Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Burlington Vermont
650 am EDT Sat may 23 2015
cool Canadian high pressure will provide clear to partly cloudy
skies across the region today before sliding east by Sunday and
allowing temperatures to moderate considerably. A strong warm front
will push through the region by later Monday into Monday night with
a period of showers, especially across northern New York. Behind
this front, a very warm and summerlike airmass will surge back into
the region from Tuesday Onward into late week along with
daily chances of scattered showers and thunderstorms.
Near term /until 8 PM this evening/...
as of 650 am EDT Saturday...quick update to drop all frost/freeze
headlines as temperatures will rise above freezing in nearly all
spots within the next hour. Otherwise just some minor tweaks
needed to sky cover and dewpoints to match current observational
trends. Prior discussion follows. Have a great morning.
Prior discussion from 335 am EDT Saturday...cool and quiet
conditions expected across the area today as unseasonably deep
closed low pulls steadily away into the Maritimes while surface
high pressure of Canadian origin slides bodily southeast from the
Great Lakes. Blended model 925-850 mb temperatures support
afternoon maximum temperatures from the middle 50s to lower 60s under
modestly gusty west to northwesterly winds and sunny/partly sunny
skies. No precipitation is expected.
Short term /8 PM this evening through Monday/...
as of 335 am EDT Saturday...surface high then pushes offshore
with winds trending calm to light west/southwesterly over time
tonight. With steady height/thickness rises minimum temperatures
will be considerably milder and within 3 degrees of seasonable
late may values in most spots (40s). There could be some passing
middle/high cloudiness from time to time, especially later at night
as deepening warm thermal advective processes begin aloft.
By Sunday deepening west to southwesterly flow on the back side of
aforementioned surface high will allow temperatures to moderate
considerably with most spots climbing well into the 70s. A weak
surface trough will approach our northern tier of counties by
afternoon and wash out by early evening with perhaps a widely
scattered shower or two in the 3-8 PM time frame across NC/NE Vermont.
Nominal boundary layer instability and lower-end sref calibrated
thunder perecentages around 20 percent support an isolated
thunderstorm in this area as well, but with such a dry boundary
layer areal coverage should be quitre low. Dry weather is expected
Then clear to partly cloudy by Sunday night under continued light to
modest south/southwesterly flow. Middle to high clouds will be
thickening by later at night as a strong warm front begins to
approach from the southwest with perhaps a stray shower far
southwest toward morning. Temperatures continue to trend warmer with
overnight lows ranging through the 50s in most spots.
As we progress into Monday surface warm front pushes into the region
with thickening clouds and increasing chances of showers, especially
across the western half of the forecast area later in the day where
better isentropic lift and moisture return are evident. Not a
washout by any means with some of our eastern Vermont counties
likely remaining dry all day. Temperatures a bit tricky with sharp
warming aloft at odds with clouds/showers. For now have advertised
an idea closer to latest sref bias-corrected means showing coolest
readings north and east (l-M 70s) and warmer south and west (upper
70s/lower 80s) where some partial sunshine may be possible south of
the front later in the afternoon.
Long term /Monday night through Friday/...
as of 335 am EDT Saturday...large scale pattern will feature
developing middle/upper level ridge across the eastern Continental U.S. By
midweek. This synoptic scale setup will result in much above
normal temperatures and daily chances for afternoon/evening
showers/storms especially as northern stream attempts to bring a
front into/across area middle/late week but it appears to hang up
somewhere across New England.
Much of this discussion is borrowed from dayshift as thinking is
generally the same...no widescale wetting rain events are
anticipated yet chance of showers/thunderstorms through week will
bring about adequate chances of eating into our precipitation
Warm front Monday night will have good 500 mb vorticity traveling from northwest to southeast
across our region...while a ribbon of enhanced 850 to 500mb relative humidity moves
from southwest to northeast. Quantitative precipitation forecast will generally be <0.25 for this
warm front feature with greatest across northern New York.
For Tuesday through Friday of next week our County Warning Area is well established
in the warm sector...as ribbon of enhanced middle level moisture and
associated vorts lift north of our region. Prognosticated 925mb temperatures range
between 18c and 22c during this period...supports highs well into the
80s with maybe a few readings near 90 in the Champlain and Saint
Lawrence valleys...especially given dry surface conditions but cloud
cover with close proximity of front may inhibit temperatures.
The lack of organized forcing will limit areal coverage/intensity of
storms during middle week with a better threat late week as front makes
attempt to push across region but may get hung up and move north as
a warm front next weekend.
These warmer than normal temperaures may place btv as the warmest
may on record.
Aviation /12z Saturday through Wednesday/...
through 06z Sunday...VFR expected through the period. Scattered-broken
5000-8000 foot cloud deck contniues to dissipate but still hanging
in a bit with northwest upslope flow across Vermont. Early this morning...gradually
dissipates overnight leading to clear skies at all taf sites and
continues through today with only some scattered middle level clouds
moving in later today and increasing to broken Sat night/Sun morning.
Northwest winds 5-10 knots early this morning and west/northwest
this morning to 8-12 knots with gusts 15-22 knots...highest mpv.
Winds turn west/southwest Saturday afternoon with gusts 15-25
knots...highest at mss slowly diminshing tonight.
Outlook 06z Sunday through Wednesday...VFR conditions continue
for Sunday into Monday...before a weak warm front will produce a
period of light rain showers on Monday afternoon into Tuesday. A period
of MVFR ceilings will be possible...especially in the mountains. The
chances for afternoon showers and thunderstorms will continue for
Wednesday...with brief MVFR ceilings/visible in the heavier storms...mainly
during the peak heating hours.
as of 335 am EDT Saturday...fine dead fuels remain quite dry
across most of the region, and with lower than average
precipitation over the past few weeks conditions remain favorable
for these fuels to burn quickly should any fires start. Low
afternoon relative humidity (15 to 25%) along with gusty west to
northwesterly flow from 20 to 30 miles per hour will exacerbate these
conditions today. Thus any fires that do start today will have the
potential to spread quickly...burn intensely and become difficult