Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 282314
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
714 PM EDT Tue Mar 28 2017

...Updated Aviation Discussion...

.Short Term...(This evening through Wednesday night)
Issued at 245 PM EDT Tue Mar 28 2017

Upper level ridging will move into the region tonight and remain
over the Ohio Valley Wed/Wed night.  This will result in dry weather
for the region through at least early Wed night.  Low clouds will be
stubborn to exit the area.  Moisture trapping under the inversion
tonight will prolong their presence.  Don`t expect low cloud cover
to improve until Wed night.  However, as low clouds are dissipating,
mid-upper level cloud cover will increase and thicken ahead of the
next weather system.  There is a small chance late Wed night into
Thu morning that showers/storms may enter areas west of I-65.

Temperatures will remain slightly above normal for this time of
year.  Highs tomorrow should range from the mid-upper 60s over
southern Indiana and much of central KY.  South central KY will
likely reach the lower 70s.  Lows tonight will mainly be in the mid
to upper 40s with some low 50s.  Slightly warmer lows in the upper
40s to upper 50s are expected for Wed night.

.Long Term...(Thursday through Tuesday)
Issued at 300 PM EDT Tue Mar 28 2017

Highly amplified synoptic weather pattern will continue in the
extended forecast as a series of deep mid-level lows progress across
the central U.S. There is reasonably good overall model-to-model
consistency on the large scale, but of course, some differences
exist on the mesoscale and in system timing/exact location.

The next system will move from the central and southern Plains
Wednesday night into the mid MS Valley on Thursday. Deep-layered
southerly flow will result in a broad area of moisture advection
into the Ohio Valley during the day Thursday within the warm sector
of the low pressure system to our west. Surface heating and
increasing low-level moisture (surface dewpoints will rise well into
the 50s, perhaps around 60 late in day) will cause air mass
destabilization. Model soundings show some elevated morning
instability above an inversion, with surface-based instability
developing in the afternoon and evening. Projected 0-3 km storm-
relative helicity (SRH) is moderate (200-300). There will likely be
scattered convective cells in the morning and/or afternoon in the
broad warm sector. However, models suggest one or more clusters or
lines of convection developing to our south and west in the
afternoon, and moving across our forecast area late in the day and
Thursday night. Dynamics/thermodynamics support the potential for
localized wind damage and hail from any bowing line segments and
discrete cells moving quickly NE in the deep southerly flow aloft.

The upper low is progged to move across the region Thursday night
and Friday. There are some model differences in location of this
low, which will have an effect on precip associated with it. For
now, will keep scattered to numerous showers and isolated storms on
Friday, especially over our eastern forecast area. Any isolated
storm activity over eastern areas Friday should have low severe
potential given expected weak instability.

High temperatures Thursday again will depend on the amount of
sunshine in the warm sector, but should reach the mid and upper 70s,
even around 80 in some places if enough sun.

Ridging aloft moves into and across the Ohio Valley over the
weekend, with tranquil weather expected. It will be cooler Saturday
with highs in the upper 50s over southern IN to lower 60s in central
KY. Temperatures moderate back into the mid 60s to lower 70s Sunday
afternoon.

By Monday, the next deep low pressure system should approach the
area. Model details vary, but there is good consensus in deep
southerly flow redeveloping over our area and upstream across the TN
Valley and Gulf Coast states. Showers and at least embedded
thunderstorms will move across our area during the day Monday and
Monday night. Some instability is expected again, but it is too
early to determine potential thunderstorm strength at this time.

This system moves away by Monday night or next Tuesday, with perhaps
yet another weather system mid next week or so.

&&

.Aviation...(00Z TAF Issuance)
Issued at 710 PM EDT Tue Mar 28 2017

Have seen some breaks in the MVFR ceilings during the day. Satellite
imagery showed a nice mid deck that punched a hole in the lower deck
from above over SDF and points southwest. That dryness should last
there for a few more hours than previously thought, but we expect
all sites to go to MVFR overnight. Fuel-alternate levels look more
likely at BWG around daybreak and at LEX after midnight. Latest high-
res guidance improves ceilings in the early afternoon at all sites.
A little hesitant that it will be that quick, so kept in a scattered
lower deck through the rest of the period.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term...AMS
Long Term...TWF
Aviation...RJS



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