Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 212323
AFDAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
623 PM CDT THU MAY 21 2015

.AVIATION...
00Z TAF CYCLE
A STALLED FRONTAL BOUNDARY SOUTH OF THE PANHANDLES WILL MOVE BACK TO
THE NORTH AND EAST BY FRIDAY NIGHT AND APPROACH THE THREE TAF SITES.
INCREASING CONVECTION MAINLY TONIGHT INTO FRIDAY MORNING...AND AGAIN
FRIDAY NIGHT INTO SATURDAY MORNING CAN BE EXPECTED AT ALL THREE TAF
SITES. MVFR CONDITIONS WILL BECOME IFR TO LIFR AFTER 08Z TO 10Z
FRIDAY...AND THEN BACK TO MVFR AGAIN AFTER 18Z TO 20Z FRIDAY. WILL
KEEP SHOWERS AND OR THUNDERSTORMS IN ALL THREE TAF SITES THROUGH 15Z
TO 19Z FRIDAY. SOUTHEAST W2INDS 5 TO 15 KNOTS WILL BECOME SOUTH 10 TO
20 KNOTS AFTER 08Z TO 12Z FRIDAY...AND THE SOUTHERLY 15 TO 25 KNOTS
WITH HIGHER GUSTS AFTER 18Z TO 20Z FRIDAY.

SCHNEIDER

&&

.PREV DISCUSSION... /ISSUED 354 PM CDT THU MAY 21 2015/

SHORT TERM...
MUCH OF THE TEXAS PANHANDLE HAS SEEN NEARLY 48 HOURS OF OVERCAST SKY
CONDITIONS IN THE WAKE OF A COLD FRONT THAT PASSED THROUGH TUESDAY
EVENING. DESPITE THE DIFFERENTIAL ADVECTION PROFILE SEEN IN THE
12Z SOUNDING...MOISTURE WAS QUITE DEEP EVEN EXTENDING ABOVE THE
EAST-NORTHEASTERLY LOW LEVEL FLOW TO NEAR 700 MB WHERE FLOW WAS MORE
SOUTHWESTERLY. VISIBLE SATELLITE SHOWS SOME BREAKS IN THE NORTHEAST
TEXAS PANHANDLE AND THE EASTERN OKLAHOMA PANHANDLE THIS AFTERNOON
AND THIS HAS BEEN COINCIDENT WITH WARMER TEMPERATURES IN THE LOWER
60S. FURTHER WEST TEMPERATURES HAVE YET TO RISE OUT OF THE 50S AND
SO A SHORT TERM UPDATE WAS SENT TO LOWER TEMPERATURES SLIGHTLY. OUR
RECORD LOW MAX TEMPERATURE FOR TODAY IS 56 SET IN 1900. BASED ON
CURRENT TRENDS IN THE OBSERVATIONS AND EXAMINING THE DIURNAL CURVE
FROM YESTERDAY UNDER SIMILAR CONDITIONS...WE SHOULD REACH OR
SLIGHTLY EXCEED THIS TEMPERATURE THIS AFTERNOON.

SHORT RANGE GUIDANCE AGREES ON TIMING OF ONSET OF DEEPER SATURATION
SEEN ON ISENTROPIC SURFACES. THIS IS CAUSING SOME CONVECTION IN
EASTERN NEW MEXICO EXTENDING EAST TO JUST ACROSS THE TEXAS STATE
LINE...NEAR BOVINA. THIS ACTIVITY SHOULD CONTINUE MOVING
NORTHEASTWARD THIS AFTERNOON WHILE EXPANDING AS ASCENT FROM
APPROACHING LEAD WAVE STRENGTHENS. GIVEN THE SHORT RANGE MODEL
AGREEMENT ON THE LARGE SCALE BELIEVE THIS IS A FAIRLY GOOD CASE FOR
SUCCESS OF CONVECTION ALLOWING MODELS WITH TIMING AND COVERAGE OF
PRECIPITATION THIS EVENING AND INTO THE NIGHT. HOURLY PROBABILITY OF
PRECIPITATION GRIDS FOLLOW THESE MODELS INCLUDING THE HRRR AND
TTU-WRF FAIRLY CLOSELY. MOST OF THE PRECIPITATION SHOULD EXIT THE
AREA EARLY TOMORROW MORNING. SUBSIDENCE/MID LEVEL HEIGHT RISES IN
THE WAKE OF THE LEAD SHORTWAVE AND PRECEDING THE CLOSED UPPER LOW
SHOULD LIMIT OPPORTUNITY FOR CONVECTION TOMORROW AFTERNOON. HAVE
SIGNIFICANT REDUCED PRECIPITATION PROBABILITIES FOR TOMORROW
AFTERNOON. MODEL FORECAST SOUNDINGS REVEAL DIFFERENCES IN MODELS
WITH HOW MOIST THE LOW LEVELS ARE AND THIS HAS IMPLICATIONS FOR BOTH
CLOUD COVER AND TEMPERATURES. THE NAM HAS GENERALLY PERFORMED WELL
THE DAY FOLLOWING A NIGHTTIME CONVECTIVE EVENT RECENTLY SO GAVE IT
SOME CREDIT BUT TOOK A BLENDED APPROACH BETWEEN THE DRIER/WARMER NAM
AND THE MOIST/COOL GFS AND ECMWF. QPF GRIDS WERE ADJUSTED SLIGHTLY
AND DEVIATE ONLY SLIGHTLY FROM WPC GUIDANCE...MAINLY IN JUST A
TEMPORAL SENSE BUT WITH SLIGHTLY HIGHER AMOUNTS. TOTALS THROUGH
TOMORROW RANGE FROM AROUND A HALF INCH IN THE NORTHWEST TO NEAR AN
INCH IN THE SOUTHEAST.

LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
SPLIT FLOW UPPER AIR PATTERN WILL MAINTAIN A WET AND ACTIVE WEATHER
PATTERN FOR THE EXTENDED PERIOD AS A SERIES OF UPPER LEVEL
DISTURBANCES PASS ACROSS THE SOUTHERN PLAINS.

A PACIFIC UPPER LOW WILL MOVE ACROSS THE GREAT BASIN AREA FRIDAY
EVENING...WITH A LEAD SHORTWAVE EJECTING OUT OF THIS SYSTEM BEFORE
MOVING OVER THE REGION LATE FRIDAY NIGHT. LOW-LEVEL MOISTURE WILL
REMAIN PLENTIFUL COURTESY OF PERSISTENT SOUTHEAST UPSLOPE SURFACE FLOW
AND A LIFTING WARM FRONT. WITH THE DRYLINE REMAINING IN EASTERN NM
LARGE SCALE ASCENT WILL BE THE PRIMARY FOCUS FOR CONVECTION
INITIATION FRIDAY EVENING...WITH THE HIGHEST CHANCES FOR PRECIP
OCCURRING BETWEEN 06-12Z SATURDAY. HIGH PW VALUES...NEAR THE 99TH
PERCENTILE...WILL SUPPORT MODERATE TO HEAVY RAINFALL. THIS IN TURN
RAISES CONCERN FOR THE FLOODING POTENTIAL PARTICULARLY OVER THE
SOUTHEAST TEXAS PANHANDLE WHERE RAINFALL TOTALS OVER 2 INCHES
OCCURRED OVER THE PAST 3 DAYS AND SOILS ARE MORE CONDUCIVE TO
FLOODING. DID CONTEMPLATE EXPANDING THE CURRENT FLASH FLOOD WATCH
FURTHER WESTWARD GIVEN ALL THE RAIN THE SOUTHERN TEXAS PANHANDLE HAS
RECEIVED RECENTLY. DECIDED TO HOLD OFF ON EXPANDING THE WATCH AS
CONFIDENCE IS NOT HIGH ENOUGH THAT ENOUGH RAINFALL WILL RESULT IN
FLASH FLOODING.

THE UPPER LOW WILL MOVE INTO THE FOUR CORNERS REGION SATURDAY EVENING
AND LIFT SLOWLY TO THE NORTHEAST SUNDAY. SEVERAL UPPER LEVEL
SHORTWAVE TROUGHS WILL MAINTAIN A THREAT OF SHOWERS AND THUNDERSTORMS
THROUGH THE HOLIDAY WEEKEND. THE DRYLINE WILL MIX A BIT FURTHER
EASTWARD SUNDAY...WHICH WILL FOCUS STORM INITIATION GENERALLY OVER
THE EASTERN PANHANDLES. IN GENERAL NOT EXPECTING MUCH IN THE WAY OF
SEVERE WEATHER ALTHOUGH POSSIBLE IF THERE IS ENOUGH DAYTIME
DESTABILIZATION...SOME STRONG TO SEVERE STORMS WILL BE POSSIBLE.

MAY SEE A BRIEF BREAK IN THE RAIN EARLY NEXT WEEK ALTHOUGH WITH THE
MEDIUM RANGE MODELS IN DISAGREEMENT IN THE SPEED OF THE UPPER
TROUGH...HELD ONTO SLIGHT CHANCE POPS MEMORIAL DAY. DECENT LOW-LEVEL
MOISTURE IN PLACE AND ANOTHER UPPER DISTURBANCE MOVING THROUGH THE
FOUR CORNERS REGION CAN GENERATE MORE SHOWERS AND THUNDERSTORMS
MIDWEEK.

CLK

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH FROM LATE FRIDAY NIGHT THROUGH LATE SATURDAY
     NIGHT FOR THE FOLLOWING ZONES: ARMSTRONG...COLLINGSWORTH...
     DONLEY...GRAY...WHEELER.

OK...NONE.

&&

$$

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