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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Saturday
• 
• High: 77 °
• Low: 61 °
• T-Storms

• Sunday
• 
• High: 84 °
• Low: 64 °
• Thunderstorm

• Monday
• 
• High: 90 °
• Low: 70 °
• Partly Cloudy

• Tuesday
• 
• High: 90 °
• Low: 66 °
• Chance of T-Storms

• Wednesday
• 
• High: 82 °
• Low: 64 °
• Chance of T-Storms

area forecast discussion 
National Weather Service Louisville Kentucky 
311 PM EDT Sat may 18 2013 


Short term (now - Sunday night)... 
issued at 300 PM EDT Sat may 18 2013 


An area of low pressure continues to spin across the forecast area 
this afternoon. Early morning light showers/drizzle gave way to a 
few hours of dry conditions. However, now, with diurnal heating, 
scattered showers have developed. Not seeing any lightning, but an 
isolated thunderstorm cannot be ruled out given the steep lapse 
rates aloft. Think the morning cloud cover helped keep instability 
down a bit. The heavier rain producing showers should reside across 
southeast Indiana and into the Kentucky Blue Grass, with isolated to 
scattered showers elsewhere. Temperatures have reached the low to 
mid 70s, with some warming still possible for several locations. 


The coverage of showers and any storm that may develop will slowly 
diminish this evening and tonight, as the upper low moves east. With 
the departing low, an upper-level ridge axis will begin to build 
across western Kentucky tonight. High resolution models continue to 
indicate we will go briefly dry by around midnight through dawn. 
Skies should become at least partly cloudy overnight, which will 
allow temperatures to drop into the low and mid 60s and perhaps some 
patchy fog or low stratus to form. Depending on the amount clearing, 
some locally dense fog could develop, especially for locations that 
receive rainfall today. 


The upper low will move to the central Appalachians Sunday, with the 
upper-level ridge axis continuing to build eastward. Expect diurnal 
scattered convection across our eastern cwa, associated with the 
upper low. Should also see some scattered convection across our 
south and southwest with a weak warm front edging into the forecast 
area. Heavy rain and of course lightning will be the main threats 
with any convection that develops. High temperatures Sunday should 
reach the upper 70s across the eastern County Warning Area and low to mid 80s across 
the west. Temperatures will drop back into the low and mid 60s under 
partly cloudy skies. Once again, could see some patchy fog develop 
around dawn Monday. 


Long term (monday - saturday)... 
issued at 310 PM EDT Sat may 18 2013 


The latest multi-model solutions continue to be in fairly good 
agreement with a large upper level trough remaining nearly 
stationary out over the plains through the first part of the 
forecast period. With the upper trough to our west, the Ohio Valley 
will see a relatively deep southwesterly flow aloft which will also 
good moisture advection and continued warm temperatures through the 
first half of the week. 


Increasing humidity levels will be evident by Monday afternoon as 
the southwesterly flow kicks into high gear. Despite having good 
moisture pooling across the region, latest model proximity soundings 
do show expanding mid-level height rises across the region. The 
height rises along with a fairly evident capping inversion will 
likely keep convection at a relative minimum Monday afternoon. 
Highs Monday should top out in the 85-90 degree range. With 
dewpoints in the upper 60s to around 70, it will feel like the lower 
90s across the region. Lows Monday night look to cool into the 
upper 60s to around 70. 


By Tuesday, the upper ridge axis looks to shift a bit more to the 
east. Correspondingly, mid-level heights lower through the day and 
the capping inversion is not as strong as what is indicated for 
Monday. As temperatures warm again into he 85-90 degree range, 
we're likely to see isolated to scattered convection develop during 
the afternoon. Latest data does not have a well defined lifting 
mechanism that stands out...other than differential heating and 
convective overturning. Therefore, still am inclined to run low 
chance pops equally across the forecast area. Given the elevated 
instability on Tuesday, a few of the storms that pop up could be on 
the strong side. The combination of high instability and weak shear 
are suggestive of pulse type convection with damaging winds and hail 
being a threat. 


By midweek, the model solutions suggest that the upper trough axis 
will slowly transition eastward from the plains into the Great Lakes 
region. Corresponding occluding surface cyclone will move from the 
Midwest into the Ohio Valley dragging a frontal boundary across the 
region. As this boundary pushes eastward, it will encounter ample 
instability and moisture to produce a large area of thunderstorms 
from the Great Lakes southward into the lower Mississippi Valley. 
Strong to severe storms will be possible as this front moves 
through. Complex and unresolvable mesoscale interactions at this 
time scale preclude defining a particular hazardous weather threat 
at this time. We feel those feature will come into clearer view 
over the next few days. 


The upper trough will slowly head eastward through the southern 
Great Lakes on Thursday with a secondary frontal cruising through on 
Thursday bringing yet another round of convection to the region. 
Upper trough then looks to push on off to the east on Friday with 
mid-level height rises taking place and surface high pressure 
building back into the region. This should result in dry conditions 
from Friday into Saturday. 


Highs Wed/Thu will be cooler due to clouds and precipitation and 
readings in the upper 70s to the lower 80s are expected with 
overnight lows in the 60s. Cooler temperatures look increasingly 
likely on Friday/Saturday with highs in the lower 70s and overnight 
lows cooling into the lower 50s. 


&& 


Aviation (18z taf issuance)... 
issued at 145 PM EDT Sat may 18 2013 


Upper low moving across the area continues to bring extensive cloud 
cover and scattered showers to our region. Ceilings at the taf sites 
are fluctuating between MVFR and VFR. Anticipate mainly VFR 
conditions. Showers should increase in coverage through the 
afternoon, with the Lex and sdf areas having the best coverage, at 
least for the next couple of hours. Coverage should be less around 
bwg. Not seeing any lighting early this afternoon, but cannot rule 
it out for later. However, given the cloud cover this morning, 
thunderstorms might be more isolated. Showers and clouds should 
decrease with loss of heating. Could see a mix of reduced visibility 
and/or low stratus form in the pre-dawn hours. Winds will remain 
southeasterly through the evening before become light and variable 
overnight. Winds will be more south-southwesterly Sunday. 


&& 


Lmk watches/warnings/advisories... 
in...none. 
Kentucky...none. 
$$ 




Short term.......mjp 
long term........mj 
aviation.........Mjp