- Day Three
acus01 kwns 231628
Storm Prediction Center ac 231627
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1127 am CDT Wednesday Apr 23 2014
Valid 231630z - 241200z
..there is a slight risk of severe thunderstorms over parts of the southern and Central
Severe thunderstorms are expected this afternoon into tonight across
parts of the central and southern Great Plains. Large hail will be
the primary initial hazard...with damaging winds and a few tornadoes
Progressive/moderately amplified pattern will prevail this
period...with Great Basin trough the main factor affecting severe weather
potential into Thursday. The trough should continue east to the High Plains by
12z Thursday as downstream ridge reaches the lower Ohio Valley.
Within the trough...main shortwave impulse now entering the lower Colorado
valley should pivot east to the Arizona-nm border this evening and into West Texas early
Thursday. At the same time...weaker downstream impulse over nm should
lift NE across the Central High plains today and into the middle MO valley
early Thursday. In the northern part of the trough...disturbance now over Wyoming
will track NE into ND by evening...advancing an associated cold front
east-southeastward across the Central Plains. Farther S...Lee trough/dry line
segments should mix east into western portions of central and Southern Plains this
afternoon...before being overtaken by the cold front tonight/early Thursday.
Both the Central Plains cold front and the dry line/Lee trough segments
farther S will promote strong to severe storm development...beginning
this afternoon and continuing into tonight.
..cntrl plains cold front this aftn/eve...
Thunderstorms should form along cold front from S central/southeast South Dakota southwestward into northwest
Kansas as the boundary accelerates east-southeastward. Current observations suggest
that moisture will remain somewhat limited...with precipitable water around 1 inch
and average surface dewpoints around 50 f. Low to middle-level lapse rates
will...however...be fairly steep...contributing to MLCAPE on the
order of 500 j/kg in northestern Nebraska to above 1000 j/kg in northwest Kansas. Deep
shear will vary across the region...ranging from 40 knots west-southwesterly in Kansas
to 50 knots south-southwesterly in northern Nebraska.
Overall setup appears favorable for relatively high-based sustained
storms/supercells capable of damaging wind and hail as northern stream
impulse glances region and weaker disturbance approaches from the
SW. The activity should merge into an east-southeast-moving mesoscale convective system in southern Nebraska/northern
Kansas by early tonight. A gradually diminishing damaging wind threat may
persist in association with embedded forward-propagating
segments/small bows through early Thursday.
..cntrl/Southern Plains Lee trough/dry line this afternoon into tonight...
Clouds associated with lead upper impulse should clear region along
Lee trough/dry line segments over western parts of the central and Southern
Plains by early afternoon...allowing for substantial heating. At the same
time...boundary layer moisture should continue to slowly increase
through advection. Surface dewpoints should average in the upper 50s to
around 60 over West Texas...with somewhat lower values extending northward into
western Kansas. Coupled with steep middle-level lapse rates...expect MUCAPE to
range from 1000 j/kg in Kansas to 2000 j/kg in Texas.
Surface heating and height falls associated with progressive nature of
large-scale trough should Foster scattered storm development along Lee
trough/dry line segments beginning late this afternoon and continuing
into tonight from western Kansas to west central Texas. More widely scattered activity may
extend S to the Texas Big Bend. Coupled with 40-45 knots west-southwesterly deep shear
and steep middle-level lapse rates...environment should be favorable for
supercells with large hail...some possibly very large...and locally
damaging wind. A risk for tornadoes also may develop...particularly this
evening/early tonight over northwest Texas/SW OK...as nocturnal and dynamic
strengthening of southerly low level jet enlarges hodographs. This window of
opportunity should diminish later tonight as the storms merge into
short line/clusters...although a limited risk for severe wind/hail may
persist near the Red River through early Thursday.
acus11 kwns 222308
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 222307
Mesoscale discussion 0384
National Weather Service Storm Prediction Center Norman OK
0607 PM CDT Tuesday Apr 22 2014
Areas affected...southeast PA...cntrl/srn New Jersey...northern Maryland...northern Delaware
Concerning...severe potential...watch unlikely
Valid 222307z - 230100z
Probability of watch issuance...20 percent
Summary...isolated damaging wind gusts are possible with thunderstorms along
a southeastward progressing cold front. Isolated nature of the threat is
expected to preclude the need for a ww.
Discussion...temperatures across the Maryland area are generally in the
upper 60s to lows 70 with 0-3 km lapse rates above 7 degree per km
noted in recent mesoanalysis. Instability is marginal but 0-6 km
bulk shear from 40 to 50 knots will continue to support at least modest
thunderstorm activity along the frontal boundary. With the shear vector
oriented perpendicular to the frontal boundary across much of the
area...activity along the cold front will have the potential to
produce occasional damaging wind gusts as it continues southeastward. Some
small hail is also possible in the strongest updrafts.
Isolated/marginal nature of the severe threat will likely preclude the
need for a ww.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 40317640 40877511 40607446 40307422 39277508 38857606
39027794 39417823 39687747 40317640