Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 162349
AFDAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
549 PM CST TUE DEC 16 2014

.AVIATION...
FOR 00Z TAFS...
INCREASING VFR CLOUDS THIS EVENING WILL EVENTUALLY LOWER TO MVFR
ACROSS THE SOUTHERN TEXAS PANHANDLE EARLY WEDNESDAY
MORNING...SPREADING NORTHWARD THROUGH THE DAY. SOUTHERLY WINDS WILL
REMAIN 8-12KTS...WITH GUSTS NEAR 20KTS EXPECTED AFTER 14 TO 16Z.
MVFR CIGS LOOK TO REMAIN THE REST OF THE DAY WEDNESDAY...WITH A
SLIGHT CHANCE FOR LIGHT RAIN FOR THE EASTERN TEXAS AND OKLAHOMA
PANHANDLES BY THE END OF THE PERIOD.

ELSENHEIMER

&&

.PREV DISCUSSION... /ISSUED 355 PM CST TUE DEC 16 2014/

DISCUSSION...

PRIMARY FORECAST CHALLENGE IS TIMING OF INTERMITTENT LOW END
PRECIPITATION CHANCES THROUGH THE END OF THE WEEK AND OCCASIONAL
PERIODS OF FROZEN PRECIPITATION POTENTIAL.

ISENTROPIC ASCENT WILL STRENGTHEN OVERNIGHT AHEAD OF AN APPROACHING
SHORTWAVE PRIMARILY ACROSS THE SOUTHEASTERN PORTION OF THE TEXAS
PANHANDLE. PRIMARY IMPACT OVERNIGHT WILL BE INCREASING/LOWERING OF
CLOUDS AS SATURATION ON 290-300K ISENTROPIC SURFACES OCCURS BY
AROUND DAYBREAK AND CONTINUING THROUGH THE EARLY AFTERNOON HOURS.
OVERALL DEPTH OF SATURATED LAYER IS GREATER TO THE SOUTHEAST ACROSS
CENTRAL TEXAS INTO OKLAHOMA AND THIS WILL BE WHERE THE BEST
PRECIPITATION CHANCES WILL RESIDE. ONCE THE RELATIVELY DRY LOW LEVELS
SATURATE BY AROUND MID MORNING...RAIN SHOWERS WILL BECOME POSSIBLE
ACROSS MAINLY THE SOUTHEASTERN THIRD OF THE FORECAST AREA. THIS WILL
PERSIST INTO THE AFTERNOON AND GRADUALLY END FROM WEST TO EAST BY
EVENING. CONSISTENT WITH PREVIOUS FORECAST MAINTAINED A RELATIVELY
TIGHT TEMPERATURE GRADIENT FROM NORTHWEST TO SOUTHEAST DUE MAINLY TO
EVAPOARTIVE COOLING WITH PRECIPITATION IN THE SOUTHEAST. THE
PRECIPITATION FREE FAR WESTERN SECTIONS COULD POTENTIALLY WARM WELL
INTO THE 50S TOMORROW AFTERNOON.

LATE TOMORROW EVENING AND THROUGH THE NIGHT MOISTURE SEEMS TO BE
SHALLOW ENOUGH IN THE EAST FOR MOSTLY DRIZZLE IF ANY MEASURABLE
PRECIPITATION OCCURS AT ALL. KEPT POPS LOW AND LIMITED TO MAINLY THE
OKLAHOMA PANHANDLE AND THE FAR NORTHEAST TEXAS PANHANDLE. THE
EXCEPTION IS THE FAR WESTERN PORTION OF THE OKLAHOMA PANHANDLE NEAR
BOISE CITY WHERE ENOUGH MOISTURE DEPTH AND SATURATION IN THE
DENDRITIC GROWTH ZONE IS SHOWN IN GUIDANCE TO SUPPORT THE
POSSIBILITY OF SNOW BEFORE DEEPER MOISTURE SHIFTS NORTHEAST OF THE
AREA AS SHORTWAVE DEPARTS. TEMPERATURES SHOULD FALL TO AT OR BELOW
FREEZING FOR AT LEAST A PORTION OF THE AREA WHERE A SHALLOW MOIST
LAYER REMAINS LATER IN THE NIGHT AND THIS RAISES SOME CONCERN FOR
FREEZING DRIZZLE. THIS IS DEFINITELY THE MOST CHALLENGING PORTION OF
THE FORECAST. NOT REAL CONFIDENT IN THIS SCENARIO BUT HAVE INCLUDED
MENTION IN THE GRIDS FOR NOW. THIS WOULD BE LIMITED TO THE FAR
NORTHERN TEXAS PANHANDLE AND THE OKLAHOMA PANHANDLE IF IT OCCURRED.
ALTHOUGH CURRENT GUIDANCE SUGGESTS ENOUGH MOISTURE DEPTH FOR THE
POTENTIAL OF MEASURABLE PRECIPITATION...THIS MAY MANIFEST ITSELF AS
MORE OF A LOW CLOUD/FOG SCENARIO. ADJUSTMENTS MAY BE MADE PENDING
MODEL TRENDS WITH MOISTURE/LIFT IN SUBSEQUENT FORECASTS.

AN ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH THE END OF THE WEEK
AND INTO THE WEEKEND WITH A SERIES OF SHORTWAVES QUICKLY PROGRESSING
EAST ACROSS THE REGION. MEDIUM RANGE MODELS ARE IN REASONABLE
AGREEMENT WITH TIMING OF INDIVIDUAL WAVES IN THE PROGRESSIVE PATTERN
BUT DIFFER SOMEWHAT ON AMPLITUDE...PARTICULARLY WITH THE SHORTWAVE
THAT WILL MOVE THROUGH THIS WEEKEND. WEAK SHORTWAVE RIDGING IN THE
WAKE OF THE FIRST SHORTWAVE TROUGH WILL OCCUR THURSDAY. WILL NEED TO
MONITOR AMPLITUDE OF RIDGING AND POTENTIAL FOR WARMER TEMPERATURES
THURSDAY AFTERNOON. THE NEXT SHORTWAVE TROUGH AND PRECIPITATION
POTENTIAL WILL OCCUR LATE THURSDAY NIGHT THROUGH EARLY
FRIDAY...ALTHOUGH NEWEST ECMWF SUGGESTS PRECIPITATION CHANCES
LINGERING LATER ON FRIDAY. FOR NOW HAVE KEPT PRECIPITATION CHANCES IN
THE SLIGHT RANGE AND TRANSITIONED FROM RAIN TO RAIN/SNOW THROUGH
MORNING WITH NO PRECIPITATION MENTION BEYOND FRIDAY MORNING.

DESPITE UNCERTAINTIES WITH THE FINAL SHORTWAVE IN THIS FORECAST
PERIOD THAT WILL MOVE THROUGH THIS WEEKEND...DUE TO ITS POSITIVE TILT
AND CONFINEMENT OF DEEPEST MOISTURE JUST SOUTHEAST OF THE AREA...DID
NOT STRAY FROM THE CONSENSUS BLEND WHICH KEPT US DRY.

BRB

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

&&

$$

18/06





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