Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 151711
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
111 PM EDT SAT JUN 15 2013
...Updated Aviation Discussion...
.SHORT TERM (Today through Sunday)...
Issued at 315 AM EDT Sat Jun 15 2013
Current upper air pattern features a 500mb trough exiting the
eastern seaboard and a compact closed low traveling east just north
of the Dakotas. The current convective complex over Iowa, a result
of moisture pooling near an occluded front, aided by a low level
jet, will quickly erode towards morning as it moves south-southeast
into much drier air over the Ohio Valley.
Relatively low dewpoints will continue today as light southeasterly
winds recycle Continental air that pushed into the southern
Appalachians a couple of days ago. Aside from some high cirrus
associated with ongoing thunderstorms over Iowa, expect mostly sunny
skies today with light south winds developing by afternoon.
Temperatures will warm a bit later today, varying from the upper 80s
near Tennessee to the lower to mid 80s over the northern Bluegrass
Humidities will slowly increase tonight and especially on Sunday as
increasing westerly flow will replace Continental air by air
originating in the Gulf that has already penetrated as far north as
After a partly cloudy night tonight with lows in the upper 60s,
temperatures Sunday will range from the mid 80s to near 90.
Moisture, especially across southern Indiana, coupled with a weak
disturbance associated with increasing westerly 500mb flow, will
bring a chance for afternoon storms Sunday.
.LONG TERM (Sunday Night through Friday)...
Issued at 315 AM EDT Sat Jun 15 2013
Sunday Night through Tuesday...
Latest guidance continues to have fairly good continuity with the
previous runs which results in only minor adjustments to the ongoing
forecast. Zonal upper level flow is expected to be in progress
across the CONUS at the beginning of the forecast period. At the
surface, a frontal boundary is likely to be draped very near the
Ohio Valley. This boundary is not forecast to move all that much
due to it becoming parallel to the upper level flow. As a result,
this boundary will serve as a focus for renewed convective
development through the first half of the forecast period.
Ongoing scattered convection is expected Sunday evening. However, we
expect this convection to diminish in intensity and coverage due to
the loss of heating Sunday Night. Some strong storms will be
possible as we should see moderate instability and 40-45 knots of
bulk shear across the region. Convection should pick up once again
on Monday as the frontal boundary will be lying across the region.
Overall strength and coverage of convection is hard to pin down at
this point, due to mesoscale evolution and expected convective
debris to be in the region. Nonetheless, the majority of the data
suggests likely PoPs for Monday and Monday night. Storms could be
on the strong side once again on Monday due the instability and bulk
shear values. Most indices would suggest a damaging wind threat as
the main hazardous weather concern.
By Tuesday, the frontal boundary is expected to push more southward
and will eventually clear our region by Tuesday night. Scattered
shower and thunderstorm activity looks to be possible on
Tuesday...mainly across Kentucky and points south.
Temperatures through the period look to be slightly below seasonal
levels. This is due to the expected cloud cover and precipitation
that will likely have an impact on afternoon solar insolation.
Highs on Monday should warm into the lower 80s and upper 70s to
lower 80s are likely on Tuesday. Overnight lows Sunday and Monday
night will be in the upper 60s to around 70.
Tuesday Night - Friday...
Latest guidance data suggest no real changes to the forecast and
currently supports ongoing forecast thinking. High pressure is
forecast to build in from the northwest and we should remain under a
northwesterly flow regime aloft. At this far out, it is difficult
to say if there will be additional perturbations coming through the
area within the mean flow aloft. So we will keep the current dry
forecast intact at this time. There is some forecast convergence
suggestive of high PoPs by late in the period another trough axis
pushes in from the west. Temperatures through the period will
remain around seasonal normals with highs in the lower to middle 80s
and gradually warming into the upper 80s by Friday. This is in good
agreement with the multi-model consensus and the bias-corrected
statistical guidance which was used to formulate the current
.AVIATION (18Z TAF Update)...
Issued at 110 PM EDT Sat Jun 15 2013
VFR conditions will prevail through the TAF period. High pressure
will continue to slide off to the east through the remainder of the
day, allowing for winds to turn more southwesterly by this evening.
Moisture will begin to slowly increase due to these southwesterly
winds out ahead of an approaching storm system. Any chances for
precipitation look to hold off towards the end of the TAF period and
beyond as a front associated with the approaching system stalls
across the Ohio Valley. Confidence in the timing and exact location
of the front and associated showers/thunderstorms remains a bit low,
thus will only introduce VCSH into the forecast at this time.