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Area forecast discussion 
National Weather Service Memphis Tennessee
1220 PM CDT Wednesday Jul 1 2015

Discussion...
updated for 18z aviation discussion.

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Previous discussion... /issued 958 am CDT Wednesday Jul 1 2015/

Update...

As of 945 am across the region...a complex of showers and
thunderstorms continues to move into the region from the northwest.
Models depict the complex maintaining through the afternoon...especially
in those areas of west Tennessee nearest the Tennessee River...and thus have
increased probability of precipitation for the rest of the morning and afternoon
primarily across northeast portions of the County Warning Area. Cloud cover will
be a hindrance to decent daytime heating today across much of west
Tennessee and east Arkansas...with the current temperature forecast being on
track with the warmest temperatures across the Delta where the
lowest cloud cover will reside. Other than the slight adjustment
to probability of precipitation the forecast is on track...with the possibility of a few
strong to severe storms this afternoon and evening.

Zdm

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Previous discussion... /issued 459 am CDT Wednesday Jul 1 2015/

Discussion...surface analysis early this morning places a quasi-
stationary boundary along I-70 in Missouri. Water vapor
satellite/regional WSR-88D VAD wind profiles indicate a mesoscale
convective system /MCS/ has developed in the past 2-3 hours across
west central Missouri near Kansas City and being fed by a 35 knots
850 mb low level jet. Meanwhile...as of 4 am CDT the middle south is
rain free with temperatures ranging from the lower to middle 70s
with the warmest readings occurring mainly along and west of the
Mississippi River. Severe thunderstorm potential today and again
on Thursday...and the potential for heavy rainfall into the Fourth
of July weekend are the predominant concerns in this morning/S
forecast.

Short term models indicate the mesoscale convective system /MCS/
north of I-44 in Missouri will continue to propagate south/south
southeast to the lower Mississippi Valley this morning...perhaps
reaching portions of northeast Arkansas and the Missouri bootheel
this morning after daybreak. This mesoscale convective system may weaken as it comes into
the middle south. However...a combination of outflow boundaries from
this overnight system combined with surface based cape values
rising to 3000-4000 j/kg...0-6 km bulk shear between 35-40
kts...favorable upper level winds aloft suggest a potential for
severe thunderstorms across the middle south today. Damaging winds
will be the predominant severe weather threat with a secondary
threat of large hail. Localized flash flooding from heavy rainfall
will also be possible as precipitable water values will increase
to around 2 inches. High temperatures today will range from the
lower 80s near the Tennessee River and middle to upper 80s
elsewhere.

At this time...feel there may be a decrease in convective activity
this evening as the atmosphere may be a bit worked over initially.
However...models suggest a 40 knots 850 mb low level jet will develop
over portions of southern Missouri/Arkansas late tonight with the
potential for another mesoscale convective system to develop and spread into the middle south
on Thursday. Favorable winds aloft combined with 0-6 km bulk shear
between 35-40 kts...moderately steep 700-500 mb layer middle level
lapse rates around 6.5 c/km and moderate instability suggest a
potential for severe thunderstorms across much of the middle south
again on Thursday. Precipitable water values around 2 inches will
pose a potential for heavy rainfall across portions of the middle
south.

Long term model trends indicate an upper level trough will remain
across the eastern United States Friday through the Fourth of
July weekend. Consequently...several shortwaves embedded within
northwest flow aloft are expected to move through the region
producing a potential for showers and thunderstorms each day.
Strong to severe thunderstorm potential along with heavy rainfall
may be possible at times during this period.

At this time...have decided to hold off on issuing a Flash Flood
Watch for portions of the middle south Thursday/Thursday night with
this forecast issuance due to some lingering timing/coverage
concerns. This may need to be considered in subsequent forecasts
especially with the potential for heavy rainfall to pose a threat
into the upcoming Holiday weekend. Stay tuned...

Cjc

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Aviation...
18z tafs

Tricky period ahead as storms could impact each site at anytime.
Best guess is for late this afternoon/early evening...and then
again late tonight/middle morning. Out of all the sites tup has a
slightly lower threat for activity. Outside of convective
activity expect VFR weather. Winds will be mainly southwest or
west at 6 to 10 kts...with initial north wind at mkl and a few
higher variable gusts during storms.

Jab

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Meg watches/warnings/advisories...
Arkansas...none.
MO...none.
MS...none.
Tennessee...none.
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