Area Forecast Discussion
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FXUS61 KBTV 301929
Area Forecast Discussion
National Weather Service Burlington VT
329 PM EDT Sat Jul 30 2016
Low humidity levels, partly to mostly sunny skies, and pleasantly
warm temperatures will characterize Saturday, as Canadian high
pressure controls our weather through tonight. Thereafter, a slow
moving upper level disturbance and associated rich moisture moving
out of the Ohio Valley will bring periods of rain showers Sunday
into Monday, possible lingering into early Tuesday. High
temperatures will reach the low 80s today, but then generally in
the low to mid 70s for the Sunday through Tuesday time frame with
abundant cloudiness. High pressure returns Wednesday through
Friday with warmer and more humid conditions.
.NEAR TERM /THROUGH SUNDAY/...
As of 140 PM EDT Saturday...Tranquil and pleasant weather
conditions through the rest near-term period. Dry northerly low-
level airstream continues east of 925mb anticyclone centered
across swrn Quebec. This will continue to provide the North
Country with relatively low humidity (2-m dewpoints in the 50s)
today. Mid-upper level clouds streaming enewd ahead of Ohio
Valley trough are staring to dissipate in the nid afternoon hours
but will still provide filtered sun especially over the srn half
of the forecast area. With 850mb temps of +11C to +13C at 21Z per
00Z GFS, looking for highs generally in the upr 70s to lower 80s.
10-meter winds generally N 5-9 mph, except locally NE across far
nrn NY. PoPs NIL.
Continued quiet tonight, though will see some mid level clouds
(8-10 KFT) increasing from SW-NE after midnight as slow-moving
500mb trough shifts newd from OH into PA/wrn NY. Included slight
chance of showers s-central VT toward 12Z Sunday, but most likely
scenario is that associated shower activity remains south of the
entire forecast area until during the day Sunday. Overnight lows
mid-upr 50s, except locally around 60F s-central VT valleys where
clouds inhibit radiative cooling. Some patchy valley fog is
possible nrn valleys after 06Z Sunday.
.SHORT TERM /SUNDAY NIGHT 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 /20Z Saturday THROUGH Thursday/...
Through 18Z Sunday...VFR conditions will persist through most of
the period. High and mid-level clouds are filtering from the south
but most are dissipating as they move into the region. Overnight
increased moisture will bring lower VFR ceilings. If ceilings
don`t not move in fast enough, there is potential for overnight IFR
fog at MPV. Have decided to leave out the mention in the TAFs for
now. Showers will move slowly in late into the period into the
southern stations after 15Z. Winds will be light and variable for
Outlook 18z Sunday through Wednesday...
18z Sunday-00z Tuesday: Intervals of MVFR in shower activity
Sunday afternoon through Monday with slow moving upper trough.
00Z Tuesday through Wednesday: Upper trough brings lingering
showers Monday night into early Tuesday with periods of MVFR and
brief IFR possible. Then clearing with VFR conditions as high
pressure returns Tuesday afternoon through Wednesday. May see
areas of nocturnal fog 06-12Z Wednesday SLK/MPV with localized