Area Forecast Discussion
Issued by NWS

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407
FXUS64 KLUB 291120
AFDLUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
520 AM CST MON DEC 29 2014

.AVIATION...
LIGHT WEST TO NORTHWEST WINDS EARLY THIS MORNING WILL VEER TO
NORTH AND BECOME BREEZY THIS EVENING INTO TONIGHT /15-16
KTS/...THANKS TO A COLD FRONTAL PASSAGE. MVFR AND POSSIBLY IFR CLOUD
DECKS WILL DEVELOP IN THE WAKE OF THE COLD FRONT. COMPUTER MODELS
HINT AT -FZDZ/-SN DEVELOPMENT WELL NORTH AND WEST OF ALL THREE TAF
SITES LATE TONIGHT. THIS WINTRY ACTIVITY WILL NOT IMPACT THE
TERMINALS DURING THIS TAF CYCLE.

&&

.PREV DISCUSSION... /ISSUED 406 AM CST MON DEC 29 2014/

SHORT TERM...
THE ARCTIC BLAST WE HAVE ALL BEEN WAITING FOR WILL BE THE FOCUS FOR
THE SHORT TERM PERIOD. THE COLD FRONT WAS NOTED ACROSS SRN
NEBRASKA/NRN KANSAS PER 08Z METARS AND WAS CHARACTERIZED BY TEMPS IN
THE TEENS AND 20S...VERSUS 30S AND 40S ACROSS THE CWA. CLOSER TO
HOME...WSW SFC WINDS WILL HAVE VEERED TO THE WNW BY AOA
SUNRISE...COURTESY OF A PRE-FRONTAL TROUGH. A MORE NRLY WIND WILL
OCCUR ACROSS THE NRN ZONES BY THE AFTN...AND MAKE FOR A SLIGHT TEMP
GRADIENT WITH 40S OCCURRING ACROSS THE NRN ZONES AND 50S ELSEWHERE.

THE MAIN BONAFIDE COLD FRONTAL PUSH IS EXPECTED TO IMPINGE ON THE FA
THIS EVENING INTO TONIGHT...USHERING IN 850 MB TEMPS OF -6 C TO -8
C. PRESSURE RISES ON THE ORDER OF 4-6 MB PER 3 HRS WILL CAUSE N-NE
WIND SPEEDS TO INCREASE TO 15-20 MPH...COUPLED WITH THE CAA WILL
MAKE FOR A CHILLY NIGHT WITH TEMPS PLUMMETING INTO THE TEENS ACROSS
ALL BUT PERHAPS THE ROLLING PLAINS WHERE LOWER 20S WILL BE COMMON. A
STRATUS DECK WILL FORM FOLLOWING THE PASSAGE OF THE COLD FRONT...AS
SUGGESTED BY MOISTENING LOW LEVELS PER MODEL SOUNDINGS.
FURTHERMORE...BROAD CYCLONIC FLOW ALOFT WILL PROMOTE INCREASED LARGE
SCALE ASCENT...THOUGH THE BETTER LIFT IS NOTED ACROSS THE CENTRAL
PLAINS. LIGHT QPF SIGNALS ACROSS ERN NEW MEXICO AND THE PANHANDLES
AS A RESULT OF THE UL SUPPORT AND MOISTENED LOW LEVELS MAY NEAR THE
FAR SW TX PANHANDLE BY THE END OF THE SHORT TERM PERIOD. SOUNDING
PROFILES QUICKLY FALL BELOW 0 C BY 30/12Z...AND HENCE THE PRECIP
TYPE WILL LIKELY BE LIGHT FREEZING DRIZZLE AND/OR LIGHT SNOW THAT
COULD NEAR THE FAR SW TX PANHANDLE. THOUGH ACCUMULATIONS WILL BE
RATHER LIGHT GIVEN THE MID-UPPER LEVELS OF THE ATMOSPHERE ARE SO DRY
DURING THE AFOREMENTIONED TIME /PWATS BELOW 0.30 INCHES/. AS
SUCH...HAVE ELECTED TO HAVE BELOW MENTIONABLE 10-11 PERCENT POPS
ACROSS THE FAR SW TX PANHANDLE ATTM.

LONG TERM...
FOCUS REMAINS ON POTENTIAL FOR PERIODS OF WINTRY PRECIP THROUGH
THE WEEK. THE INITIAL BATCH PROGGED TO COME TUESDAY...PEAKING
TUESDAY NIGHT...BEFORE DISSIPATING WEDNESDAY. MODELS IN REASONABLE
AGREEMENT SATURATING A DEEPENING PART OF THE LOWER LEVELS AS COLD
AIR BEHIND THE ARCTIC COLD FRONT DEEPENS...UP TO ABOUT 750 MB BY
TUESDAY EVENING. MID LEVELS ABOVE THE COLD AIR PROGGED TO REMAIN
DRY THROUGH THIS PERIOD WHILE SOURCE OF LIFT APPEARS TO BE
ISENTROPIC IN NATURE AND LOCATED NEAR THE TOP OF THE COLD AIR.
THIS PROFILE AND SCENARIO SUGGEST FREEZING DRIZZLE IS THE LIKELY
OUTCOME SHOULD ANY PRECIP DEVELOP...WITH A SMALL CHANCE THAT
FALLOUT FROM UPPER LEVEL MOISTURE COULD PRODUCE A SEEDER-FEEDER
MECHANISM COULD PRODUCE SOME LIGHT SNOW...MORESO TUESDAY NIGHT
WHEN MAGNITUDE OF DRY MID LEVELS IS MINIMIZED. FREEZING DRIZZLE
PRODUCES SOME OF THE MORE DIFFIUCLT TRAVEL CONDITIONS AROUND HERE
SO WILL BEGIN TO INCREASE THE POSSIBILITY WITH THE PUBLIC VIA AN
SPS.

LIFT PROGGED TO DECREASE WEDNESDAY AS MODEST SHORT WAVE RIDGING
MOVES OVERHEAD AND LIFT BECOMES MORE NEUTRAL THROUGH THE DEPTH OF
THE PROGGED SOUNDINGS. THE RESPITE IS LIKELY TO BE BRIEF...AT
LEAST FOR THE SERN HALF OF THE FCST AREA AS LIFT ASSOCIATED WITH
THE WARM CONVEYOR BELT AHEAD OF A CLOSED LOW PROGGED TO MOVE
THROUGH THE 4-CORNERS REGION INCREASES ACROSS THE ERN TWO-THIRDS
OF THE STATE...THE BACK EDGE OF THAT LIFT POSSIBLY AS FAR WEST AS
THE SERN PART OF THE FCST AREA. INCREASING MID-LEVEL TEMPS IN THIS
WARM ADVECTION PATTERN SHOULD PRODUCE A GOOD WARM NOSE AND TEMPS
ABOVE FREEZING IN A SUFFICIENT LAYER ALOFT TO MELT FALLING SNOW.
RESULT WILL BE RAIN...FREEZING RAIN...AND/OR SLEET DEPENDENT ON
SFC TEMPS AND WARM NOSE TEMPS DURING THAT PERIOD. INCREASING LIFT
FURTHER WEST ONTO THE CAPROCK COULD SPREAD PRECIP WWD WITH TIME.

FINALLY...LAST WINDOW FOR PRECIP APPEARS TO COME AS THE LOW ITSELF
EJECTS ACROSS THE PANHANDLE AND SOUTH PLAINS REGION. STILL SOME
MODEL TIMING AND TRACK ISSUES...WHICH IS TO BE EXPECTED GIVEN THE
LOW ITSELF IS STILL IN THE FORMATIVE STAGES. SUFFICE IT TO SAY
THAT PRECIP CHANCE LINGERS INTO FRIDAY NIGHT /AND POSSIBLY
SATURDAY IF FUTURE TRENDS SLOW THE PROGRESS OF THE LOW OR IF THE
TRACK ENDS UP FURTHER SOUTH AND POTENTIAL FOR WRAP-AROUND OR
DEFORMATION AXIS PRECIP INCREASES/. AS THE LOW APPROACHES...THE
WARM NOSE SHOULD GRADUALLY COOL WITH THE POTENTIAL FOR A WINDOW OF
SNOW BEFORE THE SYSTEM EXITS TO THE EAST.

SFC TEMPS ARE AN IMPORTANT COMPONENT TO THE PRECIP PHASE FCST THIS
WEEK. IN GENERAL...HAVE CONTINUED WITH A BLEND OF MOSTLY RAW MODEL
TEMPS...NEAR MOS FOR OVERNIGHT LOWS AND UNDERCUTTING FOR DAYTIME
HIGHS AS CLOUD COVER SHOULD KEEP A NARROW DIURNAL RANGE.
HOWEVER...SHOULD SEE A GRADUAL INCREASE IN TEMPS POST-WEDNESDAY AS
LOW LEVEL WARM ADVECTION INCREASES AHEAD OF THE CLOSED LOW.

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        46  15  22  10  24 /   0  10  30  40  10
TULIA         45  16  23  13  24 /   0  10  30  40  20
PLAINVIEW     49  17  24  14  24 /   0   0  30  40  20
LEVELLAND     52  19  26  16  24 /   0   0  30  40  20
LUBBOCK       51  19  26  16  24 /   0   0  30  40  20
DENVER CITY   51  20  27  19  25 /   0   0  30  50  20
BROWNFIELD    51  19  28  18  25 /   0   0  30  50  20
CHILDRESS     46  21  28  17  25 /   0   0  20  30  10
SPUR          54  22  29  18  25 /   0   0  30  40  10
ASPERMONT     54  24  31  20  27 /   0   0  20  40  10

&&

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

$$

29

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