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fxus61 kcle 181926 
afdcle 


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


Synopsis... 
high pressure centered over Virginia will move off 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/... 
radar showing a few weak echoes over far eastern end leri and just 
north of the lake. Also cumulus filed staring to show some development 
over northestern Ohio and northwest PA. Surface based cape around 1000j and only 
weak cap though mixed layer cape only around 500j. Will include 
slight chance for showers/thunderstorms there this evening. Otherwise cold 
front through the Central Lakes will approach the area overnight 
remaining just north of Lake Erie. Weak low with this front just 
north of Georgian Bay moving east. Expect showers/thunderstorms 
with the front to stay north and west of the area overnight. 
Increase in cloudiness will go with partly cloudy skies over most 
of the area...southeastern areas could stay clear. Warm night with 
lows in the upper 60s and lower 70s. 


&& 


Short term /Saturday through Tuesday/... 
lots of model differences through the period. Starting on Saturday 
NAM drop front further south than GFS. NAM drops front into 
extreme Northern Ohio with GFS keeping front north of lake. Will 
continue with slight chance probability of precipitation most of the area for Saturday 
afternoon though chance probability of precipitation far NE and far northwest in area where 
thunderstorms have the best chance to move into the area. Then 
model differ going into Sunday with GFS tracking low further south 
than NAM with European model (ecmwf) probably good compromise. Generally all would 
indicate at least chance of showers/thunderstorms for Saturday 
night and Sunday. Front should move through Sunday night. High 
pressure building in on Monday should bring dry weather. However 
left slight chance probability of precipitation going with short wave rotating around low to the NE 
providing some lift and with lingering moisture behind the front. 
Preferred European model (ecmwf) and HPC manual forecasts keeping high pressure ridge 
over region then Monday night into Tuesday...keeping precipitation out or 
only slight chance probability of precipitation at most. After another day or two of very 
warm and humid weather will see temperatures fall back a little 
for Monday into Tuesday...near or slightly below Norma.&& 


Long term /Wednesday through Friday/... 
models indicate a frontal system moving through the forecast area 
on Tuesday and Wednesday. The 00z version of the GFS had the front 
becoming quasi-stationary over the region Wed-Thu. The 00z European model (ecmwf) 
pushed the front through the region and into the southeast during 
the same time period. The 12z run of the GFS is now becoming more 
in-line with the 00z run of the European model (ecmwf) and now pushes the front 
south late in the period. A weak wave develops on the front early 
in the period and should give US our best chances of precipitation Tuesday 
night into Wednesday. I will keep slight chance into the later 
periods of the forecast due to some uncertainty in the models but 
the trend is towards a drier solution in the later periods. 


&& 


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... 
winds will remain less than 15 kts through the weekend...however the 
direction is somewhat up for grabs due to significant model 
disagreement on the exact location of a front forecast to stall over 
the Central Lakes. Southwesterly flow should prevail on 
Saturday...with a lake breeze likely from Cleveland east if skies 
can remain clear enough through the afternoon. Winds should then 
turn northerly for a time Saturday night...rebound Sunday morning to 
the south... then back to the north Sunday night as the stalled 
front finally gains enough momentum to push south of the lake. 


With the largh high pressure ridge building over the area...flow 
should remain generally out of the north through Tuesday...then 
swing around to the south as return flow begins in earnest on 
Wednesday and Thursday. 




&& 


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


&& 


$$ 
Synopsis...randel 
near term...randel 
short term...randel 
long term...Garnet 
aviation...Garnet 
marine...astifan 

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