Area Forecast Discussion

FXUS64 KJAN 171158
Area Forecast Discussion
National Weather Service Jackson MS
558 AM CST Sun Dec 17 2017
Updated for 12Z aviation discussion
12Z TAF discussion: 
Aviation weather will be poor for most of this forecast period
from today through tonight. Widespread RA/SHRA will be moving
across the forecast area this morning before exiting to the east
by early afternoon. MVFR to IFR ceilings will accompany the rain,
but expect ceilings to lower further to potentially LIFR category
when the rain ends, especially along/east of the GWO to HKS/JAN 
corridor. Fog is looking more likely as well tonight along the 
GTR/MEI/HBG corridor due to little mixing of the moist airmass 
following this system combined with the relatively cold ground. 
As anticipated, a large area of rain and embedded thunderstorms 
is moving across the ArkLaMiss early this morning in association 
with a quick-moving shortwave trough. Anomalous precipitable water
in excess of 1.5 inches is supporting heavy downpours, and at 
least a few locations will receive over an inch of rainfall in 
spite of the progressive nature of the system. Guidance has sped 
up some with the exit of the better large scale ascent by this 
afternoon, and have adjusted the forecast accordingly. However, 
expect periods of rainfall to be possible from later tonight into 
Monday as moisture convergence and subtle perturbations in the 
large scale flow help to reinitiate shower/tstm activity, 
especially for locations along/south of the I-20 corridor. 
Otherwise, milder temperatures can be expected, especially tonight
when lows should be near 15 degrees above normal. /EC/
An active late December weather pattern will continue to divulge 
through the mid and long term portions of the forecast. This next 
seven days could be the wettest we've experienced in quite some time 
in the ArkLaMiss. WPC 7 day QPF totals are in excess of 6" in 
portions of the Delta and range from 2" upwards elsewhere. If this 
forecast holds true, it will undoubtedly put a significant dent in 
our current drought and help erase some of the yearly rainfall 
deficits at some sites and add to the surplus at others before the 
year ends.
A very moist airmass will exist over the ArkLaMiss on Monday through 
Tuesday as the persistent upper level SW flow pattern and low level 
southerly flow result in Pwats near their climatological maxes. 
Significant rain chances will persist through the early week period. 
The best chances for storms will exist on Tuesday through early 
Wednesday as a surface front that is associated with a closed upper 
low that will begin to cross the southern Plains and approach our 
region, swings through the region. Southerly flow will increase 
ahead of this frontal passage and the GFS is pretty aggressive with 
atmospheric destabilization ahead of the front, depicting CAPE 
values ranging from 400-1200 j/kg Tuesday afternoon through 
Wednesday morning. A few strong storms could be possible during this 
period but it will depend heavily on clearing ahead of and the 
timing of the frontal passage. Drier air will begin to filter into 
the region by late Wednesday after the front has swept through the 
area. Another, deeper, cutoff low will approach the region later in 
the work week, pushing another front through the region, which 
will once again lead to increased rainfall chances on Friday into 
Although model similitude begins to decrease as we get closer to the 
weekend, they have come into better agreement than previous runs, as 
they continue to depict a weather situation over the holiday period 
that definitely warrants cognizance. Confidence is still too low to 
mention any solutions just yet, but hopefully we will be able to 
better gauge solutions or possible impacts in subsequent
forecasts. /JPM3/
Jackson       65  50  65  58 /  99  22  52  42 
Meridian      57  48  62  55 /  98  35  43  41 
Vicksburg     64  50  66  58 /  94  20  58  55 
Hattiesburg   63  56  66  59 /  99  42  66  41 
Natchez       66  54  66  60 /  96  35  68  42 
Greenville    57  44  62  55 /  79   6  12  57 
Greenwood     58  46  64  54 / 100   7  15  53