Area forecast discussion
National Weather Service Burlington Vermont
1047 PM EDT Friday may 24 2013
Synopsis...
deepening low pressure will bring additional widespread...and in
some cases flooding rainfall to the region tonight into early
Sunday. Conditions will remain chilly and breezy through the
period...though gradually moderate by Monday as dry weather returns.
Thereafter...warm temperatures quickly return by the middle to later
portions of next week as highs climb into the 70s to near 80.
&&
Near term /until 6 am Saturday morning/...
as of 1037 PM EDT Friday...going forecast remains on track.
Developing low pressure vicinity of Cape Cod will deepen slowly in
response to digging upper trough. Steady light to moderate rain
continues to fall across northeast New York and western Vermont.
Coverage has filled in across rest of Vermont as well. Rainfall
more scattered in nature across western Adirondacks...while it
continues mostly dry in Saint Lawrence valley. Expect rain to
continue across Vermont and northeast New York overnight...with
lower probability of precipitation for western zones. Temperatures cold enough over the highest
elevations to support snow. Not much change in temperatures overnight...
with readings mainly in the 40s...but 30s over higher elevations.
Previous discussion...
forecast remains more or less on track for tonight as deepening
upper trough remains across the region and becomes gradually
negatively tilted over time. As this occurs...upper energy will
capture a developing surface low riding northeast off the middle-Atlantic
coast...and drive copious amounts of moisture north/northwestward
into our area. Increasing Omega/frontogentical forcing along with
favorable low track all argue for continued categorical probability of precipitation
(90-100%) through the evening/overnight hours from the Adirondacks
eastward. After a period of early evening showers...the far
west...namely the slv will trend drier. Lows quite chilly under
continued northerly breezes...generally 35 to 45 with some light
snow accumulations possible above 3000 feet.
&&
Short term /6 am Saturday morning through Sunday night/...
as of 407 PM EDT Friday...by Saturday into Saturday night...deep
upper closed 500 mb trough and captured/occluding surface low near the
Gulf of Maine will continue to affect our area with widespread
moderate to heavy rainfall from the Adirondacks eastward.
Impressive Omega/frontogenetical forcing continues...especially
across the eastern Adirondacks into our central and northern
Vermont counties where widespread additional 1-2 inch rainfall
totals will be likely. This will be problematic given our recent
bout of heavy rainfall...and a Flood Watch has been issued through
Sunday to account for potential additional hydrological issues
(see Hydro disc below).
Temperatures to remain chilly under strong cold air advection with
afternoon highs holding in the 40s from the Adirondacks
eastward...though milder across the slv where lack of dynamical
cooling affects from precipitation will allow readings to climb into
the 50s. Lows Saturday night similar to tonight...35 to 45 with some
additional light to modest snow accumulations possible at The
Summit level above 2500-3000 feet.
By Sunday...deep upper system continues to fill and begin to trudge
slowly northeastward through the day. Thus showery weather in the
morning will gradually end over time as sensible weather conditions
gradually improve. Highs a tad milder from the upper 40s to lower
50s dacks east...and 50s to locally near 60 in the slv by days end
where some sun possible late.
Conditions then continue to improve Sunday night as upper trough
loses influence and is replaced by broad ridging in the lower to middle
levels moving east from the Great Lakes states. Skies should
gradually trend partly cloudy to clear overnight as lows bottom out
generally in the 30s to around 40.
&&
Long term /Monday through Friday/...
as of 330 PM EDT Friday...latest runs of the GFS/European model (ecmwf) remain in fair
agreement for the extended period. Warming trend is expected through
the five-day period as strong upper ridge builds east from the
central portion of the country. This replaces the exiting low from
the weekend. Some clouds for the NE kingdom Monday
morning...otherwise precipitation-free for Monday into Tuesday for the
entire County Warning Area. For Wednesday into Friday...models do bring warm front across the
area over the top of upper ridge. This setup will focus precipitation
into the region. Some model timing/placement and amount of quantitative precipitation forecast possible
as front meanders through area. Differences are due to potential thunderstorm
along boundary. With 925 temperatures ranging from +16c to +22c and 850
temperatures +12c to +17c...ample instability appears available to
trigger convection...especially during the daytime hours. By
Friday...focus of precipitation will occur along the northern tier zones
as front shifts northward. For temperatures in extended...staying close to
guidance with highs going from the 60s Monday to the low 80s
Thursday/Friday as airmass shifts from cold air advection on west-northwest flow Monday to
strong warm air advection middle-to-end of week as strong thermal ridge sets up over
the eastern half of the country.
&&
Aviation /03z Saturday through Wednesday/...
through 00z Sunday...mainly MVFR and IFR conditions for all taf
sites due to low ceilings and visibilities in rain and mist/fog
due developing low pressure along southern New England coast.
Exception will be mss which will be mostly VFR. Winds mainly north
at 10-20 kts...except around 10 kts between 00z-12z Saturday for
mss/slk/rut.
Outlook 00z Sunday through Wednesday...the combination of a surface
boundary and associated low pressure will keep showers in the taf
sites through the weekend. These showers will produce periods of MVFR
ceilings/visibilities with some IFR conditions possible...especially at
night. In addition...breezy northwest winds can be expected over
the weekend as surface low pressure tracks into the Gulf of Maine on
Sunday. A slow clearing trend is anticipated on Monday...with
mainly VFR conditions Tuesday into Wednesday.
&&
Hydrology...
as of 407 PM Friday... upper/closed low to bring widespread
moderate to heavy rainfall to the region tonight into early
Sunday. While stability will limit excessive hourly rainfall
rates...36-48 hour totals will nonetheless range from 1.5-3.0
inches across northern and central Vermont...and 1-2 inches in the
Adirondacks into south central Vermont. Locally run sshp model
hydrographs suggest these totals will likely bring numerous small
streams to bankfull...and several mainstem rivers into flood by
Saturday into the first half of Sunday. Thus a Flood Watch has
been issued for much of our region through Sunday to account for
this potential. At this time...the rivers of most concern would be
the missisquoi...LaMoille and Passumpsic in Vermont...and the
ausable river in northern New York. Given the current trends in
rainfall timing and amounts...most river crests are expected to
occur late Saturday night or Sunday morning.
&&
Marine...
as of 340 PM Friday...looking to be a pretty miserable start to
the prime boating season on Lake Champlain. A storm more typical
of winter will bring an extended period of strong northerly winds
over the lake. Expect winds in the 20 to 30 knot range from
tonight all the way into early Sunday. Expect frequent gusts up to
35 knots, especially across the Open Lake later tonight through
Saturday. For that reason, a lake Wind Advisory has been posted
and will remain in effect until the winds fall below 25 knots.
These winds will make for very rough conditions, with
waves across the Open Lake ultimately building upwards of 4 to 6
feet late Saturday. A steady rain and temperatures only in the 40s
on Saturday will add to the misery.
The outlook for Monday still looks like it will be the best day of
the Holiday weekend for boating. Northwest winds will be in the 10
to 15 knot range with mostly sunny skies and milder temperatures.
&&
Climate...
with the unseasonably chilly weather expected for Saturday...some
record low maximums may be approached or broken. They are listed
below.
Burlington: 51f (1921,1925)
montpelier: 48f (1967)
massena: 55f (1969,1979)
St johnsbury: 52f (1931,1925)
&&
Btv watches/warnings/advisories...
Vermont...Flood Watch through Sunday afternoon for vtz002>012-016>019.
New York...Flood Watch through Sunday afternoon for nyz028-031-034-035.
&&
$$
Synopsis...jmg
near term...jmg/rjs
short term...jmg
long term...jn
aviation...rjs/jn
hydrology...
marine...
climate...
