Scientific Forecaster Discussion
fxus63 kpah 162230
Area forecast discussion
National Weather Service Paducah Kentucky
530 PM CDT sun Jun 16 2019
issued at 528 PM CDT sun Jun 16 2019
The kvwx and kpah VAD wind profiles showing broad unidirectional
flow of 20-40 knots during the past hour or so, supportive of a
slow transition to training heavy rainfall thunderstorm activity
versus isolated severe hail and winds.
Good surface and most unstable cape of 4-5000 j/kg2 and GOES
satellite precipitable water estimates of 1.7+ inches and
unrestricted low level inflow support of high rainfall rates in
advance of mid-level shortwave (hinted at in the kpah VAD wind
profile between 8-11kft).
Made some overall quantitative precipitation forecast/pop adjustments to reflect the transition of
the rainfall through the evening hours, as well as make some
wording adjustments to text/tabular, and gridded forecast.
Short term...(tonight through monday)
issued at 114 PM CDT sun Jun 16 2019
Atmosphere is very unstable this afternoon. A weak mid level
wave/MCV to our west will continue toward the area through the end
of the day, possibly enhancing convection. We also see evidence of a
boundary from near kevv back to the west into southern Illinois from
earlier morning convection. Strong to isolated severe storms and
heavy rainfall possible as a result. Tonight through Monday,
conditions should remain unsettled with a 700 mb/500 mb open wave forecast
to move toward the area. Pops overall have been overdone by a
considerable amount. We will play middle of the Road with pops and
use scattered terminology given the uncertainty regarding clouds
and mesoscale influences. Chances should be higher Monday with the
approach of the mid level feature. Otherwise rather warm and
humid through Monday.
Long term...(monday night through sunday)
issued at 114 PM CDT sun Jun 16 2019
The extended forecast period begins with filling of a southwest MO
low/middle level low pressure center and translation of the trough
axis through the weather forecast office pah forecast area from west to east. The
movement of this system, combined with weak ridging should diminish
pops significantly Tuesday and Tuesday night. Selected model
guidance has hinted at a diminution of pops on Tuesday, but elements
of blended and ensemble guidance have masked this subtle change.
Plan to heighten the lowered pop chances for Tuesday.
Likewise, nearly all of the medium range guidance continues to
maintain higher rain chances for Wednesday into Thursday, associated
with a broader scale, Lee side of The Rockies, generated trough.
This may generate scattered to numerous coverage of convective
activity Wednesday night as the gradient of maximum lift, vorticity,
and surface convergence comes into play.
Beyond Thursday and through at least early Saturday, a more
meridional pattern develops. More dominant ridging should serve to
suppress thunderstorm chances on Friday and Friday night. With the
transition from a zonal to meridional pattern, anticipate some
timing difference on rain chances into next weekend. At this point,
plan to go with a slower eastward transport (probably closer to the
mean 700 mb hemispheric wave speed of 15 knots) of the ridge,
leading to a drier Saturday and Sunday. Lowered pops during this
time period, within collaborative limits with neighboring offices.
issued at 1123 am CDT sun Jun 16 2019
Terminal forecasts will be kept simple. Other than vc mention
within the first 6 hours, will keep convection out of the tafs
given very low confidence in timing and evolution through Monday.
MVFR cigs across the area were more prominent than expected. We
expect improvement into the afternoon to VFR conditions. We may
see lower cigs reappear late tonight into Monday morning given
similar conditions are forecast to exist. South-southwest winds 10 to 20 kts
and gusty will become light south-southwest tonight through Monday morning.