Area Forecast Discussion
Issued by NWS

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189
FXUS64 KLUB 220538 AAB
AFDLUB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LUBBOCK TX
1138 PM CST SAT FEB 21 2015

.AVIATION...
VFR CONDITIONS CONTINUE ACROSS THE AREA BUT CONFIDENCE CONTINUES
TO INCREASE FOR A TRANSITION TO MVFR THEN IFR CONDITIONS BY LATE
SUNDAY MORNING. BIGGEST UNCERTAINTY REMAINS IN THE TRANSITION FROM
LIQUID TO FREEZING PRECIPITATION. CURRENT TAFS HAVE KEPT THE SAME
GENERAL TIME LINE FOR THE TRANSITION BUT HAVE TAKEN OUT MENTION
OF SNOW AS THE PREDOMINANT PRECIP TYPE AND SWITCH IT TO SLEET/ICE
PELLETS. TEMPERATURE PROFILES CONTINUE TO DIFFER SLIGHTLY ON HOW
STRONG THE LAYER OF WARM AIR AT 5000 FEET WILL BE WHICH WILL
DETERMINE THE PRECIPITATION TYPE. REGARDLESS...PROBABILITY OF
FROZEN PRECIPITATION OCCURRING AT ALL THREE TAF SITES REMAINS HIGH
AND HAVE LEFT THIS AS THE PREVAILING PRECIPITATION TYPE FROM
SUNDAY AFTERNOON THROUGH THE END OF THIS TAF CYCLE.

JORDAN

&&

.PREV DISCUSSION... /ISSUED 541 PM CST SAT FEB 21 2015/

AVIATION...
VFR CONDITIONS IN PLACE AT ALL THREE TAF SITES AND SHOULD REMAIN
IN PLACE THROUGH THE EARLY MORNING HOURS ON SUNDAY. BEYOND
THIS...CONFIDENCE IS VERY LOW IN THE TIMING INVOLVED IN THIS
FORECAST. A STRONG COLD FRONT WILL MOVE ACROSS THE AREA EARLY
SUNDAY MORNING BEFORE SUNRISE WHICH WILL QUICKLY DROP TEMPERATURES
TO BELOW FREEZING AT THE SURFACE. ALOFT...A LAYER OF WARM AND
MOIST AIR WILL BE IN PLACE AROUND 5000 FEET. PRECIPITATION IS
EXPECTED TO DEVELOP LATE SUNDAY MORNING AND CONTINUE THROUGH
SUNDAY NIGHT INTO MONDAY MORNING. INITIALLY...THE PRECIPITATION
WILL START OFF ALL LIQUID BUT QUICKLY TRANSITION TO VARIOUS MIXES
OF FROZEN PRECIPITATION TYPES BY SUNDAY AFTERNOON. TIMING IN THESE
CHANGES REMAINS HIGHLY UNCERTAIN BUT EXPECT THAT ALL THREE TAF
SITES WILL SEE SOME FORM OF FREEZING PRECIPITATION BY TOMORROW
AFTERNOON. CEILINGS WILL ALSO DROP INTO IFR TO LIFR RANGE BY
SUNDAY AFTERNOON AND WILL REMAIN THERE THROUGH ALL OF THE DAY
SUNDAY INTO MONDAY MORNING. ONLY HIGH CONFIDENCE IN THIS
FORECAST...WINTRY PRECIPITATION WILL IMPACT TRAVEL IN AND OUT OF
AREA AIRPORTS STARTING SUNDAY AFTERNOON.

JORDAN

PREV DISCUSSION... /ISSUED 349 PM CST SAT FEB 21 2015/

SHORT TERM...
THE SHORT TERM PERIOD WILL COMPRISE OF SAYING GOODBYE TO THE ABOVE
NORMAL WARMTH WE HAVE SEEN THE PREVIOUS FEW DAYS...AND SAYING HELLO
TO COLDER TEMPS AND INCREASING CHANCES OF WINTRY PRECIP.

BROAD UA CYCLONIC FLOW CONTINUED TO DOMINATE ACROSS THE WRN
CONUS...THUS PROMOTING NEAR ZONAL FLOW ALOFT ACROSS THE SOUTHERN
PLAINS. A PIECE OF EMBEDDED ENERGY WITHIN THE BROAD UA TROUGH IN
ADDITION TO INCREASING ISENTROPIC UPGLIDE HAS ALREADY AIDED IN THE
DEVELOPMENT OF LIGHT RAIN AND SNOW ACROSS SERN CO AND NRN NM PER 21Z
METARS. LOOKING CLOSER TO HOME...THE COLD FRONT THAT BLASTED SOUTH
ACROSS THE REGION LAST NIGHT WAS NOTED ACROSS THE EDWARDS PLATEAU
AND DAVIS MOUNTAINS LATE THIS AFTN. TEMPS IN THE 50S IS THE RESULT
OF THE FROPA WHICH IS SOME 15 DEGREES OR SO COOLER THAN YESTERDAY
DURING THIS TIME /THOUGH NOT OVERLY COLD/. LIGHT SE TO NE SFC WINDS
HAVE BEEN GRADUALLY VEERING FOR THE LAST SEVERAL HOURS WHERE BY THIS
EVENING...THE ENTIRE CWA WILL BE ENCOMPASSED BY AN UPSLOPE SFC
REGIME. THIS WIND COMPONENT WILL PROVIDE INCREASING LOW LEVEL
MOISTURE...WHICH IS EVIDENT VIA MODEL SOUNDINGS AS IT SHOWS THE
DEVELOPMENT OF LOW CLOUDS AND PERHAPS FOG BY LATE THIS
EVENING/TONIGHT. THE SFC RIDGE THAT WAS RESPONSIBLE FOR THE FROPA
LAST NIGHT WILL BE OOZING SOUTH FROM CANADA TO ACROSS THE NORTHERN
PLAINS AND CREATE A SLIGHT TIGHTENED PRESSURE GRADIENT LATE
TONIGHT...AND THUS CAUSE UPSLOPE WIND SPEEDS TO INCREASE TO 15-20
MPH. CONCURRENTLY...A COLDER AIRMASS WILL ADVECT IN ACROSS THE CWA
WITH PROGGED 850 MB TEMPS DROPPING TO BELOW 0 C ACROSS THE NRN ZONES
BY 12Z. AS ISENTROPIC LIFT DEVELOPS OVER THE COLD AIR MASS...LIGHT
WINTRY PRECIP WILL COMMENCE TO IMPACT THE NRN ZONES AFTER AOA
MIDNIGHT. PRECIP TYPE REMAINS DIFFICULT AS MODEL SOUNDINGS INDICATE
A WARM NOSE BETWEEN THE 800 MB TO 700MB LAYER...WITH RELATIVELY DRY
MID-LEVELS. HENCE...PRECIP CAN TAKE THE FORM OF DRIZZLE...FREEZING
DRIZZLE OR LIGHT SNOW...WHICH IS DEPENDENT ON THE STRENGTH OF THE
WARM NOSE.

TOMORROW DURING THE DAY...THE STRENGTH OF THE WARM NOSE WILL NO
LONGER BE IN QUESTION ACROSS THE NWRN ZONES...AS IT WILL HAVE
DETERIORATED...LEAVING LIGHT SNOW AS THE PRIMARY PRECIP TYPE. AS
COLDER AIR CONTINUES TO FILTER IN ACROSS THE FA AND ISENTROPIC
UPGLIDE SPREADS TO THE REMAINDER OF THE CWA...FROZEN PRECIP WILL BE
PLAUSIBLE /SLEET AND/OR FREEZING RAIN/ HENCE INDICATIVE OF A BIT OF
A WARM NOSE REMAINING. THE EXCEPTION MAY BE ACROSS THE LOW ROLLING
PLAINS AS THE WARM NOSE IS MOST PRONOUNCED THERE AND SFC TEMPS IS
PROGGED TO REMAIN A FEW DEGREES ABOVE FREEZING /COULD MORE SO SEE
RAIN OR FREEZING RAIN/. IT IS INTERESTING TO NOTE THAT THE GFS...NAM
AND TO A LESSER EXTENT THE ECMWF DISPLAY AN EMBEDDED IMPULSE MOVING
ACROSS THE CNTRL AND SRN ZONES TOMORROW AFTN...WHICH COULD ENCOURAGE
BANDED PRECIP AND THEREFORE THE POTENTIAL FOR BRIEF MODERATE WINTRY
PRECIP LIKELY IN THE FORM OF SLEET. WHERE EXACTLY THE BANDED PRECIP
IS SHOWN TO SET UP VARIES AMONGST THE AFOREMENTIONED MODELS BUT IN
GENERAL...IS SHOWN TO OCCUR ACROSS THE SRN-HALF OF THE CWA. IF THE
EMBEDDED DISTURBANCE DOES INDEED MOVE ACROSS THE REGION AND IS
STRONG ENOUGH TO PROVIDE ADEQUATE LARGE SCALE ASCENT...THEN BANDED
PRECIP/MODERATE SLEET WILL BE PLAUSIBLE.

OVERNIGHT TEMPS IN THE UPPER 20S TO MIDDLE 30S WILL NOT IMPROVE MUCH
DURING THE DAY TOMORROW. IN FACT...MODEL GUIDANCE EXHIBIT TEMPS
FALLING THROUGHOUT THE DAY WHICH SUGGESTS  HIGH TEMPS WILL LIKELY
OCCUR AOA MIDNIGHT. THESE COLD CONDITIONS AND WINTRY PRECIP WILL
LEAD TO ROAD CONDITIONS PROGRESSIVELY WORSENING WITH TIME. CAUTION
IS ADVISED. /29

LONG TERM...
COLD AIR WILL DEEPEN SUNDAY NIGHT WHILE WEAK SUP-TROPICAL IMPULSES
LOCATED NEAR BAJA EJECT OVERHEAD. DRYING IN LOWEST 100 MB WILL BE
A FACTOR IN EXPECTED PRECIPITATION TOTALS...BUT WE BELIEVE THE
TOTAL LIFT SUNDAY NIGHT EVENTUALLY WILL MOISTEN LOWER LEVELS AND
LEAD TO INCREASING PRECIPITATION COVERAGE AND RATES. SHOULD BE
POINTED OUT THE GFS IS MORE BULLISH WITH MID LEVEL MOISTURE WHICH
LEADS TO MORE RAPID PRECIPITATION EFFICIENCY. WE ALSO ARE SEEING
MORE INDICATIONS OF BANDING AND MODEST ELEVATED INSTABILITY SUNDAY
NIGHT OVER SOUTHERN ZONES. AND A WARM NOSE BETWEEN 700 AND 800 MB
WILL WARM AS MUCH AS 3 DEGREES CENITIGRADE SUNDAY EVENING OVER
SOUTHERN ZONES WHICH IS ENOUGH TO THINK THAT FREEZING RAIN COULD
BE A VIABLE OUTCOME AT LEAST FAR SOUTH...WHILE SLEET AND SNOW ARE
STILL WELL WITHIN REALM OF POSSIBILITY CENTRAL AREAS SUNDAY
NIGHT...ALL SNOW TO THE NORTH. SOLUTIONS STILL HAVE SOME DISTANCE
TO AGREE ON ALL THIS. BUT THERE HAS BEEN ENOUGH COMING TOGETHER
THAT OUR CONFIDENCE IN AT LEAST A MODEST WINTER STORM EVENT HAS
ELEVATED ENOUGH TO ISSUE ADVISORIES FOR SUNDAY NIGHT AND EARLY
MONDAY. THE LATEST WPC WINTER WEATHER GRAPHIC SUMS UP MOST OF THIS
PRETTY WELL.

AN UPPER TROUGH WILL SWING THROUGH QUICKLY LATE TUESDAY OR EARLY
WEDNESDAY...SOLUTIONS SHOWING ENOUGH DRYING THAT WE WILL RETAIN NO
MENTION OF PRECIPITATION AT THIS TIME. A NEW AND MORE FORMIDABLE
LOOKING LONG WAVE TROUGH IS STILL EXPECTED TO CARVE OUT VIA A
SERIES OF SHARP WAVES LATE NEXT WEEK INTO NEXT WEEKEND. THIS
SHOULD SEND ANOTHER DUMP OF SHARPLY COLDER AIR INTO THE AREA BY
THURSDAY...PROBABLY MORE-OR-LESS HOLDING THROUGH THE WEEKEND...
WHILE SUCCESSIVE WAVES LINE UP TO OUR WEST. CONTINUED TO RAMP UP
INTO SLIGHTLY HIGHER...MAINLY SNOW CHANCES...BY LATE IN THE WEEK
INTO THE EARLY WEEKEND AT LEAST. /05 RMCQUEEN

&&

.PRELIMINARY POINT TEMPS/POPS...
FRIONA        29  29  14  26 /  20  50  70  50
TULIA         28  28  14  23 /  20  50  70  60
PLAINVIEW     31  31  15  25 /  20  50  70  60
LEVELLAND     31  33  16  27 /  10  50  70  50
LUBBOCK       32  33  16  25 /  10  50  70  60
DENVER CITY   34  37  18  28 /  10  40  70  50
BROWNFIELD    33  35  18  27 /  10  40  70  50
CHILDRESS     32  32  16  24 /  20  40  70  70
SPUR          33  34  17  25 /  10  50  70  70
ASPERMONT     35  36  19  26 /  10  50  70  70

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 PM SUNDAY TO NOON CST MONDAY FOR
TXZ021>044.

&&

$$

14/93/14

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