Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 060453
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1153 PM EST Wed Mar 5 2014
...Updated Aviation Discussion...
Issued 926 PM EST Wed Mar 5 2014
Threw in a chance of patchy fog in the Bowling Green region late
tonight nearest the surface ridging to our west, but otherwise no
.SHORT TERM (Now through Thursday Night)...
Issued at 300 PM EST Wed Mar 5 2014
A dry short term period is in store as an upper level low passes
well to our south. We`ll keep a northeast wind through Friday night
although it will become very light by Friday night. The main
forecast challenges will be temps and any fog/low stratus chances
for Thurs night/Fri morning.
Tonight we`ll see some upper level clouds, and low levels will be a
bit mixy so we won`t have an ideal rad cooling night. Most guidance
is in agreement that we`ll bottom out in the 20s with the usual
valleys and cool spots in the low 20s and south central KY in the
For Thursday, expect partly cloudy skies with quite the temp grad
across central KY as a sfc boundary settles to our SE. Temps will
range from the low to mid 40s across southern Indiana/northern KY to
mid 50s near the Lake Cumberland region.
Thurs/Thursday evening low level moisture will be pulled northward
into the forecast area. With NE winds becoming very light and
somewhat of an inversion developing overnight, low level moisture
looks to get trapped forming either low stratus or fog. Will
continue patchy fog for Thurs night at this time until the scenario
becomes a bit more clear. Low temps Thurs night should be in the
upper 20s and lower 30s.
.LONG TERM (Friday through Wednesday)...
Issued at 315 PM EST Wed Mar 5 2014
Friday - Saturday
Benign conditions will prevail through this time period as the
closest weather maker remains well to our south and east. A surface
low will track from the Gulf of Mexico northeastward across the
Florida/Georgia border and off into the Atlantic. At this point,
deterministic model consensus keeps the entire forecast area dry on
Friday with rain showers clipping just outside of the far southeast
corner, down by Lake Cumberland. Therefore, have continued on with
the previous forecast by keeping no mentionable PoPs in this
forecast update. Skies will be cloudier in the south as compared to
the north, thanks to this wave scooting by but that is essentially
the extent of the local impact.
All of central Kentucky and southern Indiana should see a brief
period of mostly clear skies overnight Friday but then the clouds
will reappear on Saturday, littering the skies from the northwest to
the southeast as a weak frontal boundary approaches. The front is
associated with a positively tilted upper-level trough digging
across the Great Lakes and down through the Ohio Valley, eventually
phasing out. There is a slight chance for rain showers late in the
day on Saturday, but the question is how much moisture will have
pooled into the region by this point. There seems to be just enough
to squeeze out some light rain but that`s about it and even this is
relatively low confidence that it`ll produce much of anything during
the day. If the models continue to trend slower on the approaching
showers, the next update could feasibly remove mentionable PoPs
altogether for the Saturday time frame.
As far as temperatures are concerned, they will be right around to
slightly above normal for this time of year as highs on Friday and
Saturday reach the mid to upper 50s and lows early Saturday morning
start out in the mid to upper 30s. Any cloud cover could throw off
temperatures just a bit but am not anticipating any major impacts to
what is currently forecast.
The weak front will interact with limited moisture and surface
temperatures falling into the mid 30s late Sat evening. Model
soundings suggest a very light rain and snow mix for the Nrn 1/3 of
the area. However, there is some llvl moisture, then dry in the mid
levels and lots of moisture in the upper troposphere. The srn
portion of the CWA is warmer, has weaker lift and is warmer and kept
them in the Slgt Chc to Chc POPS of rain. Thus the change is to
trim back the RASN area to the Nrn 1/3 of the area.
High zonal flow dominates with temperatures moderating to slightly
above normal as heights rise and corresponding thicknesses. It sure
appears there will be some mercury readings in the lower 60s on Tue.
All the snow should be long gone.
Tue am and Wed...
The ECM and GFS greatly disagree beyond Tuesday AM, especially in
the lower-levels (very clear on the 850mb and surface plots). For
now, plan to leave dry and let high spectrum width of model
solutions resolve themselves.
.AVIATION (06Z TAF Update)...
Updated at 1150 PM EST Wed Mar 5 2014
Not expecting a repeat of last night`s fog/stratus as low-level wind
fields are a lot more turbulent/mixy. Will keep VFR conditions
throughout the valid TAF period, with NE winds staying up around 7
kt overnight. Will keep the TEMPO group to advertise MVFR vis and a
low stratus deck (not enough for a ceiling) in BWG around daybreak,
out of respect for today`s snowmelt and BWG`s propensity for fog.
That said, low-level wind fields for Thursday night look much weaker
and will be a favorable setup for significant fog/stratus on Friday
morning. Will get to that in the next TAF set at BWG and LEX.