791 
FXUS61 KBTV 200515
AFDBTV

AREA FORECAST DISCUSSION
National Weather Service Burlington VT
1215 AM EST Wed Feb 20 2019

.SYNOPSIS...
High pressure building into the Northeast will supply another
dry but seasonably cold night tonight before warm air advection
commences Wednesday morning. A quick moving low pressure system
passing to the north and west of the St. Lawrence River will 
bring developing snowfall Wednesday night, ending as a wintry 
mix early Thursday morning. Snow and sleet amounts will range up
to a couple of inches from the Champlain Valley westward across
northern New York, with 2 to 4 inches of snow and sleet 
expected across north-central into northeastern Vermont.
Precipitation will end Thursday morning through early Thursday
afternoon, followed by drier weather and seasonably warm
temperatures to finish out the week.

&&

.NEAR TERM /UNTIL 10 AM THIS MORNING/...
As of 931 PM EST Tuesday...Have adjusted temperatures a bit,
some areas have already dropped quite a bit with clear skies and
light winds in place. Still an area of mid layer clouds south of
our Northern NY zones, but think it will have minimal impact on
our area. Previous discussion follows. 

High pressure will crest overhead tonight, allowing for one 
last crisp night with mostly clear skies and seasonably cold 
temperatures under effective radiational cooling conditions. 
Weak warm air advection will be ongoing through the night under 
light southerly return flow, especially over northern New York 
west of the center of the high, which will counter radiational 
cooling and prevent temperatures from plummeting quite as much 
as last night. However, still looking at lows well below normal 
in the -10 to +5 range...warmest in the Champlain Valley and 
coldest in northeastern Vermont closer to the core of the high. 

High pressure will shift east of the area during the day Wednesday, 
prompting winds to turn southerly with increasing warm air advection 
through the day.  While the morning will start off mostly sunny, 
high and mid-level clouds will increase through the day in advance 
of the next system, which will impact the area Wednesday night. 
Still looking like the majority of the area will stay dry through 
Wednesday afternoon into early Wednesday evening (including dry for 
the Wednesday afternoon commute) before precipitation arrives later 
Wednesday evening/Wednesday night.  Highs Wednesday will be in the 
mid to upper 20s.

&&

.SHORT TERM /10 AM THIS MORNING THROUGH THURSDAY NIGHT/...
As of 318 PM EST Tuesday...A low pressure system tracking through 
the Great Lakes Region will push a warm front through the North
Country Wednesday night. Isentropic upglide along and ahead of 
the front will spread precipitation over the forecast area 
starting as light snow in the early overnight hours Wednesday 
night. Warm air advection will continue through the night, and a
weak warm nose will develop in response to a southwesterly 850 
mb jet pushing in. The warm air advection will allow for snow to
progressively change over to a wintry mix (primarily sleet) 
through the night from west to east. A brief period of freezing 
rain is possible during this transition time, however with 
maximum temperatures in the warm layer aloft only progged 
between 0 and 2 degrees C, the overall freezing rain threat 
looks low. As far as timing of the snow to wintry mix 
transition goes, northern New York will switch over between 
midnight and sunrise Thursday morning, while Vermont will hold 
onto primarily snow through the early morning hours. Thus, there
will be a west to east gradient of snow/sleet totals for 
Wednesday night/Thursday morning, with generally 1-3" expected 
in northern New York and the Champlain Valley, and 2-4" expected
along and east of the Green Mountains in Vermont. 

Temperatures will quickly rise to above freezing Thursday 
morning, and any residual snow or sleet will become light rain. 
A rapidly advancing dry slot will quickly end most of the rain 
through the morning, and a general drying trend will be observed
for the remainder of the day. The exception will be western 
slopes of the northern Adirondacks and northern Greens, which 
could hold on to some light showers through the day. Highs 
Thursday will warm into the low to mid 40s, and winds will 
become gusty in response to steepening lapse rates during the 
daytime hours, particularly after precipitation ends. Westerly
winds 15-25 mph can be expected during the day, with gusts to 
up to 35 mph possible. 

Thursday night will be mostly dry with diminishing winds.
Temperatures will be fairly mild with lows in the 20s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 318 PM EST Tuesday...Friday starts out mostly dry with 
some lingering mountain snow showers under light northwest flow.
The snow showers shouldn't account for much in the way of 
accumulation and will likely taper off in the early evening as 
the the flow turns more zonal aloft. High pressure builds in to 
start the weekend as both Friday and Saturday should be fairly 
pleasant with highs in the mid 30s Friday and mid to upper 30s 
Saturday.

The quiet weather is short lived as a system will push into the 
Great Lakes region Saturday night and will bring widespread 
precipitation to the North Country Sunday through Monday. A 
vertically phased low pressure system will develop off the lee edge 
of the Rockies. The system will push northeast over the Great Lakes 
and will bring continuous warm southerly flow. Warm advection snow 
will start before changing over to potentially mixed precip and then 
rain for much of the North Country by Sunday afternoon. As with this 
morning's global suite there is some subtle hint of a coastal trough 
developing which would act to keep some of the low level air near 
freezing east of the Greens which would complicate the precip type 
significantly.

A dry slot then provides a brief lull in the precipitation Sunday 
evening before a cold front starts to push through transitioning 
everything back to snow on the back side Monday. High pressure and 
quiet weather return for Monday evening into Tuesday.

Based on the latest suite of guidance I'm not real bullish on any 
flooding threats outside any river locations that are not currently 
jammed with no channels. 24 hour rainfall totals appear to be on the 
order of a half to three quarters of an inch and absent quite a bit 
warmer temperatures I dont see significant snow melt running off. 
Thus there shouldn't be enough water added to the basins to lift and 
break ice. That said, we'll continue to monitor for any changes and 
specifically for those locations that already have an ice jam in 
place.

&&

.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
Through 12z Thursday...Dry/VFR conditions will persist thru 02Z
Thursday with developing S-SW winds at 5-10kt. Thereafter, an
approaching warm front will bring developing steady snow from 
SW- NE with vsby falling into the 1-2SM range between 02-03Z 
Thursday. Will see general IFR snowfall continue through 08-09Z 
before mixing with sleet and possible brief freezing rain toward
daybreak Thursday. HIR TRRN OBSCD after 02-03Z Thursday. 
Anticipate low-moderate impacts to aviation ground ops early 
Thursday morning owing to accumulation of snow and sleet (mainly
1-3" at the TAF sites).

Outlook...

Thursday: Mainly VFR, with areas MVFR possible. Chance RA, Chance
FZRA, Chance SN.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHSN.
Friday: Mainly VFR, with local MVFR possible. Slight chance SHSN.
Friday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. Chance SN.
Sunday: Mainly MVFR, with local IFR possible. Likely RA, Likely
SN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...RSD
NEAR TERM...Neiles/RSD
SHORT TERM...RSD
LONG TERM...Deal
AVIATION...Banacos