Area forecast discussion
National Weather Service Little Rock Arkansas
1157 am CDT Monday may 20 2013
Aviation...
scattered high end MVFR ceilings across central and west sections
should climb above the MVFR threshold by 21z. Thunderstorms and rain chances will
increase from west to east through the period.
55
&&
Previous discussion... /issued 1039 am CDT Monday may 20 2013/
Update...
made some changes to the forecast for today. A look at the morning
sounding reveals a very unstable atmosphere with a rather
significant cap around 850 mb. In spite of that there is abundant
moisture present and I felt it would be prudent to introduce some
relatively low probability of precipitation further to the south across the County Warning Area today. In
addition...cloud cover is a bit more extensive than previously
forecast and it looks like we will continue to have more than
forecast for the rest of the day...so I upped those values as well.
Getting back to the issue of the unstable sounding...the models
are having some difficulties with how to handle the timing of
storms this afternoon and tonight. The atmosphere is quite
unstable...surface based cape values are above 3000 j/kg in central
Arkansas this morning and the hodograph is a bit ominous. I am
concerned about the potential for the development of discrete
supercells later this afternoon and evening across the northwestern
portions of the forecast area. We will be conducting a special
sounding at 18z today to assess how things have changed by midday.
Convection that was occurring across the northern part of the
state earlier this morning has fizzled out and with the exception
of convection across western MO...not much else is happening this
morning. I cant help but wonder if upper level jet dynamics are
playing a supressing role this morning as some models are implying
a jet maximum exiting over northwest MO this morning with another speed maximum
over northern OK this morning swinging around. If that holds up the lid
could start to come off the convection by early to middle afternoon
across the northwest. 53
Previous discussion... /issued 620 am CDT Monday may 20 2013/
Discussion...
Updated to include the 12z aviation discussion below...
Aviation...
A line of rain showers/thunderstorms and rain is extending from MO into north central Arkansas
this morning...with thunderstorms in the vicinity continuing in the taf for the northern sites
this morning. Otherwise...some sites were seeing some MVFR
ceilings...which should improve to VFR levels outside any precipitation
activity later this morning. Also...some areas early in the period
could see a bit of low end low level wind shear...but should improve as surface winds
increase later this morning. Breezy srly winds will be seen trough
this afternoon and early evening as surface pressure gradient remains
fairly tight across the region. Have mentioned thunderstorms in the vicinity across the northern
sites through this afternoon as additional thunderstorms and rain could develop this
afternoon. This evening and into Tuesday morning...the potential for
rain showers/thunderstorms and rain will spread further south and east...with prob30 or thunderstorms in the vicinity
mentioned for thunderstorms and rain potential during this period of the taf. Some
MVFR or lower conditions could be seen under the precipitation activity.
Previous discussion... /issued 410 am CDT Monday may 20 2013/
Short term...today through Thursday night
Storms formed over northeast Oklahoma late Sunday evening...and
moved northeast into southern Missouri overnight. However...showers
have recently developed along the southern edge and are moving into
northern Arkansas. Have kept small rain chances across the north
through the morning hours...as much of this activity will dissipate
before noon.
Question for this afternoon will be if any development occurs on any
lingering boundaries left over from the overnight activity. The NAM
and now the hrrr is picking up on this...ahead of activity
developing off low level jet around sunset. This will have to be
monitored closely...because if any cell is discrete...severe weather
will be maximized.
This evening...storms will form across eastern Oklahoma into
southern Missouri...as front interacts with low level jet. The
storms will slowly move east during the late evening into the
overnight hours...with strong to severe storms possible. Also...with
the slow motion and copious amounts of moisture...heavy rainfall is
possible...especially across the northwest half of the state tonight.
The front will progress into the state Tuesday...with severe
potential continuing. However...tornadic potential will not be as
great due to lessening shear. Flooding remains a concern for
Tuesday...as several rounds of thunderstorms will move across the
area.
The rainfall will begin to move southeast late Tuesday into Tuesday
night...with much of the activity confined to the southeast half of
the state Wednesday. However...the front will meander around the
area through the end of the short term...with small rain chances
continuing.
Long term...Friday through Sunday
Cold front will have pushed into the state from the NE at the start
of the long term period...stalling across the state from northwest to southeast.
Mention slight chance probability of precipitation with this front over the state for
Friday...but an upper ridge to the west will begin to shift east over
the Southern Plains and southern MS River Valley region into this weekend. As
a result of the ridging aloft...decrease probability of precipitation into the weekend...as
well as increasing temperatures above normal by late in the forecast.
&&
Preliminary point temps/pops...
Batesville Arkansas 85 69 80 65 / 20 50 60 80
Camden Arkansas 89 70 87 67 / 10 20 50 70
Harrison Arkansas 82 66 78 60 / 40 80 70 60
Hot Springs Arkansas 88 71 84 67 / 20 40 60 70
Little Rock Arkansas 88 70 84 68 / 20 40 60 70
Monticello Arkansas 90 72 88 69 / 10 20 40 60
Mount Ida Arkansas 87 70 83 64 / 20 50 60 70
Mountain Home Arkansas 83 67 77 61 / 30 80 60 70
Newport Arkansas 87 70 82 67 / 20 40 60 80
Pine Bluff Arkansas 89 71 86 69 / 10 20 50 70
Russellville Arkansas 85 68 80 63 / 20 60 60 70
Searcy Arkansas 87 69 82 66 / 20 40 60 70
Stuttgart Arkansas 89 71 85 68 / 10 30 50 70
&&
Lzk watches/warnings/advisories...none.
&&
$$
Aviation...99
