Area Forecast Discussion
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636
FXUS64 KLUB 230955 CCA
AFDLUB

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE LUBBOCK TX
451 AM CDT WED APR 23 2014

.SHORT TERM...
A SHARPENING DRYLINE LATER TODAY IS EXPECTED TO BECOME THE FOCUS FOR
SCATTERED THUNDERSTORM DEVELOPMENT. AN UPPER TROUGH FROM IDAHO TO
ARIZONA TO MOVE EWD TO THE ERN EXTENT OF THE ROCKIES BY THE END OF
THE DAY. DEEPENING SWLY FLOW BUT ALSO HEIGHT FALLS AHEAD OF THE
TROUGH TO RESULT IN A DRYLINE THAT WILL BECOME MORE DEFINED THROUGH
THE DAY THEN MOVE EWD TO AROUND THE CAPROCK ESCARPMENT BY LATE AFTN.
SELY LOW LEVEL FLOW TO THE EAST OF THE DRYLINE TO BRING SOME
MOISTURE ADVECTION INTO THE ROLLING PLAINS. 00Z MODEL RUNS CONTINUE
A CONVECTIVE PRECIP SIGNAL MAINLY ACROSS THE ERN PANHANDLE INTO THE
NRN ROLLING PLAINS EWD INTO WRN OKLAHOMA AND NW TEXAS...ALTHOUGH
MAYBE NOT AS ROBUST A SIGNAL AS SEEN PREVIOUSLY. SOME CONCERNS ARE
QUALITY OF THE LOW LEVEL MOISTURE /MUST GET AS FOR SOUTH AS SAN
ANTONIO AND COLLEGE STATION BEFORE FINDING A 60F DEW POINT AS OF
08Z/...POSSIBLE LIMITATIONS DUE TO MID AND HIGH CLOUD COVER ON TEMPS
AND LAPSE RATES /MARGINAL EFFECT EXPECTED/...AND STRENGTH OF THE
CAP. AS FOR MOISTURE...SHOULD SEE MID 50S MOVE INTO THE ERN ZONES
ALTHOUGH REMAINING FAIRLY SHALLOW. STILL THAT TYPE OF MOISTURE IS
FAR FROM DISCOUNTING PRECIP. BEST PUSH TO THE DRYLINE IS EXPECTED TO
BE TO THE NORTHEAST TOWARD THE ERN PANHANDLE WITH UPPER SUPPORT ALSO
FOCUSING ON THAT DIRECTION. THIS AREA MOST LIKELY TO BREAK THE CAP
WITH AREA FURTHER SOUTH TOWARD THE SRN ROLLING PLAINS POSSIBLY
STAYING CAPPED UNTIL EARLY EVENING WHEN DEVELOPMENT OF A LOW LEVEL
JET WOULD INCREASE MOISTURE CONVERGENCE AND ADVECTION POTENTIALLY
HELPING ERODE THE CAP ENOUGH THERE FOR SOME PRECIP TO BUILD SWD PER
THE WRF-NAM SOLUTION. ALL THAT TO SAY THAT PREVIOUS POP FCST LOOKS
PRETTY GOOD. WILL MAKE SOME MINOR ADJUSTMENTS...SHIFTING WRN EDGE OF
SLIGHT CHANCE TO THE EAST WITH THE DRYLINE AND LOWERING AFTN POPS
ACROSS THE SRN ROLLING PLAINS WHERE STRONGER CAP EXPECTED.

SEVERE THREAT WILL REMAIN AS MIXED LAYER CAPE OF 1000-2000 J/KG
EXPECTED WITH BULK SHEAR SUPPORTING SUPERCELLS...PARTICULARLY AS THE
EVENT GOES ON WITH INCREASING LOW LEVEL JET INCREASING SHEAR. STORMS
LIKELY TO BE FAIRLY HIGH BASED TO BEGIN WITH WITH LARGE HAIL THE
MAIN THREAT AND TORNADO POTENTIAL LIMITED BY HIGH LCL AND LOW LEVEL
WINDS LIKELY BACKED CLOSER TO SOUTH THAN EAST. THE UPPER TROUGH
MOVING OVER THE PANHANDLE TOWARD 06Z WILL SHIFT CHANCES TO THE EAST
OF THE FCST AREA.

PREVIOUS TEMP FCST LOOKS FINE WITH MINOR ADJUSTMENT TOWARD 00Z MOS.
WINDS TO BECOME BREEZY TO WINDY WITH TIGHTENING PRESSURE GRADIENT...
AGAIN IN LINE WITH PREVIOUS FCST. COLD FRONT LATE TONIGHT BEHIND THE
TROUGH WILL SEE WINDS COME AROUND FROM THE NORTH.

&&

.LONG TERM...
THE ONLY CHALLENGING WEATHER IN THIS LONG TERM WINDOW FROM THURSDAY
THRU TUESDAY WILL UNFOLD THE WEEKEND AS A NEGATIVE TILT UPPER LOW
ENTERS THE PICTURE. BEFORE THEN...SHALLOW RIDGING ALOFT WILL MAKE
FOR TRANQUIL CONDITIONS WITH A RETURN TO SOME MOIST SOUTHERLY
WINDS BY FRIDAY BEHIND A SURFACE RIDGE. AS SOON AS FRI NIGHT...A
DRYLINE COULD ALREADY BE BISECTING THE CWA FROM SW TO NE. GRADUAL
BACKING OF WINDS ALOFT ON SATURDAY IN ADVANCE OF THE UPPER LOW
WOULD TEND TO FAVOR THIS DRYLINE NOT MIXING TOO FAR EAST DURING
THE DAY...SO WE WILL KEEP SLIGHT CHANCE POPS OFF THE CAPROCK
DURING THE AFTN AND OVERNIGHT.

PRESSURE FALLS STILL TO OUR WEST BY SAT EVNG MAY INDEED PULL THE
DRYLINE MUCH FARTHER WEST THAN MODELS INDICATE. IT/S NOT UNCOMMON
TO SEE MODELS SERIOUSLY UNDERESTIMATE THE WWD EXTENT OF
RETROGRADING DRYLINES IN THESE SETUPS...BUT IT/S STILL TOO SOON TO
EXPAND PRECIP MENTION ONTO THE CAPROCK FOR THIS POSSIBILITY.
NONETHELESS...THE STRONGEST HEIGHT FALLS AND A QUICK-MOVING
PACIFIC FRONT WILL OVERTAKE THE SOUTH PLAINS SAT NIGHT...SO THE
POSITION OF THE DRYLINE WILL PROVE CRITICAL IN DETERMINING HOW FAR
WEST POPS ARE NECESSARY. FOR THOSE WHO REMEMBER SATURDAY NIGHT
4/14/2012...A PACIFIC FRONT AND DRYLINE COLLISION WAS REALIZED
MUCH FARTHER WEST THAN MODELS PROGGED WHICH CAUGHT MANY FORECASTERS
BY SURPRISE. A SIMILAR PATTERN IS IN PLACE THIS TIME AROUND...SO
WE CANNOT ENTIRELY IGNORE THIS POSSIBILITY.

BY SUNDAY...THE NEGATIVE TILT UPPER LOW IS SHOWN TO DEEPEN WHILE
HOOKING NEWD ACROSS SERN CO AND SWRN KS. THIS IS UNFORTUNATELY A
TEXTBOOK PATTERN FOR CLASSIC SOUTH PLAINS DUST EVENTS...SO WESTERLY
WINDS HAVE BEEN RAMPED UP CONSIDERABLY SUN AFTN ALONG WITH BLOWING
DUST MENTION. HIGH WINDS MAY SPARE THE REGION AS THE 500MB AND 700MB
WIND MAXIMA DO NOT APPEAR PARTICULARLY ROBUST ATTM. FIRE WEATHER
MAY ALSO FAIL TO EMERGE AS MODELS ARE TRENDING MUCH COOLER BEHIND
THE PACIFIC FRONT...THOUGH WE/VE SEEN THIS BEFORE WHERE TEMPS PROVE
MUCH WARMER THAN PROGGED. WE DID COOL SUNDAY/S HIGHS A TOUCH...
BUT ARE STILL RESIDING ABOVE MEX AND ECM MOS. COOL AND DRY NW FLOW
THEN SETS UP EARLY NEXT WEEK AS THE UPPER LOW SLOWS AND FILLS TO
OUR NORTHEAST. GULF MOISTURE WILL SADLY BE SWEPT BACK TO ITS
ORIGIN IN THIS PATTERN...SO MEASURABLE PRECIP WILL ONCE AGAIN
BECOME A SCARCE COMMODITY.



&&

.FIRE WEATHER...
LOW END RED FLAG WARNING LOOKS REASONABLE WRN TWO COLUMNS OF
COUNTIES. WINDS WEST OF THE DRYLINE TO INCREASE TOWARD 25 MPH AT THE
20-FOOT LEVEL WITH RH BOTTOMING OUT AROUND 10 PCT. SOME QUESTION HOW
LONG THAT COMBINATION WILL LAST ACROSS THIS AREA BUT NEAR 3 HOURS IF
NOT EXCEEDING THAT DURATION SEEMS REASONABLE. WILL MAINTAIN THE
INHERITED WARNING AND UPGRADE THE WATCH AREA TO A WARNING.

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        85  44  75  44  86 /  10   0   0   0   0
TULIA         86  46  76  47  87 /  20  10   0   0   0
PLAINVIEW     87  48  77  49  89 /  20  10   0   0   0
LEVELLAND     88  47  79  52  90 /  10   0   0   0   0
LUBBOCK       88  50  79  53  90 /  10   0   0   0   0
DENVER CITY   88  50  77  53  89 /  10   0   0   0   0
BROWNFIELD    89  49  79  54  91 /  10   0   0   0   0
CHILDRESS     89  56  79  49  89 /  50  40   0   0   0
SPUR          87  53  80  53  92 /  30  20   0   0   0
ASPERMONT     89  59  80  53  94 /  30  30   0   0   0

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 9 PM CDT THIS
EVENING FOR THE FOLLOWING ZONES:
TXZ021-022-027-028-033-034-039-040.

&&

$$

07/93

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