Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 111050
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
650 AM EDT Tue Mar 11 2014
...Updated Aviation Discussion...
Issued at 625 AM EDT Tue Mar 11 2014
No real change to the zone forecast, but did update the ongoing
temps, to match current obs. Still have pockets of much colder
temperatures out there, with the Cumberland county mesonet all the
way down to freezing, where most of the other sites are in the 40s
to low 50s.
Looked at the CIPS analogs run for the 00Z models. They indicate
some threat for hail reports with the storm system coming through
late tonight. It would not take too tall of a storm to produce some
hail, so have added that wording in to the HWO and to the special
weather statement. A quick look at SREF anomalies from the 03Z run
indicates the low will be 3 standard deviations below normal at the
time it crosses us this time tomorrow morning.
.SHORT TERM (Now through Wednesday)...
Issued at 300 AM EDT Tue Mar 11 2014
...Well above normal temperatures through tonight...then briskly and
abruptly back to winter by Wednesday afternoon...
We are deep into the warm sector of what will be quick-moving storm
system coming through late tonight. Temperatures for most places
have been slow to fall, with SDF still reporting mid 50s. A few
spots where the surface has been able to decouple, have dropped into
the 40s, even mid 30s down in Cumberland county! In general though
winds have stayed up enough to keep the atmosphere mixed. Thus we
can expect a relatively warm start to the day.
A surface cyclone will deepen out ahead of an upper trough, now over
the Central Rockies. This low will keep a steady southwest wind over
us today, and should allow for highs in the 70s for most locales. By
00Z tonight, model consensus places the surface low over Central
Missouri at between 994 and 999 mb. The pressure gradient ahead of
the low will be relatively loose, meaning a continued steady south
to southwest wind. Moisture will increase tonight as this low gets
closer, and we should see some showers start developing in the
evening. By daybreak, models (even the normally higher SREF) place a
989-994 mb low near KCVG, with its trailing cold front and much
tighter gradient expected on the backside. Given our proximity to
this deepening low, thunderstorms should be scattered in within the
increasing moisture field. Could see some gusty winds out of the
stronger storms, but at this point not expecting severe winds.
That said, the winds behind the cold front look to be pretty strong.
A wind advisory is appearing more likely for the daytime Wednesday,
as sustained winds look to be in the 20-25 knot range with gusts of
30-40 knots. With that strong cold air advection, temperatures will
drop steadily through the day, and should convert any lingering
precip over to snow from north to south in the afternoon. Not
expecting accumulations during the day, as surface temperatures
should stay above freezing long enough and moisture will die off
quickly behind the front.
.LONG TERM (Wednesday Night through Monday)...
Issued at 300 AM EDT Tue Mar 11 2014
A coupled upper jet structure will lead to a rapidly deepening
cyclone across the Appalachians and eventually coastal New England
by Wednesday evening. Both the NAM and the GFS in fact both forecast
a surface pressure near 980mb just west of New York City at 00Z
Unseasonably cold air will continue to pour into the Lower Ohio
Valley Wednesday evening and overnight as arctic high pressure
builds southwards into Texas. Gusty northwest winds will continue
through the evening hours but diminish after midnight as surface
ridging approaches western Tennessee. Scattered rain or snow showers
during the afternoon Wednesday will diminish Wednesday evening as
moisture associated with the back edge of the cyclone moves to the
east. Expect cold temperatures well down into the teens early
Although skies will become mostly sunny Thursday, unseasonably cold
temperatures will continue with highs expected only in the mid 30s
to the lower 40s. At least winds will become light by afternoon, and
will back to the southwest late as surface high pressure becomes
established over the central Gulf States.
A split jet will develop across the CONUS by late Thursday. A
shortwave associated with the northern branch will move across Lake
Superior early Friday. A surface trough trailing from this feature
will move south towards Chicago and tighten the pressure gradient
along and north of the Ohio River for Friday afternoon. This will
allow temperatures to moderate substantially from Thursday highs.
Under partly cloudy skies, highs Friday will range from the lower to
upper 50s under breezy southwest winds.
For the weekend, a deep 500mb trough will develop, centered over St
James` Bay. Wintry air will spill south across Illinois and the
Great Lakes by early Sunday. However, the southern extent of this
chill is in question. It is likely that the Commonwealth will not
feel the brunt of this chill, although highs will likely fall into
the 40s by Monday. Precipitation chances Saturday through Monday are
quite uncertain, and will depend on the development, if any, of any
southern stream shortwave over Tennessee on Sunday.
.AVIATION (12Z TAF Update)...
Updated at 645 AM EDT Tue Mar 11 2014
Still have stronger winds aloft according to AMDAR soundings, and
will keep llws in for another couple of hours before the nocturnal
jet dissipates and we are left with steadier southwest winds.
Conditions will deteriorate tonight as a surface low moves up the
Ohio river and allows showers and storms to develop. Winds will pick
up quickly from the west and northwest behind the associated cold
front, with MVFR cigs likely to persist into Wednesday morning.