Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
701 am EDT sun Aug 2 2015
high pressure is ridging in from the Ohio Valley this morning. The
surface high will produce fair and dry weather for northern New
York and Vermont today. Clouds will increase tonight ahead of warm
front...with a slight to low chance of a shower or thunderstorm
west of the Champlain Valley. A cold front and an upper level
disturbance will bring greater chances of showers and
thunderstorms Monday into Monday night. A cooler and unsettled
weather pattern will continue into the middle week.
Near term /until 8 PM this evening/...
as of 434 am EDT Sunday...a nice close to the weekend is expected
for northern New York and north-central Vermont with a surface anticyclone near the Ohio
Valley and the virginias building in from the south. The short-
wave trough that produced all the showers and thunderstorms
yesterday has moved down stream over the Canadian Maritimes. Middle
and upper level heights will rise some...as the middle level flow
will be briefly zonal.
The synoptic subsidence from the surface high to the south...and
decent mixing from aloft will yield partly to mostly sunny skies
today. H850 temperatures of +12c to +14c with mixing to about h850 will
yield highs in the u70s to l80s in the valley locations...and u60s
to m70s over the mountains which are near normal or slightly above
normal for early August.
Short term /8 PM this evening through Monday night/...
as of 434 am EDT Sunday...the weak ridging aloft flattens as
another digging upper level trough will be approaching from
S-central Ontario and the northern Great Lakes region Sunday night.
The low and middle level flow will shift southwesterly ahead of the
approaching short-wave trough. A low pressure system races
northeast with the better upper dynamics towards southwest Quebec.
A warm front ahead of the wave may trigger some scattered showers/isolated
thunderstorms across northern New York...and from btv north and west in northern
Vermont. The showalter indices lower to 0c to -2c with a decent h850
low level jet segment of 30-40 kts prior to 12z Monday. Min temperatures will be
milder than this morning with mainly lower to m60s in the lower
Monday-Monday night...active stretch of weather for northern New York and upstate
Vermont. Storm Prediction Center has highlighted pretty much the entire weather forecast office btv forecast area
in day 2 of the severe weather outlook. Strong to severe
thunderstorms look possible especially in the afternoon ahead of a
cold front...and an amplifying short-wave trough. There are some
timing issues between the GFS/NAM/ECMWF. The trend seems to be for a
later passage of the cold front. 0-6km vertical bulk shear values
increase to 35-50 kts with sbcapes of 500-1500 j/kg with surface
dewpoints increasing into m50s to l60s. The GFS has h850-500 lapse
rates of around 7c/km across most of the region. Damaging winds
and or large hail could be possible with lines or multi-cell
clusters. We will highlight the severe threat in the severe weather potential statement product.
It should be noted the strength of the low level jet coupled with the deep
shear may allow for some discrete supercells if enough buoyancy
exists/surface destabilization occurs. Some locally heavy downpours
are also possible with precipitable water values rising to 1.25-1.66" ahead of
the front. Probability of precipitation were kept in the high chance/likely values Monday PM
into Monday evening. Highs on Monday will be in the m70s to m80s
for the area...with lows in the 50s to l60s. The showers should
diminish after midnight...but the upper level trough will approach
Tuesday-Tuesday night...cyclonic flow regime with multiple pieces of
energy pivoting through the upper trough. Scattered showers and isolated
thunderstorms are possible Tuesday due to the cyclonic vorticity
advection with the trough. Upslope showers may persist Tuesday night.
Temperatures will run a little cooler than normal as we head into the
Long term /Tuesday through Saturday/...
no changes to the long term due to the emergency service backup.
An unsettled weather pattern will continue and the previous
As of 245 PM EDT Saturday...large 500mb trough over eastern
Ontario will shift eastward through Wednesday, producing showers
and thunderstorms followed by several shortwaves embedded in the
cyclonic flow as the trough remains over the Canadian Maritimes.
Some surface ridging on Thursday may lead to a mostly dry day as
upper level jet departs eastward, no longer aiding in lift across
the north country.
As the aforementioned trough shifts further north and east,
another middle level shortwave will approach from the Great Lakes
region late Friday. Models differ on track and evolution of
surface feature as it tries to push precipitation shield northward into
the north country. Also ridging at the surface over Ontario and
James Bay may affect this features progression northward.
Temperatures will be slightly cooler than normal with maxes in
the 70s and mins generally in the low 50s to around 60.
Aviation /12z Sunday through Thursday/...
please see equipment
section below for krut data outage information...
Through 12z Monday...VFR through the period under south to
southwesterly flow from 5 to 10kts, occasionally gusty into the
15-18kt range from 15-22z. Approaching frontal boundary late in
the forecast period may spark a few showers at the kmss terminal
after 06z Monday, dry elsewhere.
Outlook 12z Monday through Thursday...
12z Monday - 12z Tuesday...scattered/numerous showers and
thunderstorms expected with cold frontal passage. Brief MVFR ceilings
and IFR visibilities possible beneath heavier convective cores.
Gusty winds/turbulence also possible.
12z Tuesday Onward...mainly VFR through the period. Scattered showers
possible Tuesday afternoon with brief MVFR/IFR possible. Patchy
IFR in br/fog possible 06-12z each morning, mainly at kmpv/kslk
AWOS observational data from the Rutland/southern Vermont
regional Airport (krut) remain unavailable at this time. For
aviation partners current observations may be accessed via telco.
Please reference FAA krut notam 07/007 for more information.