Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 291024
AFDAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AMARILLO TX
424 AM CST MON DEC 29 2014

.DISCUSSION...
AN ARCTIC AIRMASS IS POISED TO INVADE THE REGION TODAY AND PERSIST
THROUGH THE MIDDLE OF THIS WEEK BEFORE MODIFYING SOMEWHAT. SHORT
RANGE MODELS ARE IN BETTER AGREEMENT THIS MORNING WITH THE TIMING.
THERE WILL LIKELY BE A MAX TEMP GRADIENT FROM NORTH TO SOUTH ACROSS
THE TX AND OK PNHDLS TODAY AS THE COLD AIR BEGINS TO INVADE THE AREA.
ALSO INTRODUCED SLIGHT CHC POPS ACROSS THE OK PNHDL AND NWRN TX
PNHDL THIS AFTERNOON FOR LIGHT SNOW. FOR TONIGHT...POPS WERE INCREASED
TO HIGH CHANCE OVER OK PNHDL...DIMINISHING TO SLGT CHC VALUES OVER
MUCH OF SRN TX PNHDL. PREDOMINANT PRECIP TYPE SHOULD BE LIGHT SNOW.
THE COMBINATION OF WINDS AND COLD TEMPS TONIGHT INTO TUESDAY HAS
WARRANTED ISSUANCE OF A WIND CHILL ADVISORY ACROSS OK PNHDL AND NRN
TX PNHDL DURG THIS TIME PERIOD. LATER SHIFTS MAY NEED TO CONSIDER
EXPANDING A BIT FURTHER SWD TO ENCOMPASS SW AND SCNTRL TX PNHDL IF
NECESSARY. AT THIS TIME...CONFIDENCE IS LOW IN SNOWFALL AMOUNTS FROM
LATE TONIGHT THRU TUE NIGHT...WITH LESS THAN AN INCH EXPECTED IN MOST
PLACES EXCEPT PSBLY OK PNHDL AND PARTS OF NWRN TX PNHDL WHERE AROUND
AN INCH OF SNOW OR SLIGHTLY HIGHER MAY ACCUMULATE. HAVE DECIDED TO
HOLD OFF ON ISSUANCE OF A WINTER WEATHER ADVISORY FOR SNOW FOR PARTS
OF THE NRN ZONES DUE TO LOW CONFIDENCE IN AMOUNTS AT THIS TIME. IT
APPEARS THE MAIN MESSAGE WILL BE THE COLD TEMPS AND BITTERLY COLD
WIND CHILLS LATER TONIGHT THRU TUESDAY NIGHT.

CHC POPS FOR LIGHT SNOW CONTINUE THRU TUESDAY...TAPERING TO SLGT CHC
TO CHC FOR TUESDAY NIGHT AS DRIER AIR MOVES INTO THE REGION. NO POPS
ARE SLATED FOR WED AND WED NIGHT. WELL BELOW NORMAL TEMPERATURES WILL
PREVAIL THRU WEDNESDAY.

LATE THIS WEEK A CLOSED UPPER LOW WILL MOVE TOWARD THE REGION.
CONFIDENCE REMAINS BELOW AVERAGE AS IS TYPICALLY THE CASE WITH THIS
PARTICULAR SYNOPTIC PATTERN IN THE LONG TERM PERIOD. SEVERAL OF THE
GFS ENSEMBLE MEMBERS ARE FASTER AND MORE OPEN THAN THE OPERATIONAL
GFS. THE 00Z ECMWF IS SLOWER THAN THE PREVIOUS RUN WITH VERY SIMILAR
TIMING AND STRENGTH AS GFS. ECMWF IS SLIGHTLY FURTHER SOUTH THAN GFS
BY SATURDAY. THE BIGGEST DIFFERENCE BETWEEN DETERMINISTIC GUIDANCE
IS THAT ECMWF IS MORE RESTRICTIVE WITH WESTWARD ENCROACHMENT OF
DEEPER MOISTURE AND CONSEQUENTLY IS MUCH DRIER. GFS IS HIGHER WITH
QPF VALUES MAINLY DUE TO A MORE PROLONGED EVENT WITH A MORE
PRONOUNCED WARM/MOIST CONVEYOR BELT STRUCTURE LEADING TO LINGERING
PRECIPITATION. THIS IS MOST EVIDENT IN RH PLOTTED ON 295-305K
SURFACES. THESE ARE SMALLER SCALE DETAILS IN A STILL UNCERTAIN LARGE
SCALE PATTERN BUT IT SEEMS TO HAVE ENOUGH VALIDITY TO ACCEPT THE
INTRODUCTION OF SLIGHT CHANCE POPS EARLY SATURDAY GIVEN BY THE
EXTENDED INITIAL GRIDS.

FOR THE PREVIOUS COUPLE OF FORECASTS IT SEEMED THERE WOULD BE ENOUGH
WARM ADVECTION ABOVE A SHALLOW COLD LAYER FOR AT LEAST A SHORT
PERIOD OF RAIN FRIDAY BUT MORE RECENT RUNS ARE COLDER. WITH BELOW
AVERAGE CONFIDENCE IN THE OVERALL SYNOPTIC PATTERN WOULD PREFER TO
NOT MAKE DRASTIC CHANGES AND BROADEN THE WORDING TO BETTER ALIGN
WITH UNCERTAINTY. BOTTOM LINE IS THAT THERMAL PROFILES ARE JUST TOO
MARGINAL TO BE TOO DETERMINISTIC WITH PRECIPITATION TYPE AT THIS
JUNCTURE...AT LEAST NOT UNTIL LATE FRIDAY NIGHT AND EARLY SATURDAY
WHEN COLUMN SHOULD COOL SUFFICIENTLY FOR ALL SNOW ACROSS THE ENTIRE
AREA.

ANDRADE/BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
AMARILLO TX                38  12  18   7  24 /   5  20  50  30   5
BEAVER OK                  33   7  13   2  22 /  20  50  40  20   5
BOISE CITY OK              30   4  10  -2  23 /  20  50  50  40   5
BORGER TX                  37  13  19   7  25 /   5  20  40  30   5
BOYS RANCH TX              38  11  18   5  24 /   5  20  50  30   5
CANYON TX                  40  12  19   7  24 /   5  10  50  30   5
CLARENDON TX               41  15  22  11  25 /   5  10  40  20   5
DALHART TX                 35   9  14   2  24 /  10  40  50  40   5
GUYMON OK                  32   6  10   2  24 /  20  50  50  30   5
HEREFORD TX                42  12  21   7  24 /   5  10  50  30   5
LIPSCOMB TX                36  11  17   2  23 /   5  30  30  20   5
PAMPA TX                   37  12  19   6  24 /   5  20  40  20   5
SHAMROCK TX                41  16  23  10  24 /   5  10  30  20   5
WELLINGTON TX              44  18  25  13  25 /   5  10  30  20   5

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 4 PM CST TUESDAY
     FOR THE FOLLOWING ZONES: DALLAM...HANSFORD...HARTLEY...
     HEMPHILL...HUTCHINSON...LIPSCOMB...MOORE...OCHILTREE...
     ROBERTS...SHERMAN.

OK...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 4 PM CST TUESDAY
     FOR THE FOLLOWING ZONES: BEAVER...CIMARRON...TEXAS.


&&

$$






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