Area Forecast Discussion
Issued by NWS Nashville, TN
FXUS64 KOHX 281143
Area Forecast Discussion
National Weather Service Nashville TN
543 AM CST Tue Feb 28 2017
FOR 12Z AVIATION DISCUSSION.
The big ticket wx item in the short term forecast period continues
to be the damaging wind svr wx threat during the overnight hours
tonight and thru mainly the morning hrs on Wed. However, lets
start off by mentioning that an early this morning grouping was
broken out in the suite of forecast products to deal with iso/sct
convection developing and spreading southwest to northeast across
the mid state region. Will thus update the suite of forecast
products shortly after 28/12Z to address the latest reasoning
concerning the short term wx pattern thru at least the mid
morning hrs. Let`s lay the foundation for the forecast from 28/12Z
forward. Both WPC and SPC both lean heavily toward the most
recent EURO solution for the short term period and thus have lean
accordingly across the mid state region. Within the gridded
forecast, went into quite some detail in detailing impacts and
associated timing concerning the wx pattern today thru Wed evening
to give the variety of customers we serve the best current idea
of how the wx pattern might evolve across the mid state region.
SPC has placed for the overnight hrs tonight most of the mid state
in either a marginal or slight risk of svr tstms. As for Wed., SPC
continues to place most of the mid state in an enhanced risk for
svr tstms. As mentioned above, damaging winds are the main threat
associated with this potential svr wx outbreak, but large hail,
a few tornadoes, and brief heavy rainfall associated with the
stronger tstms can certainly not be ruled out.
As the fastest EURO solution suggests, from the mid to late
morning hrs today, most of the mid state should experience
moderate rainfall associated with numerous shwrs and sct tstms
as convection increases from the southwest to the northeast as
a warm front to our southwest moves into the mid state region.
Generally expect areal coverage of shwrs/tstms to shift ewd as
the afternoon hrs progress, but southwesterly flow aloft with
embedded disturbances within should support sct light shwrs/tstms
across most of the mid state during the afternoon hrs, with
moderate rainfall potential continuing across eastern portions
of the area.
Leaning toward the EURO solution means that during the evening hrs
that southern and eastern areas could be dry, as overall
instability and shwr/tstm potential increase toward northwestern
portions of the mid state region. Latest EURO and WPC national
guidance as strong sfc cold front near the MS River approaching
01/12Z. Expecting the development of a pre frontal strong squall
line with numerous shwrs/tstms with moderate rainfall that will
surge eastward as 500mb flow increases to near 100kts by 01/12Z.
850mb winds will be in the 50-60+ kt range also. A low CAPE but
high atm shear environment will begin to set up across western
portions of the mid state, including the above mentioned
850mb/500mb wind speeds, by at least around 01/06Z, and should
persist across the vast majority of the mid state thru 01/18Z.
With this in mind, mentioned the potential of svr tstms from
01/09Z west to 01/21Z east. Multiple atm derived EURO svr wx
indicies also support this reasoning. Latest EURO solution hinting
that this progressive squall line and associated progressive
strong sfc cold front might even move faster eastward, but at
this time believe that additional model runs along with additional
forecasters meteorological interpretation needed before trying to
shorten this time period. Safe to say that the prime time for svr
tstms across the mid state in generally will be from
01/12Z-01/18Z, i.e. thru the mid to late morning hrs on Wed.
Will continue to mention categorical tstms with moderate rainfall
across the Cumberland Plateau Region during the late afternoon
hours too, but expect almost all rainfall, expect for some
lingering iso light shwrs across the far eastern portions of the
Cumberland Plateau Region to be east of the mid state by the start
of Wed evening.
Strong sfc high pressure influences will build in from the Rockies
late Wed night, Thu, and into Thu night across the mid state
region, providing dry conditions, moclr skies, and a return to
seasonal normal temps.
Taking a closer look at temps thru the short term forecast period,
with the continued development of a WAA pattern in place, highs
today will be around 15 degrees or so above seasonal normal
values, mainly in the upper 60s to around 70, mid 60s Cumberland
Plateau Region. Lows tonight will remain mainly in the mid 60s,
lower 60s Cumberland Plateau Region, thus lows will be almost 30
degrees above seasonal normal values. Even with the svr convection
possibilities and eventual progressive eastward pushing strong
sfc cold frontal passage by Wed afternoon, highs will reach into
the lower 70s across most of the mid state, with upper 60s
northwestern portions and Cumberland Plateau Region. Then after
this strong sfc cold frontal passage, lows Wed night will drop to
near seasonal normal values as a strong CAA scenario begins to
work into the mid state region, in the mid to upper 30s. Highs on
Thu and lows on Thu night will be near seasonal normal values.
Cool, dry surface high pressure will be centered across the area
Friday. Skies will be sunny, but temps will be slightly below
normal, with highs in the mid 40s to lower 50s.
The high pressure center will move off to the east through the
weekend, allowing southerly flow to bring a warmup. Highs will be
climb into the 50s and lower 60s Saturday, and well into the 60s
Sunday. Lows will be in the seasonably chilly 30s Friday night, with
mostly 40s for Saturday night.
Looking ahead to the start of the next work week, an approaching
cold front will bring a chance for showers and thunderstorms Monday.
Passage of the cold front is expected late Monday night into Tuesday
12Z TAF DISCUSSION.
Showers and thunderstorms are expected to develop and move across
Middle Tennessee today. CKV and BNA will have most of the
SHRA/TSRA from 14Z-19Z with ocnl IFR, and CSV from 17Z-22Z with
prevailing IFR. Conditions will improve some late day through the
evening with lower rain coverage, but cigs will stay mostly MVFR.
TSRA with some possible severe storms will approach from the west
toward the end of the period, ahead of a cold front. South winds
will be gusty throughout the next 24 hours. Gusts around 20kt will
occur today, with gusts over 25kt by late tonight. A 50kt LLJ
will develop tonight, and LLWS may be included in later tafs.