Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 202353
AFDAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
653 PM CDT WED MAY 20 2015

.AVIATION...
00Z TAF CYCLE
COOL AND MOIST AIR MASS BEHIND A COLD FRONT WILL ALLOW FOR MVFR
CONDITIONS TO BECOME IFR TO LIFR OVERNIGHT TONIGHT AT ALL THREE TAF
SITES. AREAS OF FOG MAY ALSO DEVELOP TONIGHT WITH NORTHEAST TO EAST
WINDS 5 TO 15 KNOTS BECOMING SOUTHEAST AROUND 17Z TO 19Z THURSDAY.
MVFR TO POSSIBLY VFR CONDITIONS SHOULD RETURN TO ALL THREE TAF SITES
AFTER 17Z TO 19Z THURSDAY. CONVECTION IS EXPECTED TO DEVELOP CLOSER
TO 00Z FRIDAY TIME FRAME...BUT DECIDED TO HOLD OFF MENTIONING IN THIS
TAF FORECAST PACKAGE FOR NOW AS IT WILL BE TOWARD THE END OF THE
PERIOD.

SCHNEIDER

&&

.PREV DISCUSSION... /ISSUED 415 PM CDT WED MAY 20 2015/

SHORT TERM...
IN THE WAKE OF A COLD FRONT THAT PUSHED SOUTH ACROSS THE AREA
YESTERDAY EVENING...UNSEASONABLY COOL CONDITIONS WERE COMMON OVER THE
TEXAS AND OKLAHOMA PANHANDLES TODAY. THE COOL TREND WILL CONTINUE ON
THURSDAY AS A SURFACE RIDGE THAT IS CURRENTLY OVER THE EASTERN TEXAS
PANHANDLE SLIDES FURTHER OFF TO THE EAST. SOUTHEAST UPSLOPE FLOW WILL
AID IN KEEPING AMPLE MOISTURE IN AT THE SURFACE SO DESPITE LOW
AMPLITUDE RIDGING BUILDING IN OVERHEAD...WEAK ISENTROPIC LIFT WILL
SUPPORT A MENTION OF SHOWERS AND ISOLATED STORMS TONIGHT THROUGH
THURSDAY. BY THURSDAY EVENING...A PACIFIC UPPER LOW WILL MOVE OVER
SOUTHERN CALIFORNIA. AN UPPER DISTURBANCE EJECTING OUT OF THIS PARENT
UPPER LOW WILL BRING A MORE SIGNIFICANT THREAT OF SHOWERS AND
THUNDERSTORMS. PW VALUES WILL INCREASE TO NEAR THE 99TH PERCENTILE
FOR MAY...RAISING THE THREAT FOR MODERATE TO HEAVY RAINFALL. HAVE
CONCERNS THAT THIS ANTICIPATED RAINFALL ON TOP OF THE RECENT RAINS
WILL LEAD TO AREAL FLOODING...WHICH MAY NECESSITATE THE ISSUANCE OF
A FLOOD WATCH FOR MUCH IF NOT ALL OF THE CWA. WILL REVISIT THIS
POSSIBILITY TOMORROW TO SEE IF MODEL TRENDS CONTINUE DOWN THIS PATH.

LONG TERM...
THIS WET PATTERN DOES NOT LOOK TO CHANGE HEADING INTO THE HOLIDAY
WEEKEND AS THE UPPER AIR PATTERN REMAINS CONDUCIVE TO PROVIDING UPPER
LEVEL LOW PRESSURE SYSTEMS THAT MOVE ACROSS THE FOUR CORNERS REGION.
IN FACT THE AFOREMENTIONED UPPER LOW WILL LIFT NORTHEAST INTO THE
FOUR CORNERS REGION FRIDAY NIGHT. FORCING FOR ASCENT COMBINED WITH A
LIFTING WARM FRONT WILL SUPPORT A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS FRIDAY AND SATURDAY. THE DEVELOPMENT OF A DRYLINE
SUNDAY AND INCREASING UPPER LIFT AS THE UPPER LOW EDGES FURTHER
EASTWARD WILL SUPPORT ADDITIONAL SHOWERS AND THUNDERSTORMS. SOME
DIFFERENCES SHOW UP IN THE MEDIUM RANGE MODELS FOR MEMORIAL DAY WITH
THE GFS PLACING THE TROUGH ALONG WITH RAIN CHANCES EAST OF THE
FORECAST AREA. HOWEVER THE ECMWF DOES NOT TAKE THE UPPER LOW EAST OF
THE AREA UNTIL MONDAY EVENING. CONTINUED TO MAINTAIN SLIGHT CHANCE
POPS OVER THE NORTHERN AND EASTERN PORTION OF THE CWA TO ACCOUNT FOR
THESE MODEL DISCREPANCIES. LOOKS LIKE A BRIEF LULL IN THE RAINFALL
TUESDAY BEFORE THE WEATHER PATTERN BECOMES ACTIVE AGAIN TOWARD THE
MIDDLE OF THE WEEK.

CLK

&&

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

&&

$$

11/99




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