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Area forecast discussion 
National Weather Service Tallahassee Florida 
245 am EST Monday Nov 23 2009 


Synopsis... 
07z water vapor and h4 RUC analysis showing generally zonal upper 
level flow along the northern Gulf Coast this morning. Southern 
stream is quite pronounced with an abundant high level moisture 
stream extending from central Mexico...across the Gulf...and over 
the Florida Peninsula. Other features of note include broad ridging 
over the northeast states and eastern Canada...and shortwave energy 
moving from the inter-mountain west over the High Plains. 00z ktlh 
sounding showed a completely saturated layer below 800mb which has 
resulted in widespread low clouds and fog early this morning. The 
fog has become locally dense in spots and will be monitoring for a 
possible dense fog advisory if the significant visible restrictions 
expand. 


At the surface...high pressure centered along the middle-Atlantic coast 
is ridging down into the region. This ridge is resulting in a light 
north to northeast flow. Temperatures are generally in the 50s. The 
widespread lower clouds will slow any further temperature falls before 
sunrise. 


&& 


Short term (today through wednesday)... 


Today...quiet weather day on tap with high pressure continuing to 
ridge down into the forecast area. Main concern/ forecast dilemma 
will be with the lower clouds/fog this morning and just how fast 
these lower clouds will dissipate (if at all). Looking at BUFKIT 
soundings from the GFS...NAM...and local high-res WRF...appears 
that this process will be quite slow...especially north of the 
floria border. The level of moisture combined with the lower sun 
angle will add to the difficulty of breaking through. Will end 
the reduced visibilities around 9 am...but linger the lower clouds. 
Along and south of the I-10 corridor will keep the lower clouds 
through the later morning/midday...and then allow for partly 
cloudy skies to develop for the afternoon. North of I-10 toward 
Dothan/Albany and Tifton...profiles suggest the low clouds holding 
on till at least early afternoon...and any breaks of sun will likely 
hold off until late in the day. The clouds will also keep temperatures down 
across the north with Lower/Middle 60s common with upper 60s and 
lower 70s along and south of I-10. If the clouds hold all afternoon 
across the north...then the current forecasted temperatures may be a bit 
optimistic. 


Tonight...profiles remain quite saturated near the ground with an 
extensive area of drier air between 900 and 500mb. This combination 
should be good for the development of shallow ground fog after 
sunset. Have added patchy fog area-wide to the grids by around 9-10 
PM this evening and then expand to areas of dense fog after midnight. 


Tuesday and Wednesday...energy exiting the inter-mountain west is 
prognosticated to amplify across the northern/Central Plains tonight into 
Tuesday morning. This amplification of the pattern will help drag 
the southern stream flow back to the north into the central Gulf and 
set up a difficult forecast scenario for the middle of the week. 
Global guidance showing a series of southern stream disturbances 
moving into the central/eastern Gulf later Tuesday through 
Wednesday. This energy aloft will result in some degree of weak 
cyclogenesis/troughing to our south. 23/00z runs of the GFS and 
European model (ecmwf) have held on to their individual evolutions of this system. 
The GFS keeps the best lift/moisture profiles...and resulting best 
rain chances just to our south. The ec on the other hand develops a 
slightly better organized system/warm frontal feature...and does 
bring a decent swath of quantitative precipitation forecast into the southeast Big Bend (mainly from 
Perry...south and east to Mayo and cross city). Best forecast for 
now will be to blend these two solutions and bring a chance of 
showers to the eastern Big Bend Tuesday night and Wednesday with a 
slight chance of showers further west to Tallahassee and southern 
Georgia. Showers or not...the upper level disturbances should keep 
mostly cloudy conditions overhead for the eastern half of area from 
Tuesday afternoon through Wednesday. The further west one GOES the 
thinner this cirrus should should be...and the better chance for 
middle-week sun. Temperatures will be seasonable. NAM/met temperatures appear 
simply too cool (despite the clouds) and have trended the grids 
closer to the mav numbers. 


&& 


Long term (thursday through next monday)... 
much better agreement between the GFS and the European model (ecmwf) tonight on the 
general forecast pattern from late week through the weekend...with a 
consensus now fairly close to previous forecast trends. A frontal 
wave will be moving across the Florida Peninsula Wednesday night and 
Thursday. Behind this disturbance...high pressure will build 
eastward across the southeast...spreading cooler and drier air over 
the tri-state area through the weekend. Temperatures will start out 
above normal and trend downward to below normal by the weekend...and 
probability of precipitation will be below normal. 


&& 


Aviation... 
IFR ceilings and MVFR to IFR visibilities will prevail across the 
tri state area through Monday morning...becoming MVFR with some 
breaks especially across Florida during the early to middle afternoon. 
However...abundant low level moisture will remain in place...and 
widespread IFR conditions will develop once again Monday night. 
Winds will remain 5 knots or less during the afternoon hours 
becoming near calm during the night and morning. 


&& 


Marine... 
high pressure ridging down from the north will be in control of the 
northeast Gulf of Mexico through tonight. Seas are still up at the 
buoys but should come down slowly through the day. A weak area of 
low pressure is forecast to develop and move to our south during the 
middle-week period. Winds and seas will increase somewhat with the 
passage of this low and may at times approach cautionary levels on 
Wednesday. In the wake of this system there will be a better chance 
at a period of cautionary northwest winds from Thursday into Friday. 


&& 


Fire weather... 
lingering low level moisture through middle week will keep relative 
humidities above critical levels. Conditions will need to be 
monitored closely towards the end of the week into the weekend when 
high pressure builds across the southeast U.S. Spreading cooler and 
drier air across the tri-state area. 


&& 


Preliminary point temps/pops... 
Tallahassee 71 51 70 51 73 / 10 0 10 20 20 
Panama City 70 54 71 54 72 / 10 0 10 20 20 
Dothan 66 46 68 47 70 / 10 0 10 10 10 
Albany 65 47 68 48 72 / 10 0 10 10 10 
Valdosta 71 50 71 52 73 / 10 0 10 20 20 
Cross City 76 55 74 56 75 / 10 10 20 30 40 
Apalachicola 71 57 69 55 72 / 10 10 10 20 20 


&& 


Tae watches/warnings/advisories... 
Alabama...none. 
Georgia...none. 
Florida...none. 
GM...none. 


&& 


$$ 


Synopsis/short term/marine...mroczka 
long term/aviation/fire weather...Duval 

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