364 
fxus64 khun 220844 
afdhun 


Area forecast discussion 
National Weather Service Huntsville Alabama 
245 am CST sun Nov 22 2009 


Discussion... 
the long-awaited rainfall is finally moving into the Tennessee 
Valley...and will lead to a rather wet Sunday over much of the area. 
Early morning temperatures are in the 50s...and in many cases... 
warmer than the expected daytime highs today. The incoming rain 
should help drop temperatures a few more degrees...but if that does not 
happen...a forecast update will be issued around 6 am. 


Short term (today through monday)... 
one look at radar tells you the story for today...it is going to 
rain...especially in the eastern counties this morning. The models 
are in pretty good agreement that a deformation zone of precipitation will 
develop on the northwest edge of the precipitation shield today. It 
hopefully GOES without saying that the models are not good enough to 
pinpoint where this will develop...but they all are showing 
something over the area today. Assuming this deformation zone does 
develop...areas to the north of that will be unlikely to see much 
rain at all. With this in mind...I am carrying a sharp pop gradient 
from middle-chance extreme north and west to categorical from 
Huntsville south and east. Temperatures are probably going to fall a 
bit this morning and hold steady this afternoon around 50. 


The upper low will weaken and pull away this evening...taking most 
of the precipitation with it. However...weak upper waves and continued 
low-level moisture are very likely to lead to low clouds...patchy 
fog and patchy drizzle. Could still see some measurable rain showers 
mainly from Huntsville east...but precipitation will be light. Temperatures will 
only drop a few degrees at most. 


Not sure those low-level clouds are going anywhere for Monday 
either...along with continued patchy fog and drizzle...perhaps all 
day in the higher elevations. Could still see precipitation heavy enough to 
measure in the higher terrain...so will keep a slight chance pop. I 
lowered highs for Monday significantly from the previous forecast... 
and gut feeling is that I may not have lowered them enough. 


Extended (monday night through next sunday)... 
with nothing to scour out the moisture...areas of fog are likely 
Monday night...and with light winds I would not be surprised to see 
widespread dense fog. For those who look at MOS...I have no idea 
where the NAM MOS is coming up with its lows for Monday night...or 
the 40 probability of precipitation in Cullman. Have thrown that out entirely...it is not 
even supported by the NAM itself or the sref ensemble suite. 


Tuesday is the trickiest day of the forecast. The NAM shows the low 
clouds sticking around...the GFS brings in enough southerly flow to 
mix things out. However...the likelihood of hitting the GFS MOS 
highs in the upper 60s is...in my opinion...low. I took a 50/50 
blend of the GFS MOS and NAM MOS...to try to trend toward the NAM 
solution. Also removed the precipitation mention as the next approaching 
cold front has come in with slower timing. That front does pass 
Tuesday night but has almost no forcing. Could squeak out a 
shower...but it is not very likely. The airmass behind this first 
front is not particularly cold but it is much drier. 


A reinforcing front passes Wednesday night...and that one has the 
cold air. There may even be another front behind that Thursday 
night. With the drier airmass in place...rain is unlikely but not 
entirely impossible...especially in southern Tennessee. Will leave dry for now. 
Highs Friday are unlikely to go above 50...and it appears Friday 
night may be our first area-wide freeze. Next weekend looks dry with 
temperatures a couple degrees below normal as high pressure is in control. 
&& 


Preliminary point temps/pops... 
Huntsville 52 49 56 47 60 / 80 40 10 10 10 
Shoals 54 49 58 48 60 / 70 20 10 10 10 
Vinemont 52 47 56 48 60 / 100 40 10 10 10 
Fayetteville 53 48 54 49 58 / 70 40 20 10 10 
Albertville 52 47 56 47 61 / 100 50 20 10 10 
Fort Payne 51 46 55 45 59 / 100 70 20 10 0 
&& 


Hun watches/warnings/advisories... 
Alabama...none. 
Tennessee...none. 
&& 


$$ 


Je/23