502 
fxus61 kcle 061951 
afdcle 


Area forecast discussion 
National Weather Service Cleveland Ohio 
351 PM EDT Sat Sep 6 2008 


Synopsis... 
weak high pressure will build in this evening behind a cold front 
now to our east. A disturbance aloft however will move into the 
Ohio Valley from the Central Plains overnight. This upper trough 
will continue to move though the area on Sunday. Sunday night and 
Monday another area of high pressure will build in from the 
Central Plains. 


&& 


Near term /until 6 am Sunday morning/... 
main concern for the evening will be the clouds across the east 
third of the area. The remainder of the cloud cover is convective 
in nature and should dissipate rather quickly this evening. The 
east third will take a couple more hours to clear but still expect 
this to occur during the evening. Overnight expect clouds to 
increase from the west after midnight with approaching 
disturbance. Models a bit faster with the moisture vs ydays runs 
so have introduced a small chance for rain in the far northwest 
late. 


&& 


Short term /6 am Sunday morning through Tuesday night/... 
have followed the NAM forecast trends through the short term 
period although the NAM and GFS are not too far off initially. For 
Sunday both models show the upper disturbance moving east across 
the area. With minor differences in timing and intensity. Enough 
agreement however for at least middle/high chance probability of precipitation across the 
region. Drier air will move in behind the system Sunday night. So 
will go with becoming partly cloudy in zones. Monday afternoon 
brought in a slight chance in the graphics having backed off from 
chance in earlier forecasts. NAM shows upper trough digging into the 
Central Plains with surface cyclogenesis taking place in Missouri. 
Ahead of the developing low warm frontogenesis will occur from the 
low northeast across Southern Lower Michigan and Northern Ohio. Monday evening into 
Tuesday thermal gradient will continue to increase with an 850mb 
flow approaching 50 kts across the area by Tuesday morning. Most 
of the isentropic lift appears to be north of the area. Monday 
evening have increased probability of precipitation to chance in the northwest and then after 
midnight increased further to high chance. Tuesday should be the best 
chance for showers and thunderstorms as the associated cold front 
swings quickly through the area. Started probability of precipitation out with chance 
category east and likely west. For the afternoon appears enough 
dry air moves into the west to remove probability of precipitation. In the east will boost 
to likely. Tuesday night dry air continues across the remainder of 
the area so clearing and cooler looks like a good trend. 


&& 


Long term /Wednesday through Saturday/... 
models are in agreement in starting out the period on Wednesday with 
high pressure over the area which shifts into New England by late 
Thursday to allow a return flow to develop and bring increasing 
moisture and temperatures. The next weather maker will be a cold 
front that is expected to move across the area about Friday with the 
models still remaining fairly consistent with this feature so 
reasonably confident with the front although the timing could be off 
a little. Front shown to sweep through with more high pressure 
pushing in for dry weather by Saturday. 


&& 


Aviation /19z Saturday through Thursday/... 
remaining band of patchy light rain showers and dz over eastern tafs will 
continue to dissipate as moisture and energy get pulled toward the 
middle Atlantic coast where Hanna is tracking. As drier air from the 
north continue to push in expect ceilings to continue to lift and break 
up although breakout to scattered will be late in the day or into early 
evening for yng and eri. VFR should prevail tonight although cak and 
yng may see some patchy MVFR fog develop late. High and middle clouds 
spread back in from the west late tonight and Sun morning soon 
followed by scattered to numerous rain showers...especially for the northern taf 
sites but not expected to reach yng and eri through 18z. Areas of 
MVFR probably will occur with the rain showers. 


Outlook...scattered showers Sunday afternoon could produce a few 
areas of MVFR conditions otherwise VFR should dominate until a low 
and cold front move through the area Monday night into Tuesday when 
more areas of MVFR are expected in showers and possible 
thunderstorms. High pressure to provide widespread VFR Wednesday then a 
chance for more areas of MVFR should return late Thursday into Thursday night 
as scattered rain showers and thunderstorms and rain again develop. 


&& 


Marine... 
high pressure building over Lake Erie from the west should be 
putting and end to the small craft conditions over the eastern half 
around forecast issue time. Continued diminishing winds tonight as 
the high moves east across Ohio and off the East Coast through 
Monday. Some question Monday night as a S to SW flow should 
increase but the exact position of a wave of low pressure moving 
along the front will have a big difference on the potential for when 
small craft winds may develop...if not ahead of the cold front then 
almost certainly in the colder air in the wake of the front. High 
pressure and light flow return for Wednesday then an increasing S flow 
expected on Thursday. 


&& 


Cle watches/warnings/advisories... 
Ohio...none. 
PA...none. 
Marine...none. 


&& 


$$ 
Synopsis...tk 
near term...tk 
short term...tk 
long term...Adams 
aviation...Adams 
marine...Adams