Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 032339 AAA
AFDAMA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
539 PM CST TUE MAR 3 2015

.AVIATION...
CONDITIONS WILL CONTINUE TO GO DOWNHILL BOTH IN THE CEILING
DEPARTMENT AND THE VISIBILITY DEPARTMENT. RAIN AND SNOW SHOULD VISIT
THE DHT AND GUY TAF SITES FIRST...MAYBE AROUND MIDNIGHT...THEN THE
RAIN SHOULD SWITCH OVER TO SNOW BEFORE SUNRISE IN THESE AREAS. SNOW
SHOULD PREVAIL FOR MUCH OF WEDNESDAY...BUT IT COULD SHUT OFF AT GUY
BEFORE THE END OF THIS FORECAST.

AT AMA...CIGS AND VISIBILITIES WILL ALSO DECREASE THROUGH THE NIGHT
INTO EARLY WEDNESDAY MORNING. THERE COULD BE A PERIOD OF FREEZING
RAIN AFTER MIDNIGHT BEFORE THE PRECIP CHANGES OVER TO SNOW TOWARD
SUNRISE. THEN SNOW SHOULD CONTINUE FOR THE REST OF THE FORECAST.

NORTHEAST WINDS WILL INCREASE INTO THE 15 TO 25 KNOT RANGE WITH
HIGHER GUSTS AT ALL TAF STIES OVERNIGHT AND THEY SHOULD CONTINUE
INTO WEDNESDAY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 245 PM CST TUE MAR 3 2015/

DISCUSSION...

EARLY THIS AFTERNOON UPPER AIR ANALYSIS SHOWS A POSITIVELY TILTED
UPPER TROUGH APPROACHING THE ROCKIES WITH A CLOSED LOW APPROACHING
BAJA CALIFORNIA. MODEL GUIDANCE IS IN GOOD AGREEMENT IN KEEPING
THESE TWO FEATURES IN PHASE AS THEY MOVE EASTWARD TOWARD THE AREA
TONIGHT. A LEAD SHORTWAVE OVER THE NORTHERN AND CENTRAL PLAINS HAS
ALREADY FORCED A COLD FRONT THROUGH THE OKLAHOMA PANHANDLE AND INTO
THE NORTHERN TEXAS PANHANDLE. SOUTHWARD SURGE OF COLD AIR MASS
WILL CONTINUE IN ADVANCE OF APPROACHING TROUGH. MODELS HAVE NOT
HANDLED THESE SCENARIOS PARTICULARLY WELL LATELY WITH A TENDENCY FOR
A SLOWER INTRUSION OF COLDEST AIR BEHIND THE FRONT. THIS IN ADDITION TO
SMALL DIFFERENCES IN SHORT TERM GUIDANCE LEADS TO SOME UNCERTAINTY
WITH TIMING OF PRECIPITATION TYPE TRANSITION THIS EVENING AND
TONIGHT.

WATER VAPOR ANALYSIS SHOWS A FAIRLY EXTENSIVE SUBTROPICAL MOISTURE
PLUME AHEAD OF THE APPROACHING TROUGH STREAMING THROUGH NORTHERN
MEXICO INTO NEW MEXICO AND TEXAS. LARGE SCALE ASCENT INCREASES
MARKEDLY THIS EVENING AND CONTINUES THROUGH AT LEAST THE FIRST HALF
OF TOMORROW. THERE IS SOME UNCERTAINTY IN DURATION AND EXTENSIVENESS
OF MID/UPPER LEVEL MOISTURE FOR ICE CRYSTAL INTRODUCTION INITIALLY
WITH 12Z NAM TRENDING SLIGHTLY DRIER ALOFT TOMORROW THAN PREVIOUS
RUNS AND WILL NEED TO MONITOR THIS TREND FOR POTENTIALLY LOWER
AMOUNTS THAT CURRENT IN THE FORECAST. FOR NOW SNOW ACCUMULATION
TOTALS OF 2 TO 3 INCHES WILL BE COMMON ACROSS THE NORTHERN PORTION OF
THE TEXAS PANHANDLE AND THE OKLAHOMA PANHANDLE WITH 1 TO 2 INCHES
MORE LIKELY FURTHER SOUTH WHERE THE DURATION OF MIX PRECIPITATION
TYPE SHOULD LAST LONGER. LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE.
HAVE ISSUED A WINTER WEATHER ADVISORY FOR THE ENTIRE AREA FOR A MIX
OF LIGHT SNOW...FREEZING DRIZZLE...AND POSSIBLY SLEET. BUFKIT
SOUNDINGS SHOW SHALLOW COLD SUB-FREEZING LAYER BEHIND THE FRONT WITH
WARM LAYER ALOFT SUPPORTIVE OF SOME LIGHT FREEZING RAIN OR FREEZING
DRIZZLE...POSSIBLY MIXED WITH SLEET. COLUMN COOLING WITH CONTINUED
POST-FRONTAL COLD ADVECTION SHOULD RESULT IN A CHANCE OVER TO ALL
SNOW AFTER MIDNIGHT TONIGHT IN THE NORTH AND BY LATE TONIGHT OR EARLY
TOMORROW MORNING IN THE SOUTH.

OUR GUESS AT TIMING IS DETAILED IN THE WINTER WEATHER ADVISORY
PRODUCT WHICH HAS BEEN SEGMENTED INTO TWO SEGMENTS TO ACCOUNT FOR
PRECIPITATION TYPE TRANSITION. IMPACT FROM TRAVEL MAY OCCUR INITIALLY
FROM THE COMBINATION OF RAIN PRECEDING THE COLD SURGE THAT FREEZES ON
ROAD SURFACES AS TEMPERATURES FALL THROUGH THE 20S...AND A PERIOD OF
FREEZING DRIZZLE THAT MAY HAPPEN UNTIL SUFFICIENT COOLING ALOFT
OCCURS FOR ALL SNOW. THE POTENTIAL FOR SNOW ACCUMULATION INCLUDING
SNOW PACKED ROADS INCREASES LATER TONIGHT AND TOMORROW MORNING. 20-25
KNOT POST FRONTAL NORTHEASTERLY WINDS MAY BE ENOUGH FOR AREAS OF
BLOWING SNOW AND REDUCED VISIBILITIES ESPECIALLY AS RATIOS INCREASE
LATER IN THE EVENT LATE TOMORROW MORNING THROUGH TOMORROW AFTERNOON.

NO SIGNIFICANT CHANGES WERE MADE FROM PREVIOUS FORECAST DURING THE
LONG TERM PERIOD. DRY WEATHER IS EXTENDED THEN WITH THE BIGGEST
CHALLENGE BEING TEMPERATURES. UNCERTAINTY LIES IN HOW FAR EAST THE
UPPER RIDGE CAN BUILD BY LATE IN THE FORECAST PERIOD AND
CONSEQUENTLY HOW WARM WE WILL BE. TEMPERATURE SHOULD REACH AT LEAST
NORMAL VALUES FOR EARLY MARCH BY THE WEEKEND.

BRB

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM CST
     WEDNESDAY FOR THE FOLLOWING ZONES: DALLAM...HANSFORD...
     LIPSCOMB...OCHILTREE...SHERMAN.

     WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT CST
     WEDNESDAY NIGHT FOR THE FOLLOWING ZONES: ARMSTRONG...
     CARSON...COLLINGSWORTH...DEAF SMITH...DONLEY...GRAY...
     HARTLEY...HEMPHILL...HUTCHINSON...MOORE...OLDHAM...POTTER...
     RANDALL...ROBERTS...WHEELER.

OK...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 6 PM CST
     WEDNESDAY FOR THE FOLLOWING ZONES: BEAVER...CIMARRON...
     TEXAS.


&&

$$

15/18




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