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fxus64 klch 211535 
afdlch 


Area forecast discussion 
National Weather Service Lake Charles la 
1035 am CDT sun Mar 21 2010 


Update... 
first full day of Spring will feel more like winter as very cold 
airmass builds into the region. Wrap around moisture on the backside 
of an upper low moving across northern Louisiana and southern 
Arkansas will continue to bring clouds across the majority of the 
area. Some very light precipitation will fall across the extreme 
northern zones. 1000-850mb thickness values according to laps 
analysis are below 1290m in the northern zones...with 850 mb wetbulb 
between (-7c) and (-8c) with 1000mb and surface wetbulb around 
(+1c)...therefore some snow will be possible...and there have been 
reports of snow flurries recently around Fort Polk and as far 
south as between Delaware ridder and Rosepine. With surface temperatures well 
above freezing and the precipitation so light...no worries from 
this precipitation. Surface and 1000mb temperatures warm enough by 
earlier afternoon that despite the cold 850 mb temperatures...any precipitation 
that remains will be very light rain or sprinkles. 


Vwp showing 25 to 30 knots above the surface...and these winds 
should mix down to the surface causing very breezy conditions and 
a lake Wind Advisory will be in effect through afternoon. 


No changes for the marine zones. 


Rua 


&& 


Previous discussion... /issued 710 am CDT sun Mar 21 2010/ 


Discussion... 
for 12z taf issuance. 


Aviation... 
water vapor imagery shows a cutoff low sliding across the arklatex 
region this morning while surface analysis shows associated surface low 
sitting over northestern Arkansas with a trailing cold front back through near 
Mobile Bay. Satellite imagery and surface observation show wrap around 
cloudiness stretching back across eastern Texas while making slow 
progress eastward while dry air aloft begins to dissipate the cloud 
cover on the back side. Expect VFR ceilings all sites by middle- 
morning before clouds scatter out later today. Main story today 
will be the winds the combo of a tight gradient and stronger winds 
aloft mixing down after sunrise will usher in wnwrly near 20 knots 
with gusts to 30 knots. These winds will persist through the day 
before relaxing somewhat near sunset. 


25 


Previous discussion... /issued 546 am CDT sun Mar 21 2010/ 


Synopsis...a tight gradient from a stacked low over the arklatex 
and limited daytime heating will mix strong winds to the surface by middle- 
morning over all except interior southeast Texas where the gradient 
is weaker and forested areas will provide sufficient friction to 
hold winds below the sustained 20 miles per hour threshold for Our Lake 
advisory criteria. Light wraparound rain about the low will affect 
our northern zones today. Expect any mixed wintry precipitation to melt 
about 500 feet above the surface with the freezing level around 
1500 feet today per latest time height forecast profiles. 


Ridging and clearing skies will allow temperatures to rebound 
nicely on Monday. A weaker Pacific cold front will still bring a chance 
of some rain on Thursday. 


Short term...trimmed back probability of precipitation from guidance due to drier air 
punching in from the southwest per latest infrared imagery and negative vorticity advection. Went 
higher on Monday temperatures due to clearing skies and strong subsidence 
under the ridge while the polar jet retreats back to the north. 


Long term...due to model differences...blended in the warmer Euro 
with the colder GFS on Thursday as well as next weekend. 


Marine...gale force winds will likewise continue over 
the outer coastal waters until early afternoon. A Small Craft 
Advisory will continue over various zones of the coastal waters 
until middle-morning Monday when the far eastern zones will finally diminish. 
A low water advisory remains in effect until early this afternoon 
due strong winds with a northerly component pushing water out of 
the waterways and bays. 


Climate...we could set a record for the lowest maximum 
temperature on this date for Alexandria. The previous record low 
maximum was 48 degrees set in 1965. 


11 


&& 


Preliminary point temps/pops... 
klch 52 37 68 43 71 / 10 10 0 0 0 
kbpt 56 35 70 44 75 / 10 10 0 0 0 
kaex 44 36 66 39 73 / 20 10 0 0 0 
klft 50 37 66 46 73 / 10 10 0 0 0 


&& 


Lch watches/warnings/advisories... 
La...Lake Wind Advisory until 7 PM CDT this evening for the following 
zones: Acadia...Allen...Avoyelles...Beauregard... 
Calcasieu...Cameron...Evangeline...Iberia...Jefferson 
Davis...Lafayette...lower St. Martin...Rapides...St. 
Landry...St. Mary...upper St. Martin...Vermilion...Vernon. 


Texas...Lake Wind Advisory until 7 PM CDT this evening for the following 
zones: Hardin...Jasper...Jefferson...Newton...Orange... 
Tyler. 


GM...Small Craft Advisory until 10 am CDT Monday for the following 
zones: waters from Intracoastal City, la to Cameron, la 
extending from 20 nm to 60 nm...waters from lower 
Atchafalaya River to Intracoastal City, la extending from 
20 nm to 60 nm. 


Gale Warning until 1 PM CDT this afternoon for the following 
zones: waters from Cameron, la to High Island, Texas extending 
from 20 nm to 60 nm...waters from Intracoastal City, la to 
Cameron, la extending from 20 nm to 60 nm...waters from 
lower Atchafalaya River to Intracoastal City, la extending 
from 20 nm to 60 nm. 


Small Craft Advisory until 7 am CDT Monday for the following 
zones: waters from Cameron, la to High Island, Texas extending 
from 20 nm to 60 nm. 


Small Craft Advisory until 7 PM CDT this evening for the 
following zones: Calcasieu Lake...Sabine Lake...Vermilion 
Bay. 


Small Craft Advisory until 7 am CDT Monday for the following 
zones: coastal waters from Cameron, la to High Island, Texas 
out 20 nm...coastal waters from Intracoastal City to 
Cameron, la out 20 nm...coastal waters from lower 
Atchafalaya River to Intracoastal City, la out 20 nm. 


&& 


$$