Scientific Forecaster Discussion

NWS Discussion
			
				

Area forecast discussion 
National Weather Service Jackson MS 
1114 am CDT Wednesday may 22 2013 


Update... 


The current weather analysis for the arklamiss is complex but 
typical for may. A convective system has move southeast of the 
forecast area and the atmosphere will need to undergo substantial 
recovery and destabilization to produce additional thunderstorm 
activity late this afternoon. The most recent guidance including hrrr/NAM 
are not very robust with convective development...but there are signs 
of a developing instability/moisture convergence axis upstream 
along/ahead of the approaching weak cold front and this should be 
sufficient for scattered storm development. In the forecast have 
reduced thunderstorm chances based on the trends and will consider removing 
the strong thunderstorm references depending on radar/observation trends in the 
next couple of hours. The updated aviation discussion is below. /Ec/ 


&& 


Previous discussion... /issued 440 am CDT Wednesday may 22 2013/ 


Short term...drier and cooler air will filter into our area tonight 
as the shortwaves shifts east. The Ops GFS was among the coolest 
ensemble member and quite cooler than the NAM MOS. Have gone closer 
to GFS MOS ensemble means for lows tonight. Will maintain northwest 
flow aloft Thursday as upper level ridging amplifies over the central 
Continental U.S.. models differ on precipitation develop over our area with the sref and 
NAM bringing precipitation while GFS and European model (ecmwf) are mostly dry. Have included 
slight chance probability of precipitation across southern half of the area by afternoon as 
enough available moisture and a subtle shortwave combine with daytime 
heating to produce a few showers and storms. Surface high pressure 
over the Great Lakes region will spread south into our area and bring 
cooler than normal morning lows for Friday morning. /22/ 


Long term...Friday through Wednesday...the air mass will continue 
to dry Friday as high pressure becomes more established. Upper 
ridging will remain in place Saturday with weak troughing forecast 
to flatten ridging for the area Sunday. Low level southerly flow will be 
in place again by Sunday but the air mass should remain relatively 
dry. The Euro brings slightly stronger upper troughing to the region 
Sunday with increasing moisture from the northwest. Its also more 
indicative of at least isolated showers for Monday...primarily in 
the north...developing surface troughing into northern Arkansas and Tennessee while 
the GFS keeps these features farther north. The drier GFS solution will 
be followed for now in the longer range but rain chances will be 
added if it begins to trend toward the slightly more active looking 
Euro. 


Cold air advection will be ongoing early Friday in the wake of the 
secondary boundary. Will follow unseasonably cool mex MOS highs for 
Friday afternoon...cutting MOS highs slightly in the far south to 
the middle 80s considering the cooler low level temperatures advertised by the 
models/forecast soundings. Significantly cooler lows are forecast by 
mex MOS for Saturday morning...including readings in the middle 40s 
over much of the area north of I-20 and east of I-55. Have adjusted these 
slightly warmer more in line with the GFS ensemble and Euro but kept 
temperatures in the upper 40s/near 50 for many of those areas for now. A 
gradual warming trend begins Saturday afternoon with a return to 
warmer temperatures and more humid conditions for Sunday into early next 
week in low level southerly flow. /03/ 


&& 


Aviation...still expect temporary IFR conditions through midday 
across portions of the Aerodrome...at glh/gwo due to low ceilings 
and at hbg/pib due to reduced visible and low ceilings associated with 
showers and embedded thunderstorms. Otherwise expect VFR conditions to 
generally predominate today with periodic cloud ceilings from 4 to 
10 kft. There will be the chance for some thunderstorm redevelopment 
during the afternoon...roughly along and southeast of the Natchez 
trace corridor. Any storms here are not expected to be severe but 
could provide very localized instances of turbulence and IFR 
conditions. A front will be pushing south into the region later 
today through tonight causing generally light and variable winds to 
become more solidly from the west and northwest. Tonight there is a 
decent probability of low clouds and fog giving IFR restrictions at 
hks/Jan/nmm/mei/pib/hbg. /Bb/ 


&& 


Preliminary point temps/pops... 
Jackson 84 64 89 63 / 41 4 15 8 
Meridian 85 64 90 60 / 47 13 15 5 
Vicksburg 84 66 89 61 / 37 4 15 11 
Hattiesburg 84 66 91 64 / 48 17 19 10 
Natchez 85 66 90 65 / 40 4 19 15 
Greenville 84 65 88 62 / 22 4 10 10 
Greenwood 83 62 88 60 / 34 4 10 7 


&& 


Jan watches/warnings/advisories... 
MS...none. 
La...none. 
Arkansas...none. 


&& 


$$ 


Ec/03/22/bb