Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 061126 AAA
AFDAMA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE AMARILLO TX
626 AM CDT WED MAY 6 2015

.AVIATION...
GENERALLY CLEAR SKY EXPECTED TODAY WITH ONLY HIGH CLOUDS OVERHEAD.
SOUTH SOUTHWEST SURFACE WINDS EXPECTED TO GUST TO AROUND 40 KT AT ALL
TERMINALS TODAY AS STRONGER WINDS ALOFT MIX TO THE SURFACE.  AN
AVIATION WEATHER WARNING HAS BEEN ISSUED FOR AMARILLO AREA AIRPORTS
FOR GUSTS TO 40 KT BETWEEN 16Z TODAY AND 01Z THURSDAY.  SOME HIGH-
BASED CUMULUS MAY DEVELOP NEAR KAMA EARLY THIS EVENING.  ISOLATED
THUNDERSTORMS THIS EVENING EXPECTED TO REMAIN EAST OF KAMA AND OTHER
TERMINALS.  VFR FORECAST CONTINUES NEXT 24 HOURS.

COCKRELL

&&

.PREV DISCUSSION... /ISSUED 303 AM CDT WED MAY 6 2015/

DISCUSSION...

EARLY THIS MORNING WATER VAPOR IMAGERY SHOWS A CLOSED MID-UPPER LOW
MOVING NORTHEASTWARD ACROSS EASTERN COLORADO. THE TEXAS AND OKLAHOMA
PANHANDLES ARE NOW CONVECTION FREE AS REMNANT EARLIER CONVECTION
ACROSS WEST TEXAS HAS FORMED INTO A LARGE THUNDERSTORM CLUSTER IN
CENTRAL OKLAHOMA. AFTER AN INCH OR MORE OF RAINFALL AT MOST LOCATIONS
THE LAST FEW DAYS...WEAK SHORTWAVE RIDGING IN THE WAKE OF DEPARTING
SHORTWAVE WILL RESULT IN DRY AND WARMER CONDITIONS TODAY. THE
EXCEPTION MAY BE IN THE FAR SOUTHEAST SECTION OF THE TEXAS PANHANDLE
WHERE THERE IS A LOW PROBABILITY OF LATE AFTERNOON/EVENING
THUNDERSTORMS. A RETURN TO A MORE ACTIVE PATTERN WILL OCCUR FOR THE
LATTER PART OF THE WEEK INTO THE WEEKEND INCLUDING DAILY CHANCES OF
THUNDERSTORMS PRIMARILY ACROSS THE EASTERN PORTION OF THE FORECAST
AREA. ALTHOUGH DETERMINISTIC GUIDANCE GENERALLY AGREES ON SPATIAL AND
TEMPORAL DETAILS ON THE LARGER SCALE...THE TYPICAL SMALLER SCALE
DISCREPANCIES WILL BE IMPORTANT ESPECIALLY IN THIS PARTICULAR
PATTERN.

THE DRYLINE WILL SHARPEN THIS AFTERNOON ACROSS THE FAR SOUTHEAST
PART OF THE FORECAST AREA WITH FAIRLY RICH/DEEP MOISTURE ON ITS EAST
SIDE. DRYLINE CIRCULATION MAY NOT BE SUFFICIENT FOR MUCH MORE THAN
ISOLATED THUNDERSTORMS GIVEN MID LEVEL HEIGHT RISES/WARMING IN THE
WAKE OF THE AFOREMENTIONED DEPARTING WAVE. MOST OF THE SREF MEMBERS
USING KF OR SAS CONVECTIVE PARAMETRIZATION SHOW A SIZABLE CAP
REMAINING FROM 21Z THROUGH 00Z AT THE CHILDRESS BUFKIT POINT.
CONVECTION-ALLOWING MODELS DIFFER SOME WITH REGARDS TO COVERAGE OF
CONVECTIVE DEVELOPMENT TOMORROW. THE MORE AGGRESSIVE MODELS SUCH AS
THE TTU-WRF SEEM TO ALSO MIX THE DRYLINE FURTHER EAST OUT OF THE
FORECAST AREA. MEANWHILE THE SPC WRF IS MOSTLY VOID OF CONVECTION IN
OUR REGION. CANNOT ARGUE AGAINST THE FURTHER EAST MIXING OF THE
DRYLINE AS THIS WOULD FIT THE PATTERN OF FAIRLY STRONG MEAN
SOUTHWESTERLY FLOW THAT IS EXPECTED TO CONTINUE INTO TOMORROW
EVENING. HAVE SCALED PRECIPITATION PROBABILITIES BACK SOME AND
LIMITED ISOLATED THUNDER COVERAGE TO COLLINGSWORTH COUNTY FOR
TOMORROW AFTERNOON.

A PARTICULARLY CHALLENGING SCENARIO DEVELOPS DURING THE EVENING
HOURS WHEN MOST SHORT-TERM GUIDANCE SHOWS THE DRYLINE RETREATING
NORTHWEST AND A FAIRLY SUBSTANTIAL INCREASE IN LOW LEVEL MOISTURE
ACROSS ROUGHLY THE SOUTHEAST THIRD OF THE FORECAST AREA. THIS IS
PROBABLY MOSTLY IN RESPONSE TO 500 MB HEIGHT FALLS AND ITS
CORRESPONDING SURFACE PRESSURE RESPONSE IN THE LEE OF THE ROCKIES
FROM YET ANOTHER APPROACHING/DEEPENING MID-UPPER TROUGH OVER THE
WESTERN CONUS. BEHAVIOR/TIMING OF THE RETREATING DRYLINE COULD ALSO
BE AUGMENTED BY COLD POOL IF CONVECTION TO OUR SOUTHEAST IS MORE
EXTENSIVE THAN CURRENTLY EXPECTED. THERE IS ENOUGH CONCERN FOR SOME
CONVECTIVE DEVELOPMENT LATE IN THE EVENING AND OVERNIGHT TO RETAIN
LOW END PRECIPITATION PROBABILITY ACROSS SOUTHEAST PORTIONS OF THE
AREA BUT THE BETTER SIGNAL FOR WARM ADVECTION/ISENTROPIC ASCENT IS
FURTHER EAST ACROSS SOUTHWESTERN THROUGH CENTRAL OKLAHOMA. THIS WILL
LIKELY BE WHERE THE GREATEST COVERAGE IS OVERNIGHT THROUGH EARLY
THURSDAY MORNING.

CERTAINLY BY THURSDAY AFTERNOON WITH DIABATIC HEATING OF A
MOISTENING BOUNDARY LAYER...CONVECTION OF AT LEAST AN
ISOLATED-SCATTERED NATURE WOULD BE EXPECTED ACROSS THE AREA. THIS
WOULD BE ENHANCED BY ANY SMALL DIFFICULT TO RESOLVE SHORTWAVE
EMBEDDED WITHIN STRENGTHENING MEAN SOUTHWESTERLY FLOW. ONCE SUCH
WAVE IS SHOWN IN MODEL GUIDANCE TO CROSS THE NEW MEXICO MOUNTAINS
AND APPROACH THE PANHANDLES BY LATE AFTERNOON FOLLOWED BY ANOTHER
EARLY FRIDAY. THEREAFTER THE MEDIUM RANGE GUIDANCE DISAGREES SOME ON
THE TIMING OF THE MAIN UPPER LOW. ECMWF IS SLIGHTLY FASTER THAN THE
GFS. IN EITHER CASE THIS SYSTEM STRENGTHENS CONSIDERABLY AND
BECOMES NEGATIVELY TILTED WHICH WILL INDUCE A FAIRLY DRAMATIC
SURFACE RESPONSE WITH SUB-1000 MB LOW LIKELY SOMEWHERE FROM
SOUTHEAST COLORADO TO THE NORTHWEST TEXAS PANHANDLE BY LATE
SATURDAY. THIS SETUP CONCEPTUALLY WOULD RAISE CONCERN FOR THE
DRYLINE MIXING EAST INTO OKLAHOMA KEEPING OUR AREA DRY...ALTHOUGH
THE FAR EASTERN PORTION OF THE TEXAS AND OKLAHOMA PANHANDLES MAY
REMAIN EAST OF THE DRYLINE AND SEE A THREAT FOR SEVERE THUNDERSTORM
DEVELOPMENT. THE THREAT MAY OCCUR EVEN FURTHER WEST DEPENDING ON
SPATIAL/TEMPORAL DETAILS ON THE LARGER SCALE THAT ARE YET TO BE
RESOLVED.

FOR SUNDAY INTO EARLY NEXT WEEK MEDIUM RANGE MODEL AGREEMENT IS LESS
AND ENSEMBLE SPREAD IS GREATER. THE LARGE SCALE PATTERN DEAMPLIFIES
SOME WITH PERHAPS ONE MORE WAVE PASSING QUICKLY THROUGH SOMETIME
LATE SUNDAY INTO MONDAY. THERE SEEMS TO BE A TREND TOWARD UPPER
RIDGING AND DRIER WEATHER BY TUESDAY.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
AMARILLO TX                81  56  80  53  79 /   5  20  40  20  30
BEAVER OK                  84  57  84  57  79 /  10  20  50  60  40
BOISE CITY OK              80  49  78  47  74 /   5  10  20  20  20
BORGER TX                  84  57  83  58  80 /   5  20  50  20  30
BOYS RANCH TX              83  53  82  51  81 /   5   5  30  20  20
CANYON TX                  81  54  80  51  79 /   5  10  30  20  30
CLARENDON TX               85  58  79  57  78 /  10  30  40  40  40
DALHART TX                 82  49  80  47  78 /   5  10  20  10  20
GUYMON OK                  83  53  83  52  77 /   5  10  40  20  40
HEREFORD TX                82  53  81  49  80 /   5  10  20  20  20
LIPSCOMB TX                83  59  82  60  79 /  10  20  40  60  50
PAMPA TX                   81  57  79  55  77 /   5  20  50  30  40
SHAMROCK TX                83  60  78  61  79 /  10  40  40  60  50
WELLINGTON TX              85  61  80  62  80 /  20  40  30  50  50

&&

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

&&

$$

03/17






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