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