Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 191822
AFDAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
122 PM CDT TUE MAY 19 2015

.UPDATE...
AN AREA OF SHOWERS AND THUNDERSTORMS CONTINUE TO MOVE ACROSS THE
EASTERN TEXAS AND OKLAHOMA PANHANDLE...AND WITH HEAVY RAINFALL STILL
OCCURRING WITH THIS CONVECTION...ONGOING FLOOD ADVISORY LOOKS GOOD
AND WILL LET IT CONTINUE UNTIL ITS EXPIRATION TIME OF 7 PM CDT. HAVE
ALSO WENT AND BUMPED UP POPS AND QPF ACROSS THE EASTERN PANHANDLES
THIS AFTERNOON. THICK CLOUD COVER AND MOIST UPSLOPE LOW LEVEL FLOW HAS
PREVENTED TEMPERATURES FROM CLIMBING MUCH ABOVE THE LOWER 60S.
CURRENT SATELLITE IMAGERY INDICATES ANY CLEARING OF THE CLOUD DECK
WILL NOT OCCUR UNTIL LATE THIS AFTERNOON...IF AT ALL...SO WENT AND
LOWERED MAX TEMPERATURES FOR THIS AFTERNOON BY SEVERAL DEGREES.

CLK

&&

.AVIATION...
/18Z TAFS/ COMPLEX AND MESSY AVIATION FORECAST STILL ON TRACK WITH
SHOWERS AND THUNDERSTORMS DEVELOPING WEST OF THE TERMINALS. EXPECT
THIS CONVECTION TO SPREAD EASTWARD...HOWEVER THICK CLOUD COVER IS
PREVENTING MUCH IN THE WAY OF STRONG DIURNAL HEATING WHICH MAY LIMIT
THE COVERAGE OF STORMS. STILL UPPER DIVERGENCE AHEAD OF THE UPPER LOW
OVER THE GREAT BASIN CAN SUPPORT ADDITIONAL STORMS LATER THIS
AFTERNOON/EARLY THIS EVENING. HAVE GONE AND INSERTED A VCTS IN AT
KAMA/KDHT WHERE THE LIKELIHOOD OF CONVECTION WILL BE HIGHEST.
OTHERWISE EXPECT IFR TO MVFR CONDITIONS THROUGH THE ENTIRE FORECAST
PERIOD. A COLD FRONT WILL PUSH ACROSS THE TERMINALS
OVERNIGHT...SUPPORTING THE POSSIBILITY FOR LOW CLOUDS EARLY WEDNESDAY
MORNING.

CLK

&&

.PREV DISCUSSION... /ISSUED 706 AM CDT TUE MAY 19 2015/

AVIATION...
12Z TAFS...SCATTERED SHOWERS AND THUNDERSTORMS ARE INCREASING IN
COVERAGE ACROSS THE WESTERN/CENTRAL PANHANDLES AND SPREADING
NORTHEAST. LIFR TO MVFR CONDITIONS ARE EXPECTED FOR MOST OF THE DAY...AND
BY MID-AFTERNOON MOST CONVECTION SHOULD BE ACROSS THE EASTERN
PANHANDLES. CONFIDENCE IS MEDIUM THAT THUNDERSTORMS COULD DEVELOP
AGAIN THIS AFTERNOON OVER THE CENTRAL AND WESTERN PANHANDLES IF THEY
CAN CLEAR OUT...AND HAVE ADDED PROB30 GROUPS FOR THE TAF SITES TO
ACCOUNT FOR THIS. A COLD FRONT WILL MOVE INTO THE PANHANDLES TONIGHT
AND SHIFT WINDS OUT OF THE NORTH...AND HAVE MEDIUM CONFIDENCE IFR
CEILINGS WILL DEVELOP OVERNIGHT.

ELSENHEIMER

PREV DISCUSSION... /ISSUED 454 AM CDT TUE MAY 19 2015/

DISCUSSION...
ACTIVE WEATHER PATTERN TO PERSIST THROUGH THE FORECAST PERIOD AS
PERIODIC UPPER TROUGHS WITHIN AN ACTIVE SOUTHERN STREAM CONTINUE TO
IMPACT THE REGION.

SHOWERS AND THUNDERSTORMS CONTINUE TO EXPAND IN COVERAGE ACROSS THE
REGION EARLY THIS MORNING. A MOIST LOW-LEVEL AIRMASS REMAINS IN PLACE
PER EASTERLY UPSLOPE FLOW IN WAKE OF THE COLD FRONT THAT MOVED
THROUGH YESTERDAY. WATER VAPOR IMAGERY SHOWS THE LATEST IN A SERIES
OF RECENT STRONG UPPER LOWS/TROUGHS CENTERED OVER THE GREAT BASIN
REGION. INCREASINGLY DIFFLUENT FLOW AHEAD OF THIS FEATURE IS
PROMOTING LARGE SCALE LIFT ACROSS THE SOUTHERN ROCKIES AND HIGH
PLAINS...WITH A POTENT SHORTWAVE TROUGH EJECTING OUT OF THE LONGWAVE
TROUGH PROVIDING MORE FOCUSED ASCENT ON THE MESOSCALE ACROSS EASTERN
NM AND THE WESTERN PANHANDLES. A 40 KT SOUTHEASTERLY LOW-LEVEL JET
HAS DEVELOPED OVERNIGHT IN RESPONSE TO HEIGHT FALLS AHEAD OF THIS
SYSTEM. RESULTANT LOW-LEVEL MOISTURE ADVECTION AND WARM AIR
ADVECTION/ISENTROPIC LIFT ARE FURTHER AIDING CONVECTIVE DEVELOPMENT.
THUS FAR MUCAPES GENERALLY IN THE 500-1000 J/KG RANGE HAVE LIMITED
OVERALL STORM INTENSITY...ALTHOUGH ONE INTENSE ELEVATED SUPERCELL DID
MAKE IT INTO THE FAR SOUTHWEST TX PANHANDLE OUT OF EASTERN
NM...LIKELY PRODUCING LARGE HAIL ALONG WITH VERY HEAVY RAIN.

EXPECT SHOWERS AND THUNDERSTORMS TO CONTINUE TO EXPAND IN COVERAGE
THIS MORNING AND MOVE NORTHEAST ACROSS THE PANHANDLES AS FORCING FOR
ASCENT INCREASES WITH THE APPROACH OF THE AFOREMENTIONED SHORTWAVE
AMIDST BROADER UPPER DIFFLUENCE. HEAVY RAINFALL WILL LIKELY BE THE
PRIMARY CONCERN THROUGH THE MORNING HOURS AS PWATS CONTINUE TO
INCREASE INTO THE 1 TO 1.5 INCH RANGE. A FEW EMBEDDED STRONG TO
SEVERE STORMS WILL REMAIN POSSIBLE AS WELL...WITH LARGE HAIL THE MAIN
SEVERE THREAT...ALONG WITH POSSIBLY SOME STRONG WINDS IF THEY MANAGE
TO PENETRATE THE NEAR-SURFACE STABLE LAYER. DECIDED TO ISSUE A FLOOD
WATCH FOR THE SOUTHEAST TX PANHANDLE TODAY. THIS PORTION OF THE
FORECAST AREA IN PARTICULAR HAS SEEN SEVERAL ROUNDS OF HEAVY RAIN
RECENTLY...AND THIS IS WHERE THE HIGHEST PWATS ARE PROGGED
TODAY...WHICH IS REFLECTED IN QPF OUTPUT FROM SEVERAL MODELS. AT
LEAST LOCALIZED MINOR FLOODING WILL BE POSSIBLE ACROSS MOST OF THE
AREA HOWEVER GIVEN SATURATED SOILS FROM THE RECENT RAINS AND THE
MOIST AIRMASS IN PLACE TODAY...ALTHOUGH EXPECT THE PRECIP TO
GENERALLY REMAIN PROGRESSIVE ENOUGH TO PRECLUDE WIDESPREAD
SIGNIFICANT FLOODING PROBLEMS.

THIS INITIAL ROUND OF RAIN WILL TAPER OFF FROM SOUTHWEST TO
NORTHEAST THROUGH THE DAY. EXACTLY WHAT UNFOLDS THIS
AFTERNOON/EVENING WILL DEPEND LARGELY ON THIS MORNING
CONVECTION...PARTICULARLY HOW MUCH CLEARING/INSOLATION WE SEE THIS
AFTERNOON AND HOW PRONOUNCED OF A COLD POOL IS LEFT BEHIND BY THE
MORNING CONVECTION. PLENTY OF MOISTURE WILL REMAIN IN PLACE THIS
AFTERNOON...SO IF WE SEE SOME SUNSHINE AND THE LOW-LEVEL COLD POOL IS
NOT OVERLY COOL/STABLE...MODERATE INSTABILITY MAY REDEVELOP THIS
AFTERNOON. MODELS VARY IN THE DEGREE OF DESTABILIZATION THIS
AFTERNOON...BUT SHOW THE POTENTIAL FOR AN AXIS OF MODERATE
INSTABILITY TO EXTEND NORTHWEST ACROSS THE SOUTHWEST HALF OR TWO
THIRDS OF THE TX PANHANDLE THIS AFTERNOON. IF THIS DOES INDEED
MATERIALIZE IN WAKE OF THE MORNING CONVECTION...A DECENT SEVERE
WEATHER THREAT WILL EXIST THIS AFTERNOON/EVENING IN A STRONGLY-
SHEARED/VEERING ENVIRONMENT. A DRYLINE IS PROGGED TO SHARPEN NEAR
THE NM STATE LINE THIS AFTERNOON...PROVIDING A POSSIBLE FOCUS FOR
AFTERNOON CONVECTIVE DEVELOPMENT IF THIS DOES INDEED HAPPEN BEHIND
THE MORNING CONVECTION. CERTAINLY WILL HAVE TO KEEP A CLOSE EYE ON
THIS AFTERNOON/EVENING SEVERE STORM POTENTIAL AS AN ISOLATED TORNADO
THREAT WOULD BE PRESENT ALONG WITH THE POTENTIAL FOR LARGE HAIL AND
DAMAGING WINDS IF ADEQUATE INSTABILITY DEVELOPS. OF COURSE THIS WILL
HINGE STRONGLY ON HOW THE ATMOSPHERE RESPONDS TO THIS EARLY DAY
CONVECTION...AND THUS CONFIDENCE IN HOW THINGS WILL ULTIMATELY UNFOLD
REMAINS LOW AT THIS TIME.

A COLD FRONT WILL MOVE SOUTH THROUGH THE PANHANDLES TONIGHT...LEADING
TO A LITTLE QUIETER WEATHER WEDNESDAY AND THURSDAY. LOW-LEVELS REMAIN
MOIST IN WAKE OF THE FRONT...AND THUS COULD SEE SOME SHOWERS OR
PERHAPS EVEN SOME LIGHT DRIZZLE DURING THIS TIME. CAN/T TOTALLY RULE
OUT A FEW THUNDERSTORMS...BUT FORECAST SOUNDINGS STRONGLY SUGGEST THE
ATMOSPHERE WILL REMAIN CAPPED TO ANY DEEPER CONVECTION.

THE NEXT CHANCE FOR WIDESPREAD RAIN AND STORMS ARRIVES THURSDAY NIGHT
AHEAD OF THE NEXT UPPER TROUGH. THE POTENTIAL FOR HEAVY RAIN AND
FLOODING WILL RETURN DURING THE THURSDAY NIGHT THROUGH SATURDAY
TIMEFRAME AS AMPLE MOISTURE AND LIFT AGAIN COME TOGETHER OVER THE
AREA. ANY PRECIPITATION SUNDAY AND MONDAY LOOKS LESS ORGANIZED...BUT
AT LEAST SOME THUNDERSTORM CHANCES WILL CONTINUE AS A PERTURBED UPPER
FLOW PERSISTS.

KB

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR THE FOLLOWING ZONES:
     COLLINGSWORTH...DONLEY...WHEELER.

OK...NONE.

&&

$$

05/15





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