657 
fxus61 kaly 061953 
afdaly 


Area forecast discussion 
National Weather Service Albany New York 
353 PM EDT Sat Sep 6 2008 


Synopsis... 
Tropical Storm Hanna will continue to advance northeast and exit 
the region overnight. In its wake...high pressure will settle into 
the region through early next week. The next chance for wet 
weather arrives Tuesday with a passage of a cold front. 


&& 


Near term /until 6 am Sunday morning/... 
Tropical Storm Hanna continues to accelerate northeast. A 
deformation band...that the operational GFS and ruc13 are doing 
quite well depicting in the 850mb-500mb layer...has set up across 
eastern PA and is expected to be across southeast New York into northwest CT 
and the Berks this evening then into southeast Vermont tonight as upper 
jet departs northeast Canada. Based on the latest HPC guidance and 
NHC track...will keep the Flood Watch in place at this time. 
However...based on upstream projections...we will need to watch 
for this deformation band to impact Schoharie...Albany and 
Rensselaer where the watch is not in effect at this time /it will 
be close/. Rainfall amounts are expected to be around 5 inches 
across portions of the middle Hudson Valley and northwest CT and upslope 
favored locations across the Berks...with 2 to 4 inches from the 
capital region into Bennington Vermont with less than 1 inch into the 
dacks. Frontal boundary appears to be quasi-stationary across 
western/central New York where some convection did erupt today...but 
thoughts are with the approach of Hanna that subsidence will 
increase and diminish those convective trends. 


Winds upstream associated with Hanna are strongest along the coast 
with no tropical storm force winds on the northwest periphery. So 
will continue to keep winds across northwest CT and middle Hudson Valley 
below advisory thresholds. 


&& 


Short term /6 am Sunday morning through Monday/... 
in the wake of Hanna...increased subsidence and the passage of the 
upstream frontal boundary will commence at or above 12z /probably earlier 
than later/. A brisk day with 15-20kt gusts expected with a fresh 
northwest flow as higher pressure returns to the region. Based on 
upstream temperatures into the middle and upper 70s...will follow 
suit for most areas...with some downsloping for the middle Hudson 
Valley where some lower 80s are expected under a ptsunny sky. 


Tranquil weather continues through Monday as surface high tracks 
south of the County Warning Area. By late in the day...warm advection regime 
unfolds upstream late Monday. 


&& 


Long term /Monday night through Saturday/... 
went mostly with gmos data (with some minor tweaking) for this 
extended package. 


The extended starts out with high pressure...retreating to our east 
Monday night. Both the GFS/European and HPC indicates a pretty 
potent short wave approaching from the Great Lakes Monday night into 
Tuesday morning. The warm front is forecast to impact our region 
Monday night...followed the cold/occluded front by later on the day 
Tuesday. This front looks pretty potent...and will be accompanied by 
the rr quadrant of the 90kt h250 jet. Therefore found it prudent to 
include the possibility of thunderstorms as h850 temperatures are 
quickly forecast by both models to drop from around +15c early 
Tuesday to only +5c by late Tuesday night! 


Much cooler weather looks to come in Tuesday night but the air mass 
will moderate quickly as the flow aloft become fast zonal. Sprawling 
high pressure to build in Wednesday through Thursday...with the next 
system to approach Thursday night into Friday. This disturbance will 
feature another surface cyclone with associated frontal systems 
along with the chance for more showers. Another somewhat cool air 
mass is forecast to follow for Saturday. With a cyclonic flow 
continuing aloft...cooler air moving over Lake Ontario might be 
enough to produce a lake response...triggering clouds and perhaps a 
few showers...especially across the Adirondacks. For now...just went 
20 pop everywhere for next Saturday. 


&& 


Aviation /19z Saturday through Thursday/... 
radars indicate the band of rain from the remains of Hanna were 
moving northeast across the Catskills with some convection starting 
to show up across the Upper Mohawk valley and western Adirondacks 
along and close to a frontal boundary which was slowly moving 
southeast from the Saint Lawrence valley and the eastern end of 
Lake Ontario. The rain will increase in intensity this afternoon 
and be heavy at times especially south of Albany. Any embedded 
thunderstorms will result in torrential downpours. Have addressed 
threat for thunder with cumulonimbus in the tafs. Can not rule out some 
showers between steady rain. Widespread IFR flight conditions will 
occur...especially across the higher terrain south and east of 
Albany. The heavy rain should tapering off around midnight...with 
improvement to VFR expected Sunday morning. Widespread fog is 
likely to materialize Sunday night with the large amount of 
moisture. 


Outlook... 
sun...improving conditions to VFR during the am. 
Sun night...MVFR-IFR...due to widespread development of fog. 
Monday...VFR...no sig weather. 
Tuesday...VFR-MVFR...chc shras/tsra. 
Wednesday...VFR...no sig weather. 




&& 


Fire weather... 
Tropical Storm Hanna will produce 3-6 inches of 
rainfall to the south and east of Albany...1-3 inches locally...and 
less than an inch of rain north and west of Albany through tonight. 
Rainfall rates could exceed an inch per hour this evening south and 
east of Albany...at least in a few spots. 


In the wake of the storm tomorrow...a gusty northwest breeze will 
kick and relative humidity values are forecast to drop to between 40-50 
percent...except higher over the southern greens (only dropping to 
around 70 percent there). A full recovery is expected Sunday night 
with relative humidity values approaching 100 percent. 


Dry weather is forecast Sunday through Monday with next chance of 
showers Monday night into Tuesday. 


&& 


Hydrology... 
significant rainfall is expected over much of the region from the 
Catskills north and east to and including southern Vermont...with 
two to six inches total south and east of Albany. The heaviest 
rain is expected across northwestern Connecticut...but cannot rule 
out areas of heavy rain across southern Vermont or some of the 
higher terrain of the Catskills where upslope winds are likely to 
increase the amounts of rainfall. 


Modeling observed along with forecast rainfall currently suggests 
the Housatonic River will rise above flood stage from Lake Lillinonah 
upstream to the Massachusetts/Connecticut state line. A number of 
other rivers will get close to flood stage including the hoosic 
river in Massachusetts and New York...the batten kill in southern 
Vermont...and the headwaters of the Schoharie and Esopus creeks in 
the Catskills. 


Lake Lillinonah has been lowered about seven feet during the last 
couple of days in anticipation of the heavy rain. Therefore there 
is some room to store some of the excess flow...which may enable 
Power Plant operators to keep the Housatonic below flood downstream 
from Stevenson dam. 


There is considerable storage in Ashokan Reservoir and some storage 
in Schoharie Reservoir due to the dry weather the last several weeks. 
Runoff above Schoharie Reservoir is expected to bring the water level 
above The Notch but not high enough to go over the main spillway. 
No water is expected to spill from Ashokan Reservoir. However runoff 
below Ashokan will cause the Esopus below the Reservoir to rise 
around 3 feet. 


Tropical storms usually have bands of heavy rain with rainfall rates 
of 1 to 2 inches per hour...even where no thunder occurs. Small 
stream...urban and poor drainage flooding is likely in these areas 
of heavy rain. Some flash flooding is also highly possible. Persons 
living in flood prone areas should keep up with latest forecasts 
for Hanna and associated rainfall. 


For details on the rivers...please visit the advanced hydrologic 
prediction service /ahps/ graphs on our website. 


&& 


Equipment... 
tropical z/r relationship remains in effect on the 
radar...although we have noticed some overestimate on precipitation 
algorithm. We will continue to monitor trends and may make 
adjustments to the radar precipitation algorithms with collaboration from 
erh and nerfc. 


&& 


Aly watches/warnings/advisories... 
CT...Flood Watch through Sunday morning for ctz001-013. 
New York...Flood Watch through Sunday morning for nyz058>061-063>066. 
Massachusetts...Flood Watch through Sunday morning for maz001-025. 
Vermont...Flood Watch through Sunday morning for vtz014-015. 


&& 


$$ 
Synopsis...bgm 
near term...bgm 
short term...bgm 
long term...hwjiv 
aviation...rck 
fire weather...hwjiv 
hydrology...rck 
equipment...bgm 


For the latest updates...please visit our webpage at 
www.Weather.Gov/Albany 

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