993 
fxus61 kaly 181931 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
331 PM EDT Friday Jul 18 2008 


Synopsis... 
a very warm and humid air mass will remain across eastern New York 
and western New England through the weekend. A weakening cold front 
will drop southward across the region on Saturday and become 
stationary. A wave of low pressure is forecast to develop along the 
front on Sunday...which will result in a better chance for more 
widespread coverage of showers and thunderstorms lasting into Monday. 


&& 


Near term /until 6 am Saturday morning/... 


Severe Thunderstorm Watch 698 remains in effect until 8 PM for areas 
from the capital region northward. 


Mainly pulse-type storms with some organization have developed 
across our area...with more concentrated clusters of storms across 
far northern New York and New England...closer to where the main 
forcing is located along a frontal boundary and stronger flow. 
Still...SBCAPE values of 2000-2500 j/kg across all of our forecast 
area with real cape of 2300 j/kg from the 18z alb sounding. A weak 
cap noted at 525 mb...but isolated storms have already pulsed up. 
Coverage expected to be mainly isolated to scattered...as lack of 
significant forcing mechanism should preclude more widespread 
development. 0-6 km shear is mainly unidirectional but around 40 
kts...so organized storms with bowing segments may develop. A 
decent amount of downdraft-cape close to 1000 j/kg noted on alb 
sounding...so there is a potential for wet microbursts. 850-500 mb 
lapse rates have steepened to 6... while wbzero heights 
are high close to 11 kft...marginally severe hail will be possible 
as well. 


Convection should diminish by late this evening...as the forcing 
associated with a warm front will be well north of the region and the 
diurnally driven convection across central and southern areas will 
diminish due to loss of heating. It will be a muggy night...with 
dewpoints and min temperatures in the 60s. Some patchy fog will likely form 
in usual spots with no appreciable change in air mass. 


A few more showers and possibly a thunderstorms may develop towards 
sunrise across far northern areas...as a cool front attached to a 
low pressure system advancing eastward across Quebec starts to drop 
southward across the area. 


&& 


Short term /6 am Saturday morning through Monday/... 
the aforementioned cool front will gradually sag southward across 
our region during the day Saturday. The front will be weakening and 
slowing its progress as it starts to encounter the effects of a 
Bermuda high to the south. At this time cannot justify more than 
isolated showers and thunderstorms along the front for much of the 
area...except possibly scattered across the Adirondacks. SBCAPE 
values are generally forecast to be 1000 j/kg or less across much of 
the area...although there could be a few pockets of around 1500 
j/kg. Overall the 0-6 km layer bulk shear is forecast to be around 
20-25 kts ahead of and along the front...so storm organization is 
not likely. Looks like more of a pulse-type storm environment with 
possibly some brief gusty winds. Temperatures will still be very warm with 
dewpoints remaining high...with highs mainly in the upper 80s to 
lower 90s with warmest temperatures from the capital region southward. 


Convection should once again diminish after sunset Sat evening with 
weak high pressure building in. The front will become stationary but 
diffuse across the area. On Sunday...the old frontal boundary will 
start to lift back north as a warm front attached to a wave of low 
pressure advancing eastward across the central Great Lakes. Both 06z 
gefs/09z srefs showing a high probability of measurable precipitation...so 
will increase probability of precipitation to likely late in the day with showers and 
thunderstorms breaking out along the warm front. Even though it will 
remain quite humid...temperatures will be a bit cooler due to added cloud 
cover and developing showers/storms. 


Some differences still exist between NAM/GFS regarding the eventual 
track of surface wave...however positions have switched compared to 
previous runs. The GFS is showing a track from Albany south...while 
the NAM is farther north. Will keep mention of high chance to likely 
probability of precipitation Sun night as the warm front either continues to lift 
northward/NAM solution/ or remains stationary/GFS solution/ across 
the area. If the NAM verifies...we may briefly get into a dry warm 
sector Monday morning...before additional showers and storms develop 
Monday afternoon associated with a cold front trailing from the surface low 
along the Canadian border. This would result in the potential for 
organized storms given the linear forcing associated with the cold front 
and potentially very moist and unstable air pooling ahead of the 
front. However...the GFS is depicting we will be on the stable side 
of the surface wave at least in low levels...with a possibly large 
shield of heavy rainfall. Large uncertainty exists at this 
point...and will need to be watched over the next few days for the 
potential for heavy rain or possibly severe storms based on the 
eventual track of the low. 


&& 


Long term /Monday night through Friday/... 
unsettled weather as upper level trough/low will be over the region. 
Uncertainty in forecast grows as the week progresses and models the 
diverge and become out of phase by the end of week. The European model (ecmwf) 
maintaining trough over region with the GFS beginning to lift 
trough northward. Followed HPC lead for extended with frontal 
boundary becoming nearly stationary just off the East Coast with 
temperatures at or just below seasonable levels. 


&& 


Aviation /19z Friday through Wednesday/... 
in general VFR conditions are expected with MVFR-IFR conditions 
will thunderstorms this afternoon into the evening. Convection will 
be isolated to scattered in nature with the best chances across the 
northern portion of the forecast...kgfl have indicated threat with 
cumulonimbus in taf at this time. Will update taf as needed. Radiational fog 
will form again late tonight particularly at kgfl where IFR 
conditions are possible. 


Outlook... 
Sat night...VFR no sig weather. 
Sun-Monday night...VFR lowering to MVFR Sunday and possibility IFR at 
times in shra/tsra. 
Monday night-Tue...VFR-MVFR with scattered shra/tsra. 


&& 


Fire weather... 
a very warm and humid air mass will be over the region through the 
weekend...with isolated to scattered showers and thunderstorms this 
evening and Saturday. A cold front will drop southward across the 
region on Saturday and become stationary. A wave of low pressure is 
forecast to develop along the front on Sunday...which would result 
in a better chance for more widespread coverage of showers and 
thunderstorms. 


Relative humidity values will recover to near 100 percent 
tonight...then drop to between 45 and 55 percent Saturday afternoon. 


Winds tonight will be mainly from the south or southwest 5 miles per hour or 
less...shifting to the west during the day Saturday around 10 to 15 
miles per hour. 


&& 


Hydrology... 
typical middle Summer conditions are expected to continue through the 
period with river levels and flows close to seasonal lows. The 
thunderstorms that do from this evening and Saturday may produce 
locally heavy rainfall as precipitable water levels are quite high 
1 1/2 to 1 3/4 inches. Storm movement will vary from north to 
south with slowest movement across the southern portion of the 
forecast area where wind flow is weakest. Only localized minor 
flooding problems are anticipated mainly in urban and poor 
drainage locations. 


More widespread convection is expected from Sunday afternoon into 
Monday...as a wave of low pressure moves along a stationary front. 
Some heavy rain is possible...but it is too early to pinpoint 
exact rainfall amounts and specific locations due to uncertainty 
of position of main features. 


&& 


Aly watches/warnings/advisories... 
CT...none. 
New York...none. 
Massachusetts...none. 
Vermont...none. 


&& 


$$ 
Synopsis...jpv 
near term...jpv 
short term...jpv 
long term...iaa 
aviation...iaa 
fire weather...jpv 
hydrology...iaa/jpv 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)