696 
fxus62 kjax 211922 
afdjax 


Area forecast discussion 
National Weather Service Jacksonville Florida 
222 PM EST Sat Nov 21 2009 


..showers and storms possible Sunday... 


Synopsis...an nearly stacked low pressure system was tracking east 
across the Gulf Coast with an occluded closed surface low south of the 
la coast. Locally the jax County Warning Area was being dominated by a surface ridge 
that wedged down the southeast states from a center over the Ohio River 
valley. A cool and stable north-northeast flow prevailed in the low levels and 
combined with passing middle/high debris clouds from the SW...maximum temperatures 
will likely only near the middle 60s across southeast Georgia to the low/middle 70s 
across our Florida zones. 


Short term...tonight through Tuesday... 


Synopsis... 
rain chances increase tonight from west-east as the Gulf low tracks along 
the coast toward Florida. Models are in better agreement with respect to to precipitation 
timing and pop values and have used a model blend which advertises 
the highest probability of precipitation of 70-80% brushing our Suwannee Valley zones after 
midnight tonight then across our Georgia zones on Sunday. Drier air will 
filter in the middle/upper levels Sunday night...but lingering low level 
moisture Monday may continue mostly cloudy skies and a chance of 
light sprinkles as the surface low opens up across the region Monday. Temperatures 
will remain cool across Georgia with maxes in the 60s and mins in the 
50s...while farther south maximum temperatures will near 80 across our Florida zones 
with mins in the low/middle 60s. Areas of fog are likely tonight 
through early Monday. 


Severe weather potential tonight-sun... 
a warm front will begin to lift northward from South Florida tonight as 
the Gulf low tracks east. The nam12 (model of choice) positions the 
warm front across North Florida and generally keeps it near the Florida-Georgia Stateline 
Sunday due to a strong wedge holding to the north. Nam12 surface 
winds...boundary layer best lifted indices and 0-1sm srh values 
indicate the possibility of rotating storms moving inland from 
Apalachee Bay after 09z tomorrow morning along or just north of the 
warm front...however...sfc based instability will be limited to 
almost lacking per model soundings. It is not until after 15z that 
the nam12 indicates positive surface based convective available potential energy. So...even though a 
few storms may be rotating tomorrow morning...the circulations will 
likely remain elevated due to stable low levels. Midday 
tomorrow...however...there appears to be an increased potential for 
storms across the area. Models are slower to move precipitation out of the 
area...and...if any insolation can occur...there should be 
sufficient instability and dynamics to support an isolated strong or 
possibly severe storm mainly from midday through middle afternoon as 
convection moves across the County Warning Area with the main concern an isolated tornados. 


Will continue to mention possibility of an isolated severe storm in the 
severe weather potential statement on Sunday...and leave out of zfp/grids. 


Long term...Wednesday through Sat... 
an inverted surface trough is expected to amplify offshore of the Florida 
coast Wednesday as a strong upper level trough and weak surface front approach 
from the west. This will increase low level isentropic lift over 
our County Warning Area...so have indicated a low chance of showers Wednesday and Wednesday 
night. Probability of precipitation decrease Thursday as cold and dry air filter over the area 
from the northwest. Temperatures will fall below climatology values Friday and Sat with 
mins in the low/middle 40s inland with maxes in the 60s. 


&& 


Aviation...VFR conditions will prevail through at least 03z. 
Tonight...ceilings will likely lower to MVFR/IFR thresholds as 
lowering temperatures interact with easterly flow regime /elevated 
dewpoints/. In addition...visibilities will likely lower tonight in 
fog and increased shower activity. Low ceiling/visibilities will likely 
linger through Sunday morning...with conditions gradually improving 
from the west Sunday afternoon with southwesterly flow regime 
establishing across the area. 
&& 


Marine...will maintain scec headlines for the offshore legs where 
combined seas upwards of 6 feet will continue...with easterly swells 
continuing to dominate the area. Will segment zones at Fernandina Beach 
as persistent northerly wedge will linger longer across the 
southeast Georgia waters. 


&& 


Preliminary point temps/pops... 
amg 54 62 50 66 / 60 80 30 0 
ssi 59 67 58 70 / 40 70 40 0 
jax 59 73 59 75 / 40 70 30 0 
sgj 63 75 64 77 / 40 60 30 10 
gnv 60 77 60 76 / 60 60 30 0 
ocf 62 80 62 78 / 50 50 30 10 


&& 


Jax watches/warnings/advisories... 
Florida...none. 
Georgia...none. 
Am...none. 
&& 


$$ 


Enyedi/zappe/Keegan