456 
fxus61 kbtv 051902 
afdbtv 


Area forecast discussion 
National Weather Service Burlington Vermont 
302 PM EDT Sat Jul 5 2008 


Synopsis... 
other than a few light evening showers or a stray storm across the 
south...high pressure will remain the dominant influence on regional 
weather conditions through Sunday with fair and mainly dry weather 
expected. A gradual increase in temperature and humidity levels 
will occur over the next few days...with the threat of showers and 
thunderstorms returning to the region by Monday...and especially by 
the middle portions of next week as a frontal system approaches from 
the north. 


&& 


Near term /through tonight/... 
as of 212 PM EDT Saturday...basic forecast remains on track for tonight 
as surface high pressure extending from the Great Lakes into SC 
Canada/northern New England maintains fair and generally dry weather across 
the region. Only fly in the ointment is a weak shortwave currently 
across south central New York progressing slowly northeastward. Weak positive vorticity advection 
and moisture return associated this feature has sparked widely scattered light 
shower activity across the Catskills/Hudson vlly/southern Vermont this 
afternoon. With current forecast track of feature across our southern zones 
this evening...will opt to introduce a slt chance of a stray shower 
through middle evening along and south of a Newcomb-Middlebury-Fairlee 
line accordingly. Otw expect mainly clear/pc skies overnight with 
radiational cooling allowing a fairly wide range in minimum 
temperature values...and patchy fog forming once again in the 
typical/favored locales after 06z...especially eastern Vermont. 


&& 


Short term /Sunday through Monday night/... 
as of 212 PM EDT Saturday...operational/ensemble solutions remain in 
good agreement on evolution of sensible weather pattern Sunday into 
Monday...showing a gradual return of warmth/humidity levels to the 
region as frontolysis occurs across southern New England and moist 
southerly flow becomes reestablished in our region. Thus a general 
persistence forecast appears to be the best course of action at this time. 
Departing shortwave may spark an isolated shower/storm across our 
extreme southern Vermont zones during afternoon hours on Sunday...otw another 
nice day in store with ample sun and light winds. Mean 850 hpa temperature 
values would support highs a few degrees warmer than today... 
generally in the l-m80s higher terrain...and M-u80s in the valleys. 
Slightly higher relative humidity/humidity vaules are expected...but levels should 
still be within the tolerable range. 


Thereafter...solutions still onboard showing mean western Atlantic high 
becoming more established and deeper though light southerly return 
flow continuing across the area. Lack of significant dynamics will 
preclude widespread precipitation...though increasing columnar moisture 
profiles and surface based instability should allow widely scattered/scattered 
after/evening convection to form across the area...especially southeastern half of the 
forecast area. Sounding profiles would indicate fairly weak wind fields 
through the lower to middle troposphere...which will lead to rather 
slow movement of cells and locally heavier downpours/point rafl 
totals should they develop. Maximum temperatures similar to Sunday...though 
with noticeably more humidity. 


&& 


Long term /Tuesday through Friday/... 
as of 238 PM EDT Saturday...rather unsettled Tuesday through 
Wednesday with drier and slightly cooler weather anticipated for 
Thursday and Friday. A hot and humid air mass will be in place 
across the north country on Tuesday with 850mb temperatures of +16 
to +17c. This should support middle to upper 80s for high temperatures 
in most valley locations. Per the 12z GFS...elongated surface trough 
should be located northwest of the St. Lawrence Valley. Also...mid-lvl southwesterly 
flow is expected to be moderately strong...with 500mb winds of 
30-40kts. These factors suggest the Prospect of scattered afternoon/evening 
showers and thunderstorms associated with daytime instability. 
Vertical shear looks sufficient for a few severe storms...and we 
will need to monitor that potential for late in the day on 
Tuesday. 


Wednesday also looks interesting as long-range models continue to 
indicate a surface wave tracking northeastward through the St. Lawrence Valley 
and a trailing cold front moving from west-east across the north country 
during the afternoon hours. Depending on timing and amount of surface 
heating...Prospect also exists for a few strong to possibly severe 
thunderstorms associated with this front on Wednesday aftn/eve. 
Overall...potential for convective activity looks more widespread 
on Wednesday owing to stronger large-scale forcing. Have gone with 
a probability of precipitation around 60 percent across 
northern/central areas on Wednesday afternoon/evening owing to model run-to-run 
consistency with frontal passage and antecedent moist air mass with precipitable water 
values around 1.5 in. 


Following frontal passage...air mass should dry out Thursday/Friday with any precipitation 
exiting northestern Vermont Thursday morning based on current indications. 
Temperatures will be near seasonably norms /around 80f in the valleys/ 
for high temperatures Thursday and Friday. We/ll need to watch for 
some periods of cloudiness with possible upper trough moving across 
northern zones Thursday night /and perhaps isolated rain showers/...but 
timing and position of that feature remains uncertain at 138 hours. 


&& 


Aviation /19z Saturday through Thursday/... 
through 18z Sunday...generally VFR across the forecast area this 
afternoon. However...a weak/slow-moving shortwave trough located over 
east-central New York is lifting northeastward...and is bringing some lower clouds 
and possible isolated -shra activity to S-central Vermont through 02z. 
Have left out -shra for the krut taf due to isolated nature of 
expected activity. Any lowered ceilings across that area will 
generally remain above 3000 feet...so Don/T anticipate any MVFR or 
IFR conditions through the remainder of the daylight hours. 


For the overnight period...some cirrus clouds will remain 
areawide associated with aforementioned shortwave trough...but some 
increase in low-level moisture and radiational cooling should be 
sufficient for dense nocturnal at kmpv and kslk after 06z through 
about 12z. Elsewhere...any fog should be brief overnight. Winds 
return to the S and SW during the 12-18z period on Sunday at light 
speeds around 5 kts with generally VFR conditions once morning fog 
dissipates. 


18z Sunday through Thursday...there is a slight chance of afternoon/evening 
thunderstorms across S-central/central Vermont Sunday...followed by a 
greater threat of afternoon/evening activity across much of Vermont and the eastern 
slopes of the Adirondacks on Monday. The storms on Monday should 
be slow /nwd/ moving...and may be associated with brief heavy 
rainfall and local IFR conditions. Greater instability on Tuesday 
will lead to scattered to numerous showers Tuesday afternoon and 
evening with local/brief IFR conditions. On Wednesday...an area of 
low pressure is expected to track northeastward through the St. Lawrence 
Valley. A trailing cold front will move from west-east across the north 
country with associated band of showers and thunderstorms. Look 
for generally MVFR conditions on Wednesday...with IFR conditions 
in the heavy showers and possible thunderstorms. Conditions should 
improve following the frontal passage on Thursday with a drier air mass 
filtering into the north country and generally VFR conditions 
based on current indications. 


&& 


Equipment... 
the ASOS at Massena (kmss) is inoperative...only altimeter is 
being reported. Technicians are aware of the problem. In 
addition...the Massena ASOS will be out of service from Tuesday 
July 8 through July 17 as Concrete work begins on the sensor 
foundations. 


&& 


Btv watches/warnings/advisories... 
Vermont...none. 
New York...none. 


&& 


$$ 
Synopsis...jmg 
near term...jmg 
short term...jmg 
long term...banacos 
aviation...banacos 
equipment... 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)