713 
fxus61 kcle 181652 
afdcle 


Area forecast discussion 
National Weather Service Cleveland Ohio 
1252 PM EDT Friday Jul 18 2008 


Synopsis... 
high pressure over the Ohio Valley will move to the middle Atlantic 
coast tonight. This will keep the area under a southwesterly flow 
of very warm and humid air through the weekend until a cold front 
moves through Sunday night. Upper level low pressure will move 
into the area early next week will bring unsettled weather and 
cooler temperatures for the first half of the week. 


&& 


Near term /through tonight/... 
limited cape for today across the area and with subsidence under 
the high will keep forecast dry. Guidance temperatures near 90 or so look 
good. Models show increasing moisture aloft/convective debris 
across the area during the day however expect this to be thinning 
as it moves in so pc should be good for sky condition. 


&& 


Short term /Saturday through Sunday night/... 
cold front through the central Great Lakes will approach the area 
tonight and by Saturday 12z manual charts have the front just 
north of Lake Erie. Looking at the nam12 925mb temperatures and winds 
suggests the front drops into the northern tier of counties during 
the day. Expect the front will not drive too far south however 
given the developing low to our west. For now have decided to 
cut probability of precipitation across the southern tier of counties but will continue 
with small chance pop across the northwest and northeast corners. 
Also have a slight chance in the graphics for the central Lakeshore. 
Will continue with chance probability of precipitation Saturday night as the low moves 
through the central Great Lakes as NAM shows fairly deep moisture 
remaining across the area. Sunday the low will move east of the 
area and the front will again head south and will sweep across the 
region. With the front in the area will need to continue with the 
mention of showers and thunderstorms. Will keep probability of precipitation in the chance 
category. 


&& 


Long term /Monday through Friday/... 
not a lot of change in the forecast for the extended portion. Both 
the GFS and European model (ecmwf) bring an upper low into the Great Lakes early in 
the week. Would expect cooler temperatures and at least scattered 
showers and thunderstorms across the area given the instability 
from the cool air aloft. Will need to keep chance probability of precipitation in the 
forecast through middle week. Have lowered temperatures from HPC guidance by 
a couple degrees Tuesday through Thursday with highs generally 80 to 
85 across much of the area and 75 to 80 extreme northestern Ohio and northwestern 
PA. Expect warmer and drier conds late week as the upper low pulls 
northeast as an upper ridge builds across the nations midsection. 


&& 


Aviation /18z Friday through Wednesday/... 
ridge continues over the taf locations through the period. The 
weak cold front to the northwest may impact the forecast area 
Saturday afternoon but the models are inconsistent with the 
impacts at this time. The main concern this afternoon is the 
instability over the eastern areas. Northwest PA and parts of NE Ohio are 
unstable this afternoon. Model soundings from eri show cape over 
1500 this afternoon with a very weak cap. I expect some isolated 
thunderstorms over the east this afternoon but coverage will be 
limited. I will keep the mention of thunder out of the tafs at 
this time but will monitor the development ttstms his afternoon. 
Cumulus fields should range from 4kft to 5 kft over the area. The local 
height is lower over the east and with the instability it is 
possible the cumulus could go broken. It is much more stable over the 
west and few cumulus should develop in this area. Bases will be higher 
in the west and I do not expect the cumulus to go broken in this area. 
There is a better chance of thunderstorms as Saturday as the front moves 
closer to the region. 


Winds will once again become weak overnight. With the high 
dewpoints in place...haze is a distinct possibility overnight. 
MVFR haze conditions are possible over most taf locations overnight. 


Outlook...VFR conditions will remain over the area this weekend 
into early next week. Some isolated thunderstorms are possible as 
a weak frontal boundary moves through the region Saturday and 
Sunday. This storms could produce brief MVFR conditions but the 
general weather pattern will remain VFR. 


&& 


Marine... 
high pressure moving to the southeast coast will allow a weak cold front to 
drop southeast across Lake Erie later Saturday...aided by lake breeze 
enhancement. A wave of low pressure is expected to move east-northeast across 
the lower part of the lakes Sat night and Sunday which should lift 
the front back north of Lake Erie early Sunday before finally 
pushing the front well southeast of Lake Erie late Sunday and Sunday 
night. Monday and tuesday's weather features more uncertain but 
think a trough will cross the area late Monday night then high 
pressure will spread southeast into Lake Erie later Tuesday. 


&& 


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


&& 


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