Area Forecast Discussion
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FXUS64 KLUB 220056
AFDLUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
756 PM CDT MON APR 21 2014

.UPDATE...
ADDED ISOLATED THUNDER TO NORTHWEST COUNTIES AS A WEAK IMPULSE
WITH MODEST MID LEVEL MOISTURE WAS EDGING SOUTHEAST INTO THE AREA.
LATEST HRRR CONTINUES TO GENERATE ISOLATED WEAK CONVECTION ACROSS
OUR NORTHWEST ZONES FOR THE NEXT COUPLE HOURS. EXPECT ONLY LIGHT
RAINFALL. THESE HAVE DONE WELL JUST TO ARRIVE WITHIN A FAIRLY COOL
AND DRY AIRMASS WITH BUILDING HEIGHTS ALOFT...SO HAVE EARNED
AMENDED FORECAST STATUS. RMCQUEEN

&&

.PREV DISCUSSION... /ISSUED 604 PM CDT MON APR 21 2014/

AVIATION...
VFR EXPECTED TO DOMINATE. AN UPPER LEVEL HIGH PRESSURE RIDGE WILL
BUILD ACROSS THE AREA TONIGHT AND TUESDAY. VERY WEAK HIGH-BASED
CONVECTIVE SHOWERS MAINLY NORTH AND WEST OF THE TAF SITES EXPECTED
TO DISSIPATE BEFORE APPROACHING EITHER LOCATION. MODEST LOW LEVEL
SOUTH TO SOUTHEAST FLOW WILL DEVELOP TUESDAY AS A SURFACE LOW
PRESSURE TROUGH FORMS ALONG THE LEE-SIDE OF THE SOUTHERN AND
CENTRAL ROCKIES. RMCQUEEN

PREV DISCUSSION... /ISSUED 357 PM CDT MON APR 21 2014/

SHORT TERM...
A CUMULUS FIELD IS GRADUALLY DEVELOPING ACROSS THE CAPROCK. THE CU
ARE QUIET SHALLOW AT 230 PM...BUT THERE IS SOME SATELLITE INDICATION
OF MORE BUNCHING AND VERTICAL DEVELOPMENT IN EASTERN NEW MEXICO.
WATER VAPOR IMAGERY IS SHOWING A WEAK SHORTWAVE MOVING TOWARD THE
AREA FROM COLO AND NM...WHILE RAP/SPC ANALYSIS SUGGESTS THAT CIN IS
MINIMAL ON THE CAPROCK WITH ABOUT 500 J/KG OF MLCAPE. IN THIS
REGIME...WE STILL THINK WE/LL SEE SOME ISOLD T-STORM ACTIVITY
DEVELOP LATE THIS AFTERNOON...PERHAPS FOCUSED FROM THE FAR SRN TX
PANHANDLE INTO THE NRN SPLNS. RAINFALL SHOULD BE PRETTY SPOTTY. AND
ANY SHOWERS OR STORMS SHOULD DIE OUT PRETTY QUICKLY THIS EVENING AS
THE BOUNDARY LAYER COOLS. THIS WILL SET THE STAGE FOR A QUIET NIGHT
AND TUESDAY AS A LOW-AMPLITUDE SHORTWAVE RIDGES SLIDES OVER THE
REGION. WINDS WILL BE LIGHT OVERNIGHT AND THEN BEGIN TO PICK UP
TUESDAY AFTERNOON AS LEE TROUGH DEEPENS TO OUR WEST. LATE IN THE
DAY...THE MID-LVL FLOW WILL BEGIN TO BACK AS A DEEP UPPER-LEVEL
TROUGH DIGS INTO THE GREAT BASIN AND DESERT SW. SOME
OROGRAPHICALLY-AIDED CONVECTION MAY DEVELOP IN NM LATE IN THE DAY
BUT LIMITED MOISTURE ACROSS THE CWA SHOULD KEEP SKIES MOSTLY SUNNY
THROUGH 7 PM. TONIGHT/S LOWS SHOULD BE MAINLY IN THE UPPER 40S AND
50S...WHILE HIGHS ON TUESDAY WILL BE MAINLY IN THE 80S.

LONG TERM...
BY WEDNESDAY EVENING...WEST TEXAS LOOKS TO BE SITUATED ALMOST
DIRECTLY UNDERNEATH THE AXIS OF A STOUT UPPER RIDGE...WITH A
POTENT TROUGH RIGHT ON ITS HEELS ACROSS THE GREAT BASIN REGION.
WHILE THE BULK OF THE IMPACTS OF THIS TROUGH WILL LIKELY OCCUR ON
WEDNESDAY...PRESSURE FALLS ALONG MOST OF THE FRONT RANGE WILL
STEADILY INCREASE SOUTHERLY LOW LEVEL FLOW ACROSS THE AREA...THUS
BEGINNING THE SLOW RETURN OF QUALITY MOISTURE INTO THE AREA. WHILE
THE MODIFIED AIRMASS WEDNESDAY NIGHT ACROSS EASTERN NEW MEXICO
WILL STILL FEATURE ONLY MARGINAL DEWPOINTS...UPSLOPE FLOW INTO THE
HIGH TERRAIN IS LIKELY TO INITIATE A FEW SHOWERS AND
THUNDERSTORMS...AND GIVEN A DEVELOPING SOUTHERLY LOW LEVEL
JET...GRADUALLY IMPROVING MOISTURE AND INCREASING STEERING FLOW
OVERNIGHT...A FEW OF THESE SHOWERS AND PERHAPS A WEAK THUNDERSTORM
MAY BE ABLE TO REACH PORTIONS OF THE SOUTH PLAINS DURING THE
EVENING AND OVERNIGHT HOURS. OPTED TO INCREASE POPS INTO THE 10
PERCENT RANGE TO ACCOUNT FOR THIS...ALTHOUGH LEFT OUT EXPLICIT
MENTION IN THE GRIDS FOR THE TIME BEING GIVEN THE EXPECTED SPARSE
COVERAGE.

BY WEDNESDAY AFTERNOON...THE UPPER TROUGH AXIS WILL LIKELY HAVE
REACHED THE SPINE OF THE ROCKIES...SPREADING MODERATE TO STRONG
SOUTHWESTERLY UPPER FLOW ACROSS WEST TEXAS.  MEANWHILE AT THE
SURFACE...A DRYLINE WILL GRADUALLY TIGHTEN UP DURING THE AFTERNOON
HOURS ACROSS THE HIGH PLAINS...AND LATEST MODEL GUIDANCE ALL SEEMS
TO SUGGEST THAT IT WILL LIKELY BE LOCATED SOMEWHERE BETWEEN THE I27
CORRIDOR AND THE CAPROCK ESCARPMENT BY MID/LATE AFTERNOON.  MODEL
GUIDANCE CONTINUES TO BE VERY BULLISH REGARDING LATE AFTERNOON
THUNDERSTORM INITIATION ALONG THIS DRYLINE...AND IF STORMS DO MANAGE
TO DEVELOP IT APPEARS THAT SHEAR PROFILES WILL BE MORE THAN
SUPPORTIVE OF ROTATING UPDRAFTS.  HOWEVER...WHILE THE PERSISTENCE OF
VIGOROUS DRYLINE CONVECTION IN OPERATIONAL GUIDANCE DOES LEND
CONFIDENCE IN INITIATION...CAPPING DOES REMAIN A CONCERN
PARTICULARLY ALONG THE SOUTHERN EXTENT OF THE DRYLINE.  ALSO...MODEL
GUIDANCE SEEMS TO SUGGEST THAT DRYLINE CONVERGE MAY BE LESS THAN
IDEAL UNTIL LATE IN THE AFTERNOON...ALTHOUGH THIS MAY BE MITIGATED
SOMEWHAT BY EXPECTED SURFACE TEMPERATURES IN THE MID 80S.  SHOULD
STORMS DEVELOP...SUPERCELL STORMS WILL LIKELY BE THE DOMINANT STORM
MODE WITH THE POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS.  THE
TORNADO THREAT MAY BE SOMEWHAT LIMITED DESPITE FAVORABLE LOW LEVEL
HODOGRAPHS...DUE TO DEWPOINT SPREADS BETWEEN 25 TO 30 DEGREES AND
RESULTING HIGH LCLS.  ALL OF THIS IS TO SAY THAT WE OPTED TO KEEP
POPS MOSTLY UNCHANGED GIVEN THE COMBINATION OF UNCERTAINTIES
REGARDING INITIATION AND ALSO COVERAGE LIMITATIONS THAT USUALLY
RESULT FROM DISCRETE DRYLINE STORMS.  ANOTHER THING TO CONSIDER FOR
WEDNESDAY WILL BE THE POTENTIAL FOR FIRE WEATHER ACROSS THE SOUTH
PLAINS ON THE DRY SIDE OF THE DRYLINE.  THIS WILL BE MOST LIKELY
NEAR THE TX/NM BORDER WHERE RELATIVE HUMIDITIES WILL BE NEAR THE 15
PERCENT THRESHOLD FOR THE LONGEST PERIOD OF TIME.

OVERNIGHT WEDNESDAY...A COLD FRONT WILL PLUNGE SOUTHWARD...RESULTING
IN A SLIGHTLY COOLER AND VERY PLEASANT DAY THURSDAY.  MODELS THEN
HANG THIS FRONT UP ACROSS SOUTH CENTRAL TEXAS...AND ON FRIDAY
SOUTHERLY SURFACE WINDS WILL BEGIN TO GRADUALLY DRAW MOISTURE BACK
NORTHWARD. TEMPERATURES FRIDAY WILL LIKELY BE BACK UP INTO THE
UPPER 80S AND LOW 90S AS WELL...GIVEN OUR POSITION UNDERNEATH A
FLAT UPPER RIDGE.

THE FORECAST FOR THE WEEKEND THEN GETS INTERESTING AGAIN...ALTHOUGH
IT IS STILL RIFE WITH UNCERTAINTIES. OPERATIONAL GUIDANCE CONTINUES
TO EXHIBIT MAJOR PATTERN DIFFERENCES REGARDING THE EVOLUTION OF A
POWERFUL UPPER TROUGH...AND THIS WILL DRAMATICALLY IMPACT THE
POTENTIAL WEATHER FOR OUR AREA SATURDAY AND SUNDAY.  THE GFS
SOLUTION CONTINUES TO DIG THIS TROUGH WELL SOUTH INTO THE FOUR
CORNERS REGION...WHERE IT BEGINS TO CLOSE OFF INTO A VERY DEEP
CLOSED LOW.  IN ADDITION...IT ALSO DEVELOPS A SHARP DRYLINE AND
KEEPS THIS FEATURE FROM ADVANCING TOO FAR TO THE EAST.  UNDER THIS
SETUP...AN EPISODE OF SEVERE WEATHER WOULD BE LIKELY ACROSS AT LEAST
THE ROLLING PLAINS...AND POTENTIALLY A SIGNIFICANT ONE.  ON THE
OTHER HAND...THE ECMWF SOLUTION MAINTAINS AN OPEN WAVE FOR MUCH
LONGER...AND FAILS TO DIG THIS TROUGH NEARLY AS DEEP INTO THE FOUR
CORNERS REGION LIKE THE GFS.  THIS SCENARIO WOULD ALSO LIKELY RESULT
IN A MUCH MORE EASTERLY POSITION OF THE DRYLINE...AND A DAY OF WINDY
AND DRY CONDITIONS ACROSS THE MAJORITY OF THE CWA.  DESPITE MODEL
DIFFERENCES...OPTED TO INCLUDE A LOW MENTION OF THUNDERSTORMS ACROSS
THE ROLLING PLAINS GIVEN THE PERSISTENCE OF THE GFS.  BY
SUNDAY...BOTH SOLUTIONS SUGGEST THAT DRY AIR WILL BE FIRMLY IN
PLACE...WITH THE POTENTIAL FOR STRONG WESTERLY WINDS...BLOWING DUST
AND FIRE WEATHER.

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        50  80  55  81  45 /  20   0  10  10  10
TULIA         51  80  56  83  47 /  10   0  10  10  10
PLAINVIEW     53  80  58  84  49 /  10   0   0  10  10
LEVELLAND     52  82  58  85  48 /  10   0  10  10  10
LUBBOCK       55  82  59  86  51 /   0   0   0  10  10
DENVER CITY   53  84  60  84  51 /  10   0  10  10  10
BROWNFIELD    54  83  60  86  48 /   0   0   0  10  10
CHILDRESS     55  83  54  86  58 /   0   0   0  30  30
SPUR          56  84  57  86  54 /   0   0   0  20  20
ASPERMONT     59  86  57  91  60 /   0   0   0  20  20

&&

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

$$

05/99





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