Area Forecast Discussion
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054
FXUS64 KLUB 111618
AFDLUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
1118 AM CDT SAT APR 11 2015

.UPDATE...
LATEST MORNING MODEL RUNS HAVE OFFERED LITTLE REASON TO CHANGE THE
FORECAST FOR THIS AFTERNOON. THE MAIN ISSUE MODELS AND FORECASTERS
SEEM TO BE STRUGGLING WITH IS IF WE WILL SEE STORM INITIATION BY
LATE THIS AFTERNOON. THERE IS STILL NO DISCERNIBLE SHORTWAVE IN
THE FLOW ALOFT WHICH WILL MAKE INITIATION A LITTLE MORE DIFFICULT.
WE WILL HAVE TO RELY ON DRYLINE CONVERGENCE AND ABUNDANT SURFACE
HEATING. LOW STRATUS HAD FORMED WHEN MORNING CONVECTION CLEARED
OUT BUT IS NOT EXPECTED TO PERSIST FOR MUCH LONGER ALLOWING FOR
FULL SUNSHINE.

OTHERWISE...THERMODYNAMIC PARAMETERS LOOK GOOD FOR SEVERE
THUNDERSTORM DEVELOPMENT. SURFACE HEATING INTO THE 70S WILL ALLOW
FOR SURFACE BASED INSTABILITY TO REACH BETWEEN 1500 AND 2000 J/KG
WITH MINIMAL CIN NEAREST THE DRYLINE. THERE WILL BE AN INCREASING
CAP TO THE EAST PREVENTING MUCH DEVELOPMENT IN THE ROLLING PLAINS.
LOW LEVEL THETA-E VALUES WERE ON THE INCREASE THIS MORNING AS
DEPICTED IN THE RAP ANALYSIS. LOW AND DEEP LAYER SHEAR VALUES ARE
FAVORABLE FOR ROTATING UPDRAFTS. DEW POINTS IN THE 50S WILL NOT
GIVE US LOW LCLS BUT WILL NOT BE VERY HIGH WITH TEMPERATURES ONLY
IN THE 70S. MODELS ARE AGREEING UPON A SLIGHT BULGE IN THE DRYLINE
DIRECTLY OVER THE SOUTH PLAINS WHICH MAY ALLOW THE STRONGEST AREA
OF INTEREST TO BE OVER THE NORTHERN SOUTH PLAINS AND SOUTHERN
TEXAS PANHANDLE. GIVEN THE ABOVE REASONING...IF WE DO SEE
INITIATION...STORMS WOULD LIKELY BECOME SEVERE QUICKLY. THERE IS
A CHANCE OF TORNADOES GIVEN THE FAVORABLE LOW LEVEL SHEAR BUT
LARGE HAIL WILL BE THE PRIMARY THREAT.

&&

.PREV DISCUSSION... /ISSUED 624 AM CDT SAT APR 11 2015/

AVIATION...
SCATTERED -TSRA WERE EAST OF KLBB AND KPVW EARLY THIS
MORNING...WHILE ISOLATED -SHRA/-TSRA HAVE DEVELOPED WEST AND EAST
OF KCDS AND HAVE THEREFORE INSERTED A VCSH FOR A FEW HOURS AT
KCDS. COMPUTER MODELS HINT AT -TSRA POPPING UP NEAR KLBB AND KPVW
THIS MORNING BUT CONFIDENCE OF INSERTING A MENTION IS LOW AT THIS
TIME. VFR DECKS ARE EXPECTED TO DETERIORATE TO MVFR CRITERIA LATER
THIS MORNING AT ALL THREE TAF SITES UNTIL EARLY AFTN WHEN
CONDITIONS IMPROVE TO VFR. ADDITIONAL -TSRA ARE EXPECTED TO
DEVELOP WEST OF KLBB AND KPVW THIS AFTERNOON...AND COULD POSSIBLY
AFFECT ALL THREE TAF SITES AS THE ACTIVITY SHIFT EASTWARD WITH
TIME. FURTHERMORE...SOME STORMS COULD BECOME STRONG TO SEVERE WITH
HAIL AND GUSTY WINDS BEING THE PRIMARY THREATS. NOT CONFIDENT
ENOUGH TO INSERT A PRECIP MENTION FOR THIS AFTERNOON BUT WILL OF
COURSE AMEND AS NECESSARY. TONIGHT AS THE PRECIPITATION ACTIVITY
SHIFT EAST AND AWAY FROM THE TERMINALS...COULD SEE VFR/MVFR FOG
AND MVFR DECKS DEVELOP GIVEN THE MOIST ATMOSPHERIC
CONDITIONS...THOUGH S-SE WIND SPEEDS STAYING UP A BIT MAY
MITIGATE FOG POTENTIAL.

PREV DISCUSSION... /ISSUED 328 AM CDT SAT APR 11 2015/

SHORT TERM...
SOUTHWESTERLY FLOW ALOFT HAS SHARPENED IN THE LAST 24
HOURS...COURTESY OF A CLOSED UA LOW ACROSS THE ERN PACIFIC /WELL
WEST OF BAJA OF CALI/ THAT IS GRADUALLY DRIFTING SSEWRD. AS SUCH...A
PLUME OF RICH PACIFIC MOISTURE IS STREAMING ACROSS THE SOUTHERN
PLAINS. LOOKING AT THE SFC...THE SOUTH PLAINS AND ROLLING PLAINS WAS
ENVELOPED BY AN UPSLOPE SFC REGIME PER 07Z METARS...WHICH HAS
GARNERED DEWPOINTS TO INCREASE INTO THE 30S AND 40S AND HENCE HAVE
PWATS OF 0.75-0.85 INCHES. THIS RISE IN LOW LEVEL MOISTURE...COUPLED
WITH A 25-35 KT LLJ AND AND INCREASING ISENTROPIC UPGLIDE...HAS LED
TO THE DEVELOPMENT OF ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS ERN NM THAT HAS TRANSLATED ENEWRD TO ACROSS THE
SW SOUTH PLAINS AND PORTIONS OF THE CNTRL SOUTH PLAINS EARLY THIS
MORNING. THE TTU MESONET SITE LOCATED 7 MILES WNW OF DENVER CITY
RECORDED 0.13 INCHES OF RAINFALL WITHIN 20 MINUTES DUE TO THIS
ACTIVITY. COULD ALSO SEE BRIEF WIND GUSTS OF 20-30 MPH AS THIS
ACTIVITY IS PROGGED TO MOVE ACROSS PORTIONS OF THE ROLLING PLAINS
LATER THIS MORNING. FURTHERMORE...THE SURGE IN MOISTURE COULD
PROMOTE MVFR CLOUD DECKS BY DAYBREAK.

THIS AFTN COULD SHAPE UP TO BE QUITE INTERESTING. S-SE SFC WINDS
WILL PREVAIL ACROSS THE CWA WHILST SWRLY SFC WINDS OCCUR MORE SO
ACROSS ERN NM...THUS SHARPENING THE DEVELOPMENT OF A DRYLINE ALONG
THE TX/NM BORDER. AT FIRST A BIT OF CIN WILL NEED TO BE OVERCOME BUT
BY LATE AFTN...CIN IS QUITE NEGLIGIBLE ESPECIALLY NEAR THE AXIS OF
THE DRYLINE AND THUS MODEL SOLUTIONS BREAK OUT PRECIP ACROSS LOCALES
ON THE CAPROCK AS THE DRYLINE BULGES A BIT EWRD. STEEPENING LAPSE
RATES...MUCAPE VALUES INCREASING TO AOA 1000 J/KG AND A WEAK IMPULSE
EMBEDDED IN THE FLOW ALOFT MOVING ACROSS THE REGION BY LATE AFTN
WILL LEAD TO CONCERNS FOR STORMS TO REACH STRONG TO POSSIBLY SEVERE
LEVELS. MAIN SEVERE CONCERNS WILL BE HAIL AROUND THE SIZE OF GOLF
BALLS AND WIND GUSTS OF 58 MPH OR GREATER. HOWEVER...VEERING
VERTICAL WIND PROFILES AS WELL AS ADEQUATE VEERING AT THE LOW LEVELS
/0-6 KM BULK SHEAR VALUES OF 35-45 KTS/ DOES SUGGEST STORMS WILL BE
ROTATING...AND THUS AN ISOLATED TORNADO CAN NOT BE RULED OUT. THOUGH
LCL/S ARE NOT TERRIBLY LOW /5000 FT AGL OR SO/. MAKE SURE YOU STAY
ABREAST OF THE LATEST WX CONDITIONS BY LISTENING TO YOUR NOAA WX
RADIO...GOING TO OUR WEBSITE /WWW.WEATHER.GOV/LUBBOCK/ AND/OR
WATCHING YOUR FAVORITE MEDIA OUTLET. TONIGHT...BEST POPS WILL SHIFT
EWRD TO ACROSS THE ROLLING PLAINS AND THE RETURN OF THE LLJ /30-40
KTS/ WILL AID IN FEEDING THE STORM ACTIVITY UNTIL IT EXITS THE
REGION. ENSUING S-SE SFC WINDS MAY BRING ABOUT THE DEVELOPMENT OF A
STRATUS DECK AND/OR FOG LATE TONIGHT/EARLY SUNDAY MORNING.

AN UPTICK IN 850 MB TEMPS WILL LEAD TO TEMPS A FEW DEGREES WARMER
THAN YESTERDAY /70S/ FOLLOWED BY A MILD NIGHT /50S AND 60S/.

LONG TERM...
AN EXTENDED PERIOD OF RAIN CHANCES STILL LOOKS GOOD FOR THE FCST
AREA THROUGH MONDAY NIGHT WITH THE APPROACH OF AN UPPER LEVEL LOW
THAT AS OF EARLY THIS MORNING WAS STILL WELL OFF THE COAST OF SRN
AND BAJA CALIFORNIA. MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH
THE EVOLUTION OF THIS LOW...STILL TRACKING IT SLIGHTLY FURTHER TO
THE SOUTH WITH EACH RUN. ATTM SUNDAY LOOKS LIKELY TO BE DRY UNTIL
LATER IN THE AFTN WHEN THE COMBINATION OF LARGE SCALE ASCENT FROM
THE UPPER LOW AND AFTERNOON HEATING WORK ON A REASONABLY MOIST AIR
MASS TO BEGIN SPREADING SCATTERED SHOWERS AND THUNDERSTORMS NWD
FROM THE PERMIAN BASIN. SUNDAY NIGHT WILL BEGIN TO SEE RAIN
CONCENTRATED ALONG THE DEFORMATION AXIS TO THE NORTH OF THE UPPER
LOW...THE LOCATION OF WHICH WILL DEPEND ON THE TRACK OF THE
LOW...THUS A FARTHER SOUTH TRACK SIMILAR TO THE 00Z WRF-NAM WILL
BE MORE FAVORABLE FOR THE FCST AREA. MONDAY MIGHT END UP BEING THE
WETTEST...AT LEAST AS FAR AS HOW MUCH OF THE FCST RECEIVES
RAINFALL...AS EVEN IF THE TRACK OF THE LOW IS FARTHER NORTH...
DIURNAL DESTABILIZATION OF THE MOIST AIR MASS UNDERNEATH THE LOW
ITSELF WOULD LIKELY LEAD TO QUITE A BIT OF SHOWER ACTIVITY. EFFECT
OF A COLD FRONT DRAPED ACROSS THE AREA CANNOT BE DISCOUNTED
EITHER...POSSIBLY SERVING AS ANOTHER FOCUS FOR CONVECTIVE
DEVELOPMENT. ALL IN ALL CONFIDENCE CONTINUES TO INCREASE AND WILL
NUDGE POPS UP IN THAT SUNDAY NIGHT THROUGH MONDAY NIGHT PERIOD.

THE LATTER HALF OF THE PERIOD STILL LOOKS GENERALLY BENIGN...
ALTHOUGH MODELS CONTINUE TO STRUGGLE WITH THE EVOLUTION OF THE
NEXT UPPER TROUGH. 00Z GFS AND ECMWF HAVE TRENDED TOWARD A
SOLUTION WITH MORE ENERGY IN THIS TROUGH...CUTTING OFF A FAIRLY
STRONG LOW OVER THE CNTL PLAINS THEN DRIFTING IT EWD. COULD SEE A
BRIEF PERIOD FOR SHOWERS WEDNESDAY AFTN OR NIGHT AND INTRODUCED A
SLIGHT CHANCE FOR THEN. OTHERWISE...COOLER AIR SHOULD MOVE SWD
BEHIND THIS DEVELOPING TROUGH/LOW WITH TEMPS COOLING AGAIN FOR
THURSDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        75  51  78  48 /  20  20  30  60
TULIA         72  56  79  54 /  40  20  30  60
PLAINVIEW     73  57  79  56 /  40  20  30  60
LEVELLAND     78  57  79  51 /  30  20  40  60
LUBBOCK       76  58  80  54 /  30  20  40  60
DENVER CITY   80  57  78  53 /  20  20  40  50
BROWNFIELD    78  58  80  52 /  30  20  40  50
CHILDRESS     73  60  82  60 /  50  30  30  60
SPUR          73  60  80  56 /  50  20  40  60
ASPERMONT     77  62  83  60 /  50  30  40  50

&&

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

$$

01

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