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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 35 °
• Low: 31 °
• Partly Cloudy

• Tuesday
• 
• High: 40 °
• Low: 32 °
• Snow

• Wednesday
• 
• High: 47 °
• Low: 38 °
• Partly Cloudy

• Thursday
• 
• High: 52 °
• Low: 34 °
• Rain

• Friday
• 
• High: 43 °
• Low: 27 °
• Partly Cloudy

area forecast discussion 
National Weather Service Louisville Kentucky 
1152 PM EST sun Feb 12 2012 


..updated aviation discussion... 


Short term (tonight and monday)... 
updated at 300 PM EST Feb 12 2012 


Overall, a quiet short term period. High pressure crossing the 
Tennessee and Ohio valleys tonight will give US mostly clear 
skies, with light breezes and chilly low temperatures from the 
mid teens to lower 20s (locally cooler in the usual cold low spots, 
which we have accounted for in the grids). 


On Monday the surface high to our east will begin to weaken and an 
upper trof will approach from the west. High clouds will begin 
streaming in late tonight into Monday morning, and gradually lower 
and thicken over the course of the day. There will be very dry air 
in the low levels to overcome, but by late afternoon we could see 
some flurries or very light graupel west of I-65. High temperatures 
will be in the middle 30s to around 40, so any light precipitation 
should have little to no impact. 


Long term (monday night through sunday)... 
updated at 313 PM EST Feb 12 2012 


..another round of wintry weather expected Monday night and Tuesday 
morning... 


Monday night through Wednesday... 


The latest suite of model data continue to agree on bringing a 
mid-level trough axis through the region Monday night and Tuesday 
morning. With a broad southwest flow in place...a decent amount of 
moisture should lead in widespread precipitation development across 
the area. The problem here is that as the precipitation heads in 
our direction, the southwesterly flow will likely bring in some 
slightly warmer air aloft. This warm air moving up and over a 
pre-existing cold airmass will likely lead to a mixed bag of wintry 
precipitation. 


As we get into Monday night, surface temperatures will likely fall 
back to near freezing. Current model consensus suggests that 
surface temperatures will likely fall into the 31-33 degree range 
during the evening as precipitation overspreads the region from 
southwest to the northeast. Extensive analysis of vertical 
temperature profiles from the 12z NCEP runs along with the 09z sref 
data suggest that thermal profiles will be cold enough initially for 
snow to fall as initial dry atmosphere will likely wetbulb down for 
a few hours. However, as the night GOES on, the majority of the 
guidance suggests some low-level warm air advecting up into the 
region with 950-850 hpa temps pushing 0-2 degrees celsius across 
southern Kentucky during the overnight hours. This will likely result in 
snow changing over to a wintry mix of rain/sleet and possibly some 
freezing rain at times across the southern half of Kentucky. 
Further north...perhaps along and north of a the weak and bg parkways, 
thermal profiles look to remain cool enough for snow to remain the 
predominant precipitation type. However...if the mid-level warm 
layer becomes established, then a mix of sleet and snow would 
probably be the likely outcome. I do have some concerns about the 
models trying to scour the cold air out too quick. This would be 
especially true if we had more of a northeasterly low-level flow as 
this system approaches, but in this case our winds are going to be 
more southerly given that we'll have a high pressure cell of to the 
east. Should the cold air hang tough, we could have more potential 
for some freezing rain...so this will have to be something to watch 
over the next 24 hours as the system draws closer. At this 
time...accumulations look fairly small as our surface temperatures 
are expected to be around freezing. Best chances at accumulations 
would likely be across southern Indiana and portions of 
north-central and east-central Kentucky where up to an inch could 
fall. 


By Tuesday morning, warm air surge looks to continue and we'll 
likely see the wintry precipitation change over to plain rain. The 
rain probably will continue through much of the day and end during 
the afternoon from west to east. Drying conditions along with some 
partial clearing is expected for Tuesday night with lows falling 
back down into the lower 30s. 


Wednesday through Sunday... 


Latest datasets continue to be in fairly good agreement with this 
portion of the forecast period. Fairly potent mid-level wave is 
forecast to eject out of the plains early Thursday and into the 
Great Lakes by Friday morning. Associated surface low pressure 
system looks to move from the OK/Kansas area then northeastward to just 
north of Toronto by Friday morning. Broad southwesterly flow within 
the low and middle layers of the atmosphere will allow plenty of 
Gulf moisture to infiltrate the region early in the period. Surface 
cold front looks to surge through the region early Thursday with 
widespread rains showers accompanying the system. Overall, 
instability looks rather marginal as lapse rates are not all that 
steep. The GFS has backed off slightly with its more bullish 
solution that was seen in the 12/00z runs. With that said...feel 
that the thunder threat is quite low with the best probability 
residing well south of our region. 


After this system passes through, a period of dry conditions looks 
likely for Friday and Saturday as a temporary period of zonal flow 
sets up across the Ohio Valley. There are some slight differences 
with regards another mid-level wave swinging through here late 
Saturday and Sunday. The GFS is a a bit quicker with the system 
than the Euro. However, the GFS has had a tendency this season to 
be too progressive in days 6-7...so have trended the forecast closer 
to a 50/50 Euro/GFS blend here. With moisture rather scant...we're 
planning on keeping the forecast dry...but some increase in clouds 
will be possible as this wave moves through late in the period. 


As for temperatures, they will be above average on Thursday as the 
strong southwest flow ahead of the front will allow temperatures to 
warm into the Lower-Middle 50s. Temperatures for Friday and 
Saturday look to warm into the mid-upper 40s in the north and upper 
40s to around 50 in the south. Upper 40s to around 50 look 
reasonable for Sunday as well. Overnight lows through period will 
generally be in the upper 20s to the lower 30s. 


&& 


Aviation (06z taf issuance)... 
updated at 1153 PM EST Feb 12 2012 


High pressure centered over western Tennessee at this time, with a 
ridge axis across the border with central Kentucky. Thus winds are 
light and variable at this time with clear skies. During the day 
Monday, expect increasing mid/high clouds as a large upper trough 
moves out of The Rockies toward the region. Cigs will drop steadily 
into the evening hours, and we may see some light snow fall at kbwg 
and ksdf just after sunset. Still do not expect flight restrictions 
until after midnight for any site, which only shows up at this point 
in the 30-hr ksdf taf. Outside of light and variable winds early 
this morning, expect a more southerly component to the winds as the 
high shifts east of our longitude Monday. 


&& 


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




Short term.......13 
long term........mj 
aviation.........Rjs