Area forecast discussion
National Weather Service Albany New York
143 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/...
line of convection moving across north New York state...crossing our northern
most counties. This activity is healthy...but not severe. Further
south and area of rain showers will move across mhwk valley capital district.
Most of the activity continues to weaken. Its impacts in grids
were largely addressed in 10pm Wednesday update.
In this update temperatures were adjusted slightly and winds are 5 to 10
kts above forecast...and adjustments were made. Otherwise a warm humid Summer
like night with -shra and thunderstorms north.
Previous discussion...the concern for the overnight is the convection over
eastern Great Lakes and across eastern PA and central New York and the
potential for heavy rainfall with some portions of the forecast
saturated from heavy rains Tuesday night and Wednesday afternoon.
Precipitable water values from albany's 00z sounding is 1.51
inches and buffalo's 1.48 inches. The hrrr-3km 15 minute composite
reflectivity is handling the current convection placement and
intensity pretty well. Have used this for probability of precipitation and timing into the
early morning hours. The convection is expected to weaken as it
moves east mainly after midnight and we are seeing some signs of
this. Have showers likely with scattered thunderstorms with heavy
rainfall and gusty winds. The Storm Prediction Center has much of
forecast area in slight risk...may mention of strong storms in our
hazardous weather outlook.
Cold front slowly approaches the region on Thursday...not clearing
County Warning Area until Friday morning.
Slowly moving front will provide environment for bouts of heavy
rain through the period. Precipitable waters remain in the 1.5 inch range
through Thursday...only slowly dropping off into Friday.
Approaching upper level jet tomorrow brings right rear quadrant into
forecast area for the afternoon. See Hydro section for discussion
on flood risk.
Severe potential tomorrow is not clear cut now. Model cape looks
to be in the 1000 j/kg range with bulk shear respectable in the
30-40 knot range. Middle level lapse rates are relatively weak at
5.5c/km. Storm Prediction Center has region in see text. From today/S Vantage Point
that looks appropriate.
&&
Short term /Friday through Sunday night/...
the trend that began appearing in the model suite two days ago...is
now consensus for the weekend. GFS/NAM/12utc European model (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 become 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 hourlys 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. Clouds and -shra should dim
Sunday with increasing sun along west prtns of fca. Skies will finally
clear sun nt across fca as 500hpa ridging builds into the Great Lakes
and surface high builds into east Great Lakes.
&&
Long term /Monday through Wednesday/...
high pressure should begin to build in Monday and especially
Tuesday. It appears the high should hold on for Wednesday.
Temperatures are expected to moderate toward seasonable levels
Monday with the help of sunshine but still be below normal by
around 5 degrees.
The growing season is underway across the middle Hudson Valley...
greater capital district...Lake George Saratoga region...the Mohawk
Valley...eastern Catskills...Taconics...Berkshires...Bennington and
eastern Windham counties Vermont and Litchfield County. It will start on
may 25th for the southern Adirondacks and western Windham County.
&&
Aviation /06z 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 Saturday. 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
Thursday night...and lower to 45 to 60 percent Thursday afternoon.
Winds will generally be south at 5 to 10 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
5-7.5 inches of rain in County Warning Area into Sunday. Gefs show average of 2.25
inches through weekend with 4 members pushing in excess of 3
inches. While not quite ready to accept totals of Euro and
GFS...enough guidance available to at least warrant potential of
heavy rain threat in severe weather potential statement. First challenge for heavy rain will come
tomorrow with 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.
Will monitor closely for at least potential of flash flood or
Flood Watch Thursday into weekend.
&&
Aly watches/warnings/advisories...
CT...none.
New York...none.
Massachusetts...none.
Vermont...none.
&&
$$
Synopsis...Snyder
near term...iaa/okeefe/Snyder
short term...Snyder
long term...iaa
aviation...NAS
fire weather...okeefe
hydrology...Snyder
