Area Forecast Discussion
Issued by NWS Jackson, MS

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FXUS64 KJAN 190201

Area Forecast Discussion
National Weather Service Jackson MS
901 PM CDT Wed Oct 18 2017

Updated for evening discussion.


Minor adjustment made to temps early to account for slightly
quicker initial cooldown this evening. Temps still expected to
bottom out in the mid to upper 40s across the region, with a few
southern and western locations settling near 50. Skies will
remain clear and winds light as high pressure continues to
influence the region.

Prior discussion below:

Tonight and Thursday...

Strong high pressure ridging will
continue to prevail over the region through the period. Strong
radiational cooling once again tonight will allow for low
temperatures to fall into the mid/upper 40s. Clear to partly cloudy
skies will prevail over the region on Thursday. With temperatures
climbing to around 80 for much of the area. /15/

Thursday night through Wednesday...

The period will start off with ridging across the Southeast CONUS
with a respective ridge axis oriented through the Mississippi River
Valley in response to a digging upstream trough over the Pacific
Northwest. Anomalous mid-level temperatures in the 90th
percentile will help keep max temps warm in the low 80s across
much of the area on Friday. The ridge axis will shift east of the
ArkLaMiss by Saturday morning and will allow for moisture return
off the Gulf of Mexico around the west side of the ridge ahead of
a cold front advancing through the Great Plains in association
with the progression of the aforementioned trough. Subtle height
falls in concert with dewpoints surging into the low to mid 60s
and 1.5"+ PWATs will result in scattered warm air advection
afternoon showers and storms on Saturday mainly along and
southwest of the Hwy 49 corridor. 25-30 kts of deep layer bulk
shear and mid-level lapse rates of 6 C/km will be sufficient to
support a few strong storms with gusty winds but widespread severe
weather is not expected. Max temps will once again reach the low
80s on Saturday.

By Sunday morning, the longwave trough axis is progged to be
centered over the Great Plains with the surface cold front entering
western Arkansas. Mid to upper 60s dewpoints and PWATs nearing 2
inches will provide plenty of moisture for widespread showers and
storms on Sunday. While some timing differences remain (the GFS is
slightly faster), both the GFS and Euro are in agreement on
bringing through multiple rounds of convection with the first
associated with a pre-frontal convergence/moisture axis Sunday
afternoon/evening followed by a second round along the actual
front Sunday evening/Monday morning where frontal Fn vector
convergence will be maximized. There`s also good agreement,
although somewhat inconsistent, that a cold core upper-level low
will close off and keep rain chances across the CWA through
Monday. Extensive cloud cover should limit the degree of
destabilization and the strongest shear will lag behind the front
so at this time widespread severe weather is not expected on
Sunday. A few strong storms with gusty winds will be possible
mainly east of I-55. Explicit model QPF has widespread 1-2" totals
with higher amounts possible, which isn`t surprising given the
aforementioned moisture parameters and plentiful synoptic forcing,
but given the antecedent dry conditions will hold off on any
heavy rainfall and flooding mention in the HWO/graphics until the
models come into better agreement on exact spatial and temporal
evolution of any heavier rainfall totals. The progressive pattern
and uncertainty as to whether the upper low closes off will also
play a big role in how much rainfall is realized.

Much cooler and drier air will filter in behind the frontal
passage with fall like conditions through the rest of the period
next work week. The widespread rainfall with the frontal passage
should preclude any fire weather concerns despite the drier air
advecting in. /TW/


00Z TAF discussion:
VFR conditions are expected through the next 24 hours. Winds will
be light and generally out of the east to southeast through the
period. /28/


Jackson       48  82  52  83 /   0   0   0   0
Meridian      45  80  49  83 /   0   0   0   0
Vicksburg     45  82  51  84 /   0   0   0   0
Hattiesburg   49  81  53  83 /   0   0   0   0
Natchez       50  81  54  83 /   0   0   0   0
Greenville    47  80  50  82 /   0   0   0   0
Greenwood     46  80  49  82 /   0   0   0   0




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