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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 81 °
• Low: 64 °
• T-Storms

• Thursday
• 
• High: 72 °
• Low: 45 °
• T-Storms

• Friday
• 
• High: 70 °
• Low: 41 °
• Partly Cloudy

• Saturday
• 
• High: 73 °
• Low: 48 °
• Partly Cloudy

• Sunday
• 
• High: 75 °
• Low: 52 °
• Mostly Cloudy

area forecast discussion 
National Weather Service Louisville Kentucky 
310 am EDT Wednesday may 22 2013 


Short term (today through thursday)... 
issued at 310 am EDT Wed may 22 2013 


Areas of low pressure will move from Iowa to lower Michigan today, 
with surface trofs dropping to the south. One such trof, combined 
with an upper shortwave, should help to spark renewed showers and 
thunderstorms today. A few stronger storms could develop, with 
marginally severe wind gusts as the main threat and marginally 
severe hail as a secondary concern. Any tornadic activity would be 
confined to just a brief spin-up where local convective boundaries 
interact. 


High temperatures today will be highly dependent on cloud and shower 
coverage. Will go for highs around 80, which is consistent with 
current guidance, the inherited forecast, and surrounding offices. 
The warmest temperatures should be in the east. 


Shower and thunderstorm activity should wane this evening, with a 
fairly quiet overnight period. The Mercury will drop to around the 
60 degree mark. 


On Thursday the upper trof axis will finally swing through and give 
US one Last Chance of showers and thunderstorms with this system. 
Moisture will be more shallow and instability not as great, so 
severe weather is not expected. Some small hail could fall from the 
taller storms, though, as the upper trof moves in and wet bulb zero 
heights drop. High temperatures will be in the lower to middle 70s. 


Long term (thursday night - tuesday)... 
issued at 300 am EDT Tue may 22 2013 


An amplified 500mb pattern continues late Thursday with a deep 
stationary closed low forecast over the Pacific northwest. A narrow 
ridge is expected to extend north into the Canadian Front Range. 
Closer to home, a very deep, cold and yet progressive trough is 
expected to extend southward from hudson's Bay through the Great 
Lakes. It is this feature that will usher in a very pleasant weekend 
with cool temperatures for late may. 


A relatively sharp cold front will move southeast of the Ohio River 
late in the afternoon on Thursday. Much drier air will move south 
overnight all the way through Tennessee as strong high pressure of 
Canadian origin builds southward along the Mississippi River valley. 
Brisk northwest winds late Thursday afternoon will become northerly 
and continue at 10 to 15 mph through the evening hours. 


Residual cloudiness Thursday evening will clear by dawn Friday. 
Temperatures will cool off rapidly and bottom out in the upper 40s. 
Expect mostly clear skies and cool temperatures Friday through late 
Saturday. With high pressure building right over Indiana on Friday, 
winds will become light from the northeast during the afternoon and 
will become nearly calm by early Saturday. Despite nearly cloud-free 
skies Friday afternoon, highs will struggle to reach 70, with upper 
60s likely across the Bluegrass. After another cool night with lows 
in the upper 40s, Saturday will warm a couple of degrees into the 
lower 70s. 


500mb heights will begin to build over the Southern Plains by 
Sunday. Eventually, ridging is forecast to expand across the plains 
and eventually into the lower Ohio Valley from Tuesday through the 
rest of the upcoming work week. This will eventually bring mid-Summer 
heat to much of the mid-section of the Continental U.S.. 


During this period of transition, Sunday through Tuesday, northwest 
flow aloft will persist over the lower Ohio Valley. A boundary will 
develop by late Sunday across the region, separating cool dry air and 
easterly winds over Ohio from more humid air advancing north along 
the Mississippi River. In general, this front may lie over northern 
Kentucky late Sunday, slowly moving north of the commonwealth 
through Tuesday. Moisture pooling along this boundary coupled with 
occasional disturbances sliding southeastward may bring occasional 
rounds of convection. The European model (ecmwf) is the farthest south with 
precipitation of any of the long-term guidance, developing 
widespread showers during the day Sunday right over Kentucky. Prefer 
the slightly farther north GFS, which presents greater chances of 
occasional convection across southern Indiana and the Bluegrass 
region. 


Despite increasing clouds, low dewpoints will keep Sunday quite mild 
with highs in the mid to upper 70s. Both temperatures and humidities 
will rise towards Tuesday with highs in the lower to mid 80s 
expected. 


&& 


Aviation (06z taf issuance)... 
issued at 127 am EDT Wed may 22 2013 


The morning hours should be quiet at all three taf sites, with south-southwest 
winds around 6-9 knots. The low level jet is increasing, but should 
remain right at or just below low level wind shear criteria. It's almost all speed 
shear, with very little if any directional shear. 


LIFR ceilings formed at ckv and hop earlier, and fog was seen to 
form on the Mammoth Cave np web cam. These are a concern for bwg, 
but right now the hope is that there is enough of a breeze and upper 
cloud cover to prevent sub-VFR conditions at the Airport. Will 
continue to monitor. 


During the daylight hours winds will pick up from the south-southwest and 
convection may reform by afternoon as the atmosphere warms. 


For now will allow the convection to die back in the evening and 
keep the tafs dry for tonight. 


&& 


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




Short term.......13 
long term........jsd 
aviation.........13