Area Forecast Discussion
Issued by NWS

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858
FXUS64 KLUB 181111
AFDLUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
611 AM CDT FRI APR 18 2014

.AVIATION...
WIDESPREAD IFR CIGS LOOK TO LINGER QUITE A BIT LONGER THAN
PREVIOUSLY EXPECTED. LOW CIGS AT LBB SHOULD RISE TO MVFR LATER
THIS MORNING BEFORE SCATTERING OUT TO VFR NEAR 17Z. SIMILAR STORY
AT CDS...ALBEIT A SOLID 2-3 HOURS LATER DUE TO THICKER STRATUS.
LIGHT AND VARIABLE WINDS TO TREND SLY AROUND 10 KNOTS THROUGH THE
MRNG.

&&

.PREV DISCUSSION... /ISSUED 447 AM CDT FRI APR 18 2014/

SHORT TERM...
LIGHT BUT MOIST EASTERLIES HAD OVERSPREAD MUCH OF THE AREA AS OF
3AM COMPLETE WITH ABUNDANT LOW CLOUDS. DEPTH OF THIS STRATUS IS
QUITE SHALLOW...SO WE STILL EXPECT INSOLATION TO DO ITS JOB AND
ERODE THIS COMPLETELY BY LATE MORNING. BIGGEST EXCEPTION TO THIS
LOOKS TO BE IN THE ROLLING PLAINS WHERE THIS SATURATED DEPTH IS
DEEPER AND ALSO WINDS HERE WILL BE DELAYED IN VEERING SOUTH
COMPARED TO POINTS FARTHER WEST. WHAT FOG HAS MANAGED TO DEVELOP
THUS FAR HAS NOT BEEN PROBLEMATIC...BUT UNTIL DEWPOINT DEPRESSIONS
RISE BY MID-MORNING WE/LL KEEP PATCHY FOG MENTION INTACT AREA
WIDE.

BY MIDDAY...AN UPPER RIDGE AXIS WILL HAVE SHIFTED ATOP THE SOUTH
PLAINS IN ADVANCE OF A PRONOUNCED SOUTHERN STREAM TROUGH SOON TO
SET ITS SIGHTS ON THE DESERT SOUTHWEST. THIS RIDGE IS ALREADY
TRENDING A BIT DIRTY FROM A PLUME OF SUBTROPICAL CIRRUS THAT
SHOULD REACH OUR DOORSTEP THIS AFTERNOON. ADD TO THIS MOIST
SOUTHERLY WINDS SUPPRESSING MIXING HEIGHTS AND THE RESULT WILL BE
BELOW NORMAL HIGHS ONCE AGAIN.

ONLY CHANGE OF SIGNIFICANCE TO THE FORECAST WAS TO NIX THE MENTION
OF PRECIP LATE TONIGHT IN OUR WESTERN COLUMN OF COUNTIES. LARGELY
MERIDIONAL PRESENTATION TO THE AFOREMENTIONED TROUGH AND ITS SLOW
MOVEMENT CERTAINLY POINT TO A DELAYED ONSET OF HEIGHT FALLS AND
DEEPER SATURATION NECESSARY FOR PRECIP.

LONG TERM...
MODEL DATA FROM TONIGHT PAINT A COMPLICATED PICTURE FOR RAIN
CHANCES THIS WEEKEND AND THERE WERE SOME PRETTY SIGNIFICANT
CHANGES TO THE FORECAST. THE SYNOPTIC MODELS ALL HAVE A SOMEWHAT
SIMILAR EVOLUTION OF THE MID-LEVEL PATTERN WITH THE CLOSED LOW
OFF THE CALIFORNIA COAST MOVING OVER THE SOUTHWESTERN CONUS AND
OPENING UP INTO A DEEP TROF AS IT MOVES EAST TONIGHT. BY SATURDAY
MORNING...THE FIRST IN A SERIES OF SHORTWAVE EJECT OUT AHEAD OF
THE MAIN TROF AND MOVE OVER THE AREA. THE FIRST OF THESE WILL
ARRIVE OVER THE WESTERN SOUTH PLAINS AROUND SUNRISE AND SLOWLY
MOVE NORTHEASTWARD ACROSS THE FORECAST AREA. A SECOND SHORTWAVE
WILL THEN MOVE OVER THE AREA THROUGH EARLY SUNDAY MORNING AND BE
NORTHEAST OF THE FORECAST AREA BY MID-DAY. MEANWHILE...THE MAIN
TROUGH WILL BE WEAKENING AS IT MOVES TOWARDS THE CENTRAL PLAINS
WITH THE MAIN TROF PASSING OVER THE REGION ON THE HEELS OF THE
SECOND SHORTWAVE...FINALLY PASSING EAST OF THE AREA BY LATE SUNDAY
NIGHT.

THE TIMING OF THESE FEATURES HAS CHANGED THE TIMING FOR
PRECIPITATION AND THE AMOUNT OF COVERAGE AS WELL. SATURDAY MORNING
LOOKS AS IF PRECIPITATION WILL NOT BE AS WIDESPREAD AS INITIALLY
THOUGHT AND HAVE REMOVED POPS ACROSS THE ROLLING PLAINS AND
STARTED OFF WITH A SLIGHT CHANCE ACROSS THE SOUTH PLAINS. AS
THE FIRST SHORTWAVE MOVES OVER THE AREA SATURDAY...LOW LEVEL
MOISTURE WILL ALSO BE ON THE INCREASE ESPECIALLY ACROSS THE
ROLLING PLAINS. MODELS ARE STILL INDICATING SOME INSTABILITY ALOFT
ACROSS THE ENTIRE FORECAST AREA WITH SBCAPE VALUES AROUND 500 J/KG
BUT KEEP THE ROLLING PLAINS UNDER A STRONG CAP. ANY PRECIPITATION
WILL HAVE TO DEVELOP TO THE WEST OF THE AREA AND MOVE IN AS CAP
STRENGTH IS WEAKER CLOSER TO THE MAIN TROF. ALL THE SYNOPTIC
MODELS PLAY OUT THIS SCENARIO AND THE DETERMINISTIC TTU WRF HAS
ALSO PICKED UP ON THIS AS WELL. ENSEMBLE PROBABILITIES HOWEVER ARE
SOMEWHAT LESS OPTIMISTIC FOR PRECIPITATION CHANCES BUT STILL FAVOR
A PROGRESSION FROM WEST TO EAST THROUGH SATURDAY. ALL THIS LENDS
TOWARDS LESS COVERAGE IN PRECIPITATION AND OPTED TO REDUCE POPS BY
10 PERCENT IN THE PEAK TIME FRAME OF SATURDAY AFTERNOON AND
EVENING TO ACCOUNT FOR LESS COVERAGE ACROSS THE AREA.

IT APPEARS THAT THERE WILL BE A LULL IN PRECIPITATION SATURDAY
NIGHT INTO SUNDAY MORNING WITH THE SECOND SHORTWAVE. ATMOSPHERE
LOOKS TO BE IN RECOVERY MODE FROM THE RAIN ON SATURDAY WHICH
PREVENTS MUCH FROM DEVELOPING WITH THE SECOND SHORTWAVE.
HOWEVER...ANOTHER ROUND OF PRECIPITATION DEVELOPS LATE SUNDAY
MORNING AS THE MAIN TROUGH TOWARDS AND THEN OVER THE REGION.
MODELS GENERATE A MORE OPTIMISTIC 1000 J/KG SBCAPE OVER THE
ROLLING PLAINS MAINLY DUE TO MID-LEVEL COOLING WITH THE
APPROACHING TROF. HOWEVER...LOW CLOUDS MAY HAMPER THE AMOUNT OF
SURFACE BASED HEATING COMPARED TO WHAT THE MODELS ARE HOPING FOR.
MODERATE LIFT AHEAD OF THE TROF WILL HELP TO PROVIDE LARGE-SCALE
ASCENT POSSIBLY HELPING IN SOME PRECIPITATION DEVELOPMENT BY
ERODING THE CAP SLOWLY THROUGH THE MORNING. PUTTING THIS ALL
TOGETHER MEANS SUNDAY WILL FAVOR THE EASTERN HALF OF THE FORECAST
AREA FOR PRECIP WHILE A BIT OF DRIER AIR PUSHES IN BEHIND THE TROF
AND REDUCES THE AMOUNT OF MOISTURE AVAILABLE FOR PRECIPITATION
ACROSS THE SOUTH PLAINS. THIS WEAK DRYLINE MAY BE ENOUGH TO FOCUS
LIFT FOR STORMS ACROSS THE ROLLING PLAINS AS WELL AND HAVE KEPT
LOW- END CHANCE POPS ACROSS THIS AREA THROUGH 00Z. WITH THE TROF
AXIS EAST OF THE FORECAST AREA BY 00Z AND DRIER AIR CONTINUING TO
MIX EAST THROUGH THE DAY...LEFT POPS BELOW MENTION FOR THE ROLLING
PLAINS SUNDAY NIGHT BUT ANY SLOWER MOVEMENT OF THE TROF MAY
WARRANT A SLIGHT CHANCE IF MODELS START TO REFLECT A SLOWER TROF
PROGRESSION.

A WEAK COLD FRONT PUSHES IN BEHIND THE DEPARTING TROF FOR MONDAY
WHICH WILL MAINLY KEEP HIGH TEMPERATURES FAIRLY CLOSE TO WHAT IS
FORECAST FOR SUNDAY. SLIGHTLY DRIER AIR WILL ALSO PUSH IN BEHIND
THE FRONT BUT DEWPOINTS WILL STILL REMAIN AROUND 40 DEG F IN THE
POST-FRONTAL AIRMASS. A SHORTWAVE RIDGE WILL MOVE ACROSS THE AREA
ON TUESDAY BUMPING UP TEMPERATURES A FEW DEGREES MORE. RETURN FLOW
DEVELOPS AT THE SURFACE AND WE START TO SEE LOW-LEVEL MOISTURE
INCREASE OVERNIGHT THROUGH THE DAY WEDNESDAY. A BROAD TROF WILL
ALSO DEVELOP ACROSS THE WESTERN CONUS THROUGH THE FIRST PART OF
THE WEEK AND WE WILL RETURN TO SOUTHWESTERLY FLOW ALOFT BY
WEDNESDAY. THIS WILL HELP REDEVELOP THE LEE SURFACE TROF WEDNESDAY
AFTERNOON AND SHARPEN UP THE DRYLINE SOMEWHERE ACROSS THE AREA
DURING THE DAY. UNFORTUNATELY THERE WILL BE LITTLE IN THE WAY OF
STORMS AS A STRONG CAP REMAINS IN PLACE AND MODELS SHOW NO
PRECIPITATION AS A RESULT.

BEYOND WEDNESDAY...MODELS REALLY START TO DIFFER. ECMWF BRINGS A
COLD FRONT INTO THE FORECAST AREA THURSDAY MORNING DRIVEN
SOUTHWARD BY THE TROF BECOMING NEGATIVELY TILTED AS IT SWINGS OUT
INTO THE NORTHERN PLAINS BY THE MIDDLE OF NEXT WEEK. THE GFS
CONTINUES TO DEEPEN THE TROF AND THEN SWINGS IT OUT A FULL DAY TO
DAY AND A HALF LATER THAN THE ECMWF. THIS PATTERN FAVORS A MORE
WINDY/DUSTY DAY FOR THURSDAY. TOO MANY DIFFERENCES IN THE LAST 3
DAYS OF THE FORECAST TO WARRANT ANY SIGNIFICANT CHANGES AS THIS
TIME BUT THE MODELS DO HINT AT SOME PRECIPITATION WEDNESDAY
AFTERNOON INTO EARLY THURSDAY MORNING ALONG THE DRYLINE...
SOMETHING WE WILL KEEP OUR EYE ON.

JORDAN

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        72  49  75  49  75 /   0   0  30  30  20
TULIA         71  51  76  53  77 /   0   0  20  30  20
PLAINVIEW     70  52  77  53  79 /   0   0  20  30  20
LEVELLAND     72  53  77  54  79 /   0   0  30  30  20
LUBBOCK       71  53  79  55  80 /   0   0  30  30  30
DENVER CITY   73  55  76  54  80 /   0  10  40  30  20
BROWNFIELD    72  54  76  54  80 /   0  10  30  30  20
CHILDRESS     70  52  79  56  81 /   0   0  10  30  30
SPUR          73  53  78  57  83 /   0   0  20  30  30
ASPERMONT     73  55  78  60  83 /   0   0  10  30  30

&&

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

$$

93/14/93

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