Area Forecast Discussion
Issued by NWS Louisville, KY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLMK 021921
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
321 PM EDT Thu Jul 2 2015

.SHORT TERM (Now through Friday Night)...
Issued at 250 PM EDT Thu Jul 2 2015

...Flash Flooding Possible Through Friday Across Southern Indiana
and Central Kentucky...

As of mid-afternoon, a surface analysis showed a weak area of low
pressure across southern Missouri while a stationary boundary lied west
to east from southern Illinois into southern Indiana and northern
Kentucky. A pool of very moist air lies along this feature
characterized by dewpoints in the upper 60s to low 70s and light
southwesterly winds.

For the remainder of this afternoon and into this evening, the patch
of clearing clouds across southwest into south-central KY has
resulted in modest amounts of instability across the area. Daytime
heating is also bringing 1000 to 2000 J/kg of SBCAPE to the area. In
the presence of 20 to 30 kts of deep layer shear, scattered
thunderstorms that do develop will have the potential to put down
some gusty winds. The two areas likely to see greater coverage of
showers/storms is 1) along the Ohio River in the vicinity of the
stalled boundary and 2) closer to south-central Kentucky which has
had the most clearing/destabilization.

Water vapor imagery shows that another upper level disturbance will
arrive later this evening through early Friday morning, which will
push the surface low and front through the region. Additional
showers and thunderstorms are expected to spread across the area.

Main threat through Friday morning is flash flooding thanks
to torrential rainfall. PWATs are running 1.5 to 2.0 inches with
relatively high warm cloud depths. Soil moisture is running high
thanks to a couple weeks of higher than normal rainfall and
especially across some areas after last night`s rainfall. Lowest
flash flood guidance pockets are across southern Indiana and
south-central Kentucky. The flash flood watch continues and was
expanded/extended for the area. For more details, see the Hydrology
section below.

Diurnal temperature ranges will be low as clouds/rain keep highs
below normal and lows on the mild side. Sided with the higher
performing model consensus, putting highs in the mid 70s to around
80s and lows in the upper 60s.

.LONG TERM (Saturday through Thursday)...
Issued at 310 PM EDT Thu Jul 2 2015

Saturday/Saturday Night...

An upper trough axis should move east through the area shunting a
sfc boundary to the south of the Ohio River.  It`s still in question
as to how far south the boundary will settle on Sat and that may be
a determining factor on where convection fires later in the day.
The latest trend in mid range models has been to push the boundary
into south central KY or TN.  However, the latest NAM keeps it a
little farther north.  Still will keep the southern trend going and
limit precip chances to 30-50% Sat afternoon.  Scattered
convection is likely to continue into the evening hours before
diminishing after midnight.  With fairly meager wind profiles and
ridging building into the region Sat night, feel that storms will
generally stay below severe limits.  At this point it is fairly
difficult to pinpoint exactly who will and won`t see convection Sat
afternoon/evening.

As for temperatures, highs should be quite pleasant in the upper 70s
to lower 80s.  Low temperatures Sat night should be in the mid 60s.

Sunday/Monday...

Upper level ridging should work into the region for Sun helping
suppress convection both Sun/Mon.  Soundings indicate good capping
over the Ohio Valley for the beginning of the week, so will trend
POPs downward even making Sun night dry.  Any storms that do develop
should stay on the weak side.  Temperatures will be on the increase
as thicknesses increase over the region.  Highs should range through
the low to mid 80s both Sun/Mon with Monday being the warmer day.

Tuesday - Thursday...

The next weather system will approach our area Tuesday bringing
potentially several rounds of showers and storms for mid week.
Another sfc front looks to become stalled over the Midwest with
rounds of storms occurring daily as various waves ride along the
boundary.  The 12Z Euro looks quite wet leaving the boundary nearly
stationary over our area for much of mid week.  The 12Z GFS wobbles
the boundary a little more and wouldn`t be quite as wet as the
Euro.  High temps look to remain at or slightly below normal while
low temps will remain at or slightly above normal.

&&

.HYDROLOGY...
Issued at 200 PM EDT Thu Jul 02 2015

24 hour precipitation analysis shows widespread 0.5 to 1 inch
amounts across south central Kentucky into southern Indiana. A
locally higher swath occurred from Ohio County southeastward toward
Allen/Monroe counties, where 1 to locally 4 inches were observed.
Finally, between 2 and 4 inches fell across parts of Dubois and
Crawford counties.

As a result, 1 and 3 hour flash flood guidance remains very low
given the recent rainfall plus the above average precipitation in
the past 2 to 3 weeks. 1 hour guidance across portions of southern
Indiana and southern Kentucky is 1 inch or less, which is quite
attainable given the anomalous high PWATs, stagnant low level
moisture and favorable synoptic features for heavy rainfall.

The flash flood watch was expanded to include the remaining portions
of the forecast area given both antecedent conditions and the
expectation that more showers/storms will redevelop this afternoon
through Friday morning. Beyond Friday morning, the threat could
continue with additional storms and after coordination with
surrounding offices, the watch was also extended in time to 00z
Saturday /8 PM EDT/.
&&

.AVIATION (18Z TAF Update)...
Issued at 105 PM EDT Thu Jul 2 2015

Afternoon destabilization ahead of a surface low combined with a
stalled frontal boundary across the area will support an uptick in
showers/storms through the early evening hours. Highest chances are
centered around 21-00z timeframe...and BWG to LEX looks to have the
greatest chance of seeing aviation restrictions.

As precipitation wanes this evening, attention turns to fog
potential. Light/variable winds tonight combined with the moisture
and recent rainfall leads to higher confidence for periods of MVFR
to IFR fog potentially. Guidance hits LEX/BWG...so have trended TAFs
toward that possibility. By Friday morning, another weather system
could bring more showers/storms to the area.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...FLASH FLOOD WATCH through Friday morning FOR KYZ023>043-045>049-
     053>057-061>067-070>078-081-082.

IN...FLASH FLOOD WATCH through Friday morning FOR INZ076>079-083-084-
     089>092.

&&

$$

Short Term........ZT
Long Term.........AMS
Hydrology.........ZT
Aviation..........ZT





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.