351 
fxus64 kjan 202113 
afdjan 


Area forecast discussion 
National Weather Service Jackson MS 
413 PM CDT Sat Mar 20 2010 


Short term...tonight through Monday night...the Vernal equinox began at 
12:32pm CDT and for today...it has felt like Spring. Temperatures 
have risen into the upper 60s and lower 70s across the arklamiss. 
Many locations are running just a couple of degrees cooler than 
yesterday as increasing clouds have hampered optimal insolation. 
These clouds come ahead of our next storm system...which is taking 
place just to our west...and should affect our region later this 
evening into the overnight hours. 


Currently...light rain with isolated thunderstorms are located 
across west central Louisiana from the East Texas line to around 
Shreveport. This is in association with a rather strong cold front 
that extends from near Longview Texas...to Huntsville Texas...down 
to the southern tip of Texas. Behind the front...potent cold air 
advection is taking place as locations across south/central Oklahoma 
and northern Texas have remained in the upper 30s all day with snow 
and blowing snow reported in some locations(dont tell them that it 
is the first day of Spring!). blustery northerly winds with speeds 
20-30mph gusting to 40mph have prevailed today. This is all a 
prelude for whats to come across the arklamiss tonight into Sunday. 


For tonight...cloudy skies will continue ahead of the front. Expect 
the bulk of the precipitation to hold off until 00z and after...as this is 
when the front should be on our doorstep. This system should be 
fairly fast moving and be through most of the arklamiss by 12z. Not 
too confident in how much actual thunder we will get with showers 
tonight. Instability will be very very limited with this system and 
models show that the best area for thunder activity would be further 
south of my County Warning Area. That being said...I have removed thunder for areas 
north of I-20 as I feel there should just be showers here and left 
in a small chance in the south. As has been the trend...severe 
weather does not look likely and the best we would likely see would 
be a strong storm or two in the southeast....if that. 


The bulk of the moderate precipitation should be to our east by middle morning 
Sunday as the surface low hangs up over Arkansas. Following on the heels 
of the surface low...the middle level low will drop down into our 
region. This will allow significant cold air advection to take place 
following frontal passage overnight across the northwest and continuing into 
Sunday across the entire County Warning Area. Highs for eastern portions of the County Warning Area 
could even occur early in the period before dropping during the day. 
This cold core will cool the atmosphere to below freezing with the 
exception of a small shallow layer close to the surface. As the 
moisture wraps around these lows...there is the possibility for some 
light snow/flurries to mix in with the light rain Sunday morning and 
afternoon...mostly across areas north of I-20. However...I did add 
mention of snow further south. As the cold core drops south Sunday 
evening and night...some of the moisture wrapping around may be warm 
enough to be rain across the north and colder just to the south of 
this yielding snow. Snow will be hard pressed to stick to much of 
anything given above freezing surface temperatures and the warm soil conditions 
as of late. Locations further to the south of I-20 should see a 
smaller chance for some light rain as it appears a drier punch of 
air will move in behind this region. 


As the middle level low departs the region Sunday night into 
Monday...rain chances will persist as moisture continues to wrap 
around the low into the region. By 12z Tuesday...the region will 
resume drier weather. 


As for other elements...the passage of the cold front and tightened 
pressure gradient will bring gusty west winds to the region. Due to 
this...and induced instability caused by colder air over warmer 
lakes...we will hoist a lake Wind Advisory for the western larger 
lakes beginning 03z tonight and expanding it for all lakes in the 
County Warning Area for tomorrow through 00z Monday. Lastly...I stuck fairly close 
to mav numbers though did increase probability of precipitation some in the north for Sunday 
given proximity to moisture around the lows. Temperatures came in good as it 
will be a chilly first full day of Spring. This will hopefully be 
Winters last hurrah! /28/ 


Long term...Tuesday through Friday... flat upper ridging develops 
by Monday night with surface ridging into the area by early Tuesday. 
Forecast soundings show clouds clearing with the possibility of some 
fog developing Monday night. Weak high pressure continues Tuesday 
before shifting east of the area Tuesday evening. The first in a 
series of shortwaves lifts into the area in developing SW flow 
Wednesday. Moisture will be on the increase by Wednesday night in 
developing southerly flow ahead of a cold front that will shift into the 
arklamiss Thursday night. There will be enough instability lapse rate 
wise and some cape for showers and mostly elevated thunderstorms with 
this system for Wednesday night through Friday. The rains will end 
from the west by Friday night. 


Went close to mostly ensemble guidance as the upper flow flattens out 
for the period until the system for Thursday into Friday. Made some 
downward adjustments to MOS probability of precipitation for Wednesday as the system 
approaches. Also increased probability of precipitation slightly for Thursday night into 
Friday. Otherwise went close to mex probability of precipitation for the rest of the period. 
/17/ 




&& 


Aviation...VFR conditions will prevail this afternoon with ceilings 
generally above 5000 feet. Very poor flying conditions will develop 
tonight and persist through Monday. A strong cold front will pass 
across the area overnight and will be accompanied by widespread 
rain/thunderstorms and IFR conditions...initially at glh around 00z then 
shifting to gwo/Jan by around 02z then to gtr/mei/hbg around 04z. The 
bulk of rain/thunderstorms should end prior to 12z...but as the upper low 
moves across there will be widespread MVFR restrictions due to 
stratus with more IFR conditions developing from west to east later 
Sunday into Sunday evening due to poor visibility in light 
rain/drizzle and low stratus. /Ec/ 




&& 


Preliminary point temps/pops... 
Jackson 39 45 35 49 / 100 59 49 14 
Meridian 43 48 33 49 / 100 77 43 15 
Vicksburg 37 44 35 51 / 100 55 49 14 
Hattiesburg 47 50 36 54 / 100 41 22 14 
Natchez 35 48 34 52 / 100 41 39 1 
Greenville 40 44 35 50 / 100 75 59 19 
Greenwood 41 46 34 48 / 100 76 56 22 


&& 


Jan watches/warnings/advisories... 
MS...lake Wind Advisory from 7 am to 7 PM CDT Sunday for msz026-030- 
031-043-049-052. 


La...Lake Wind Advisory from 10 PM this evening to 7 PM CDT Sunday 
for laz009. 


Arkansas...lake Wind Advisory from 10 PM this evening to 7 PM CDT Sunday 
for arz075. 


&& 


$$ 


28/17/ec 

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