Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Paducah Kentucky
636 am CDT sun Jul 5 2015
updated aviation section for 12z taf issuance
Short term...(today through Tuesday night)
issued at 328 am CDT sun Jul 5 2015
Upper level cyclonic circulation center over north middle
Tennessee is well-defined on satellite and radar imagery early
this morning. Some showers have been pivoting westward into Todd
County Kentucky the past several hours. As the low center pulls slowly
east/northeast today...the organized precipitation will continue to move
off to our east. Some of the high res models /namely the 00z nmm/
develop some isolated convection this afternoon on the western
periphery of the circulation. Isolated storms are
possible...generally along and east of the kevv/khop corridor
during the more unstable afternoon hours. Clouds should be less of
a factor than Saturday...allowing highs to reach the middle to upper
Tonight...mainly clear skies are expected as weak ridging develops
in the wake of the upper low. Lows will be mainly in the upper
On Monday...southwest low level flow will increase ahead of a cold
front over the plains. Daytime heating is expected to result in
seasonably strong instability...with convective available potential energy locally over 3000 j/kg
on the nmm model. Very little forcing would be needed to initiate
convection given little cap and dew points around 70. A weak 500
mb shortwave will progress as far east as the middle-Missouri Valley
by evening. This shortwave may be enough to trigger convection
late in the day. Forecast probability of precipitation will be in the slight chance
category. Highs should be near 90.
Precipitation chances will increase Monday night...reaching the likely
category on Tuesday as the cold front moves into southeast
Missouri and southern Illinois in the afternoon. The models remain
consistent with the idea that the front will stall over the lower
Ohio Valley Tuesday night. The tropical humidity and relatively
weak steering winds suggest that heavy rainfall will again be the
primary hazard. Wpc average amounts in the one to two inch range
look reasonable for Tuesday through Wednesday...with lesser amounts south
of the front along the Tennessee border. High temperatures will be only
80 to 85 with precipitation on Tuesday. Lows should remain around 70.
Long term...(wednesday through saturday)
issued at 328 am CDT sun Jul 5 2015
Medium confidence in the long term as models not in good
agreement on timing and placement of synoptic features and/or
precipitation chances. This uncertainty is partially responsible
for precipitation chances over all or part of our County Warning Area every 12
hour block of the long term forecast.
The long term period starts off with a quasi-stationary frontal
boundary stalled east-west over the northern half of our County Warning Area. The presence
of the boundary coupled with pooled-up moisture and instability will
likely generate showers and thunderstorms across the region through
at least Thursday. From Thursday night on is where models really
begin to diverge.
Thursday night the GFS shows zonal flow aloft beginning to back
around to the southwest. Short wave energy lifting northeast across
the plains will induce a surface low on the boundary and lift it to
the northeast. Beyond that through the end of the period the GFS
indicates weak 500 mb ridging with little to no precipitation chances.
Through the entire period the European model (ecmwf) keeps the area under zonal flow
aloft with the frontal boundary waffling back and forth across our
County Warning Area. As a result...it indicates shower and thunderstorm chances over
all or most of our County Warning Area every period. Will be interesting to see how
this plays out. Climatologically speaking...this time of year having
the 500 mb ridge building across the area would be the norm...but then
again with little to no flow...frontal boundaries with no push
behind them have difficulty displacing hot and humid airmasses.
Temperatures starting off below normal are expected to warm back to
near normal by the end of the period.
issued at 636 am CDT sun Jul 5 2015
Widespread IFR visibilities in fog early this morning will improve to 5 or
6sm in haze by middle-morning as the sun Burns it off. Some visibilities were
near zero at sunrise...mainly the kpah/kcgi areas. Soon after the
fog Burns off this morning...expect diurnal cumulus clouds to form.
Cloud coverage should be mainly scattered...but areas of VFR ceilings
are likely. Winds will remain light. Isolated showers/storms are
possible this afternoon in the kevv/kowb areas...but not certain
enough to include in tafs. Cumulus clouds will diminish this
evening...with visual flight rules through at least 06z.
Fog appears likely to form again late tonight. MVFR conditions are
expected. The probability of IFR is too low to include in tafs at
this time...but it may become necessary in future tafs.