Scientific Forecaster Discussion
fxus63 kpah 162306
Area forecast discussion
National Weather Service Paducah Kentucky
506 PM CST Sat Nov 16 2019
Short term...(tonight through Monday night)
issued at 200 PM CST Sat Nov 16 2019
Surface high pressure extends from the Great Lakes down through
the lower Ohio River valley, while a trof of upper energy drives
a cold front into the upper Mississippi River valley tonight.
Time/height cross sections show we'll stay very dry below about
600 mb thru tonight...so maybe just some high clouds move in from
the west with the approaching trof as the night wears on. MOS
hints at (fzg) fog formation late tonight, but its same time
depressions conflict somewhat. Given this uncertainty, we'll more
or less refrain from any mentions in the grids, following the
The trof of upper level energy lifts across the Great Lakes
tomorrow, and drags the front into/across our region mainly during
the late afternoon/evening hours. While it is moisture starved,
time/height cross sections do show saturation further down the
column tmrw night. We'll go ahead and include a small evening pop
in our north with its passage, and this areal coverage may need
adjusted as the event nears.
Given the upper air evolution to deepening northwesterly flow
aloft with time, we'll stay in a cooler than seasonal airmass.
Highs will run 5-10f below climo, with lows about 5f below norms,
Long term...(tuesday through saturday)
issued at 200 PM CST Sat Nov 16 2019
Clouds will be on the decrease on Tue as a mid level shortwave moves
away from the pah forecast area, and surface ridging combines with
northwesterly flow aloft. The surface wind shift early Tue is
expected to have little effect on the surface temps and dewpoints.
Wed is expected to be partly cloudy and quite pleasant, with near-
seasonable highs in the upper 50s/lower 60s.
A closed mid level low offshore Baja California was shown with
reasonable agreement by the mid range models to eject northeastward
across the southern rockies and rapidly transition to an open wave
by Wed night. As the wave continues to move through the Central
Plains and into the upper Midwest, the strength of an associated
surface low should be enhanced by additional northern stream
shortwave energy by Thu, increasing widescale lift of moisture. The
deterministic model solutions began to differ some by then, with the
GFS not suppressing a southern Continental U.S. Ridge as much as the European model (ecmwf)/CMC,
making for a much wetter solution for Thu night and Fri as moisture
return is almost immediate in the deep southwesterly flow. The
alternative (possibly more likely) solution depicted a significant
dry punch from the northern stream that cuts off moisture return. At
this time, the nbm suggests rain showers will start over
southeastern MO/southern Illinois Wed night, with the best pop and
coverage of rain showers across the entire region during the day
Thu, diminishing from the northwest during the afternoon, and
diminishing over the remainder of the region Thu night.
The dry punch should be indicated by high surface pressure, partly
cloudy skies, and cooler temps in our region by more than ten
degrees Fri and Fri night. The National blend appeared to support
the possibility of a resurgence of pcpn late Fri night/Sat, mainly
based on more mid level energy ejecting out of the southwestern
conus, which may or may not combine with northern stream energy.
There is a low-confidence forecast of a possible wintry mix early
Sat with surface temps just below freezing.
issued at 506 PM CST Sat Nov 16 2019
Main focus for the 00z Sunday weather forecast office pah taf issuance will be
increased coverage of opaque cirrus cloud cover spilling over
mid-upper level ridge axis moving across the area. VFR ceiling
conditions should dominate for the entire forecast period.
There was some concern for longer duration fog development, but
the probability appears to be much lower than initially
anticipated, so eliminated the mention of any fog development with
this set of taf's.