Area forecast discussion
National Weather Service Albany New York
616 am EDT Thursday may 23 2013
Synopsis...
a cold front will push slowly across the region today and stall
along the Atlantic Seaboard Friday. Low pressure will organize...intensify
and linger on this front near the New England coast much of the
weekend. High pressure will build into the eastern Great Lakes
Memorial Day and drift over our region into midweek.
The period will start warm and humid with showers and scattered
thunderstorms...which will give way to chilly temperatures and
showers for the weekend.
&&
Near term /through tonight/...
some partial clearing over eastern New York and western New England this
morning. Showers still mainly west of the region...and made some
adjustments to the timing of the showers...and eventually
thunderstorms through the day. Added heavy rain with the Flash
Flood Watch in effect. So...other than the minor changes to
rain chances and sky cover...not much change to the forecast
through today.
Previous afd below...
Most of the convection has exited or dissipated early this morning
but there is a weak low level dew point boundary across central
New York...possibly the old outflow boundary from previous convection.
Additional rain and embedded thunderstorms in western PA/New York should
track into the region later this morning and afternoon. The rain
and thunderstorms could get enhanced as it tracks into our
region...after some daytime heating since we should have some
periods of sun through middle and high clouds this morning to warm
temperatures well into the 70s to around 80.
The instability should not be quite as impressive as the last couple
of days...but still...some isolated severe weather could be
possible. There may be more of a threat for some localized flooding
as the axis of deepest moisture tracks through the region...and with
increasing upper dynamics...and a tightening boundary layer thermal
gradient with strengthening frontogenesis. Issuing a Flash Flood
Watch for areas that have seen the most rain in the last couple of
days...which would be areas along and north of the Mohawk Valley
through southern Vermont...including the capital district. The
current low level dew point boundary may become the focus for the
enhanced convection later today...will keep an eye on that.
Showers and thunderstorms should evolve into just an areas of steady
rain late tonight as the low level cooling gradually spreads
east...and the strengthening upper feature begins to cut off and
track along the northeast coast tomorrow into the weekend.
&&
Short term /Friday through Sunday night/...
the trend that began appearing in the model suite two days ago...is
now consensus for the weekend. Ooutc GFS/NAM/ECMWF have cold front
stalling along I-95 corridor by Friday morning. Sharp 500hpa trough from
qb to Appalachians moving east...as series of short waves dive
southward into it and cut it off.
During Friday it cuts off over the Middle Atlantic States...coastal
cyclogenisus ensues off Long Island...and the slowly deepening surface
low and the 500hpa cut off becoming vertical off S new eng coast
Sat...then drift slowly north Sunday into Gulf of Maine.
Needless to say this is going to feel more like a late October
weekend in the northeast. During Friday -shra will transition to
periods of rain in Anna type front between surface front and 500hpa axis.
At same time gradient between 1031mb high over Midwest...and
deepening surface low off Long Island will result in a 14mb wind
gradient across New York state Friday & Sat. North winds will increase to 10-20 miles per hour and
result will be a rainy raw Friday and Sat.
GFS quantitative precipitation forecast of 1-2.5 inches...European model (ecmwf) 0.75 to 1.0 Friday night through
Sat nt.
During the day Friday temperatures will just hold steady near
morning lows...before falling during Friday afternoon in strong cold air advection. They
will fall further Friday nt into the 40s with 30s in western
periphery. Sat highs will be in the 50s and low 60s with clouds
and periods of rain. Maximum min temperatures in guidance are probably not
much use...as alot of non-diurnal effects going on Friday into Sat.
Will use 3 hourlies and let maximum/mins fall out.
Of note is that the western edge of the precipitation/clouds with this
system will be a very sharp transition...somewhere on the western
periphery of fca. Precipitation could be spotty or non-existent along west
edge of fca...and there may be periods of thinning clouds which
would allow temperatures to drop to near freezing during mornings.
Sun the vertical system will continue to drift through the Gulf
of Maine...into the Maritimes sun nt. The GFS has clouds and -shra
dim Sunday with increasing sun along west prtns of fca. The European model (ecmwf) keeps it
cloudy and wet into sun evening. The o6utc NAM/GFS are a tad more
progressive with this system and has clouds and rain only from hud
valley east Sat...and the system clearly exiting region Sat nt.
For now forecast reflects 00utc model suite timing...with skies finally
clearing sun nt across fca as 500hpa ridging builds into the Great Lakes
and surface high builds into east Great Lakes. But if the emerging trend
continues on later runs...conditions might noticeable improve
across fca for Sunday.
&&
Long term /Monday through Wednesday/...
after a soggy Holiday weekend...the cutoff and surface system depart
as ridge at 500hpa builds into Great Lakes and surface high builds from
Great Lakes to Carolinas Monday. This pattern will shift east as large
500 hpa ridge builds over east USA and surface high settles off the East
Coast. Temperatures will return to near normal Monday..and build upward
into the week. Fca in warm air advection regime throughout. The GFS brings a
warm front and chance -shra/thunderstorms late Tuesday and Wednesday...while European model (ecmwf) keeps it
dry into Thursday. Only 6 members of the gefs are in line with the
operational run precipitation Wednesday...the rest of their plumes are flat
lined. Wpc holds precipitation off till end of efp on Thursday. So for now will
have a fair warm efp...with a very noticeable warming trend to above
normal temperatures. Will populate with wpc from midnight shift.
&&
Aviation /10z Thursday through Monday/...
most of the shower and thunderstorm activity is over for the night.
So...with varying layers of clouds across the region...most areas
are MVFR/VFR...although as any low clouds break up...and middle and
high clouds thin to some degree...some new development of low clouds
and fog could occur between 07z-11z. With light winds at kgfl and
kpou ... area of strong winds above the surface...acknowledged
wind shear through the early morning hours...until the winds aloft
weaken toward sunrise.
Some low clouds and fog could linger beyond 11z...but will look at
trends later to see if it needs to be extended after 12z. Once the
early morning low clouds and fog lift...there should be mixed middle
and high clouds through the morning before new convection develops
along a cold front. Just leaving the thunderstorms in the vicinity at all sites for the
afternoon until everything develops and more specific timing and
associated brief reductions in visibility and ceilings California be
assessed.
Outlook...
Thursday-Thursday night...MVFR with IFR possible. -Shra/-tsra likely.
Friday...mainly VFR. Chance -tsra mainly in the am.
Sat-Mon...VFR/MVFR. Chance -shra.
&&
Fire weather...
no fire weather concerns into Sunday. Periods of rain...moderate
to heavy at times will continue into the Holiday weekend.
Relative humidity values will increase to 85 to 100 percent tonight...and
Friday night...and lower to 45 to 60 percent Thursday afternoon
and only 60-80 percent Friday afternoon.
Winds will generally be south at 5 to 10 miles per hour today...turning north
Friday and increasing to 10 to 15 miles per hour. .
&&
Hydrology...
European model (ecmwf) and GFS very aggressive in bringing heavy rainfall into County Warning Area
into the Memorial Day weekend. Operational European model (ecmwf) and GFS produce
2.50 to 5.0 inches of rain in County Warning Area into Sunday. Gefs show average
of 2.0 inches through weekend with 8 members pushing in excess of
3.5 inches.
First challenge for heavy rain will come with todays slowly moving
front. Eastern County Warning Area and central County Warning Area have seen heaviest rain over
the last two days and would appear to be the region where flash
flood threat is at highest. A Flash Flood Watch will be issued for
these areas.
&&
Aly watches/warnings/advisories...
CT...none.
New York...Flash Flood Watch from noon EDT today through Friday morning
for nyz032-033-038>043-047>054-082>084.
Massachusetts...none.
Vermont...Flash Flood Watch from noon EDT today through Friday morning
for vtz013>015.
&&
$$
Synopsis...Snyder
near term...NAS
short term...Snyder
long term...Snyder
aviation...
fire weather...Snyder
hydrology...Snyder
