732 
fxus61 kcle 212034 
afdcle 


Area forecast discussion 
National Weather Service Cleveland Ohio 
334 PM EST Sat Nov 21 2009 


Synopsis... 
high pressure will be over the area tonight and then move east 
Sunday. A weak disturbance will move across the area Monday night 
and Tuesday. A cold front is expected to cross the region Wednesday. 


&& 


Near term /until 6 am Sunday morning/... 
the question is will the clouds go away over the eastern counties 
and will dense fog develop over Northwest Ohio and the areas where 
the skies clear. Will keep the clouds going in the extreme eastern 
counties but with the low level moisture some patchy dense fog 
could develop there. Elsewhere skies will be or become mostly 
clear with areas of dense fog developing. The dew points did drop 
a little over Northwest Ohio but saturation should occur quickly. 
A dense fog advisory may be needed...at this time not confident 
enough to issue it. Will update the severe weather potential statement hazardous weather outlook to 
talk about dense fog. This time of year the fog will be slow to 
burn off Sunday morning. Over Northwest Ohio went a little lower 
than guidance with the dense fog expected to develop. 


&& 


Short term /6 am Sunday morning through Tuesday night/... 
some morning fog Sunday...otherwise partly to mostly sunny. With 
some sun the warmer MOS guidance looks good. If the fog stays too 
long temperatures may not recover as much as expected. 


For Sunday night partly cloudy with some cirrus in the area. Could 
be a little wind...not forecasting dense fog in the zones/grids at 
this time. Went with the cooler guidance. 


The models don't agree with the forecast for Monday through 
Tuesday night. The NAM is dry Monday and through Tuesday while 
the other models try to bring in some light quantitative precipitation forecast with a warm front 
ahead of the low. At this time with confidence low kept the probability of precipitation 
in the 20% range. For Tuesday night when the front gets closer the 
threat of showers will be better. The European model (ecmwf) is a little slower 
with the initial front...none the less will have the threat of 
showers. 


Went warmer for Monday than the guidance with some sunshine. For 
Monday night if the NAM is correct and there aren't many clouds it 
will be cooler. Using the other models so went with the warmer MOS 
guidance. Otherwise the HPC/gridded most guidance was reasonable. 


&& 


Long term /Wednesday through Saturday/... 
Wednesday and Wednesday night the threat of showers is the best as 
the front will be around even with the models having different 
timing. Even with the faster GFS it will still be warm enough for 
rain. 


Goodbye fall...hello winter. This forecast period will see the 
transition from the Fall weather pattern to where we should be this 
time of year. 


Models are in agreement that a surge of Arctic air will plunge south 
toward the forecast area on Thanksgiving day and continue into early 
Saturday. Precipitation is expected to remain all rain on Thursday 
but 1000 to 850 mb thickness values expected to drop to near 1300 
and this would suggest a mix of rain and snow by Thursday afternoon. 


Colder temperatures expected for Thursday night in the wake of the 
Arctic front will change precipitation over to all snow and will 
continue through Friday into Friday night. As high pressure moves 
east into the region...flow will become well aligned for some lake 
effect to develop across the snowbelt region of northeast Ohio and 
northwest Pennsylvania. 


Drier air will work into the region Saturday and flow will begin to 
shift away from the lake to cause the lake effect snow showers to 
gradually come to an end by Saturday night. Weather should be good 
for Holiday travelers heading home on Saturday across the region. 




&& 


Aviation /21z Saturday through Thursday/... 
skies are starting to clear out in the west as upper level 
shortwave rotates east through the area. Some residual cloud cover 
will linger in through much of the night in the east. Clearing 
should work its way east and be at Erie by tomorrow morning. 


Main problems of the day are the height of the low ceilings around 
2500 feet in the east. This should gradually lift as well through 
the evening hours. Other problem is dirty air mass in place. A lot 
of haze present reducing visibilities down to around 5 miles in 
many places. I think this should continue through the evening with 
fog development across the area. With clearing skies in the 
east...visibilities will drop down to at least 2 miles at Toledo 
and Findlay. There is the possibility for lower visibilities for a 
period of time but will stick with the 2 miles for now as wind 
flow remains light but shifts around to the southeast toward morning. 


Noticed on latest visible satellite imagery what appears to be a 
mesoscale convective vortex moving through extreme northeast Ohio 
and northwest Pennsylvania. Air mass is fairly dry across the area 
and this is limiting production of showers across the region. 


Outlook...MVFR Tuesday through Thursday. 


&& 


Marine... 
Lake is expected to be quiet through much of the week. Next trouble 
will come Friday as winds pick up in association with low pressure 
and high pressure gradient increasing over the region. This will 
likely cause small craft advisories to be issued once again. Will 
have to monitor these weather features for the potential for 
increasing winds by weeks end. 


&& 


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


&& 


$$ 
Synopsis...kieltyka 
near term...kieltyka 
short term...kieltyka 
long term...kieltyka/Lombardy 
aviation...Lombardy 
marine...Lombardy