Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 281800 AAB
AFDAMA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
1200 PM CST SUN DEC 28 2014

.UPDATE...
UPDATED FOR 18Z AVIATION DISCUSSION.

&&

.AVIATION.../18Z TAFS/
VFR CONDITIONS CAN BE EXPECTED OVER THE NEXT 24 HOURS WITH WINDS
TURNING TO THE NORTH NORTHWEST BETWEEN 02Z-07Z WITH COLD FRONTAL
PASSAGE.

KNS

&&

.PREV DISCUSSION... /ISSUED 539 AM CST SUN DEC 28 2014/

AVIATION...
FOR THE 12Z TAFS...GENERALLY QUIET WEATHER IS EXPECTED FOR THIS FCST
CYCLE. SOME HIGH LEVEL CLOUDS WILL MOVE ACROSS THE REGION ON OCCASION.
A COLD FRONT WILL BEGIN TO AFFECT THE TERMINAL SITES LATE TONIGHT AND
EARLY MONDAY...AND THIS IS REFLECTED IN THE TAFS. OVERALL...VFR
CONDITIONS WILL PREVAIL THROUGH 12Z MONDAY.

ANDRADE

&&

.PREV DISCUSSION... /ISSUED 404 AM CST SUN DEC 28 2014/

A BROAD UPPER LEVEL TROUGH WILL EVOLVE OVER THE WESTERN AND CENTRAL
CONUS TODAY. THIS TROUGH WILL BECOME ELONGATED AND POSITIVELY TILTED
BY TUESDAY WITH THE WESTERN END CLOSING OFF BY MID WEEK AND MOVING
SLOWLY EASTWARD THROUGH THE END OF THE WEEK. THIS PATTERN WILL BRING
PERIODIC PRECIPITATION CHANCES WITH ONLY LIGHT AMOUNTS THROUGH THE
END OF THE WEEK.

IN THE SHORT TERM...SURFACE LEE SIDE TROUGH WILL STRENGTHEN TODAY AS
MID/UPPER FLOW INCREASES AND BECOMES INCREASINGLY CYCLONIC.
SOUTHWESTERLY WINDS WILL STRENGTHEN TODAY AND TEMPERATURES WILL BE
WARMER THAN YESTERDAY. NAM/MET GUIDANCE SEEMS TO BE TOO COOL IN THE
NORTHWEST LIKELY DUE TO RESIDUAL SNOW COVER IN ITS ANALYSIS. LAST
VISIBLE IMAGE RIGHT BEFORE SUNSET SHOWED MOST HAD MELTED AND HAVE
ADJUSTED HIGH TEMPERATURES FOR TODAY UPWARD IN THE NORTHWEST. AN
ARCTIC COLD FRONT SHOULD ENTER THE NORTHERN PORTION OF THE AREA AS
EARLY AS LATE MORNING ON MONDAY AND THEN PROGRESS THROUGH THE AREA.
THIS IS ONE OF THE COLDEST AIR MASSES OF THE SEASON SO FAR AND ONCE
THE FRONT PASSES TEMPERATURES ARE NOT EXPECTED TO RISE DURING THE
AFTERNOON. FOR THIS REASON MAXIMUM TEMPERATURE WERE DERIVED FROM
HOURLY TEMPERATURE GRIDS WHICH SHOW STEADY OR FALLING TEMPERATURES
THROUGH THE DAY ON MONDAY.

THE COLD AIR MASS MODERATES SOME THROUGH THE END OF THE WEEK BUT
WILL REMAIN COLD ENOUGH FOR WINTRY PRECIPITATION TO BE A
CONCERN. MODELS ARE GENERAL AGREEMENT WITH MOISTENING ALOFT AND
WEAK ISENTROPIC ASCENT CONTRIBUTING TO THE DEVELOPMENT OF LIGHT SNOW
IN THE NORTHWEST PORTION OF THE AREA TOMORROW NIGHT WITH ANOTHER
POTENTIALLY MORE ROBUST ROUND OF MOISTURE/ASCENT FOR ADDITIONAL LIGHT
SNOW TUESDAY NIGHT ACROSS THE ENTIRE AREA.

WARM/MOIST ADVECTION AND A GRADUAL INCREASE IN ASCENT AHEAD OF
APPROACHING CLOSED LOW WILL RESULT IN INCREASED PRECIPITATION CHANCES
THURSDAY NIGHT THROUGH FRIDAY NIGHT. UNCERTAINTY IS HIGHER THAN
TYPICAL DURING THIS PERIOD DUE TO INHERENT DIFFICULTIES WITH MEDIUM
RANGE GUIDANCE AND CLOSED MID/UPPER LOWS AND DUE TO SIGNIFICANT
SPREAD AMONG ENSEMBLES. HAVING SAID THAT...DETERMINISTIC MEDIUM RANGE
GUIDANCE HAS COME MORE IN LINE WITH TIMING AND PLACEMENT. WITH THE
CURRENT SCENARIO DEPICTED BY THE GFS AND ECMWF...PRECIPITATION TYPE
WILL BE DIFFICULT. THERE IS SOME POTENTIAL FOR FREEZING RAIN AND/OR
SLEET THURSDAY NIGHT DUE TO AN INCREASINGLY WARM LAYER JUST ABOVE THE
SURFACE. BY FRIDAY THE COLUMN SHOULD HAVE WARMED SUFFICIENTLY FOR ALL
RAIN ACROSS THE SOUTHEASTERN HALF OF THE AREA. A MORE CLOSED
MID/UPPER LOW WOULD FAVOR A PERIOD OF SNOW WITHIN THE DEFORMATION
AREA AS THE SYSTEM DEPARTS FRIDAY NIGHT AND PERHAPS EARLY SATURDAY
FOR PORTIONS OF THE AREA DEPENDING ON THE EXACT TRACK.

BRB

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
OK...NONE.

&&

$$




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