Area Forecast Discussion


500 
FXUS64 KLUB 131139
AFDLUB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
639 AM CDT TUE AUG 13 2013
.AVIATION...
A COLD FRONT MOVING THROUGH THE AREA WILL BRING A N-NE WIND SHIFT
TO KLBB BY ABOUT 13Z...FOLLOWED BY PREVAILING E-NE WINDS AT BOTH
TERMINALS THROUGH THE REMAINDER OF THE FCST. SCATTERED SHOWERS AND
THUNDERSTORMS MAY AFFECT EITHER/BOTH TERMINALS THIS AFTERNOON AND
EVENING AND WE HAVE A PROB30 MENTION AT BOTH. THE SHOWER ACTIVITY
MAY CONTINUE OVERNIGHT BUT WITH LOW CONFIDENCE IN THE PARTICULARS.
ALSO...THERE IS SOME INDICATION THAT LOW CEILINGS NEAR OR BELOW
2000 FT MAY DEVELOP AT EITHER TERMINAL...MORE LIKELY AT KCDS. WE
WILL LEAVE MENTION OUT OF TAF FOR NOW UNTIL THERE IS A STRONGER
INDICATION.
&&
.PREV DISCUSSION... /ISSUED 419 AM CDT TUE AUG 13 2013/ 
SHORT TERM...
INITIAL OUTFLOW BOUNDARY MOVED THROUGH MOST OF THE AREA LAST NIGHT 
WITH WEAK EASTERLY WINDS NOTED ACROSS ALL BUT THE SW SPLNS...WHERE 
WINDS REMAINED SOUTHERLY. WE/VE SEEN SOME MORNING SHOWER ACTIVITY 
CROP UP JUST WEST OF THE STATE LINE AS WE CONTINUE TO SEE SOME WEAK 
UPPER-AIR RIPPLES ROTATE AROUND A VERY FLAT RIDGE CENTERED OVER SW 
TX. FARTHER TO THE NORTH...A W-E BAND OF MORE WIDESPREAD SHOWERS AND 
THUNDERSTORMS STRETCHED ACROSS THE NRN TX PANHANDLE WITH A 
WELL-DEFINED OUTFLOW/COLD FRONT BOUNDARY MOVING SOUTH...APPROACHING 
KAMA AT 3 AM. THIS BOUNDARY SHOULD MOVE INTO OUR NRN ZONES EARLY 
THIS MORNING...AND POSSIBLY FARTHER SOUTH BEFORE LOSING MOMENTUM. 
SURFACE WINDS WILL BECOME FAIRLY LIGHT ACROSS THE AREA 
TODAY...LIKELY WITH A SMALL NORTH TO EAST COMPONENT. THIS SHOULD 
MAINTAIN HEALTHY MOISTURE IN PLACE IN THE LOW-LEVELS. ALOFT...WATER 
VAPOR IMAGERY THIS MORNING SHOWS A SHORTWAVE LIFTING NORTH ACROSS 
THE GREAT BASIN...ANOTHER SWINGING SOUTH THROUGH THE DAKOTAS...WITH 
CONVOLUTED FLOW IN-BETWEEN THESE TWO SYSTEMS FROM THE SRN ROCKIES 
INTO THE HIGH PLAINS. AN UPPER-LVL JET WILL ADVANCE INTO SRN CO/KS 
TODAY...WITH A BELT OF 30+ KT MID-LVL WINDS DEVELOPING ACROSS NE NM 
TO WRN OKLA THIS AFTERNOON...AND SPREADING INTO THE NRN SPLNS TO RED 
RIVER VALLEY TONIGHT. LIFT WITH THE JET WILL COUPLE WITH LOW-LVL 
LIFT IN THE FRONT/OUTFLOW ZONE AND A MODERATELY UNSTABLE AIRMASS TO 
SUPPORT CONVECTIVE CHANCES THROUGH THE DAY AND ON INTO THE NIGHT. 
HIGH-RES GUIDANCE SUGGESTS THAT THE ACTIVITY IN THE PANHANDLE WILL 
SAG SOUTH INTO OUR NRN ZONES THIS MORNING AND WEAKEN. THEN THIS 
AFTERNOON...WE SHOULD SEE SCATTERED CONVECTIVE DEVELOPMENT PRIMARILY 
ACROSS THE NW PORTIONS OF THE SPLNS AND SWRN TX PANHANDLE...ALTHOUGH 
WE CAN/T RULE OUT DEVELOPMENT ALMOST ANYWHERE. STORMS WILL GENERALLY 
MOVE EAST AND WILL TAP INTO MLCAPES RUNNING 1000 TO 2000 J/KG AND 
0-6 KM BULK SHEAR OF 30 KTS SOUTH TO 40+ KT NORTH. THIS ENVIRONMENT 
WILL SUPPORT SOME SEVERE STORM POTENTIAL /MAINLY DAMAGING WIND 
GUSTS/ THIS THREAT WILL BE HIGHER ACROSS THE NRN ZONES WHERE THE 
SHEAR WILL BE GREATER...BUT WE WILL HAVE TO MONITOR JUST WHERE THE 
OUTFLOW BOUNDARY ACTUALLY SETS UP TO ENHANCE LOW-LVL CONVERGENCE AND 
LIFT. ALSO...STORM CELLS POSSIBLY TRAINING ON THE COLD SIDE OF THE 
BOUNDARY COULD LEAD TO SOME LOCALLY HEAVY RAIN POTENTIAL THIS 
EVENING. AS WE HEAD INTO THE OVERNIGHT HOURS...THE FORECAST 
CONFIDENCE DECREASES AS BEST UPPER-LEVEL LIFT WILL REMAIN POSITIONED 
ACROSS THE NORTH...BUT BEST LOW-LVL FOCUS WILL KEEP SHIFTING 
SOUTH...WITH THE FRONT MOVING ON INTO THE PERMIAN BASIN BY EARLY WED 
MORNING. THE BULK OF GUIDANCE KEEPS THE HIGHEST RAIN CHANCES PINNED 
ACROSS THE NORTH. OVERALL COVERAGE AND STRENGTH OF ACTIVITY IS 
EXPECTED TO WANE AFTER MIDNIGHT...ALTHOUGH WE WILL HAVE TO WATCH 
BACK TO THE WEST WHERE A OVERNIGHT COMPLEX MAY BEGIN TO FORM NEAR 
THE STATE LINE WHERE LIFT FROM NEXT SHORTWAVE STARTS TO IMPINGE ON 
POST-FRONTAL UPSLOPE. 
LONG TERM...
AN UNSETTLED STRETCH OF WEATHER WILL KICK OFF THE EXTENDED FORECAST 
THANKS TO A PERIOD OF NORTHWESTERLY FLOW ALOFT AND A FRONTAL 
BOUNDARY IN/NEAR THE AREA. HOWEVER...THE DEVIL IS IN THE DETAILS 
WITH MUCH UNCERTAINTY IN THE SPATIAL AND TEMPORAL DISTRIBUTION OF 
THE BEST SHOWER/STORM CHANCES RESULTING FROM UNKNOWNS REGARDING
THE EXACT FRONTAL POSITION AND TIMING OF SUBTLE SHORTWAVES MOVING
THROUGH THE FLOW ALOFT. 
NORTHWESTERLY MID-LEVEL FLOW WILL BEGIN TO TAKE SHAPE ON WEDNESDAY 
AS AN UPPER RIDGE AMPLIFIES OVER THE ROCKIES DOWNSTREAM OF A LARGE 
VORTEX CENTERED OFF THE COAST OF BRITISH COLUMBIA. WEST TEXAS WILL 
BE POSITIONED BETWEEN THE RIDGE AND LARGE-SCALE TROUGHING ACROSS THE 
EASTERN PORTION OF THE CONTINENT. AT THE SFC...A FRONTAL BOUNDARY IS 
PROGGED TO SETTLE SOUTHWARD THROUGH MOST IF NOT THE ENTIRE CWA EARLY 
WEDNESDAY...WITH RICH POST-FRONTAL MOISTURE ADVECTING IN ON UPSLOPE 
WINDS. THIS MOIST ENVIRONMENT WILL READILY SUPPORT PRECIPITATION AND 
EFFICIENT RAINFALL RATES GIVEN ANY SUBTLE FORCING FOR ASCENT. 
INITIALLY THE FRONTAL FORCING AND PERHAPS WEAK UPPER SUPPORT WILL
KEEP DECENT RAIN CHANCES GOING ON WEDNESDAY...WITH ADDITIONAL
CONVECTION FOCUSED ALONG AND BEHIND THE FRONT AS DAYTIME HEATING
PEAKS AND A POSSIBLE WEAK SHORTWAVE TROUGH APPROACHES. ONE
QUESTION MARK IS HOW MUCH HEATING CAN DEVELOP WEDNESDAY AFTERNOON
WITH THE NAM SUGGESTING LOW CLOUDS MAY HOLD TOUGH MUCH OF THE DAY
AND LIMIT POTENTIAL INSTABILITY. THE ECMWF AND GFS ARE MORE
OPTIMISTIC AND PROJECT SBCAPES CLIMBING TO NEAR OR IN EXCESS OF
1500 J/KG. IF THE STRONGER INSTABILITY IS REALIZED IT COULD BRING
THE POTENTIAL FOR A FEW STRONG TO SEVERE STORMS AS 0-6 KM SHEAR
CLIMBS TO AROUND 35 KNOTS. WE WILL ALSO LOOK FOR THE POSSIBILITY
OF A MCS ROLLING IN LATE FROM THE NORTH...THOUGH THE COOLER AND
MORE STABLE NAM SOLUTION DOES NOT SUPPORT THIS. FOR NOW...HAVE
MADE ONLY MINOR ADJUSTMENTS TO THE POP/WX GRIDS...MAINTAINING A
30-40 PERCENT CHANCE OF STORMS WEDNESDAY AND WEDNESDAY NIGHT. THE
OVERALL SETUP WILL NOT CHANGE MUCH THURSDAY...THOUGH THE FRONTAL
ZONE MAY RETREAT A BIT...SO THUNDER CHANCES WILL CONTINUE WITH NWP
CURRENTLY SUGGESTING ANOTHER SHORTWAVE WILL APPROACH FROM THE
NORTHWEST LATE KEEPING STORM CHANCES GOING LATE INTO THE NIGHT.
THE UPPER FLOW WILL TURN MORE NORTHERLY ON FRIDAY AS THE WESTERN 
RIDGE FURTHER AMPLIFIES AND BEGINS TO EDGE EASTWARD. THIS WILL 
REDUCE THE CHANCE THAT CONVECTION ORIGINATING OVER THE HIGHER 
ELEVATION OF NM AND CO CAN MAKE ITS WAY TO THE SOUTH PLAINS...BUT 
WITH THE RESIDUAL FRONTAL BOUNDARY STILL IN THE AREA AND A SHORTWAVE 
GRAZING WEST TEXAS FROM THE EAST...HAVE MAINTAINED LOW STORM 
CHANCES. DRIER AIR WILL GRADUALLY ADVECT IN ALOFT OVER THE WEEKEND 
AS THE UPPER RIDGE BENDS FURTHER EASTWARD AND A DRYING TREND WILL 
LIKELY ENSUE. THIS RIDGE WILL GRADUALLY BREAKDOWN LATE WEEKEND INTO 
EARLY NEXT WEEK AS A TROUGH EMERGES FROM THE CENTRAL/NORTHERN 
ROCKIES. THIS COULD BEND THE MONSOON MOISTURE EASTWARD...PERHAPS 
REJUVENATING STORM CHANCES. 
REGARDING TEMPERATURES...TENDED TO FAVOR THE COOL SIDE OF GUIDANCE 
GIVEN THE EXPECTED CLOUD COVER AND RAIN IN THE AREA MID TO LATE
WEEK. TEMPERATURES WILL GRADUALLY TREND UPWARD BY THIS WEEKEND AS
THE UPPER RIDGE BENDS OVER AND SOUTHERLY LOW-LEVEL FLOW RETURNS TO
WEST TEXAS.
&&
.PRELIMINARY POINT TEMPS/POPS...
FRIONA        86  62  84  61  86 /  30  50  40  40  30 
TULIA         86  64  82  63  84 /  30  50  40  40  30 
PLAINVIEW     90  65  81  64  84 /  30  40  40  40  30 
LEVELLAND     92  66  84  65  88 /  20  30  40  40  30 
LUBBOCK       92  68  83  66  86 /  20  30  40  40  30 
DENVER CITY   93  66  88  65  91 /  20  20  40  30  30 
BROWNFIELD    93  68  86  65  90 /  20  20  40  40  30 
CHILDRESS     91  68  85  68  87 /  40  60  40  40  30 
SPUR          95  70  86  68  89 /  20  30  40  40  30 
ASPERMONT     98  72  89  69  90 /  20  30  40  40  30 
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
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