Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KBTV 210800
Area Forecast Discussion
National Weather Service Burlington VT
400 AM EDT Fri Oct 21 2016
Strengthening surface low pressure system has started bringing
widespread rain to the North Country and will continue to do so
through Sunday. Occasionally heavy rainfall is expected across the
Saint Lawrence Valley and Northern Adirondacks through Friday. As
the front pushes east of the area by early next week a return to
drier weather and seasonably cooler temperatures is expected.
.NEAR TERM /THROUGH SATURDAY/...
As of 203 AM EDT Friday...Rain over Nrn NY continues with most of
VT remaining dry outside of NW VT. Breaks in the Champlain valley
as water vapor hits development of baroclinic leaf around wrn
Ohio. This will likely result in area of rain pivoting more
westward over the North Country...keeping St Lawrence and
Adirondacks in the rain through Friday afternoon.
Previous discussion...Another consideration for Friday is sub-
tropical system weakening as it heads north far off the Carolina
coast, but moisture looks to get absorbed or wrapped into the low
affecting the Northeast, and could result in resurgence of heavier
precip over eastern VT late Friday into Friday night, per the 00Z
ECMWF. This may be dependent on when the 500mb trough becomes more
neutral or negatively tilted late Friday.
Winds are also concern as strong low level jet enters the region
this afternoon. Southerly jet of 40-55kts at 850mb stays over the
North Country through Friday. This will lead to strong winds
across the higher terrain. Best chances for strong winds to mix
into the valleys would be early Friday as the precip shield pivots
slightly NW, allowing for breaks in precip over VT. Have gusts up
to 15-25kts across most of the area on Friday, before the surface
low tracks over the area.
In summary, cloudy and wet pattern expected throughout the near
term with temperatures in the mid 50s to mid 60s today as we
remain in the warm sector. Tonight temperatures remain mild in the
mid 40s to upper 50s. Forecast max temperatures will be very
tricky on Friday as the surface low and associated front traverse
across the North Country. Timing of FROPA will dictate wind shift
of NW-N and colder air filtering in, especially through the
valleys and lower terrain.
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
-- Changed Discussion --As of 400 AM EDT Friday...Rain will gradually change to snow over
the higher elevations of the Adirondacks and Green Mountains
Saturday night as a closed upper low moves over the region which
will provide dynamical cooling aloft with a change to snow over
the higher elevations. Have leaned toward the warmer GFS MOS
guidance for min temperatures Saturday night, as the NAM MOS
guidance looks too cold. Also, combination of cloud cover and
gusty west winds will help to keep air well mixed and will help to
keep temperatures up. Thus, have lowered snowfall amounts a bit
from the previous forecast given a slower changeover to snow in
the higher elevations.
Models showing precipitation winding down across the region Sunday
morning, with most of the activity done by midday on Sunday.
Models show the region will still be under cyclonic flow Sunday
night from the departing surface low pressure area over Quebec
Sunday night. Have kept in some slight chance pops for rain or
snow showers Sunday night.
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.LONG TERM /MONDAY THROUGH THURSDAY/...
-- Changed Discussion --As of 400 AM EDT Friday...The north country remains under
cyclonic flow from the departing surface low pressure area over
eastern Quebec Monday and Tuesday. Thus, have kept in slight or
low chance pops for rain or snow showers for Monday and Tuesday.
High pressure will build slowly east from the Great Lakes Tuesday
night, with mainly fair and dry weather from Tuesday night through
early Thursday. On Thursday, a warm front will approach the region
from the Great lakes and the Ohio valley. Have put in a chance of
rain showers into the forecast for mainly Thursday afternoon.
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.AVIATION /08Z Friday THROUGH Tuesday/...
Through 06z Saturday...MVFR/IFR conditions persist throughout
this long duration event, coming to an end Sunday night. Rain more
persistent over Nrn NY this morning through early afternoon. Then
increased moisture from subtropical system feeds into the NE low
affecting our area Friday afternoon. This will allow resurgence in
moisture and rain to spread east as the NE low swings from PA to
the srn New England coast Friday night.
Winds gusty where it isn`t raining and LLWS possible over SLK
this morning. Low level jet weakens and exits east early Friday.
Outlook 06z Saturday through Tuesday...
06z Saturday through 00z Monday: A prolonged period of unsettled
conditions is expected with widespread MVFR/IFR in periods of
00z Monday through 00z Wednesday: A mix of VFR/MVFR with upslope
showers in NW flow.
As of 350 PM EDT Thursday...A widespread and long duration
rainfall of 1 to 3 inches with amounts near 4 inches across the
St Lawrence Valley from tonight through Sunday. There will be
some breaks throughout the event, especially across portions of
Vermont. Given most of the region is in moderate to severe
drought...we are not anticipating any widespread hydro issues.
However...some minor urban and street flooding is possible
associated with the heavier rainfall rates on Friday with leaves
clogging storm drains. Otherwise...some modest rises in local
rivers and streams are likely this weekend...but no widespread
flooding is anticipated. The latest guidance from the NERFC brings
Ausable River near minor flood stage by Saturday Afternoon.