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Area forecast discussion 
National Weather Service Memphis Tennessee
1154 PM CDT Tuesday Jul 7 2015

Update...

Updated for the 06z aviation discussion

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Previous discussion... /issued 550 PM CDT Tuesday Jul 7 2015/

Update...

Based on latest radars and latest models including the hrrr and
NAM expanded the Flash Flood Watch a couple of counties further
south and also went a little further east to include much of
northwest Tennessee. The Flash Flood Watch has been sent. In the process
of updating the zone forecasts...grids and hazardous weather
outlook. Looks like boundary will set up through this region with
thunderstorms training west to east with very heavy rainfall. Also
increased rainfall amounts in the Flash Flood Watch to between 3 and
5 inches...locally more.

Added 20 percent chance of thunderstorms across all of north MS
based on current radar...but think these will gradually dissipate
with loss of daytime heating.

Jcl

Discussion... /issued 348 PM CDT Tuesday Jul 7 2015/

A heavy rain and flash flood threat should develop this evening
across portions of northeast Arkansas...the Missouri
bootheel...and far northwest Tennessee. A Flash Flood Watch will
be issued for these areas beginning this afternoon and extending
through early Wednesday afternoon.

Showers and thunderstorms continue to develop southeast along
outflow from earlier convection to the north over Missouri. This
boundary will likely be the new focus for training thunderstorms
with the threat for very heavy rainfall. Precipitable water values
in these areas are prognosticated by model guidance to exceed 2.25
inches. In addition...lift should be enhanced along this boundary
as a low level jet strengthens and noses into boundary in response
to a shortwave lifting northeastward out of Texas. This scenario
should pose a threat for heavy rainfall and flash flooding in
these areas into Wednesday morning...before refocusing further
north along a retreating synoptic warm front during the day as
the shortwave and associated surface low lift further northeast
into the middle Mississippi Valley. Rainfall amounts in the Flash
Flood Watch area should range between 2 and 4 inches...with
isolated higher amounts. These amounts have been coordinated with
HPC and surrounding offices and align well with the HPC moderate
risk for excessive rainfall.

Showers and thunderstorms should diminish in coverage later
Wednesday morning with redevelopment of scattered coverage of
storms as the atmosphere destabilizes Wednesday afternoon mainly
across northern areas. A strong storm or two cannot be ruled out
as overall shear remains strong and MLCAPES exceed 1500 j/kg.
Overall weak middle level lapse rates should limit a more widespread
severe event. Temperatures should warm back into the upper 80s
north to lower 90s south. Humid conditions should also continue
areawide as the middle south remains well entrenched in the warm
sector.

Upper level ridging will build back into the middle south from the
east by Thursday and remain in place across the region through the
weekend. This should lead to hotter and drier conditions
overall...but there may still be isolated afternoon convection
across southern and eastern sections Friday and Saturday. This
occurs as the ridge retrogrades west and slightly Lower Middle level
heights spread back over these areas. Heat indices will also creep
back up to between 100-105 which will make for uncomfortable
conditions. Conditions will be watch for possible heat
advisory...but at this time appears to remain below criteria.

The retrograding upper ridge should eventually break down along
its eastern periphery and over the eastern half of our forecast
area by early next week. This will allow for the northwest flow to
set up again with a series of shortwaves moving through the flow.
This will help to increase chances for showers and thunderstorms
and also provide slightly cooler but still humid weather
conditions.

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Aviation...
06z taf cycle

VFR conditions will continue for most of the forecast period.
Thunderstorms will continue to move across northern sections of
the forecast area overnight with ceilings and visibilities
dropping to MVFR levels at times. Winds will be mainly from the
south at around 10 knots with some higher gusts for much of the
forecast period.

Ars

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Meg watches/warnings/advisories...
Arkansas...Flash Flood Watch through Wednesday afternoon for Clay-Craighead-
Greene-Lawrence-Mississippi-Poinsett-Randolph.

MO...Flash Flood Watch through Wednesday afternoon for Dunklin-
Pemiscot.

MS...none.
Tennessee...Flash Flood Watch through Wednesday afternoon for Benton Tennessee-
Carroll-Crockett-Dyer-Gibson-Henry-Lake-Lauderdale-Obion-
Weakley.

&&

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