Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
144 am EDT Tuesday Apr 21 2015
a wave of low pressure will move across the region overnight.
Weak high pressure will follow for Tuesday. A cold front will pass
on Wednesday...allowing for a cool air mass to settle in late this
week into the weekend.
Near term /until 6 am this morning/...
low pressure over east central New Jersey will mv east toward eastern Long
Island near the axis of the greatest 3 hour pressure falls. This will
keep the warm front just south of most of the local area.
Thunderstorms developed near the triple Point of the approaching low east
of the occluded front and along and north of the warm front.
They produced brief heavy downpours along with frequent lightning
strikes as they quickly moved NE across the region.
The leading edge of drier air was advecting east across central
PA...near the back edge of enhanced infrared clouds.
A dense fog advisory remains in effect for land and sea until 6 am
once the boundary mvs east of the region.
Short term /6 am this morning through 6 PM Wednesday/...
shortwave is forecast to move through in the morning with
stronger lift generally over the northern zones. Have kept a
chance for showers in there. Otherwise...turning partly to mostly
sunny. Highs are a MOS blend.
Long term /Wednesday night through Monday/...
500 mb low currently spinning over Minnesota/WI will slowly track eastward through
the week...then stall over Quebec and northern ME this weekend.
The approaching 300 mb jet on Wednesday appears it should produce enough
upper divergence to allow for the development of showers. In
addition...there should be some low level convergence as the associated
cold front tracks through. As a result...indicated scattered showers in the forecast.
As this system slides offshore Wednesday night...the precipitation ends and the
remainder of the forecast period is dominated by cyclonic flow aloft
and marginal middle level lapse rates. The steepest lapse rates will be north
of the County Warning Area across northern New England. Will therefore forecast fair weather
Thu-Mon. Scattered-broken clouds...especially during the day...as temperatures hit
convective which is prognosticated to be in the upper 40s to 50s per GFS
bufr data. There could even be periods of overcast skies as the cumulus
flattens due to decent shear. Cant rule out some isolated
sprinkles...but the probability is too low at this time to include in the forecast.
Temperatures a blend of guidance and generally blw climatology through the
extended. Highs could be a little warmer than forecast on Wednesday
depending on the amount of cloud cover and speed of the developing
showers ahead of the front.
Aviation /06z Tuesday through Saturday/...
rain showers/thunderstorms and rain moving across the terminals through 09z. No winds or
hail...but there will be locally heavy rain and lightning
associated with any storms.
Otherwise...LIFR/vlifr conds in fog/drizzle until cold front
begins to work its way across the terminals in the morning. Conds
improve to VFR behind the passage of the cold front.
VFR with a gusty west flow develops by midday. Gust up to 25 knots
Outlook for 06z Tuesday through Saturday...
Wednesday-Wednesday night...MVFR possible in the afternoon and
night in -shra. SW-west-southwest winds g20-25kt possible.
Thursday-Friday...mainly VFR...with low chance MVFR in any
-shra. West-northwest winds g15-20kt possible.
dense fog advisories in effect on all waters for visibility below 1 nm in fog.
Seas remain elevated on the ocean through at least Tuesday afternoon.
West flow for Tuesday mainly below Small Craft Advisory...but there could be a few
afternoon near-shore gusts to 25 knots especially across the waters
in vicinity of NYC and the Long Island South Shore.
Winds and seas will be close to Small Craft Advisory levels Wednesday through the weekend.
The best chance for reaching criteria will be on the ocean Wednesday-Thursday
in vicinity of a cold front.
heavier showers/thunderstorms could produce localized 1/4 to 1/2 inch rainfall
amts overnight. Otherwise...areal quantitative precipitation forecast is less than 1/4 inch overnight.
Around a quarter inch of rain is possible on Wednesday as a cold front tracks
through the hsa.
CT...dense fog advisory until 6 am EDT early this morning for
New York...dense fog advisory until 6 am EDT early this morning for
New Jersey...dense fog advisory until 6 am EDT early this morning for
Marine...dense fog advisory until 6 am EDT early this morning for
Small Craft Advisory until 6 PM EDT this evening for anz350-