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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Sunday
• 
• High: 84 °
• Low: 68 °
• Thunderstorm

• Monday
• 
• High: 84 °
• Low: 66 °
• Partly Cloudy

• Tuesday
• 
• High: 86 °
• Low: 68 °
• Chance of T-Storms

• Wednesday
• 
• High: 86 °
• Low: 68 °
• Chance of T-Storms

• Thursday
• 
• High: 75 °
• Low: 61 °
• Partly Cloudy

area forecast discussion 
National Weather Service Louisville Kentucky 
319 PM EDT sun may 19 2013 


Short term (now - Monday night)... 
issued at 300 PM EDT sun may 19 2013 


The upper low is currently shifting east of eastern Kentucky while 
an upper-level ridge axis builds over western and central portions 
of the state. The subsidence inversion associated with the ridge 
will act to shut down rain chances and shift the greatest potential 
east. There are some isolated showers trying to form along the warm 
front in western Kentucky, southeast Illinois, and southwest 
Indiana, but these are capped by the ridge aloft, have limited 
vertical extent, and should not last long. Otherwise, isolated to 
scattered showers and thunderstorms will have the best potential 
across south-central Kentucky and northeastward through the Kentucky 
Blue Grass. These will dissipate this evening with loss of heating 
and loss of forcing from outflow boundaries associated with previous 
convection. 


The upper ridge will hold over the area keeping things dry tonight. 
Expect a light southerly flow, which should keep temps mild. Lows 
should only drop into the mid and upper 60s. Light winds should also 
keep down fog potential, particularly locally dense fog. 


Upper ridge axis will continue to hold through the day Monday. We 
will see no rain, but much warmer and humid conditions. As mentioned 
in the previous discussion, 850 mb temps jump to around 18 c with only 
partly cloudy skies and breezy south-southwest winds. Temperatures 
should top out in the mid and upper 80s. Louisville, the heat 
island, will make a run at 90 degrees, which will be close to the 
record of 91 (1934). The ridge axis will begin to shift east Monday 
night. Latest suite of guidance indicates convection that develops 
across the middle Mississippi Valley Monday afternoon and evening 
will approach our northwestern County Warning Area late Monday night. This should 
approach in a weakening state with it arriving late at night, plus 
the upper ridge will still have some influence on the area. Clouds 
will increase through the night, which should hold lows in the mid 
and upper 60s, with some locations around 70. 


Long term (tuesday - sunday)... 
issued at 319 PM EDT sun may 19 2013 


Overall, not much change in the long term as the multi-model 
consensus continue to show good run to run continuity. Stacked 
upper low over the southern Midwest is forecast to slowly drift 
eastward into the southern Great Lakes before merging with a larger 
upper level wave over southeast Canada. Associated surface cyclone is 
forecast to move from the northern plains and into the the Great 
Lakes while dragging a surface cold front through the Ohio Valley. 
The models have started to converge on a singular solution here with 
the frontal boundary passing through Wednesday night...with a 
secondary frontal boundary passing through on Thursday evening. 


Before this system gets here, we're going to see a generally 
summertime pattern here in the Ohio Valley. Fairly healthy high 
pressure system over the western Atlantic working in tandem with the 
low off to our northwest will result in continued southwesterly flow 
into the Ohio Valley. This will result in well above normal 
temperatures at the beginning of the period along with increasingly 
humid conditions. Convection chances for Tuesday continue to look 
more or less scattered at this point. Still not seeing a well 
defined lifting mechanism here other than differential heating and 
convective overturning. With deeper moisture and less capping over 
the west/northwest sections, feel that convective coverage would 
generally be more west of I-65 on Tuesday afternoon/evening. Model 
proximity soundings still suggest a high instability/low shear 
profile suggestive of pulse type multi-cellular convection with a 
threat of damaging winds and perhaps some hail. Further east out 
toward the I-75 corridor, a bit more capping is expected and thus 
convective coverage looks to be less at this point. High Tuesday 
will warm into the mid-upper 80s with overnight lows in the upper 
60s. 


By Wednesday, surface cold front will be moving in closer from the 
west. Despite having a little stronger wind field coming into the 
region along with better upper divergence, instability looks less on 
Wednesday. This is due to more mid-high level cloud cover expected 
due to convective debris moving in from the west. This would reduce 
effective insolation during the afternoon. Nonetheless, strong 
storms will be possible given the overall profiles with damaging 
winds and large hail being the primary severe weather threats. 
Convection will likely continue into Wednesday night and Thursday as 
we wait for the secondary front to push through along with the upper 
trough. So plan on keeping chance pops running through Thursday 
night. Highs Wednesday will be in the upper 70s to the mid 80s with 
overnight lows in mid-upper 60s. 


With the secondary front pushing through Thursday night, we'll see 
drier and cooler air push in late in the period. The model 
consensus has sped up the pattern progression here and it appears 
that Friday and Saturday will remain dry and mild. Highs Fri/Sat 
look to top out in the 70-75 degree range with overnight lows in the 
50s. 


As usual for the later period, model differences start to emerge by 
Sunday as some of the new data suggests that the cold front from 
Thursday will stall out over the southern US and then retreat back 
northward into the Ohio/Tennessee Valley. This may serve as focus 
for convective development as we head toward Memorial Day. For now, 
will introduce some slight chc pops for Sunday, but if the latest 
Euro trends continue, higher precipitation chances will be warranted 
in future forecasts. 


&& 


Aviation (18z taf issuance)... 
issued at 125 PM EDT sun may 19 2013 


A weak upper low continues to meander around east Kentucky today, 
with a weak frontal boundary across the Tennessee Valley. These two 
disturbances will provide focus for isolated to scattered showers 
and storms through the afternoon. Will continue with just scattered 
shower coverage around Lex with isolated thunder. VFR conditions 
will prevail through the afternoon and evening hours with a steady 
south-southwest wind between 5 and 10 mph. Fog may become a concern again once 
again tonight. However, surface winds are expected to stay up a bit, 
which could limit fog, particularly dense fog, production. 


&& 


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




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