Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KBTV 310550
Area Forecast Discussion
National Weather Service Burlington VT
150 AM EDT Sun Jul 31 2016
-- Changed Discussion --Slow moving low pressure to our south across Pennslyvania and the
southern tier of New York will bring periods of showers across
central and southern Vermont today, and a mix of clouds and sun
with less frequent showers further north. An associated upper
level trough translating across the North Country will bring more
widespread shower activity tonight into Monday. High pressure
returns Tuesday afternoon through Friday with warmer and more
humid conditions. A cold front approaching from the west will
bring the potential for scattered showers and thunderstorms
late Friday or Friday night.
-- End Changed Discussion --
.NEAR TERM /UNTIL 11 AM THIS MORNING/...
As of 959 PM EDT Saturday...Temperatures running a few degrees
colder in spots, mainly across the north, and so with this update
I`ve made some slight adjustments to temps to get those more in
line. Northern extent of shield of rain across southern New
England, Hudson Valley area ahead of a warm front continues to
make very slow northward inroads. Current radar trends depict
showers in southern parts of Bennington and Windham counties to
our south. Recent HRRR and RAP output suggest a continued slow
northward advance in rain showers is expected and have left PoPs
alone for now as they seem to reflect these ideas pretty well.
Skies will remain clear across areas to the north where the
coldest lows - in the mid 50s - will be found. Comparatively
warmer lows in the upper 50s to lower 60s across southern VT.
Previous near-term discussion from this afternoon follows...
Looks fairly quiet tonight, though will see some lowering and
thickening clouds especially in the south as a slow moving 500mb
trough moves slowly east. The 500mb ridge axis is over the area
right about 12z Sunday and should hold off precip for most areas
until the but looks like a rising chance in south central VT by
daybreak Sunday. Models vary on timing of precip northward on
Sunday but general consensus is that it basically takes much of
the day for the rain to move north reaching the international
border by late afternoon/eve. It looks like most of the rain will
be light stratiform variety but some moderate rainfall will be
embedded with relatively weak qg forcing from 850mb warm
advection. Looks like any instability will be off to our south and
west for the bulk of the day so little chance of any thunder
through the day. Temperatures a bit tricky with less clouds north
vs south so lows tonight generally cooler north in the lower 50s
in the NEK to the lower 60s south and west where its cloudy. Highs
on Sunday will be warmest north in mid to upper 70s while in the
south it may not reach 70 depending upon the time the rain
.SHORT TERM /11 AM THIS MORNING THROUGH MONDAY NIGHT/...
As of 325 PM EDT Saturday...Rain shield will continue to slowly
advance northward Sunday night and into Monday, offering a wet
close to the weekend. Both global and mesoscale model QPF output
continues to suffer from model- generated convective bullseyes in
their respective QPF fields in various different locations. While
PWAT values are seasonably high around 1.5 to 1.7", there really
isn`t much in the way of instability to speak of given the time of
day, overcast skies and poor low and mid-level lapse rates.
Because we aren`t likely to see much in the way of thunder to
enhance rainfall rates, think higher QPF as seen in some guidance
and WPC seems a bit overdone. Generally stuck close to 15z
SREF/12z GFS/12z NAM blend for PoPs/QPF/Wx. A steady light to
moderate rainfall seems the more likely outcome with the heaviest
precip falling Sunday night into early Monday. It appears the
steadiest precip generally comes in two waves - one is the south-
to-north moving axis associated with the warm front, and another
later in the day Monday from the upper trough axis. While rainfall
should provide beneficial given the dryness, there may be areas of
localized ponding in poor drainage areas. Factoring in rainfall
for Sunday, forecast amounts are between 0.75" to 1.25". Should
greater instability be realized that currently indicated, these
values may be locally higher.
Temperatures Sunday night stand to be pretty mild and more humid.
With anticipated cloud cover and at least a light south wind, expect
temperatures to fall very slowly to lows in low to mid 60s, a few
degrees warmer than recent MAV/MET MOS output. On the flip side,
high temperatures Monday were undercut a couple degrees compared to
MOS given the extensive cloud cover. Values are in the low 70s, only
a few degrees higher than lows the evening before. Lows Monday night
in the upper 50s to lower 60s.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 325 PM EDT Saturday...After a wet Monday, global models
then point to mid-level height rises associated with ridging aloft
Tuesday through Thursday. GFS and ECMWF want to show isolated
showers or thunderstorms but this seems overdone and have kept the
forecast dry. 850 mb temperatures warm each day and are up in the
+13 to +15C range supporting another period of above-normal
temperatures in the low to mid 80s.
Thursday will continue the trend of above-normal temperatures, but
we will start to see more of a southwesterly breeze and also an
increase in humidity levels. Still dry but warm and humid with highs
into the upper 80s (maybe spot 90) with lows Thursday night in the
It appears Friday potentially may have a window for active weather
as mid-level flow tightens across the Great Lakes and wind fields
strengthen, as a cold front moves into a warm and humid
antecedent air mass. There`s some difference between the GFS and
ECMWF when the front crosses through our area Friday, which has
implications on available instability, with the GFS suggesting an
afternoon frontal passage. It`s very early but on the synoptic
scale, there appears to be potential for stronger thunderstorms
Friday. Definitely is something that should be monitored in
subsequent model runs.
.AVIATION /06Z Sunday through Thursday/...
-- Changed Discussion --Through 12Z Monday...The North Country TAF sites will be affected
to varying degrees by slow-moving low pressure centered across
central PA early this morning. Several bands of rain showers
across e-central NY into srn VT will lift slowly northward
today...bringing periods of showers and MVFR conditions to
KRUT...but more sporadic activity further north. Generally VFR
with increasing mid-level clouds MPV/SLK/BTV/PBG this morning
through afternoon. Best chance for showers at BTV generally 23Z
through 04Z with periods of MVFR possible. Anticipate VFR and dry
conditions at KMSS furthest removed from. Winds will be light,
generally less than 8 kts across the area.
Outlook 12z Monday through Thursday...
12z Monday-06z Tuesday: Intervals of MVFR in shower activity
Monday into the first half of Monday night with slow moving upper
trough across the region.
06Z Tuesday through Thursday: Isold -SHRA late Monday night into
Tuesday morning with intervals of MVFR still possible. Clearing
with VFR conditions as high pressure returns Tuesday aftn. May
see areas of nocturnal fog 06-12Z Wednesday SLK/MPV with localized
-- End Changed Discussion --