Area forecast discussion
National Weather Service New York New York
435 am EDT sun may 19 2013
Synopsis...
low pressure developing over Quebec will track east dragging a
warm front across the area late tonight. The low will continue
across the Canadian Maritimes with its cold front dropping through
the area on Tuesday. The front then remains in close proximity to
the area before lifting back north as a warm front on Thursday. A
cold frontal passage occurs late in the week or early weekend.
&&
Near term /through tonight/...
low pressure developing over Quebec early this morning will track eastward
today with its attending warm front moving through the area
tonight. Meanwhile a stationary frontal boundary extending from
the Middle Atlantic States to the Midwest won't move much
today...then dissipate tonight.
Weak warm air advection has caused light rain to lift into NE New Jersey and metropolitan New York
early this morning. 00z model guidance as well as hrrr are in good
agreement and indicate a cloudy and wet day as this area continues
to expand and gradually move across the area. Some uncertainty in timing
of warm frontal passage tonight...so probability of precipitation may be on the high side after 06z
although increasing Theta-E would imply abundant low clouds and
areas of fog and drizzle once it moves through....highs will only
reach the lower to middle 60s across the area...which is 5 to 10
degrees below normal. Lows tonight will be near to slightly above
normal levels in the middle to upper 50s.
&&
Short term /Monday through Tuesday/...
the region will be warm sectored on Monday as a cold front
approaches from the north. Expect at least partial clearing to
occur...but this will determine how unstable we will get. The
front will align with the flow aloft which is relatively weak
(10-20kt) and could lead to training of slow moving thunderstorms.
Precipitable waters are forecast to be around 1.5 inches which is around 175% of
normal and could cause some minor urban flooding issues. Confidence
in all of this is low at this time.
Convection diminished Monday evening with the front dropping through the
area. High uncertainty just how far S the boundary gets...so have
kept the chance probability of precipitation for afternoon showers and thunderstorms on Tuesday...mainly north and
west of NYC.
Temperatures will be around 5 degrees above normal both Monday and Tuesday with
a noticeably more humid airmass in place as well.
&&
Long term /Tuesday night through Saturday/...
predictability issues during this time period have to do with the
interaction of eastern Canadian troughing and central US troughing
this week. The interaction of these two energies will determine the
magnitude of East Coast ridging for the midweek. Models signaling a
return to East Coast troughing for the weekend as East Coast ridging
builds offshore into the western Atlantic.
Showers and thunderstorms could continue Tuesday night...with
indications of a wave of low pressure tracking east along the
sagging frontal boundary. Moisture pooling and steering flow
parallel to the surface boundary would present a flash flood
threat if this pattern materialized.
Then for the middle-late week period the interaction of the earlier
mentioned upper features will be critical to the location of the
frontal boundary. Latest guidance has strongly converged on the
backdoor cold front pushing south through the region Tuesday
night...and then back north as a warm front on Thursday. If the
front does pass south...onshore flow and clouds would likely drop
maximum temperatures to seasonable or slightly below seasonable levels for
Wednesday...several degrees cooler then forecasted.
Regardless of where the warm front ends up...if this boundary
remains close to the region...shortwaves at the southern edge of the
westerlies may allow for convective complexes to form and track west
to east along this boundary through the middle-late week period. Any
mesoscale convective system would bring the threat for heavy rain and severe weather.
By the end of the week...models are signaling varying degrees of
phasing of the Midwest upper trough and eastern Canadian upper
trough. This will have a cold front passing through the region
sometime Friday into Sat...with shower and thunderstorm activity
finally exiting in it wake. Degree of phasing of upper energies will
determine timing and activity along the front.
&&
Aviation /09z Sunday through Thursday/...
high pressure passes to the east today as a frontal boundary
remains to the south.
Ceilings may bounce around from MVFR to VFR this morning...and
trends will need to be watched. Do expect on and off light rain
this morning for most terminals. Kgon may not see rain until this
afternoon.
Please see individual terminal forecasts for specifics and best
deterministic forecasts...but MVFR ceilings likely prevail through
much of the afternoon with a lower probability of ceilings under
1 kft.
Do expect IFR or lower ceilings/visibilities by evening.
Winds generally southeast...with higher sustained winds during the
daytime hours.
Outlook for 06z Monday through Thursday...
Tonight...IFR or LIFR conditions...in periods of light rain and
fog.
Monday...improvement to VFR by middle to late morning. Scattered
showers...and isolated thunderstorms with brief MVFR conds possible
in the afternoon.
Monday night...MVFR or lower conditions likely with low clouds and
fog.
Tuesday-Thursday...chance of MVFR of lower conditions in showers
and thunderstorms.
&&
Marine...
high pressure passes east of the waters today. As it does
so...southerly winds will increase to around 20 kts...mainly across
the ocean waters.
By tonight...low pressure passes to the north of the waters. Winds
turn toward the southwest through Monday. A frontal boundary
approaches from the north by Tuesday...and winds lighten and could
shift around to the northeast or east depending on how far south
the front moves.
Eventually this front is expected to move back to the north
resulting in a wind shift to the south once again by middle week.
Wave watch has been running high...but latest guidance has captured the
trends and slowly builds seas today. May undercut ocean sea forecasts
slightly early in the week...but seas remain rather rough through
Monday on the ocean waters due to persistent southerly fetch and
swells.
Will follow wind direction and speed climatology for sea/wave forecasts
across Li sound and the surrounding harbors and bays.
&&
Hydrology...
up to 1/4 inch of rainfall is expected through tonight.
Periods of showers and thunderstorms are possible Monday through
Friday...which would be capable of producing locally heavy rainfall.
There is currently a low threat of flash flooding from organized
shower thunderstorm activity during this time period.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 PM EDT Monday for anz353-355.
Small Craft Advisory from noon today to 6 PM EDT Monday for
anz350.
&&
$$
