Area forecast discussion
National Weather Service Albany New York
740 PM EDT Thursday may 23 2013
Synopsis...
a cold front will slowly move southeastward across the region
this evening and overnight...then stall along the Atlantic
Seaboard Friday. Low pressure will develop...intensify...and
linger on this front near the New England coast through 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 eventually returning.
&&
Near term /until 6 am Friday morning/...
as of 730 PM EDT...bands of showers with downpours continue to
surge northward into a limited area of southeast Dutchess and much
of Litchfield CT...with additional activity noted upstream on kokx
radar. Thus will continue the Flash Flood Warning for the next
several hours despite lack of reports to this point. Otherwise...a
broken line of showers and a few thunderstorms with downpours
continue to track eastward across the southern Adirondacks and
down the Mohawk Valley...associated with a pre-frontal surface
trough. This activity is not expected to intensify as instability
continues to wane this evening. Most of the best cape is located
over the middle Atlantic region...which is where the most robust
convection should occur.
Bands of showers with some thunder should pass through the entire
area this evening into the overnight hours...so will continue to
mention categorical probability of precipitation and heavy rain embedded within any
thunderstorms. The real surface cold front is positioned from the
St Lawrence River valley extending southwestward through central
and western New York...and will continue to push southeastward across
the region tonight. The Flash Flood Watch remains in effect
through the night.
&&
Short term /6 am Friday morning through Sunday/...
the convective rainfall tonight will transition into more of a
synoptic widespread shower event as an upper level low cutoffs over
the Middle Atlantic States on Friday and a surface low develops along
the stalled boundary to our east. As these lows drift slowly
northeast...they will keep on and off rain/showers over the region
into Saturday night. For much of this period have forecast likely to
categorical probability of precipitation for the eastern two-thirds of the forecast
area...and chance to likely probability of precipitation over the west.
The combination of the widespread cloudiness/rain and the cold pool
aloft associated with the closed upper low will result in an
unseasonably cool period of weather. Temperatures on Friday will remain
steady or slowly fall from their starting point in the 50s and lower
60s. Lows Friday night will be in the upper 30s and 40s. Highs
Saturday only in the upper 40s to middle 50s...and lows Saturday night
in the middle 30s to lower 40s.
On Sunday the upper/surface lows should be far enough away from the
region to produce only scattered rain showers...mainly over the
eastern half of the forecast area...while the western part of the
forecast area may be dry or only have isolated showers. The European model (ecmwf) is
the most pessimistic with precipitation lingering into Monday...but have
forecast closer to the other models. Temperatures on Sunday will be a
little warmer with highs between 50 and 60...which is still 10 to 15
degrees below normal.
&&
Long term /Sunday night through Thursday/...
the lows are expected to be out of the region Sunday night with
high pressure at the surface and aloft starting to build in. Have
forecast dry conditions Sunday night...with fair and warmer weather
expected through Wednesday. Lows Sunday night will be 35 to 45.
Highs Monday in the 60s. Lows Monday night in the upper 30s to middle
40s. Highs Tuesday in the middle 60s to lower 70s. Lows Tuesday night
40 to 50. Highs Wednesday in the 70s.
A warm front will bring the threat of showers and thunderstorms Wednesday
night and Thursday. It will get even warmer with lows Wednesday
night in the low or middle 50s...and the highs Thursday in the middle 70s
to lower 80s.
&&
Aviation /00z Friday through Tuesday/...
unsettled weather with poor flying conditions will persist through
much of the 24 hour period ending 00z Saturday. Kpou/kpsf
terminals remain on the western periphery of one batch of
showers to the east...while kalb/kgfl will see showers with some
embedded downpours and a chance of thunder moving in from the west
this evening. Variable conditions will occur...with mainly
MVFR/IFR expected through 06z with periods of showers continuing.
Thereafter a cold front will push through from northwest to
southeast across the terminals...which will shift winds from
southerly to a northwest direction. First at kgfl later this
evening...then kalb to kpsf overnight...and eventually kpou
towards daybreak. Will continue to mention MVFR/IFR conditions
through the overnight and even much of the morning due to mainly
low ceilings with occasional showers. Some improvement to MVFR is
possible Friday afternoon but with overcast skies and showers
continuing.
Outlook...
Friday night-Sat...MVFR/IFR. -Shra likely. Breezy north winds.
Sat ngt-sun...VFR/MVFR...chc -shra. Breezy north winds.
Sun ngt-Tue...VFR. No sig weather.
&&
Fire weather...
wet conditions for Friday...
No fire weather concerns into Sunday. Periods of showers...moderate
to heavy at times will continue into the Holiday weekend along with
thunderstorms through tonight.
&&
Hydrology...
models indicate the potential for heavy rain into the early part of
the weekend as a frontal boundary slowly slides to the east of the
forecast area tonight...then stalls on Friday. After that the
deepening upper level trough to our west is forecast to cut off
along the middle Atlantic coast...with surface low development also
occurring along the old boundary. The upper level and surface lows
will then slowly drift northeast during the first half of the
Holiday weekend.
Heavy rainfall possible tonight ahead of the cold front due to the
potential for heavy convective rains and training of convective
cells. After that expect more in the way of possible heavy synoptic
rainfall from the upper and surface lows.
All of this rainfall will come on already saturated soils across
much of the forecast area due to the periods of heavy/torrential
rainfall that has occurred during the past two days.
A Flash Flood Watch remains in effect through 12z Friday...and
additional watches may be needed for the potential heavy rainfall
and flood threat Friday into Saturday.
&&
Aly watches/warnings/advisories...
CT...Flash Flood Watch through Friday morning for ctz001-013.
New York...Flash Flood Watch through Friday morning for nyz032-033-
038>043-047>054-058>061-063>066-082>084.
Massachusetts...Flash Flood Watch through Friday morning for maz001-025.
Vermont...Flash Flood Watch through Friday morning for vtz013>015.
&&
$$
Synopsis...gjm/jpv
near term...gjm/jpv
short term...gjm
long term...gjm
aviation...jpv
fire weather...gjm
hydrology...gjm
