Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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FXUS64 KFWD 270946
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
346 AM CST FRI FEB 27 2015

.DISCUSSION...

...A WINTER WEATHER ADVISORY REMAINS IN EFFECT ACROSS THE NORTHERN
HALF OF NORTH TEXAS...

LONGWAVE UPPER LEVEL TROUGHING IS CURRENTLY IN PLACE OVER NORTH
AMERICA WITH AN ARCTIC AIRMASS NESTLED ACROSS THE MAJORITY OF THE
CONUS. WATER VAPOR IMAGERY DEPICTS A SHORTWAVE OVER NEW MEXICO
MOVING EAST TOWARDS THE SOUTHERN PLAINS...WITHIN WHAT CONTINUES TO
BE AN ACTIVE STORM TRACK OVERHEAD. IMPRESSIVE COLD AIR ADVECTION
PERSISTS ACROSS NORTH TEXAS WITH TEMPERATURES FALLING BELOW
FREEZING OVER JUST ABOUT ALL OF THE REGION EARLY THIS MORNING.
WITH THE COLD AIR WELL IN PLACE...OUR MAIN MAIN CONCERNS FOR THE
NEXT COUPLE OF DAYS WILL BE THE AMOUNTS AND TYPES OF PRECIPITATION
WHICH WILL OCCUR.

A ZONE OF ENHANCED LIFT CURRENTLY INCREASING IN ADVANCE OF THE
SHORTWAVE IS ALREADY RESULTING IN LIGHT SNOW JUST WEST OF THE
REGION. SOME OF THIS ACTIVITY HAS REACHED AS FAR EAST AS OUR
SOUTHERN COUNTIES...DROPPING FLURRIES ALONG THE HWY 190 CORRIDOR
FROM LAMPASAS TO TEMPLE TO NORTH OF HEARNE. THE LATEST RADAR
TRENDS INDICATE THAT THIS AREA OF PRECIPITATION WILL WEAKEN THE
FARTHER EAST IT GETS. WE WILL KEEP AN EYE ON THIS ACTIVITY...BUT
AT THIS TIME WE DO NOT EXPECT ACCUMULATIONS IN THESE AREAS.

BACK TO THE APPROACHING SHORTWAVE...NEAR-TERM GUIDANCE SHOWS THAT
THE REGION OF ENHANCED UPWARD VERTICAL VELOCITIES WILL INTENSIFY
AROUND 12Z WHILE SPREADING EAST-NORTHEAST INTO OUR NORTHWESTERN
COUNTIES. THIS IS ROUGHLY THE TIME WE EXPECT ACCUMULATING SNOW TO
BEGIN WEST OF I-35 AND ALONG/NORTH OF I-20. STRONG LIFT WILL
CONTINUE TO SPREAD EAST ALONG AND NORTH OF THE INTERSTATE 20
CORRIDOR...REACHING THE DALLAS-FORT WORTH METROPLEX BY 15Z AND ALL
THE WAY EAST TO THE PARIS AREA BEFORE 18Z. THIS WOULD LIKELY BRING
THE ONSET OF SNOW AROUND 9 AM IN THE METROPLEX AND PRIOR TO NOON
ACROSS ALL OF THE ADVISORY AREA. COUNTIES SOUTH OF THE ADVISORY
ARE PLENTY COLD ENOUGH TO EXPERIENCE SOME SNOW...BUT AT THIS TIME
IT APPEARS PRECIP WILL BE LIGHT ENOUGH TO ONLY RESULT IN MINOR
ACCUMULATIONS IF ANY.

THE SHORTWAVE WILL CONTINUE OFF TO THE EAST-NORTHEAST...BRINGING A
A BRIEF LULL IN PRECIPITATION LATE AFTERNOON AND EARLY EVENING.

A SHIFT IN THE UPPER LEVEL PATTERN WILL BEGIN THIS EVENING AS AN
UPPER TROUGH DEEPENS ALONG THE WEST COAST. THIS WILL CREATE
SOUTHWESTERLY FLOW ALOFT...SETTING US UP FOR AN OVERRUNNING
SITUATION TONIGHT AND SATURDAY. NORMALLY THIS WOULD NOT BE TOO BIG
OF A DEAL...BUT WITH TEMPERATURES AT OR BELOW FREEZING...THE LIGHT
RAIN OR DRIZZLE WILL FREEZE UPON SURFACE CONTACT. THIS THIN
COATING OF ICE ON TOP OF A POTENTIAL LAYER OF SNOW COULD CREATE
HAZARDOUS DRIVING CONDITIONS...HENCE THE CONTINUATION OF THE
ADVISORY INTO SATURDAY.

A WARM ADVECTION REGIME SHOULD STRENGTHEN ENOUGH TO ALLOW
TEMPERATURES TO CLIMB ABOVE FREEZING SATURDAY NIGHT...SO
THE ADVISORY WILL END AT SUNSET TOMORROW. WE WILL NEED TO KEEP AN
EYE ON TEMPERATURES SATURDAY...AND POSSIBLY EXTEND THE ADVISORY
IF CERTAIN AREAS OF SUB-FREEZING TEMPERATURES LINGER. ALSO...THE
POTENTIAL EXISTS FOR EXTENDING THE ADVISORY SOUTH DEPENDING ON HOW
TEMPERATURES AND PRECIPITATION SHAPE UP OVERNIGHT AND TOMORROW.

ISENTROPIC ASCENT AND A WET PATTERN WILL CONTINUE SUNDAY AND
MONDAY AS THE WEST COAST SYSTEM FURTHER INTENSIFIES. THE SYSTEM
WILL MOVE ACROSS THE SOUTHWESTERN STATES LATE MONDAY AND
TUESDAY. A LEADING SHORTWAVE WILL RACE EAST AHEAD OF THE MAIN /NOW
OPEN/ TROUGH...MOVING ACROSS THE SOUTHERN PLAINS ON TUESDAY.
MARGINAL CAPE WILL BE PRESENT AS TEMPERATURES CLIMB INTO THE 60S
AND 70S. THIS COMBINED WITH LIFT FROM THE SHORTWAVE SHOULD
GENERATE SCATTERED SHOWERS AND THUNDERSTORMS TUESDAY. THE MAIN
UPPER TROUGH WILL BRING ANOTHER CHANCE FOR SHOWERS ALONG WITH A
COLD FRONT WEDNESDAY. COOLER...DRIER CONDITIONS ARE EXPECTED
DURING THE SECOND HALF OF NEXT WEEK BEHIND THIS FRONT.


30

&&

.AVIATION...
/ISSUED 1121 PM CST THU FEB 26 2015/
ONLY CHANGES TO THIS TAF SET ARE TO BRING VISBY DOWN TO 3SM IN
THE SNOW FRIDAY...AND ADD IFR CEILINGS/VISBY EARLY MORNING
SATURDAY IN THE -FZDZ. EVENING GUIDANCE HAS QPF AND SNOW
ACCUMULATIONS PRETTY SIMILAR TO PREVIOUS RUNS AND WE STILL EXPECT
1" TO 2" IN THE METROPLEX. 9 AM START TIME FOR SNOW IS STILL
INDICATED.

I HAVE LESS CONFIDENCE ON TIMING OF CHANGEOVER TO -FZDZ BUT TIMED
IT BASED ON FORECAST SOUNDINGS THAT SHOWED THE DENDRITIC GROWTH
REGION DRYING OUT BY MID EVENING. MY GUESS IS THAT AS LONG AS
THERE ARE DENDRITES GROWING...THEY ARE VERY GOOD AT ACCRETING OUT
ANY LOW LEVEL SUPERCOOLED WATER (BR/DZ DROPS) AND THE FZDZ SHOULD
NOT OCCUR UNTIL THE DENDRITES STOP FORMING. THERE MAY BE SOME
SLEET OR GRAINY SNOW MIXED IN DURING THE CHANGEOVER AS WELL.
LATEST GUIDANCE STILL SHOWS SURFACE TEMPS CLIMBING PAST FREEZING
BY NOON SATURDAY...WHEN CHANGEOVER TO -DZ/-RA WILL OCCUR. 84


&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  32  26  36  36  52 /  60  60  60  40  40
WACO, TX              35  29  41  39  59 /  20  40  60  40  40
PARIS, TX             30  24  36  35  50 /  50  60  60  40  40
DENTON, TX            30  25  34  34  50 /  70  60  60  40  40
MCKINNEY, TX          31  25  35  35  52 /  60  60  60  40  40
DALLAS, TX            32  27  37  37  53 /  60  50  60  40  40
TERRELL, TX           33  27  39  38  55 /  40  40  60  40  40
CORSICANA, TX         35  28  41  41  59 /  20  40  60  40  40
TEMPLE, TX            36  30  41  40  60 /  20  50  60  40  40
MINERAL WELLS, TX     29  25  35  34  55 /  70  60  60  40  30

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM CST
SATURDAY FOR TXZ091>095-100>106-115>120-129>133-141.


&&

$$

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