000 FXUS64 KLUB 051031 AFDLUB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LUBBOCK TX 431 AM CST THU DEC 5 2013 .SHORT TERM... COLD AIR CONTINUES TO SURGE SWD EARLY THIS MORNING AND WILL CONTINUE TO BE REINFORCED THROUGH THE DAY AS HIGH PRESSURE KEEPS BUILDING INTO THE SRN HIGH PLAINS. TEMPS LIKELY TO STRUGGLE TO GAIN MUCH TRACTION TODAY DESPITE A LACK OF LOW CLOUDS ACROSS THE AREA. THICK HIGH CLOUD COVER SHOULD SLOWLY LOWER WITH SLOW TOP-DOWN MOISTENING AHEAD OF AN UPPER TROUGH THAT WILL SOON BEGIN ITS SWING EWD. THIS CLOUD COVER AND STRENGTH OF THE COLD AIR WILL HELP KEEP DIURNAL SWING NARROW...FAVORING PREVIOUS FCST AND COLDER MAV GUIDANCE. PRECIP TIMING AND AMOUNT A BIGGER CONCERN. DRY LOW LEVELS AND LACK OF ANY SIGNIFICANT LARGE-SCALE ASCENT KEEPING PRECIP AT BAY. DO NOT SEE THIS CHANGING THROUGH THE MORNING AND HAVE CUT BACK POPS SIGNIFICANTLY. PRECIP CHANCES SHOULD BEGIN TO INCREASE MID TO LATE AFTN ACROSS THE WRN ZONES. MODELS SHOWING POTENTIAL FOR SOME MODEST MOIST ISENTROPIC LIFT TO DEVELOP THERE THIS AFTERNOON POSSIBLY ENHANCED BY A FAST MOVING SMALL-SCALE TROUGH AND JET STREAK NOTED ON WATER VAPOR CROSSING BAJA CALIF EARLY THIS MORNING. BETTER CHANCES FOR PRECIP TO COME TONIGHT WITH LARGE-SCALE ASCENT ASSOCIATED WITH THE PASSAGE OF THE MAIN UPPER TROUGH. ITS PROGRESSIVE AND OPEN NATURE SUGGEST PRECIP CHANCES WILL BE IN A FAIRLY NARROW WINDOW...AND GIVEN LIMITED AVAILABLE MOISTURE... AMOUNTS SHOULD BE LIGHT /BARRING ANY UNFORESEEN MESOSCALE FORCES/. COULD SEE A QUICK 1/2 TO 1 1/2 INCH SNOWFALL UNDER THIS SCENARIO THAT WILL JUSTIFY CONTINUATION OF THE WINTER WX ADVISORY. DESPITE THE POSSIBILITY THAT MUCH OF THE FCST AREA WILL REMAIN DRY THROUGH FIRST PERIOD...AM HESITANT TO DELAY ONSET OF THE ADVISORY AND WILL WORD THE TEXT OF THAT PRODUCT TO FOCUS ON TONIGHT. REGARDING PRECIP PHASE...SHOULD ANY PRECIP FALL TODAY PROGGED SOUNDINGS ACROSS THE NWRN AREAS FAVOR SNOW WHILE SRN ZONES FAVOR FZRA OR IP GIVEN PERSISTENT WARM TEMPS OVER THE SHALLOW BUT DEEPENING COLD AIR MASS. BY 00Z COLD AIR SHOULD BE DEEP ENOUGH TO ELIMINATE FZRA POSSIBILITY WHILE ALOFT COOLER TEMPS WILL FAVOR A TRANSITION TO SNOW AS THE NIGHT PROGRESSES. && .LONG TERM... ARCTIC AIR MASS IS FINALLY SHOWING ITS TEETH THIS MORNING WITH DOUBLE DIGITS BELOW ZERO NOW IN THE PLAINS OF COLORADO AND NEARLY -30F SAMPLED IN LARAMIE WYOMING. THE FORECAST CHALLENGES HERE REMAIN THE LONGEVITY OF THIS INTENSIFYING ARCTIC AIR...RECORD COLD TEMPS AND EVEN CHANCES FOR FREEZING DRIZZLE ON SATURDAY. REMNANT SNOW AND SLEET LEFTOVER FROM TONIGHT SHOULD BE FOUND EXITING OUR EASTERN COUNTIES BY 12Z FRIDAY AHEAD OF A QUICK MOVING UPPER TROUGH. THE EXTENDED DURATION OF THIS PRECIP THRU 18Z PER THE ECMWF IS AN OUTLIER FOR SUCH A PROGRESSIVE WAVE...SO THE WINTER WX ADVISORY HAS BEEN TRIMMED BACK TO A 12Z EXPIRATION TIME. BY LATE FRIDAY...THE COLDEST AXIS OF 850MB TEMPS WILL BE FOUND DRAINING INTO THE REGION COMPLETE WITH DIMINISHING CLOUDS. THIS PATTERN NOW LOOKS MORE LEGITIMATE FOR WIDESPREAD SINGLE DIGIT LOWS...PARTICULARLY IN THE ROLLING PLAINS IMMEDIATELY WITHIN THE SURFACE PRESSURE RIDGE AND LIGHT WINDS. FARTHER WEST...LIGHT UPSLOPE COMPONENT SHOULD KEEP TEMPS ON THE CAPROCK FROM CRATERING AS SEVERELY. EVEN WITH MARGINAL WINDS AROUND 10 MPH...A WIND CHILL ADVISORY MAY BE ON THE HORIZON FOR VALUES FROM -5 TO -10F. BY 06Z SATURDAY...AGGRESSIVE ISENTROPIC LIFT IS STILL PROGGED TO OVERSPREAD THE CAPROCK BEFORE EXPANDING INTO THE ROLLING PLAINS AFTER 12Z. NAM AND GFS SOUNDINGS INDICATE A TYPICAL FREEZING DRIZZLE SCENARIO WITH SUPERCOOLED DROPLETS OCCUPYING THE LOWEST 5K FEET OR SO WHERE TEMPS ARE NEAR OR WARMER THAN -10C. MUCH OF THIS SATURATION STICKS AROUND THRU SAT NIGHT BEFORE STRONG SWLY FLOW ALOFT AHEAD OF THE NEXT PROGRESSIVE TROUGH ENTERS THE PICTURE. ALL MODELS ARE INCREDIBLY OPTIMISTIC THAT THIS SUBSIDENCE AND DRYING WILL RAPIDLY TURN OVER THE ARCTIC AIR AS FAR EAST AS WESTERN OKLAHOMA WE CONTINUE TO RAISE RED FLAGS WITH THIS SCENARIO SIMPLY FOR THE FACT THAT MODELS ARE HISTORICALLY AWFUL WITH THE EROSION OF THESE STRONG ARCTIC DOMES. WE WOULD NOT AT ALL BE SURPRISED TO SEE THESE MILD AND BREEZY SWLY WINDS LITERALLY DEFLECT OFF THE COLD DOME AND FAIL TO OVERTURN THE DENSITY GRADIENT. THE EXCEPTION TO THIS IS IN OUR SWRN COUNTIES WHERE THE ARCTIC LAYER WILL BE MUCH THINNER AND MORE PRONE TO EROSION COMPARED TO OFF THE CAPROCK WHERE COLD AIR DAMMING SHOULD REIGN SUPREME. SO INSTEAD OF BLINDLY FOLLOWING MODEL GUIDANCE...WE/LL APPLY SOME RATIONAL THINKING AND KEEP MOST HIGHS ON SUNDAY BELOW FREEZING. ANOTHER ARCTIC REINFORCEMENT ARRIVES BEHIND SUNDAY/S OPEN TROUGH AHEAD OF MORE SUB-FREEZING HIGHS FOR MONDAY. THEREAFTER...THE LARGE SCALE PATTERN TRENDS LESS AMPLIFIED...SO THIS COLD OUTBREAK WILL GRADUALLY EASE ITS GRIP UNDER INCREASINGLY ZONAL UPPER FLOW AND DOWNSLOPING WINDS. && .PRELIMINARY POINT TEMPS/POPS... FRIONA 21 13 23 10 18 / 50 70 10 10 10 TULIA 22 13 22 8 18 / 20 70 10 10 10 PLAINVIEW 25 13 24 8 19 / 20 70 10 10 10 LEVELLAND 29 16 25 11 21 / 40 70 10 10 10 LUBBOCK 28 15 24 8 19 / 30 70 10 10 10 DENVER CITY 32 20 27 12 21 / 50 70 10 10 10 BROWNFIELD 30 18 25 10 20 / 40 70 10 10 10 CHILDRESS 29 16 23 4 18 / 20 70 10 10 10 SPUR 30 16 23 4 19 / 20 70 10 10 10 ASPERMONT 32 18 25 4 20 / 20 70 10 10 10 && .LUB WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR THE FOLLOWING ZONES: TXZ021>044. && $$ 07/93