Scientific Forecaster Discussion
fxus63 kpah 290415
Area forecast discussion
National Weather Service Paducah Kentucky
1115 PM CDT Tue Mar 28 2017
issued at 1100 PM CDT Tue Mar 28 2017
Updated for 06z aviation only.
Short term...(tonight through Thursday night)
issued at 121 PM CDT Tue Mar 28 2017
More atmospheric evolution/transformation will be occurring during
the next 24-36 hours of the forecast, as we prime up for another
system taking shape in the Desert Southwest...and poised on a
track that is not too dissimilar from the last system. In fact,
the destabilization and re-moistening of the lower trop looks to
be on similar track as well, and the wind fields aloft too look
similar. This means a slight risk for svr thunderstorms as the
system tracks in, beginning late Wed night and extending thru
thurs PM/evening, the latter time portion of which could be most
similar to yesterday's system in the spatial and intensity fields.
At this writing, however, the enhanced risk is a tad further to
Adjusted highs/lows to collaborate with slightly warmer readings
with our eastern neighbors (lmk), and slightly cooler west
(sgf/lsx), on a couple time periods.
Long term...(friday through tuesday)
issued at 121 PM CDT Tue Mar 28 2017
With the latest deterministic runs of the 12z Tuesday GFS and the
00z Tuesday (12z coming in at this time) ECMWF, both guidance models
take the current closed low south of the four corner's region in the
Desert Southwest U.S. The system becomes more vertically stacked
slowing it's progress toward and through the weather forecast office pah forecast area
through daybreak Friday.
The timing, location, and intensity of these systems a quite similar
through 18z Thursday, in line with the Tuesday wpc's extended
Given the expected vertically stacked nature of this system and to a
lesser degree the influence of transient systems to the north and
south of the closed low in the extended forecast period, am inclined
to go with the slower GFS eastward movement of the systems. This
would be closer to the classic system wave movement of 15 knots
forward movement. At the same time, prefer to blend the more
northerly European model (ecmwf) closed low track with the more southern GFS
guidance, allowing for a more southerly occluded surface pattern.
From a sensible weather basis, this will likely yield to lingering
rain shield in west Kentucky and southwest Indiana early Friday
morning. Ridging should then dominate through at least Sunday
evening across the weather forecast office pah forecast area behind the low and keep
things relatively dry through the weekend.
With the train of weather systems moving across the Southern Plains
and lower Mississippi Valley recently, antecedent moisture should
provide a Rich Reservoir of buoyancy for surface based air parcels.
This ambient moisture source may integrate into a more southerly
baroclinic zone, shifting the leading convective shield further
south than what the 00z European model (ecmwf) is advertising for next Monday
morning. This would place the weather forecast office pah forecast area in the
deformation zone in next week's system, reducing the severe
potential somewhat, but increasing precipitation efficiency (heavy
rain?) Over parts of the area.
With the slightly more southerly track, plan to lead toward the
colder bias regionally blended model guidance for temperatures,
dewpoints, and wind fields.
For next Monday and Tuesday, anticipate main convective activity
will be focused in the afternoon and evening hours. Better chances
of thunderstorm activity should remain within those time frames next
issued at 1047 PM CDT Tue Mar 28 2017
Satellite showing clearing of low clouds from south to north
across the area. So have improved fcst to VFR with only mid clouds
for the overnight and some patchy fog where the light winds may
die off. Bring in cumulus deck Wednesday after sunrise and bring
winds around to easterly.