000
FXUS64 KLUB 230453
AFDLUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
1153 PM CDT WED MAY 22 2013

.AVIATION...
40+ KT SOUTHERLY LLJ EXPANDING ACROSS THE TERMINALS LATE THIS
EVENING. WINDS ARE UP ENOUGH AT KLBB TO KEEP LLWS AT BAY...BUT
LIGHTER AND BACKED WINDS AT KCDS ARE ENOUGH TO RAISE CONCERNS OF
LLWS THERE. THE LLJ WAS GRADUALLY CARRYING BETTER MOISTURE
NORTHWARD AND THERE IS SOME RISK OF MVFR CIGS AT KCDS TOWARD
MORNING...BUT CHANCES STILL APPEAR TOO LOW TO INCLUDE IN THE TAF.
OTHERWISE...THUNDERSTORMS WILL LIKELY DEVELOP ON THE NOSE OF THE
JET TOWARD MORNING...BUT THIS ACTIVITY IS EXPECTED TO BE WELL
NORTHEAST OF KCDS. INSTEAD...THE PRIMARY FOCUS FOR THUNDERSTORM
DEVELOPMENT AT/NEAR THE TERMINALS WILL BE AROUND MID TO LATE
AFTERNOON ON THURSDAY. THUS...WE CONTINUE TO INCLUDE PROB30 GROUPS
FOR THIS LIKELIHOOD. CONVECTION WILL LINGER IN THE AREA THROUGH
THURSDAY EVENING. STRONG INSTABILITY AND WIND SHEAR WILL SUPPORT A
SEVERE WEATHER THREAT WITH VERY LARGE HAIL...DAMAGING WINDS AND
LOCALLY HEAVY RAINS WITH THE MOST INTENSE STORMS FROM LATE
AFTERNOON INTO THE EVENING HOURS. IF ONE OF THESE STORMS DIRECTLY
IMPACTS A TERMINAL A PERIOD OF IFR TO LIFR CONDITIONS WILL BE
POSSIBLE...IN ADDITION TO THE STRONG WINDS.

&&

PREV DISCUSSION... /ISSUED 400 PM CDT WED MAY 22 2013/

SHORT TERM...

.THE SEVERE WEATHER POTENTIAL FOR THURSDAY REMAINS THE PRIMARY
FOCUS IN THE SHORT-TERM...

ALOFT THIS AFTERNOON...WATER VAPOR IMAGERY SHOWS A SHARP UPPER-LEVEL
RIDGE APPROACHING WEST TEXAS...DOWNSTREAM FROM AN UPPER LOW SPINNING
OVER THE PACIFIC NW...WHILE AN UPPER TROUGH SWINGS NEWD FROM THE MS
VLY INTO THE MIDWEST. THE LATTER TROUGH HAS DRIVEN A COLD FRONT
SOUTH INTO THE CENTRAL PLAINS THIS AFTERNOON...AND THIS FRONT WILL
BE A CRUCIAL PLAYER IN OUR CONVECTIVE CHANCES TOMORROW.

ALSO AT THE SURFACE...AN STATIONARY FRONT OVER SOUTH TX WAS
BEGINNING TO WASH OUT/LIFT NORTH WITH INCREASING SRLY FLOW AND MOIST
ADVECTION NORTH OF THE OLD FRONTAL ZONE. THE WAA REGIME WILL
INCREASE TONIGHT AS THE LOW-LVL JET KICKS IN...DRAGGING MID 50S TO
MID 60S DEWPOINTS INTO THE AREA BY THURSDAY MORNING. THIS WILL
RESULT IN A MILD NIGHT ACROSS THE AREA WITH LOWS RANGING FROM MID
50S NW TO NEAR 70 SE.

INTERESTINGLY...THE MORNING MODEL GUIDANCE SHOWS A HIGH-DEGREE OF
SPREAD REGARDING THE DEVELOPMENT OF EARLY MORNING ELEVATED
CONVECTION DOWNSTREAM OF THE UPPER RIDGE ALONG THE COLD FRONT/WARM
FRONT INTERSECTION IN CENTRAL TO NW OKLAHOMA. THIS IS IMPORTANT FOR
US BECAUSE THIS ACTIVITY WILL HAVE THE POTENTIAL TO
ENHANCE/ACCELERATE THE FRONT TO THE SW...AND HELP DETERMINE WHERE
THE BOUNDARY IS LOCATED BY THURSDAY AFTERNOON. SINCE THIS BOUNDARY
IS EXPECTED TO BE OUR PRIMARY FOCUS FOR CONVECTIVE INITIATION...THE
MODEL DISAGREEMENT DOES NOT PARTICULARLY HELP OUR CONFIDENCE IN THE
LOCATION OF INITIAL CONVECTION. IN GENERAL THOUGH...WE EXPECT THE
FRONT TO BACKDOOR INTO OUR NE ZONES AROUND MID-DAY...AND PROGRESS
WESTWARD THROUGH THE AFTERNOON.

THE UPPER RIDGE AXIS WILL SHIFT EAST OF THE AREA BY THURSDAY
AFTERNOON...LEAVING THE FA IN MODEST...ALBEIT
INCREASING...UPPER-LEVEL FLOW. RELATIVELY WEAK DEEP-LAYER SHEAR WILL
LIKELY BE ENHANCED ALONG AND EAST OF THE BOUNDARY WHERE LOW-LVL
WINDS WILL HAVE A MORE EASTERLY COMPONENT. ON THE CAPROCK...SHALLOW
MOISTURE WILL MIX OUT ACROSS THE WESTERN ZONES...AND A DRYLINE IS
LIKELY TO SET UP IN VICINITY OF THE CAPROCK ESCARPMENT. WHILE CAPPING
MAY INITIALLY BE A CONCERN EAST OF THE FRONT AND DRYLINE...FCST
SOUNDINGS ALONG AND TO THE WEST OF THE BOUNDARIES SHOULD CINH GOING
TO ZERO BY AROUND 21 UTC. THE DRYLINE/FRONT INTERSECTION WILL BE THE
PREFERRED AREA FOR CI AND AS OF THIS AFTERNOON IT LOOKS LIKE THIS
AREA WILL LIKELY BE FOUND ACROSS BRISCOE...FLOYD COUNTIES AND
POSSIBLY AS FAR WEST AS SWISHER/HALE COUNTIES. FORECAST MLCAPE VALUES OF
2000 TO 3000 J/KG IN THIS AREA SHOULD SUPPORT RAPID CELL
INTENSIFICATION. SHEAR SHOULD BE AUGMENTED ALONG THE BOUNDARY AND
SUPPORT SUPERCELL DEVELOPMENT. LARGE HAIL AND DAMAGING WIND GUSTS
LOOK LIKE A STRONG BET TO ACCOMPANY THESE STORMS.
ADDITIONALLY...FCST 0-1 KM EHI VALUES > 2 NEAR THE BOUNDARY SUGGEST
POTENTIAL FOR A COUPLE OF TORNADOES AS WELL. LCL/S WILL INITIALLY BE
SOMEWHAT HIGH BUT WILL LIKELY DECREASE AROUND 0 UTC. HOWEVER...IF
THE FRONTAL BOUNDARY CONTINUES TO MOVE WEST THEN STORMS WILL ONLY
HAVE A SMALL RESIDENCE TIME ALONG THE BOUNDARY AND WILL KEEP THE
WINDOW OF TORNADIC THREAT FAIRLY SHORT.

FORECAST PWATS APPROACHING 1.5 INCHES WILL SUPPORT POTENTIAL FOR
LOCALLY HEAVY RAINFALL WITH ANY SUPERCELLS INITIALLY...THEN PERHAPS
EXPAND IN COVERAGE AS CONVECTION GROWS UPSCALE IN THE EVENING AS
DISCUSSED BELOW.

MEANWHILE...BACK TO THE WEST...MORE ISOLD TO WIDELY SCATTERED
HIGH-BASED T-STORM ACTIVITY IS EXPECTED TO DEVELOP ALONG THE SFC
TROUGH NEAR THE TX-NM STATE LINE. THIS ACTIVITY SHOULD HAVE SOME
STRONG WIND GUST POTENTIAL.

LONG TERM...
A PROTRACTED ACTIVE WX PATTERN LIES AHEAD THROUGH AT LEAST THE
MEMORIAL DAY HOLIDAY AND POTENTIALLY MUCH OF THE FINAL WEEK OF
MAY AS SEASONABLY RICH GULF MOISTURE BECOMES ESTABLISHED OVER
MOST OF WEST TEXAS. LIGHT TO MODERATE SOUTHWEST FLOW ALOFT DURING
THIS ENTIRE PERIOD SHOULD ENSURE MINIMAL EASTERLY DRYLINE MIXING
EACH AFTERNOON AND THIS WILL OPEN THE WINDOW FOR PRECIP CHANCES
TO THE ENTIRE CWA...SOMETHING WE HAVEN`T BEEN ABLE TO SAY FOR A
LONG TIME! BECAUSE OF SUSTAINED S-SELY LOW-LEVEL WINDS...OPTED TO
RAISE DEWPOINTS A FEW DEGREES EACH DAY AND NARROW THE DIURNAL
TEMP RANGE IN ANTICIPATION OF MILDER NIGHTS AND NOT-AS-HOT
AFTERNOONS.

THURSDAY NIGHT SHOULD SEE AN UPTICK IN TSTORM COVERAGE OVER THE
MIDDLE OF THE CWA AS A FRONTAL BOUNDARY EDGES SOUTHWEST /LIKELY
AIDED BY CONVECTIVE OUTFLOWS/ AND RECEIVES SOME CONTRIBUTION OF
LIFT FROM AN INTENSIFYING SELY LLJ. COUPLING OF THIS LLJ WITH A
SUBTROPICAL JET STREAK SHOULD ONLY BOLSTER DEEP ASCENT SUPPORTIVE
OF NUMEROUS TSTORMS IN THE ROLLING PLAINS...LIKELY IN THE FORM OF
AN MCS IF MODELS ARE CORRECT. PROVIDED THIS IS CORRECT...THEN THE
SEVERE THREAT SHOULD TEND TO WANE AS WINDS ALOFT ARE NOT
PARTICULARLY ROBUST OR DRY ENOUGH FOR AN ORGANIZED CONVECTIVE WIND
EVENT. HOWEVER...CONCERN FOR HEAVY RAINS AND LOCALIZED FLOODING
WILL BE ON THE RISE GIVEN SLOW STORM MOTIONS EMBEDDED WITHIN
UNSEASONABLY RICH PWATS AOA 1.5 INCHES. ADD TO THIS FAVORABLE CORFIDI
VECTORS SUPPORTIVE OF STORM PROPAGATION/REDEVELOPMENT INTO A LOW-
LEVEL MOIST AXIS AND THE STAGE COULD BE SET FOR SOME IMPRESSIVE
RAIN TOTALS IN SOME LOCALES OFF THE CAPROCK. RECENT SURVEY BY OUR
REGIONAL HYDROLOGIST SHOWED MINIMAL COVERAGE OF FUELS IN SOME
AREAS FAVORED TO RECEIVE HEAVY RAINS TOMORROW NIGHT...SO THIS
WOULD ONLY AMPLIFY RUNOFF AND THE THREAT FOR FLOODING. ADDITIONAL
ISO-SCT STORM DEVELOPMENT REMAINS PLAUSIBLE AFTER MIDNIGHT BEHIND
THIS MCS GIVEN A PERSISTENT SELY LLJ DIRECTED OVER THE CWA.

HISTORY WOULD TEND TO FAVOR THESE NOCTURNAL STORMS DIMINISHING IN
COVERAGE BY DAYBREAK FRIDAY AND NOT LINGERING THROUGH THE MORNING
AS SHOWN BY THE GFS OR ECMWF CAMPS. IF THIS IS CORRECT...THEN
ROUND TWO OF TSTRMS SHOULD BE IN STORE FRI AFTERNOON AS AN UPPER
RIDGE AXIS SHIFTS FARTHER EAST EXPOSING THE SOUTH PLAINS TO A MORE
UNSETTLED SWLY FLOW. IN A NUTSHELL...THIS FLOW REGIME CAMPS OUT
THROUGH MUCH OF NEXT WEEK BEFORE A TROUGH LIFTS OUT OF THE SRN
ROCKIES BY MIDWEEK. LOW CONFIDENCE IN THE TIMING OF THIS WAVE...SO
HAVE ENDED MENTION OF ISOLATED DRYLINE TSTORMS BEGINNING
TUESDAY...THOUGH THIS MAY INEVITABLY BE EXTENDED IN FURTHER IN
TIME IN LATER FORECASTS IF SUFFICIENT MODEL CONTINUITY EXISTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        54  89  59  82  60 /  10  20  30  40  20
TULIA         61  89  62  83  62 /  10  40  50  40  20
PLAINVIEW     62  90  64  84  63 /  10  30  50  40  20
LEVELLAND     64  92  64  84  64 /   0  20  40  40  20
LUBBOCK       66  93  66  86  65 /   0  20  50  40  30
DENVER CITY   63  92  65  85  64 /   0  20  30  50  20
BROWNFIELD    66  93  65  86  65 /   0  20  40  40  30
CHILDRESS     62  88  65  85  66 /  10  60  60  30  20
SPUR          67  92  67  87  66 /  10  30  60  40  30
ASPERMONT     71  95  69  87  67 /  10  20  60  30  30

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

23/07/23