Area forecast discussion
National Weather Service New York New York
502 am EDT Wednesday may 22 2013
Synopsis...
a stalled front will move back north as a warm front today. A cold
front will then slowly approach from the west...then pass through
Thursday night into Friday morning. Canadian high pressure will then
build in for the Memorial Day weekend and early next week.
&&
Near term /until 6 PM this evening/...
continuing to monitor an area of showers and thunderstorms across
southwestern Connecticut early this morning. Convection appears
outflow-dominated which suggests eventual weakening.
Otherwise...similar day on tap today with plenty of clouds and fog
in the morning and chance pop for showers and thunderstorms during the
afternoon and evening.
&&
Short term /6 PM this evening through 6 PM Thursday/...
showers and thunderstorms this afternoon and evening. Convection should
be scattered at best with only marginal instability in place.
Showers and thunderstorms will become more widespread as the upper
level trough and associated surface cold front approach the area
late tonight with activity continuing through Thursday.
Highs today will be in the middle 80s...except along the coast. With
highs on Thursday in the middle to upper 70s.
&&
Long term /Thursday night through Tuesday/...
main issue for the start of this period is the interaction of the
eastward moving central US trough with several northern stream
shortwaves rotating around a persistent eastern Canadian trough. The
complex interaction is resulting in timing and amplification issues
as this trough slides to the East Coast. GFS continues to be slower
than all the guidance Friday into Sat as the upper low negatively tilts
and closes off as it approaches the Middle Atlantic States. This would
result in a prolonged period of Post-frontal rain into Sat. With
majority of 00z operational guidance trending a bit slower...have
also trended a bit slower with precipitation gradually tapering off Friday
afternoon into Friday night. Subsequent model trends will need to be
closely monitored to see if the frontal system slows down even
further.
As for the sensible weather...cold front slowly crosses the region
Thursday night into Friday. Although instability will likely be falling to
marginal levels Thursday night...widespread shower and thunderstorm
development is likely with abundant moisture streaming ahead of
approaching shortwave energy/cold front. The severe threat should
diminish into Thursday night...with heavy rain the main threat
with precipitable waters about 2 Standard above normal and steering flow nearly aligned
with the slow moving front. Will have to monitor the extent of
interaction of the front with a subtropical plume streaming up the
coast Thursday night...which if closer to the coast would enhance
the flash flood threat. Convective threat should decrease in
the wake of the cold front...but potential wave development could
prolong light to moderate Post-frontal stratiform rains through
Friday into Friday night...particularly across eastern sections.
Average basin rainfall should be close to an inch...with localized
higher amounts.
A drying northwest flow set ups Friday night into Sat with strong cold advection.
High pressure builds across the Great Lakes and into the Middle
Atlantic States through early next week with temperatures several
degrees below seasonable levels.
&&
Aviation /09z Wednesday through Sunday/...
a back door cold front will move across the area terminals early
this morning...then lift to the north later this morning.
As the back door cold front pushes through...ceilings and
visibilities are lowering to IFR and could fall as low as vlifr at
the coastal terminals especially between 10z and 12z. Conditions
improve early Wednesday morning...mainly between 13z to 15z. Wind
will be light from the south through the night then increase to 10
to 15 knots during Wednesday.
Showers and thunderstorms will be possible after 16z mainly north
and west of the New York terminals...however due to low confidence
of timing and placement...have not included any showers or
thunderstorms in the tafs.
..NY 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: amendments expected through 15z for changing
flight categories in stratus and/or fog.
Klga fcster comments: amendments expected through 15z for changing
flight categories in stratus and/or fog.
Kewr fcster comments: amendments expected through 15z for changing
flight categories in stratus and/or fog.
The afternoon kewr haze potential forecast is yellow...which implies
slant range visibility 4-6sm or greater outside of cloud.
Kteb fcster comments: amendments expected through 15z for changing
flight categories in stratus and/or fog.
Khpn fcster comments: amendments expected through 15z for changing
flight categories in stratus and/or fog.
Kisp fcster comments: amendments expected through 15z for changing
flight categories in stratus and/or fog.
Outlook for 06z Thursday through Sunday...
Wednesday night...scattered rain showers and thunderstorms possible. IFR possible in fog
and stratus.
Thursday-Friday...numerous rain showers and thunderstorms possible. IFR possible in
fog and stratus.
Saturday...residual rain showers behind a cold front with MVFR. Becoming VFR
with northwest winds increasing to 20-30kt.
Sunday...VFR with northwest winds 20-25kt.
&&
Marine...
dense fog across the waters will continue through this morning.
Shallow back door cold front should bring southeast-east winds today to the
eastern-most ocean waters...also Long Island Sound and the bays of
Long Island. Otherwise...S-SW sub Small Craft Advisory winds should continue
through tonight. Seas slowly build this afternoon to Small Craft Advisory
levels and remain above Small Craft Advisory levels through Thursday.
A cold front will move east across the area waters late Thursday
through Friday afternoon...with high pressure building through the
weekend. Winds should gradually fall below marginal Small Craft Advisory levels
Thursday night...with Small Craft Advisory seas on the ocean likely remaining above
Small Craft Advisory criteria through Saturday morning with residual southerly
swells. Undercut wavewatch by a foot during this time as it was
slower bringing the frontal system across the area. There is though
some uncertainty with the seas due to the timing differences amongst
the models.
&&
Hydrology...
scattered showers/thunderstorms this afternoon will be capable of producing
locally heavy rainfall...with the best chances north/west of NYC.
Total basin average quantitative precipitation forecast for Wednesday-Thursday could be 1/4 to 1/2 inch...with
locally higher amts in thunderstorms.
Showers and thunderstorms ahead of an approaching cold front late
Thursday into Friday morning...should produce average basin
rainfall amounts close to an inch...with localized higher amounts.
There is the potential for training of thunderstorms which could
result in flash flooding. Additional lighter rainfall amounts are
likely Friday...possibly into Friday night.
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...dense fog advisory until 10 am EDT this morning for anz330-335-
340-345-350-353-355.
Small Craft Advisory from 5 PM this afternoon to 6 PM EDT
Thursday for anz350-353-355.
&&
$$
