Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
656 PM EST Friday Nov 27 2015
Short term...(this evening through Saturday night)
issued at 237 PM EST Friday Nov 27 2015
Cold front stretching from southeast lower Michigan to northwest Arkansas will continue to
sag very slowly southeast...with its associated rain showers
gradually making their way into eastern Kentucky. There is good model
agreement on the front finally making its way into the forecast
area Saturday night. Rain chances will gradually increase as the
front draws closer with rain becoming likely in the northwest part
of the forecast area Saturday morning...and rain becoming likely
in the southeast part of the forecast area Saturday night.
There was another large temperature difference between the ridges
and valleys last night...with a low of 52 at jkl and a low of 33
at the quicksand Kentucky mesonet site just 3 miles away. It will be a
different story tonight with higher dewpoints and clouds
continuing to thicken and lower. Tonight the colder valley
locations will only be a few degrees cooler than ridge
locations...with lows mainly in the upper 40s and lower 50s.
Clouds and rain will keep temperatures a little cooler on Saturday
than today...but still mild with highs mostly in the upper 50s to
lower 60s. Another mild night is in store Saturday night with
temperatures again in the upper 40s to lower 50s.
Long term...(sunday through friday)
issued at 348 PM EST Friday Nov 27 2015
A stalled frontal boundary is expected to be situated near the
southern edge of the forecast area at the start of the period.
Precipitation due to elevated warm air advection/overrunning will
likely be occurring at times near and north of the front. A large
upper low over the western Continental U.S. At the start of the period will
slowly move east toward the Great Lakes. This will lead to surface
cyclogenesis over the middle of the nation...which will pull the
frontal boundary north as a warm front...but also propel a cold
front eastward through the region Tuesday and Tuesday evening.
This will bring a continuation of rain. As the front is exiting
the area...the parent low will be pulling away to the NE and the
front will become more parallel to the upper level flow and will
slow down. This may allow some showers to linger into Tuesday
night. Dry weather is expected for Wednesday and Wednesday
night...but there is not enough confidence to go with a dry
forecast for Thursday into Friday. The GFS has a portion of the
upper trough lingering over the middle of the nation after the
main system pulls out...and as this lingering trough moves east...
surface low pressure develops along the southeast coast and throws
precipitation as far northwest as our area Thursday into Friday.
Meanwhile...the European model (ecmwf) is dry. Have only given minimal weighting to
the GFS...but this does result in low probability of precipitation in the forecast.
Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 655 PM EST Friday Nov 27 2015
Ceilings will gradually lower tonight through Saturday in advance
of an approaching cold front...possibly flirting with MVFR
heights by tomorrow afternoon. Rain will hold off until late
Saturday morning into early Saturday afternoon for the southern
and eastern part of the forecast area...but rain is expected to
spread into the northern part of the forecast area by Saturday
morning...around 11z at sym. The heaviest rains will likely bring
some MVFR visibilities to sym by tomorrow morning...and by early
afternoon elsewhere. Winds will remain light and generally from
the S to SW. Beyond the taf forecast period ceilings will
continue to lower and rain will spread across the area with
conditions deteriorating to MVFR to IFR Saturday night.