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Area forecast discussion 
National Weather Service Buffalo New York 
729 PM EST Wednesday Mar 10 2010 


Synopsis... 
high pressure over eastern Canada and New England will only slowly 
retreat during the next couple of days as sprawling low pressure 
approaches from the plains and Ohio Valley. This will result in 
plenty of cloud but only a few showers across our region Thursday and 
Friday along with very mild temperatures. There is a threat of more 
significant rain on Saturday into Sunday as the low moves across 
Pennsylvania to the coast. Slow improvement is expected early next 
week. 


&& 


Near term /through Thursday/... 
high pressure over eastern New York and New England slides east this 
evening. Some limited moisture ahead of a warm front over the Ohio 
Valley will lift northeast tonight and a couple of weak short waves 
will also move NE across western New York. This will bring a threat of a 
few showers across the southern tier this evening and then across 
the Niagara Frontier and western Finger Lakes later tonight. The high 
will keep areas east of Lake Ontario mainly clear to partly cloudy early 
this evening with clouds incfreasing overnight. Expect lows tonight 
to be milder than last night with lows ranging from around 32 east 
of Lake Ontario, to around 40 from the Genesee Valley west. 


On Thursday, the models continue to suggest that across most of the 
region it should stay dry. The axis of higher level moisture lifts NE 
from The Finger lakes into areas east of Lake Ontario. Will carry low 
chance shower from Rochester eastward early in the morning and bring chance 
of a few showers to areas east of Lake Ontario in the afternoon. 
Further to the west from the Genesee Valley westward, after morning 
clouds the models show a wedge of drier air lifting NE from the Ohio 
Valley into western New York during the late morning and into the 
afternoon so expect skies to become partly to even mostly sunny. Expect 
highs generally from the middle to upper 40s east of Lake Ontario where 
clouds will persist. Across areas from The Finger lakes 850 temperatures of 
+5 to +7c shld give another warm day with highs generally from the middle 
50s to even a few low 60s possible across the central Genesee Valley 
and some areas south of Buffalo to western portions of the southern 
tier. The one exception will be areas along the South Shore of Lake 
Ontario from near Rochester westward, where a east-northeast wind off Lake 
Ontario will keep temperatures closer to 50. 


&& 


Short term /Thursday night through Friday night/... 
this period will feature an east to southeast flow ahead of a 
huge upper low slowly approaching from the Ohio Valley. One surge 
of moisture will lift north and across our region late Thursday nt 
int midday Friday...then a semi dry slot will follow later 
Saturday. Will increase probability of precipitation into likely range to account for this 
feature...then drop back to chance/scatd Friday afternoon. Quantitative precipitation forecast with this 
feature should average 0.25 inch or less. Most of Friday nt will be 
dry before next surge of rain approaches toward Sat morning. Friday 
temperatures will be mild...followed mav temperatures plus a degree or two with 
some downsloping...although southeast flow will turn east-NE in afternoon. 


&& 


Long term /Saturday through Wednesday/... 
models now in fairly good agreement during this period...with some 
significant quantitative precipitation forecast possible...most likely in the 18z Sat to 15z sun 
period. This will have to be watched as waterways will be running 
high due to the melting snows of the last few days. 


Models bring huge upper low to PA/Maryland area later Sat and only slowly 
drift it east later sun and off the coast Monday. There will be a 
surface reflection as well...but of most importance is the anomalous 
70-80 knots ll east-southeast jet setting up later Sat and Sat nt. This is another 
example of this unusual winter with several of these east to west 
features. The heaviest rains will be along the nose and just left of 
this jet...but it is tough to pin down 3-4 days ahead. Models vary 
with this "fire hose" ... from Delaware-Maryland-Virginia to southern PA...GFS NYC to 
central New York...ECMWF...RI to northern New York. Our region will not be impacted the 
greatest...simply because we are so far away from the ocean and due 
to some downsloping effects...but we still could be along downwind 
axis of heaviest quantitative precipitation forecast...so strip of 1 to 2 inches is possible. Will 
monitor closely. For now will just increase probability of precipitation to categorical Sat and 
Sat nt and slowly decrease into likely range Sunday. 


Threat for heavier rain eases on Sunday but we'll see see general 
lighter rain and cooler temperatures on the backside of the system as winds 
back to NE and north. Still...850 mb temperatures hold near zero so any precipitation 
will stay liquid. 


Unlike yesterday's runs when GFS held system along northeast coast 
all week...they now agree with Gem and European model (ecmwf) in pulling system off 
the coast on Monday will improving weather settling in from the north and 
northwest. Will play it pessimistic and keep chance probability of precipitation in Monday and 
Monday nt but will bring some clearing in on Tuesday with a fine day for 
Wednesday as ridging builds across the lakes. Temperatures still look moderately 
mild with 850 mb temperatures of zero to +2...supporting M-u40s/near 50 maxes 
Tuesday and Wednesday...normal maxes for middle March are in l-M 40s. Looks like 
our snowless March will stay that way through about the 20th at 
least. 


&& 


Aviation /00z Thursday through Monday/... 
a warm front over the upper Ohio Valley this evening will lift 
across western Pennsylvania...and eventually western New York late 
tonight and early Thursday. This will result in lowering ceilings across 
western New York with some spotty light rain showers. Ceilings will 
lower to between 1500-2500 feet late tonight...especially over the 
western southern tier where ceilings could drop below 1000 feet. In 
general...the VFR conditions are expected to deteriorate to MVFR as 
the overnight progresses. Sites east of Lake Ontario will remain VFR 
through the night. 


On Thursday...there may be several hours of MVFR ceilings during the 
morning over the western counties but those ceilings will rise to VFR 
levels by midday. Otherwise...VFR conditions should prevail across 
the region. 


Outlook... 
Thursday night and Friday...mainly VFR with a chance of rain 
showers. 
Saturday through Monday...MVFR/IFR with rain likely. 


&& 


Marine... 
light easterly winds tonight and Thursday morning will gradually 
freshen up Thursday afternoon and become brisk Thursday night and 
Friday as the gradient increases between a large high over Quebec 
and New England and approaching low pressure from the Ohio Valley. 
The brisk easterlies will gradually back to northeast Friday night 
and Saturday as the low moves across Pennsylvania. Small craft 
advisories will likely be necessary for the central and western 
portions of Lake Ontario from Friday on through the upcoming 
weekend. 


&& 


Hydrology... 
warmer weather in store through Friday but quantitative precipitation forecast looks minor...just a 
bit late Thursday nt/Friday am. Most of snow should be gone from lower 
elevs by end of Friday...but still a decent amount of ice in some of 
the buf area creeks so we will have to keep an eye out for any 
jams later Thursday or Friday. In addition...heavier quantitative precipitation forecast is likely on 
Sat/Sat nt...perhaps over an inch...and this would result in Hydro 
issues. We will monitor and mention has been made in severe weather potential statement. 


&& 


Buf watches/warnings/advisories... 
New York...none. 
Marine...none. 


&& 


$$ 


Synopsis...sfm 
near term...jjp 
short term...sfm 
long term...sfm 
aviation...jjp/rsh 
marine...jjp/sfm 
hydrology...sfm 

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