool aloft and weak instability shown by
MUCAPE of almost 100 j/kg. Therefore...isolated thunderstorms
cannot be ruled out and with the much colder temperatures aloft...hence
some showers or thunderstorms could produce small hail.
A mav/met/nam12 blend used for highs but adjusted downward with
highs mostly in the upper 50s to near 60 in urban northeast New
Jersey.
For Saturday night...advections decrease in efficiency with upper
level low stacking and surface low in Gulf of Maine halting in
further deepening...losing structure. Winds will begin to lighten.
Drier conditions will begin to materialize with probability of precipitation gradually
lowering through the night. Colder night than Friday night with
mav/met blend used once again. Lows forecast into the low to middle
40s.
There is a moderate risk of rip currents at Atlantic Ocean beaches
on Saturday.
&&
Long term /Sunday night through Friday/...
models in general agreement into early next week as upper closed
low opens...eventually lifting to the northeast. High pressure
ridge builds...with it/S axis remaining to the west through much
of the week.
At the surface...low pressure departs as high pressure builds. A warm
front then approaches Tuesday from the west or southwest.
By middle week...there are differences on handling of surface features with
subtle differences noted aloft. Will follow wpc with the forecast at
this time...which leans toward European model (ecmwf). It does appear that showers
and possible thunderstorms could ride along the front...in the northwest
to southeast upper flow as the axis remains to our west. However...not too
sure how far north any of this activity will propagate...but will
need to introduce probability of precipitation late Tuesday through Tuesday night.
Weak low on the front moves east Wednesday as the front lifts to the
north. Vorticity advection rides along the northwest/southeast upper flow...with
potential higher coverage for showers/thunderstorms mainly to the north
Thursday. Low pressure riding along the front moves east by
Friday...allowing the front to drop south across the area. As
such...at least minimal probability of precipitation warranted Wednesday...with slight
chance at best Thursday and Friday.
Temperatures still run below normal Sunday as cold pool slowly loses it/S
grip across the northeast. Then near normal temperatures of 50s at night
and 70s during the day will slowly warm up by late week as ridge
axis makes eastward progress. Temperatures about 5 degrees above
normal...or around 80 to the Lower/Middle 80s away from the south
facing shores looks reasonable per wpc/ec MOS late week.
&&
Aviation /06z Saturday through Wednesday/...
low pressure near Cape Cod will deepen over the Gulf of ME tonight and
Sat.
Expect a strong northwest flow on the backside of the deepening offshore
low through the forecast period. Winds ramping up during the day on
Sat with gusts 35-40kt. In the after. Moderate to high confidence of a
wind direction right around 320 true.
Ceilings will generally be MVFR overnight...then gradually increase to
VFR by around noon Sat. NYC and lower Hudson Valley terminals may
fluctuate between MVFR and VFR tonight.
There is the potential for small hail in rain showers Sat with cold temperatures
aloft.
Outlook for 00z Saturday through Wednesday...
Sat night...areas of MVFR with a chance showers. Northwest gusts around
35 knots.
Sun...VFR. Northwest gusts 30-35kt.
Monday...VFR.
Tue-Wed...MVFR or lower possible in the vicinity of a warm front.
&&
Marine...
minor changes made to reflect the latest trends in observations
and guidance. Forecast appears on track.
Gusty northwest winds will result in small craft conditions tonight and
gales on Saturday in response to low deepening in the Gulf of
Maine. The winds begin to subside late Saturday night as that low
weakens. Seas on the ocean remain elevated in the 5-8 feet range for
the short term through Saturday night.
Low pressure passes well to the northeast Sunday and Monday as high
pressure builds. Gusty northwest flow backs in time to the west or
southwest as speeds diminish. A warm front approaches the waters
Tuesday and Wednesday with south to east winds prevailing this time frame.
Rough ocean seas per wave watch iii early Sunday will subside as the
storm departs.
&&
Hydrology...
additional rainfall will be around 0.25 to 0.5 inch with locally
higher amounts possible through Saturday night. No flooding
problems are anticipated.
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.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 am EDT early this morning for
anz330-335-338-340-345-350-353-355.
Gale Warning from 6 am this morning to 6 am EDT Sunday for
anz330-335-338-340-345-350-353-355.
&&
$$
Synopsis...jm/pw
near term...maloit/jm
short term...jm
long term...precipitable water
aviation...jc
marine...maloit/jm/pw
hydrology...jm/pw
