Area forecast discussion
National Weather Service Albany New York
1038 am EDT Thursday may 23 2013
Synopsis...
a cold front will move slowly across the region this
afternoon into tonight...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 with fair and dry weather.
&
Near term /through tonight/...
as of 1030 am EDT...a cold front remains west of the region over
the Ohio Valley and the eastern Great Lakes region this
morning...with a prefrontal trough moving across west-central New York and
PA. This prefrontal trough in the warm sector has produced scattered
showers over the southern dacks and west-central Mohawk Valley...and other
showers have blossomed over the lower to middle Hudson Valley in
advance of the middle level short-wave. Probability of precipitation have been readjusted to
likely values over the southern tier.
The satellite picture is cluttered with cloud cover which will
inhibit widespread convection at this time. Dewpoints remain in the
u50s to m60s...so any holes in the cloud cover may allow sbcapes
values of 500-1000 j/kg to develop. The middle level lapse rates look
poor at this time...but the better upper level jet dynamics arrive
in the late PM and evening /our forecast area gets in the right
rear quadrant of the jet streak/...and the deep shear strengthens to
40-50 kts...especially from the capital region northward between 18z-
00z. The amount of heating and surface destabilization remains the
question for the possibility of severe thunderstorms. No enhanced
wording in the zones and grids yet. Some multicells evolving into
lines and bands look possible based on the model soundings and
hodographs.
The Flash Flood Watch remains up for the northern half of the forecast
area. Zonal ffg values in the 1/3/6 hour time frame have lowered to
1-2 inches over portions of the capital region and southern Vermont due to
the heavy rains the past few days. The slow movement of the
boundary coupled with the anomalous precipitable water values could produce some
flash flooding in a few spots.
Temperatures look on track with maxes in the 70s to around 80.
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. 00 UTC 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 /15z Thursday through Monday/...
some low clouds and fog lingering for an hour or two at kpou and psf
this morning with MVFR/IFR conditions. Otherwise...some partial clearing
over eastern New York and western New England should last to around
16z...when showers and thunderstorms could develop and approach
the taf sites. The one exception is kgfl where a few showers may
impact the terminal between 12z-14z.
Since current shower activity is well west...and
the timing of development and tracking of thunderstorms is so
uncertain...just putting generic thunderstorms in the vicinity at all sites between 16z and
22z...as more specific timing will be provided in later taf
issuances. Steadier rain and/or thunderstorms should be around the
airports by 22z-24z...so lowered conditions at all taf sites to
MVFR ceilings and visibilities in showers for this evening and
tonight. Again...uncertainties in how the thunderstorms will
evolve later this afternoon and evening...so just indicating
showers. Later taf issuances will address the thunderstorm timing.
Winds are south to southwest at around 10 knots...with a few gusts
around 15 knots early this morning...and should continue through the
day. Winds should trend to southwest and west after midnight tonight
as the cold front tracks through.
Outlook...
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 through Friday morning for nyz032-033-
038>043-047>054-082>084.
Massachusetts...none.
Vermont...Flash Flood Watch through Friday morning for vtz013>015.
&&
$$
Synopsis...Snyder/wasula
near term...NAS/wasula
short term...Snyder
long term...Snyder
aviation...NAS/wasula
fire weather...Snyder
hydrology...Snyder
