FPUS51 KBTV 230959

Zone Forecast Product for Vermont
National Weather Service Burlington VT
555 AM EDT Sun Aug 23 2020

Including the cities of Johnson and Stowe
555 AM EDT Sun Aug 23 2020

.TODAY...Mostly cloudy this morning, then becoming partly sunny.
Patchy dense fog this morning. A chance of showers. A chance of
thunderstorms this afternoon. Some thunderstorms may produce
gusty winds and heavy rainfall this afternoon. Highs in the upper
70s. Southwest winds around 10 mph, becoming west this afternoon.
Chance of rain 50 percent. 
.TONIGHT...Partly cloudy with a chance of showers and
thunderstorms until midnight, then mostly cloudy with a slight
chance of showers and thunderstorms after midnight. Some
thunderstorms may produce gusty winds and heavy rainfall until
midnight. Lows in the lower 60s. Light and variable winds. Chance
of rain 40 percent. 
.MONDAY...Partly sunny with a chance of showers. A chance of
thunderstorms. Some thunderstorms may produce gusty winds and
heavy rainfall in the afternoon. Highs in the lower 80s. Light
and variable winds, becoming southwest around 10 mph in the
afternoon. Chance of rain 50 percent. 
.MONDAY NIGHT...Partly cloudy with a chance of showers and
thunderstorms. Some thunderstorms may produce gusty winds and
heavy rainfall. Lows in the mid 60s. Southwest winds 10 to
15 mph. Chance of rain 50 percent. 
.TUESDAY...Showers likely with a chance of thunderstorms. Highs
in the lower 70s. West winds 15 to 20 mph with gusts up to
30 mph. Chance of rain 70 percent. 
.TUESDAY NIGHT...Partly cloudy with a 30 percent chance of
showers. Lows around 50. 
.WEDNESDAY...Mostly sunny. Highs in the mid 60s. 
.WEDNESDAY NIGHT...Mostly clear. Lows in the mid 40s. 
.THURSDAY...Partly sunny. Highs in the upper 60s. 
.THURSDAY NIGHT...Partly cloudy. Lows in the upper 40s. 
.FRIDAY...Partly sunny with a 30 percent chance of showers. Highs
around 70. 
.FRIDAY NIGHT...Partly cloudy with a 40 percent chance of
showers. Lows in the mid 50s. 
.SATURDAY...Mostly cloudy with a 50 percent chance of showers.
Highs in the upper 60s. 


ASUS41 KBTV 231030
600 AM EDT SUN AUG 23 2020




BURLINGTON     MOCLDY    62  56  80 CALM      30.01S                  
MONTPELIER     FOG       54  54 100 CALM      30.09S VSB 1/4          
MORRISVILLE    CLOUDY    54  53  97 CALM      30.05S FOG              
ST. JOHNSBURY*   N/A     54  54 100 MISG      30.05S                  
LYNDONVILLE*   FOG       51  50  97 CALM      30.09R VSB<1/4          
RUTLAND*       PTCLDY    57  57 100 SE10      30.06R                  
SPRINGFIELD    CLOUDY    58  57  97 CALM      30.08R                  
HIGHGATE*      MOCLDY    61  58  87 SE3       30.00S                  
NEWPORT*       FAIR      54  52  94 SW5       30.06S                  
BENNINGTON     CLEAR     57  55  93 CALM      30.06R                  
ISLAND POND*     N/A     46 N/A N/A CALM        N/A                   
GALLUP MILLS*    N/A     46 N/A N/A MISG        N/A                   
LAKE EDEN*       N/A     54 N/A N/A CALM        N/A                   
MT. MANSFIELD*   N/A     61 N/A N/A W12         N/A                   


BURTON ISLAND*   N/A     68  59  73 SE10        N/A                   
COLCHESTER RF*   N/A     66  63  88 S16         N/A                   
DIAMOND ISL*     N/A     64  63  94 S8          N/A                   


FXUS61 KBTV 230735

Area Forecast Discussion
National Weather Service Burlington VT
335 AM EDT Sun Aug 23 2020

The next few days will feature late summer warmth with
temperatures in the low to mid 80s for most and scattered 
showers and thunderstorms increasing in areal extent during the 
afternoon hours. A few strong storms will be possible for today 
and Monday, capable of producing brief heavy rainfall, gusty 
winds, and frequent lightning. A strong frontal boundary will 
cross the region late Monday night into Tuesday, which will 
bring cooler, drier weather for the mid-week period.


As of 327 AM EDT Sunday...Upper ridge is working its way eastward
with a warm front noted in Theta E fields crossing the St. Lawrence
shortly. With the warm advection is a pocket of showers with
embedded thunder tracking east towards St. Lawrence County. This
activity should skirt the region through this morning, outracing the
better push of warm advection and moist inflow into our dry airmass.
Mesoanalysis also indicates our region has lower mid-level lapse
rates, so this elevated convection should begin to struggle as it
heads further east. Clouds will be on the increase as warm, moist
air air advects into the region with temperatures warming into the
upper 70s to mid 80s.

We should see a break in shower activity while the upper ridge moves
overhead, and height rises act to suppress activity for a bit. Once
we get past noon, we should see activity first initiate over
elevated heating surfaces, and then pulse up and down around outflow
boundaries, areas of terrain convergence, etc. Instability for 
today will rise upwards to 1000-1500 J/kg of CAPE, with pockets 
of 2000 J/kg over portions of Rutland County. A weak, zonally 
oriented front positioned near the International Border will 
slowly sag southwards as well. It appears the best shear over 
the Northeast Kingdom and the best instability in the lower 
Champlain and Hudson Valleys will not be collocated. The best 
frontal dynamics will also remain north of the border. While 
ingredients are not lined up very well, the strong instability 
and boundary layer convergence over portions of the eastern 
Adirondacks into the southern half of Vermont could generate a 
few strong storms capable of heavy rain and frequent lightning, 
with the potential for strong to locally damaging wind gusts. 
Activity will decline after sunset, but showers may continue 
overnight as the front stalls near the International Border.

Monday should be a rinse and repeat. A warm night for Sunday evening
with sunrise temperatures on Monday in the mid 50s to mid 60s.
Presence of the upper ridge hangs on during the morning, but will
give way to a more defined shortwave trough. Temperatures again
climb into the upper 70s to mid 80s, allowing 1000-2000 J/kg to
develop. Shear remains rather marginal at 20-25 knots, so only short-
lived pulse convection is expected with the potential for heavy
rain, locally damaging winds, and frequent lightning. Activity will
wane after sunset, but with a stronger upper trough on the horizon,
we could again hold onto some overnight shower activity.


As of 327 AM EDT Sunday...Main focus for this period will be a cold
front/upper trough that will swing through the North Country
sometime Tuesday morning. Although model guidance differs in the
specific details, consensus has grown that this will be a fairly
potent front with convection to fire along/just ahead of it as it
passes through the region. Westerly flow will increase overnight
Monday night ahead of the system with some slightly drier air
working in, so expect we'll see a bit of a break in the activity
during the evening hours once Monday's showers wane. The front makes
its approach from the west late Monday night into early Tuesday.
Showers and thunderstorms will redevelop as dynamic support
increases with the incoming upper trough and moisture converges
along the front. Timing will be key for the intensity of the
convection and the location of the strongest thunderstorms. The NAM
is a bit faster than the other models, going with an early-mid
morning frontal passage, while the GFS is the slowest, with a late
morning-early afternoon passage. Have leaned more towards the
earlier frontal passage as the GFS appears to be an outlier.
Regardless, showers and thunderstorms increase during the morning
hours and push southeast as the front advances. Instability will
increase with the heating of the day; NAM's a bit less robust given
the earlier timing, but still indicates 1000+ J/kg of SB CAPE ahead
of the front. Shear will be highest post-front, but still expecting
30-35kt ahead of it. Hence some storms could be on the strong side
with gusty winds and heavy rainfall. This is particularly true
should the slower GFS solution hold true. Drier air will quickly
work in behind the front, rapidly bringing most of the
showers/thunderstorms to an end by Tuesday evening. Tuesday night
will be dry under partly to mostly clear skies.

The differences in frontal timing also make for a difficult
temperature forecast through this period. Monday night lows will be
on the milder side as we will see ample moisture and southwest
winds. As the front passes through on Tuesday, winds will turn to
the northwest and become fairly gusty as lapse rates steepen due to
cold air advection. 925mb temperatures will fall sharply, especially
during the late afternoon/evening hours. Wouldn't be surprised to
see some locations along the international border see falling
temperatures late in the afternoon, though increasing sun under
clearing skies will likely temper the cold air advection. Have gone
with a model blend for temperatures, cooling Tuesday's highs a
couple of degrees from the previous forecast but not going with the
coldest guidance. This gives highs in the low-mid 70s in higher
elevations with the wider valleys in the mid-upper 70s to around 80.
Tuesday night will be quite cool, though radiational cooling will
not be optimized due to continuing northwest winds. Lows will mainly
be in the mid 40s to around 50, with perhaps some upper 30s in any
sheltered valleys that are able to see lighter winds.


As of 327 AM EDT Sunday...High pressure will build over the region
for Wednesday into Thursday, with the deepening upper low slowly
spinning into the Canadian Maritimes. A weak upper disturbance will
traverse through the northwest flow on Thursday, but high pressure
looks to keep it and any associated precipitation shunted just to
our southwest. Models diverge thereafter with considerable spread in
the handling of Tropical Storm Laura's remnants. Unlike 24 hours
ago, the GFS is now fastest with picking the remnant low up and
phasing it with northern stream energy toward the end of the week.
The result is a swath of rain spreading across the North Country
late Friday through Saturday, with 24-hr QPF amounts of 2-3 inches.
Meanwhile, the ECMWF does not phase Laura's remnant low and the
northern upper trough, instead building high pressure in behind a
quick frontal passage and keeping us nearly dry for that same 24-hr
timeframe. The CMC lies somewhere in the middle of these two
extremes. Needless to say, have stayed with a model blend for late
week owing to these wide differences in model solutions.


Through 06Z Monday...Pockets of fog developing in the valleys,
impacting KRUT and KMPV at this time with 1/4SM to 4SM
visibility. Some fog should also shortly develop over KSLK
before high clouds begin to bring visibilities back upwards
towards 10Z. The remainder of the region is VFR. Warm front
edges east towards 09Z, with a shower or possible near KMSS.
More widespread shower activity will develop after 14Z. Mentioned
mainly VCSH, except at KMPV where VCTS is mentioned and KRUT 
with -TSRA from 20Z-22Z. Thunderstorms could produce brief 
drops to ceilings and visibilities, as well as gusty winds. We 
should see southwest winds at 4 to 8 knots transition to 
northwest around 18Z-22Z as a weak cold front slides south, but 
it is forecast to stall in our region. Timing of the wind shift 
may vary some in timing and location. Showers decline after 00Z 
and winds become light and variable.


Monday: VFR. Chance SHRA, Chance TSRA.
Monday Night: Mainly VFR, with local MVFR possible. Chance SHRA,
Chance TSRA.
Tuesday: Mainly VFR, with local MVFR possible. Likely SHRA,
Slight chance TSRA.
Tuesday Night: VFR. Slight chance SHRA.
Wednesday: VFR. Slight chance SHRA.
Wednesday Night: VFR. Chance SHRA.
Thursday: VFR. Chance SHRA.




NEAR TERM...Haynes
SHORT TERM...Hastings
LONG TERM...Hastings

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