Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 210505 AAC
AFDAMA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
1105 PM CST THU NOV 20 2014

.AVIATION...
FOR THE 06Z TAFS...A LITTLE LESS CONFIDENT IN DENSE FOG TO
DEVELOP...BUT STILL EXPECT KGUY AND KAMA TO SEE VISIBILITIES DROP TO
AT LEAST MVFR CONDITIONS. KDHT SHOULD STAY CLEAR OF BR OR FZFG. WITH
FREEZING TEMPERATURES...FZFG WILL BE A CONCERN WHERE DENSE FOG
DEVELOPS. IN AREAS OF DENSE FOG...VERTICAL VISIBILITIES COULD ALSO
DROP CEILINGS TO IFR LEVELS. SOUTH TO SOUTHWEST WINDS WILL QUICKLY
DRY DISIPATE ANY FOG BY MID-MORNING.

NF

&&

.PREV DISCUSSION... /ISSUED 925 PM CST THU NOV 20 2014/

UPDATE...
MADE A FEW ADJUSTMENTS TO OVERNIGHT TEMPS AND DEW POINTS. MAINLY
BUMPED LOWS UP ABOUT 3 DEGREES AND INCREASED DEW POINTS BY A FEW
DEGREES TO MATCH LATEST GUIDANCE VALUES. STILL THINKING PATCHY FOG
AND FREEZING FOG WILL DEVELOP MAINLY ACROSS THE EASTERN PORTIONS OF
THE CWA TONIGHT...BUT COULD SEE SOME EXTEND INTO WESTERN COUNTIES. NO
FREEZING FOG ADVISORY IS ANTICIPATED AT THIS TIME...BUT WILL MONITOR
TRENDS OVERNIGHT.

NF

PREV DISCUSSION... /ISSUED 548 PM CST THU NOV 20 2014/

AVIATION...
FOR THE 00Z TAFS...GENERALLY LIGHT WINDS AND VFR CONDITIONS TO START
THE PERIOD AT ALL SITES. THIS SHOULD LAST THROUGH APPROX 09Z TO
12Z...WHEN BR OR FG WILL LIKELY DEVELOP. SINCE TEMPERATURES ARE
EXPECTED TO BE BELOW FREEZING BY THAT POINT...THIS WOULD BE FREEZING
FOG. THE DENSEST FOG SHOULD STAY EAST OF THE TAF SITES...THOUGH KAMA
AND KGUY COULD SEE IFR VISIBILITIES AS LOW AS 1 TO 2 MILES. KDHT
EXPECTED TO REMAIN VFR OVERNIGHT. SOUTHERLY WINDS AND CLEARING SKIES
SHOULD RETURN BEFORE 18Z.

NF

PREV DISCUSSION... /ISSUED 335 PM CST THU NOV 20 2014/

SHORT TERM...PRIMARY FORECAST CONCERN IN THE SHORT TERM CENTERS ON
THE FOG/FREEZING FOG POTENTIAL LATE TONIGHT.

A WEAK SURFACE LOW OVER EASTERN NEW MEXICO AND INTO THE SOUTHWESTERN
TEXAS PANHANDLE THIS AFTERNOON HAS RESULTED IN LIGHT AND VARIABLE
WINDS ACROSS THE AREA. A PASSING UPPER-LEVEL SHORTWAVE TROUGH ALLOWED
FOR THE VEIL OF HIGH CLOUDS OVER THE AREA EARLIER TODAY TO
DISSIPATE. HOWEVER LOW-LEVEL MOISTURE WILL INCREASE LATER THIS
EVENING AS WINDS VEER AROUND OUT OF THE SOUTHEAST. THIS WILL LEAD TO
AN INCREASE IN LOW CLOUDS ALONG WITH THE POSSIBILITY OF PATCHY FOG
AND FREEZING FOG. WINDS WILL GENERALLY BE LIGHT AND VARIABLE
THOUGH...WITH THE EASTERN PANHANDLES MAINLY UNDER THE INFLUENCE OF
THIS SOUTHEAST UPSLOPE FLOW. SO WHILE THE EASTERN ZONES WILL BE THE
MOST FAVORED AREA FOR FOG DEVELOPMENT LATE TONIGHT...FORECAST
SOUNDINGS INDICATE A RATHER SHALLOW MOIST LAYER OVER ALL OF THE AREA.
SO HAVE GONE AND EXPANDED THE MENTION OF PATCHY FOG/FREEZING FOG TO
ENCOMPASS ALL OF THE CWA. GIVEN THE SHALLOWNESS OF THE MOIST LAYER
AND THE LACK OF GOOD ISENTROPIC LIFT...THE POSSIBILITY OF
DRIZZLE/FREEZING DRIZZLE IS LOW.

ANY LINGERING FOG SHOULD DISSIPATE BY MID MORNING FRIDAY AS SURFACE
WINDS FURTHER VEER OUT OF THE SOUTH-SOUTHWEST. THIS WILL ALSO HELP
TO PUSH TEMPERATURES UP A COUPLE OF DEGREES...WHERE HIGHS IN THE 50S
CAN BE EXPECTED AREA WIDE. MEANWHILE AN UPPER-LEVEL LOW OVER THE
WESTERN CONUS WILL DIG SOUTHWARD...OVER NORTHWESTERN OLD MEXICO
TOWARD THE EVENING. MODEL GUIDANCE HAS COME IN SLOWER WITH THIS
SYSTEM...BUT STILL TAKES THE LOW TOO FAR SOUTH FOR IT TO HAVE MUCH OF
AN IMPACT ON THE SENSIBLE WEATHER OVER MUCH OF THE PANHANDLES. THE
SOUTHEASTERN TEXAS PANHANDLE STILL STANDS TO HAVE THE BEST CHANCE OF
SEEING ANY ISOLD SHOWERS AND THUNDERSTORMS AHEAD OF THIS
TROUGH...ALTHOUGH NOW IT LOOKS LIKE THE BEST OPPORTUNITY FOR THIS TO
OCCUR WILL BE LATE FRIDAY NIGHT.

LONG TERM...RAIN CHANCES SATURDAY AND THE NEXT SURGE OF ARCTIC AIR
THANKSGIVING DAY WILL BE THE MAIN CONCERNS IN THE LONG TERM.

THE AFOREMENTIONED UPPER TROUGH WILL ACQUIRE A NEGATIVE TILT AS IT
LIFTS OVER EAST TEXAS AND NORTHERN LOUISIANA OVER THE WEEKEND. THE
TRACK OF THIS UPPER SYSTEM WILL PLACE AN AXIS OF HEAVY RAINFALL AND
POTENTIAL SEVERE WEATHER WELL EAST AND SOUTH OF THE AMA CWA. HOWEVER
DESPITE THIS...DIVERGENCE ALOFT AND AN INCREASE IN LOW-LEVEL
MOISTURE FROM A DEVELOPING LOW-LEVEL JET IN EAST TEXAS CAN SUPPORT
A MENTION OF SHOWERS AND THUNDERSTORMS SATURDAY. SEVERE WEATHER DOES
NOT LOOK TO BE MUCH OF A THREAT GIVEN THE LOW INSTABILITY INDICATED
ON THE FORECAST SOUNDINGS.

SINCE THIS UPPER TROUGH WILL EXIT THE AREA QUICKLY...ANY SHOWERS AND
THUNDERSTORMS WILL END SATURDAY NIGHT. MEANWHILE AN UPPER TROUGH
OVER THE NORTHERN/CENTRAL PLAINS WILL DEEPEN AS IT SLIDES EAST
SUNDAY. THIS WILL PUSH A COLD FRONT THROUGH THE AREA...WHICH WILL
KNOCK HIGH TEMPERATURES BACK FROM THE 60S SATURDAY TO THE UPPER 40S
TO THE UPPER 50S SUNDAY. AN UPPER-LEVEL JET ALONG THE SOUTHERN
PERIPHERY OF THIS UPPER TROUGH WILL SLIDE ACROSS THE CENTRAL PLAINS
SUNDAY NIGHT. WHILE LIFT FROM THIS UPPER JET AND ALONG THE COLD FRONT
MAY SQUEEZE OUT SOME LIGHT SNOW/FLURRIES MAINLY OVER THE NORTHERN
ZONES SUNDAY NIGHT...DRY AIR NEAR THE SURFACE SHOULD PREVENT MUCH IF
ANY PRECIP FROM REACHING THE GROUND.

AMPLIFIED UPPER RIDGE WILL BUILD OVER THE WESTERN CONUS EARLY NEXT
WEEK...KEEPING THE AREA UNDER THE INFLUENCE OF NORTHWEST FLOW ALOFT.
THIS WILL HOLD HIGH TEMPS MAINLY IN THE 50S EARLY NEXT WEEK BEFORE
THE UPPER FLOW BACKS TO THE WEST MID WEEK. MEDIUM RANGE MODELS
GREATLY DIVERGE FROM THIS POINT WHERE THE GFS MOVES THE UPPER RIDGE
OVER THE SOUTHERN PLAINS WHILE THE ECMWF HOLDS THIS RIDGE OUT WEST.
THUS THE GFS SOLUTION IS QUITE A BIT WARMER THAN THE ECMWF AS THE
ECMWF INDICATES A SURGE OF ARCTIC AIR IN TIME FOR THANKSGIVING DAY.
THE ECMWF ALSO INDICATES A POSSIBILITY FOR LIGHT SNOW THANKSGIVING
NIGHT. SINCE THIS IS A WEEK OUT...OPTED TO GO WITH A MODEL BLEND WRT
POPS BUT DID LOWER HIGHS A FEW DEGREES.

CLK

&&

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

&&

$$

06/17





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