Winter Storm in Texas, February 12, 2013

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
1132 PM CST MON FEB 11 2013

.AVIATION...
FOR THE 06Z TAFS...A VERY FAST EVOLVING SYSTEM HAS LED TO SOME
CHANGES FROM THE 00Z TAF ISSUANCE. THE BIGGEST CHANGE IS THE FASTER
ONSET OF SN. ALREADY SN IS REPORTED IN WESTERN PANHANDLES AND SHOULD
BEGIN IN KDHT AND KAMA WITHIN THE NEXT HOUR...AND KGUY WITHIN THE
NEXT 2 HOURS. EXPECT INTERMITTENT SHSN THROUGH 09Z...BEFORE IT
TRANSITIONS TO A MORE WIDESPREAD EVENT. ANOTHER CHANGE IS THE
OBSERVATION OF TSSN IN THE SOUTHERN TX PANHANDLE...INCLUDING N OF
KAMA. AT THIS POINT WILL NOT INCLUDE ANY TSSN IN THE TAFS AS THE
INITIAL THREAT IS N OF KAMA AND VERY UNLIKELY TO GET AS FAR N AS KDHT.
THE RAP INDICATES SOME INSTABILITY BETWEEN 09 AND 12Z...AND THUS SOME
THREAT AGAIN FOR TSSN BUT THE LIKELIHOOD OF IT REDEVELOPING IS
LOW...AND WOULD BE ISOLATED AT BEST...SO WILL NOT INCLUDE IN THE
TAFS. STILL THINK THE HEAVIEST SN...AND THUS LOWEST VISIBILITIES WILL
BE AT KAMA...WHERE 1/2SM IS LIKELY...AND BRIEF PERIODS OF 1/4SM ARE
POSSIBLE. OUTSIDE OF THE HEAVIEST BANDS OF SN...EXPECT VISIBILITIES
MAINLY BETWEEN 1 AND 3SM FOR THE MAJORITY OF THIS EVENT. THIS IS
MORE PESSIMISTIC THAN THE GFS LAMP...BUT GIVEN UPSTREAM OBS...THINK
THE LOWER VISIBILITIES ARE LIKELY. MODELS ARE ALSO TRENDING FASTER NOW WITH
THE SN LEAVING THE AREA...THINK THAT THE MAJORITY OF THE SN WILL BE
BEFORE 18Z. ONCE THE SN LEAVES...MAY BE A PERIOD OF MVFR
CEILINGS...BEFORE CONDITIONS RETURN TO VFR.

JOHNSON
&&

.PREV DISCUSSION... /ISSUED 954 PM CST MON FEB 11 2013/

UPDATE...

HAVE MADE A FEW CHANGES TO GOING FORECAST AS RECENT MODEL TRENDS HAVE
TRENDED EARLIER...COLDER...AND A BIT HEAVIER WITH THE IMPENDING SNOW.
SNOW HAS ALREADY SPREAD INTO THE WESTERN TEXAS PANHANDLE...WITH
TEXLINE REPORTING MODERATE SNOW.

TIMING...
HAVE SHIFTED ALMOST ALL AREAS FORWARD ABOUT 3 HOURS FOR THE ONSET OF
SNOW GIVEN RECENT HRRR AND NAM RUNS. THIS BRINGS TOTALS UP TO 1-3
INCHES SW OF A CANADIAN TO GUYMON LINE BEFORE THE MORNING COMMUTE.
THE I40 CORRIDOR EAST OF AMARILLO WILL LIKELY SEE THE HEAVIEST SNOWS
BEFORE 12Z AND THROUGHOUT THE EVENT. HAVE ALSO BROUGHT THE SNOW TO
AN END QUICKER...WITH ALL SNOWS LIKELY EAST OF THE PANHANDLES BY 00Z.

AMOUNTS...
THE MAIN CHANGE WAS TO INCREASE AMOUNTS IN AN AREA BOUNDED
BY ROUGHLY I27 ON THE WEST AND I40 ON THE NORTH. IT PREVIOUSLY
APPEARED THAT THE DAYTIME TIMING AND SUBSEQUENT LOWER SNOW TO LIQUID
RATIOS WOULD KEEP TOTALS DOWN A BIT IN THESE AREAS. HOWEVER...THE
BULK OF THE SNOW NOW LOOKS TO FALL BETWEEN 09Z-15Z...MEANING THAT
RATIOS WILL LIKELY BE HIGHER AND AMOUNTS GREATER. GIVEN SOME LIKELY
MODEL UNDERESTIMATION OF DYNAMIC COOLING IN THESE AREAS...FELT A
BUMP UP IN TOTALS PRUDENT. CURRENT THINKING IS THAT THE AMARILLO AREA
COULD SEE 4-7 INCHES...WITH HIGHER AMOUNTS FURTHER EAST. GIVEN RECENT
MODEL TRENDS...AM A BIT CONCERNED WE COULD END UP SEEING AN ISOLATED
BIG NUMBER IN THE DOUBLE DIGITS SOMEWHERE IN THE ROBERTS/GRAY/
HEMPHILL/WHEELER COUNTY AREA.

UPDATED GRIDS/ZONES WILL BE OUT VERY SOON.

SIMPSON

PREV DISCUSSION... /ISSUED 543 PM CST MON FEB 11 2013/

AVIATION...
FOR THE 00Z KAMA TAF...VFR CONDITIONS ARE EXPECTED THROUGH 06Z...THEN
A WINTER STORM LEADS TO A MORE COMPLICATED AND LOWER CONFIDENCE
FORECAST AFTER 06Z THROUGH THE END OF THE TAF PERIOD. HIGH CONFIDENCE
THAT THE TERMINAL WILL SEE SN...PRIMARILY BETWEEN 09 AND 18Z...AND
IFR OR LOWER CONDITIONS THROUGH THIS TIME. THOUGH WINDS WILL BE
BREEZY BETWEEN 12 AND 18Z...DO NOT EXPECT TOO MUCH BLSN DUE TO THE
SNOW TO LIQUID RATIO BEING A BIT LOW. SN WILL SLOWLY TAPER OFF
AFTER 18Z...AND SHOULD BE OUT OF THE AREA BY 21Z. CONDITIONS SHOULD
IMPROVE TO VFR ONCE THE SN ENDS.

FOR THE 00Z KDHT AND KGUY TAFS...VFR CONDITIONS ARE LIKELY THROUGH
06Z...WITH THE ONLY POSSIBLE EXCEPTION OF LIGHT SN STARTING IN KDHT
POSSIBLY AS EARLY AS 03Z. AFTER 06Z...THERE IS LOWER CONFIDENCE GIVEN
THE INCOMING WINTER STORM. AT THIS POINT...EXPECT SN TO START IN KDHT
LIKELY AROUND 06Z...AND KGUY BETWEEN 09 AND 12Z. FOR THE MOST PART
THROUGH THIS EVENT...EXPECT LOW MVFR OR IFR CONDITIONS. SN AT THESE 2
TERMINALS IS NOT EXPECTED TO BE AS DEEP OR HEAVY AS KAMA. SN SHOULD
BEGIN TO TAPER OFF NEAR 18Z...AND SHOULD BE OUT OF THE AREA BY 21Z.
ONCE THE SN ENDS...EXPECT VFR CONDITIONS THROUGH THE REMAINDER OF THE
TAF PERIOD.

JOHNSON

PREV DISCUSSION... /ISSUED 400 PM CST MON FEB 11 2013/

DISCUSSION...
THROUGH TONIGHT: UPPER TROUGH MOVING ACROSS THE FOUR CORNERS WILL
DEEPEN AS IT APPROACHES THE PANHANDLES TONIGHT. AHEAD OF THIS UPPER
TROUGH, EASTERLY UPSLOPE WINDS AND ISENTROPIC LIFT WILL INCREASE
MOISTURE SUBSTANTIALLY AS THE NIGHT PROGRESSES. THE COMBINATION OF
THE LOW- AND UPPER-LEVEL LIFT AND MOISTURE SHOULD TRIGGER THE
DEVELOPMENT OF PRECIPITATION ACROSS NORTHEAST NEW MEXICO LATER THIS
EVENING AND THEN SPREAD INTO THE NORTHWEST PANHANDLES AFTER 9 PM. AS
TEMPERATURES COOL, THIS PRECIPITATION IS EXPECTED TO FALL AS SNOW,
ROUGHLY WEST OF A GUYMON TO BOOTLEG LINE THROUGH MIDNIGHT. SOME LIGHT
ACCUMULATIONS OF AROUND ONE HALF OF AN INCH WILL BE POSSIBLE ACROSS
THE WESTERN PORTIONS OF CIMARRON AND DALLAM COUNTIES. AFTER MIDNIGHT,
CHANCES FOR PRECIPITATION WILL INCREASE AND CONTINUE ACROSS THE
NORTHWEST. A SECOND, MORE CONCENTRATED, SWATCH OF PRECIPITATION IS
EXPECTED TO SPREAD NORTHWARD INTO THE SOUTHEASTERN TEXAS PANHANDLE
AFTER 3 AM. FORECAST SOUNDINGS AFTER 3 AM WILL BE SUPPORTIVE OF WET
SNOW ACROSS MOST OF THESE AREAS. HOWEVER, FOR LOCATIONS SOUTH AND
EAST OF A LINE FROM CLARENDON TO SHAMROCK, WET BULB ZERO HEIGHTS WILL
REMAIN ABOVE 2,000 FEET...WHICH WILL KEEP THE PRECIPITATION TYPE AS
RAIN. AS THE COLUMN COOLS TOWARDS SUNRISE, THE RAIN IS EXPECTED TO
TRANSITION TO SNOW IN THESE LOCATIONS. IN BETWEEN THESE TWO AREAS,
INCLUDING AMARILLO, BORGER, AND PERRYTON, THERE MAY NOT BE MUCH IN
THE WAY OF PRECIPITATION OVERNIGHT. HOWEVER, WE KEPT A MENTION OF
SNOW IN THE FORECAST, BUT AMOUNTS IN THESE LOCATIONS WILL BE A
DUSTING TO ONE HALF OF AN INCH AT MOST.

TUESDAY-TUESDAY NIGHT: THE BEST COMBINATION OF DYNAMICS AND MOISTURE
WILL OCCUR DURING THE DAY ON TUESDAY. AS THIS OCCURS, SNOW IS
EXPECTED TO DEVELOP ACROSS ALL OF THE PANHANDLES WITH THE HIGHEST
CHANCES BEING SOUTHEAST OF A GUYMON TO HEREFORD LINE. DUE TO STRONG
DYNAMICS IN PLACE, SOME OF THE SNOW COULD BE HEAVY AT TIMES. THE
TIME FRAME FOR THE HEAVIEST SNOW LOOKS TO BE BETWEEN 8 AM AND 3 PM.
MOISTURE WILL BE LOWEST ACROSS THE NORTHERN AND WESTERN PORTIONS OF
THE PANHANDLES. AS A RESULT, THESE LOCATIONS WILL LIKELY SEE THE
LIGHTEST SNOWFALL ACCUMULATIONS, BUT TOTAL SNOWFALL AMOUNTS WILL
STILL BE BETWEEN 2 AND 5 INCHES WITH LOCALLY HIGHER AMOUNTS UP TO 6
INCHES. DEEPER MOISTURE WILL BE CONFINED TO THE SOUTHEAST THIRD OF
THE PANHANDLES WHERE TOTAL SNOWFALL ACCUMULATIONS WILL BE BETWEEN 6
AND 9 INCHES WITH LOCALLY HIGHER AMOUNTS POSSIBLE. THE HEAVIEST
SNOWFALL TOTALS ARE EXPECTED TO OCCUR IN AN AREA EAST OF A LINE FROM
CANADIAN TO PAMPA TO CLAUDE AND GENERALLY NORTH OF INTERSTATE 40.
IT'S NOT OUT OF THE QUESTION SOME LOCATION IN THIS AREA COULD
RECEIVE AS MUCH AS 10 INCHES OF SNOW. WE DO HAVE SOME CONCERN THAT
MODELS HAVE BEGUN TRENDING SLIGHTLY FARTHER NORTH WITH THE UPPER
TROUGH. THIS COULD SIGNIFICANTLY REDUCE THE SNOW AMOUNTS IN THE
SOUTHERN PART OF THE TEXAS PANHANDLE AND SHIFT THE HIGHER TOTALS
FARTHER NORTH. WE'LL NEED TO WATCH THIS CLOSELY IN CASE THE WINTER
STORM WARNING NEEDS TO BE ADJUSTED. WE HAVE HIGH CONFIDENCE THAT
EVERY LOCATION WILL SEE AT LEAST SOME SNOW OVER THE NEXT 24 HOURS,
AND THIS IS SUPPORTED BY THE CIPS ANALOG GUIDANCE.

THE SNOW IS EXPECTED TO BEGIN TAPERING OFF FROM NORTHWEST TO
SOUTHEAST BY LATE TUESDAY AFTERNOON. THERE IS A POSSIBILITY THAT
TEMPERATURES WILL RISE ABOVE FREEZING DURING THE AFTERNOON ACROSS
MOST OF THE AREA, ESPECIALLY ACROSS THE NORTHWEST HALF OF THE
PANHANDLES AND THE FAR SOUTHEASTERN TEXAS PANHANDLE. THIS WILL
LIKELY HELP LIMIT/SIGNIFICANTLY CUT DOWN ON ADDITIONAL SNOWFALL
ACCUMULATIONS. TUESDAY EVENING, SNOW IS EXPECTED TO CONTINUE EAST OF
A BEAVER TO CLAUDE LINE THROUGH TUESDAY EVENING BEFORE ENDING BY
MIDNIGHT. LOW TEMPERATURES IN THE TEENS TO LOWER 20S WILL BE LIKELY
DUE TO LIGHT WINDS, CLEAR SKIES, AND SNOW COVER.

JACKSON

WEDNESDAY-MONDAY: AN UPPER TROUGH WILL MOVE EAST OF THE PANHANDLES
WEDNESDAY WITH A DRY NORTHWESTERLY UPPER FLOW ACROSS THE PANHANDLES
WEDNESDAY AND THURSDAY. A NORTHERN STREAM SHORTWAVE TROUGH WILL DROP
SOUTHEAST OUT OF THE ROCKIES BY LATE THURSDAY AND ALLOW FOR A STRONG
COLD FRONT TO PUSH THROUGH THE FORECAST AREA WEDNESDAY NIGHT AND
THURSDAY MORNING. SCATTERED RAIN OR SNOW SHOWERS ARE EXPECTED TO PUSH
SOUTH AND EAST ACROSS THE NORTHERN SECTIONS OF THE PANHANDLES
THURSDAY NIGHT...AND THEN ACROSS MUCH OF THE PANHANDLES FRIDAY. SNOW
COVER WEDNESDAY AND POSSIBLY EVEN INTO THURSDAY WILL HOLD
TEMPERATURES DOWN...SO UNDERCUT MOS GUIDANCE. COLDER FRIDAY AND
TEMPERATURES SATURDAY WILL DEPEND ON ANY SNOW COVER FROM THE THURSDAY
NIGHT AND FRIDAY SYSTEM. OTHERWISE...MODERATING CONDITIONS LATE THIS
WEEK AND INTO THE WEEKEND AS HIGH PRESSURE PREVAILS WITH A DRY
NORTHWESTERLY FLOW ALOFT.

SCHNEIDER

FIRE WEATHER...
AN UPPER TROUGH WILL APPROACH THE TEXAS AND OKLAHOMA PANHANDLES
TONIGHT AND TUESDAY BRINGING INCREASING CHANCES FOR SNOW. ALTHOUGH
THE SNOW IS EXPECTED TO END BY TUESDAY EVENING AS THE UPPER TROUGH
MOVES OFF TO THE EAST OF THE PANHANDLES...THE SNOW COVER WILL LINGER
THROUGH WEDNESDAY. THEREFORE...NO ELEVATED OR CRITICAL FIRE WEATHER
CONDITIONS ARE EXPECTED THROUGH WEDNESDAY.

SCHNEIDER

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR THE FOLLOWING
     ZONES: DALLAM...DEAF SMITH...HANSFORD...HARTLEY...MOORE...
     OCHILTREE...OLDHAM...SHERMAN.

     WINTER STORM WARNING FROM 3 AM TO 6 PM CST TUESDAY FOR THE
     FOLLOWING ZONES: ARMSTRONG...CARSON...COLLINGSWORTH...
     DONLEY...GRAY...HEMPHILL...HUTCHINSON...LIPSCOMB...POTTER...
     RANDALL...ROBERTS...WHEELER.

OK...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR THE FOLLOWING
     ZONES: BEAVER...CIMARRON...TEXAS.

&&

16/09

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
1006 PM CST MON FEB 11 2013

OKZ001>003-TXZ001>020-121615-
CIMARRON-TEXAS-BEAVER-DALLAM-SHERMAN-HANSFORD-OCHILTREE-LIPSCOMB-
HARTLEY-MOORE-HUTCHINSON-ROBERTS-HEMPHILL-OLDHAM-POTTER-CARSON-
GRAY-WHEELER-DEAF SMITH-RANDALL-ARMSTRONG-DONLEY-COLLINGSWORTH-
1006 PM CST MON FEB 11 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE TEXAS AND OKLAHOMA
PANHANDLES.

.DAY ONE...TONIGHT.

SNOW WILL SPREAD ACROSS THE PANHANDLES OVERNIGHT. A WINTER STORM
WARNING IS IN EFFECT FOR THE SOUTHERN AND EASTERN PORTIONS OF THE
TEXAS PANHANDLE BEGINNING AT 3 AM TUESDAY. A WINTER WEATHER ADVISORY
IS IN EFFECT FOR THE OKLAHOMA PANHANDLE AND NORTHWESTERN PORTIONS OF
THE TEXAS PANHANDLE BEGINNING AT 12 AM TUESDAY...MIDNIGHT TONIGHT. 1
TO 3 INCHES OF SNOW WILL BE POSSIBLE IN AREAS SOUTH AND WEST OF A
CANADIAN TO GUYMON LINE BEFORE THE SUN COMES UP.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

SNOW IS EXPECTED ACROSS ALL OF THE PANHANDLES TUESDAY...TAPERING OFF
LATE IN THE AFTERNOON. A WINTER STORM WARNING WILL REMAIN IN EFFECT
FOR THE SOUTHERN AND EASTERN PORTIONS OF THE TEXAS PANHANDLE UNTIL 9
PM TUESDAY...WHERE SNOWFALL ACCUMULATIONS OF 6 TO 9 INCHES ARE
EXPECTED AND LOCALLY HIGHER AMOUNTS POSSIBLE. A WINTER WEATHER
ADVISORY WILL REMAIN IN EFFECT FOR THE OKLAHOMA PANHANDLE AND
WESTERN PORTIONS OF THE TEXAS PANHANDLE UNTIL 6 PM TUESDAY...WHERE
SNOWFALL ACCUMULATIONS OF 3 TO 5 INCHES ARE EXPECTED AND LOCALLY
HIGHER AMOUNTS UP TO 6 INCHES WILL BE POSSIBLE. THE HIGHEST SNOWFALL
ACCUMULATIONS WILL LIKELY BE ACROSS THE SOUTHEASTERN HALF OF THE
TEXAS PANHANDLE.

THERE IS ALSO A CHANCE FOR RAIN AND SNOW SHOWERS ACROSS THE
PANHANDLES ON THURSDAY NIGHT INTO FRIDAY. ANY ACCUMULATIONS OF SNOW
ARE EXPECTED TO BE LIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME. OBSERVERS ARE
REQUESTED TO REVIEW SNOW MEASURING PROCEDURES...AND TO BE PREPARED TO
RELAY SNOWFALL REPORTS TO THE NATIONAL WEATHER SERVICE IN AMARILLO.