Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 140727
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
327 AM EDT Fri Mar 14 2014
.SHORT TERM (Now through Saturday)...
Issued at 320 PM EDT Fri Mar 14 2014
...Gusty Southwest Winds Today...
Windy conditions in a tight pressure gradient ahead of an
approaching weak cold front are likely today. South winds of 20-25
mph with wind gusts in the 35-40 mph range are expected. This falls
just below wind advy criteria so a wind advy was not issued although
it was heavily considered. Cannot rule out a few gusts in the lower
40 mph range. 0Z NAM and GFS Bufkit soundings are quite robust with
these higher gusts although it should be noted that they can be a
little too high in these warm air advection regimes. Also
increasing mid-upper level clouds this afternoon may limit wind
gusts. Still will keep an eye on upstream wind gusts and continue
the SPS highlighting the gusty winds.
The other issue of concern for today will be elevated fire danger
over portions of south central and east central KY. Fuels are
running a bit dry in the 6-10% range and we will definitely have the
windy conditions. However, with the southwest winds will come
better low level moisture and prevent min RH from dropping below the
upper 20 percent range. Thus, will not issue a red flag warning,
but will continue the mention of elevated fire danger in the SPS.
Temperatures will warm nicely into the low to mid 60s for highs this
For tonight, expect the weak cold front to swing through during the
evening hours with just some passing clouds to accompany it. The
airmass looks to dry to allow any precip with this feature. Expect
low temps to fall into the upper 30s and lower 40s.
For Saturday, expect dry conditions with clouds increasing from the
south especially late in the day. Relatively mild conditions will
continue with high temps in the upper 50s and lower 60s.
.LONG TERM (Saturday Night through Thursday)...
Issued at 307 AM EDT Fri Mar 14 2014
...A chance for a rain snow mix late Sunday into Monday...
Upper air pattern late Saturday will feature a split flow across the
eastern CONUS with a zonal northern jet over Michigan and a southern
zonal jet over the interior Gulf States. A sharp ridge will move
onshore across California. A strong digging jet on the eastern side
of this western ridge will actually deepen a southern stream
shortwave which is forecast to lie over New Mexico at this time. For
Sunday into Monday this trough will sharpen greatly as it crosses
the lower Mississippi Valley late Sunday. Think that the NAM is too
aggressive in practically closing off a 500mb low over Mississippi.
the GFS and ECMWF are more open with this still sharp upper wave,
and brings a narrow positively tilted upper trough across western
Kentucky early Monday.
In either case, low surface pressure will develop late Sunday over
western Tennessee, and move east across the northern Gulf States
Monday. This potential track of the low coupled with high pressure
building over the Great Lakes, will increase northeast winds over
the Commonwealth by late Sunday and pull in much colder air.
Expect increasing cloudiness Saturday night with a relatively wide
range in low temperatures, ranging from the mid 30s in southern
Indiana to the upper 40s near Tennessee. Northeasterly winds will
become apparent even by dawn Sunday as both the temperature and
pressure gradient tighten.
A cold rain will overspread the Commonwealth Sunday from southwest
towards the northeast and everyone will see at least light rain by
early afternoon. Freshening northeast winds up to 15 to 20 mph will
really bring a raw day Sunday. Highs will stay steady or even fall
by late afternoon as colder air from Ohio overspreads southern
Indiana and northern Kentucky. By late Sunday, drier air will move
across Tennessee. However, a deformation band of lingering
precipitation is expected to become established along the Ohio River
and back west towards southern Illinois. By late in the day, surface
and boundary layer temperatures may cool enough for rain to change
into snow. Current thinking is that this may occur across southern
Indiana and northern Kentucky. This type of system is one that could
bring accumulating snow depending on the exact location of this
Light rain or snow will end during the morning hours Monday, with
cold temperatures and some cloudiness remaining in the afternoon.
With some clearing late, expect highs Monday in the lower to mid
The GFS and the ECMWF forecast a strong jet ejecting from the
Rockies late Tuesday. This will help develop a compact surface low
near Kansas late Tuesday. This cyclone is then forecast to move east
towards the lower Michigan by late Wednesday. Developing
southwesterly winds ahead of this system will bring warming
temperatures Tuesday and Wednesday with a chance of showers on
Wednesday associated with the passage of its associated cold front.
High temperatures Tuesday and Wednesday will rise into the 50s.
.AVIATION (06Z TAF Update)...
Updated at 125 AM EDT Fri Mar 14 2014
VFR conditions will prevail through the period. Winds will be the
main concern as we sit in a broad SW flow and tight pressure
gradient ahead of an approaching cold front.
LLWS was observed at all TAF sites early this morning. VAD wind
profiles are reading a bit stronger than observed AMDAR soundings.
Still a SW wind of 38-42 kts is likely between 1.5-2 kft with sfc
winds primarily out of the S between 6-8 kts. Expect LLWS to
continue through the early morning hours.
After sunrise as mixing increases, southwesterly sfc winds will
increase to 20 to 25 knots, with gusts of 30 to 35 knots possible.
Mid and high clouds will slowly increase through the day.
Tonight a cold front will cross the region mainly between 3-7Z
through the TAF sites. While evening gradient wind speeds may
decline into the 15-20 kt range, the front may mix down wind gusts
of 30-35 kts...possibly higher. Wind gusts will cease and wind
direction will veer more westerly after the fropa.