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

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000
FXUS64 KFWD 250043 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
643 PM CST TUE FEB 24 2015

.AVIATION...
/00Z TAFS/

CONCERNS...MVFR AND IFR CIGS. A RAIN/SNOW MIX OVERNIGHT
TRANSITIONING TO ALL SNOW AT DFW AND POSSIBLY WACO.

KACT...MVFR CIGS BELOW 2KFT WILL CONTINUE INTO WEDNESDAY MORNING.
THE PRECIPITATION FORECAST IS CHALLENGING...BUT STILL EXPECTING A
MIX OF RAIN AND SNOW...WITH POSSIBLY A BRIEF PERIOD OF
SLEET...BETWEEN 09-15Z. IT IS LIKELY THAT FOR A PERIOD OF TIME
BETWEEN 11-14Z...ALL SNOW COULD OCCUR WITH < 1" ACCUMULATION. WILL
CONTINUE TO MONITOR THE DATA THIS EVENING TO TRY AND PINPOINT
IF/WHEN A TRANSITION TO ALL SNOW WILL OCCUR...BUT IT DOES LOOK
LIKE THE HEAVIEST SNOW BANDS WILL OCCUR NORTH OF KACT. THE WINDS
THROUGH THE PERIOD WILL MOSTLY BE LIGHT AND VARIABLE BUT WILL
PREVAIL MORE FROM THE WEST ON WEDNESDAY. AS THE PRECIPITATION ENDS
WEDNESDAY MORNING...CIGS WILL IMPROVE TO VFR BY THE AFTERNOON.

DFW AIRPORTS...SCATTERED MVFR CIGS ARE OCCURRING ACROSS THE
METROPLEX THIS EVENING...RESULTING IN OCCASIONAL BKN CIGS BETWEEN
2500-3000 FEET. WILL CARRY A TEMPO FOR BKN025 FOR A FEW HOURS BUT
EXPECT MOSTLY VFR CONDITIONS TO PREVAIL THIS EVENING. AS THE
PRECIPITATION MOVES INTO THE DFW METROPLEX BETWEEN 07-09Z...IT
WILL INITIALLY BE A RAIN/SNOW MIX WITH POSSIBLY SOME SLEET MIXING
AT TIMES. BY 11-12Z...EXPECT THE MIX TO TRANSITION TO ALL SNOW
WITH MODERATE TO HEAVY SNOW POSSIBLE IN SNOW BANDS BETWEEN
12-15Z. ACCUMULATIONS OF SNOW WILL AVERAGE 1-3" WITH SOME LOCALLY
HIGHER AMOUNTS. THERE IS STILL SOME UNCERTAINTY IF ANY OR ALL OF
THE AIRPORTS WILL BE AFFECTED BY HEAVY SNOW BANDS...BUT CONFIDENCE
IS INCREASING THAT THE DFW AIRPORTS MAY BE AFFECTED BY A SNOW
BAND. WHEN THE PRECIPITATION ARRIVES...EXPECT CIGS TO LOWER INTO
LOW MVFR CATEGORY AND LIKELY IFR WITHIN PERIODS OF MODERATE TO
HEAVY SNOW. VISBY WILL ALSO BE AFFECTED. THE SNOW IS EXPECTED TO
END BETWEEN 15-16Z WITH THE VISBY AND CIGS IMPROVING TO VFR IN THE
AFTERNOON. EXPECT LIGHT AND VARIABLE WINDS THROUGH MOST OF THE
PERIOD BUT THEY MAY PREVAIL MORE FROM THE WEST ON WEDNESDAY.

82/JLD

&&

.SHORT TERM...
DESPITE TEMPERATURES REMAINING BELOW FREEZING INTO THE AFTERNOON
HOURS...AND LINGERING CLOUD COVER...RESIDUAL ICE ON ROADWAYS HAS
EFFECTIVELY MELTED TODAY. IN ADDITION TO SUBLIMATION FROM THE TOP
OF THE ICE LAYER...DIFFUSE SUNLIGHT HAS BEEN SUFFICIENT TO WARM
THE PAVEMENT AND MELT THE ICE FROM BELOW. WITH TEMPERATURES ABOVE
FREEZING THIS EVENING...A REFREEZE OF ANY MELTWATER IS NOT
EXPECTED. THUS...ANY IMPACTS TO TRAVEL LATE TONIGHT AND WEDNESDAY
MORNING WILL BE A RESULT OF NEW PRECIPITATION.

AN UPPER LOW...RESPONSIBLE FOR THE THUNDERSTORMS IN THE MOUNTAINS
OF CENTRAL ARIZONA...WILL RACE INTO WEST TEXAS THIS EVENING.
GUIDANCE REMAINS IN EXCELLENT AGREEMENT WITH RESPECT TO THE TIMING
OF ITS PASSAGE THROUGH NORTH AND CENTRAL TEXAS. HOWEVER...THE
CRUCIAL DISPARITY AMONG OPERATIONAL SOLUTIONS WITH THE TRACK OF
THE FEATURE REMAINS...MAINTAINING A LEVEL OF UNCERTAINTY IN THE
EVOLUTION OF THE PRECIPITATION TONIGHT AND WEDNESDAY.

UNDETERRED BY THE CONSENSUS...THE 18Z NAM CONTINUES TO BE BULLISH
ON SNOW. THIS IS LARGELY A FACTOR OF ITS BOWLING BALL LOW IN THE
MID-LEVELS THAT TAKES A TRACK BETWEEN I-20 AND THE RED RIVER. WITH
SUFFICIENT COLD AIR...THIS IS ONE OF THE MOST FAVORABLE SETUPS FOR
SIGNIFICANT SNOWFALL IN THIS REGION. THE SCENARIO BEARS SOME
SIMILARITY TO THE SNOW EVENT OF FEBRUARY 3-4 OF 2011...WHICH WAS
THE SECOND OF A TRIO OF WINTER WEATHER EVENTS IN AN OTHERWISE
PLACID WINTER SEASON. WHILE THAT EVENT RESULTED IN SNOWFALL
AMOUNTS EXCEEDING WARNING CRITERIA FROM DALLAS TO SULPHUR
SPRINGS...THE ARE SOME MITIGATING FACTORS WITH THIS EVENT.

MITIGATING FACTORS
- SURFACE TEMPERATURES ARE 10-15 DEGREES WARMER THAN THE DAY THAT
  PRECEDED THE FEBRUARY 2011 EVENT. NO LOW-LEVEL COLD ADVECTION
  IS EXPECTED...AND DYNAMIC COOLING ALONE IS UNLIKELY TO RESULT
  IN SUB-FREEZING TEMPERATURES THROUGHOUT THE PRECIPITATION
  EVENT.
- THIS SYSTEM WILL SWING THROUGH MUCH FASTER...LIMITING
  THE DURATION OF THE PRECIPITATION...ONLY A PORTION OF WHICH
  WILL BE SNOW.
- IN ADDITION...THE CONSENSUS (GFS/ECMWF/CANADIAN) FAVORS AN
  OPENING RATHER THAN DEEPENING WAVE...LIMITING THE SCALE OF THE
  ASSOCIATED LIFT.

THERMAL PROFILES SUGGEST THE PRECIPITATION WILL BEGIN AS RAIN. AS
THE UPPER LOW APPROACHES...DYNAMIC COOLING OF THE COLUMN WILL
GRADUALLY RESULT IN A TRANSITION TO SNOW OR A RAIN/SNOW MIX. ITS
PASSAGE AT THE DIURNAL MINIMUM OF TEMPERATURE WILL AID IN THIS
TRANSITION TO FROZEN PRECIPITATION. THIS TRANSITION MAY NOT OCCUR
IN SOUTHERN ZONES (OUTSIDE OF THE ADVISORY AREA) UNTIL DAYBREAK.
SURFACE TEMPERATURES WILL BE NEAR OR ABOVE FREEZING WHEN THIS
TRANSITION OCCURS...LIMITING THE EVENTUAL ACCUMULATIONS.
HOWEVER...THIS WET SNOW SHOULD COOL THE SURFACE LAYER A FEW
DEGREES...AND IN THE BAND OF HEAVIEST PRECIPITATION...THE SNOWFALL
RATES ALONE SHOULD ASSURE SOME ACCUMULATIONS ARE REALIZED. THE
RESULT WILL BE SHORT DURATION EVENT OF MODERATE IMPACT...BUT ONE
THAT DIRECTLY IMPACTS MORNING COMMUTE TIME

THE CONSENSUS OF SYNOPTIC GUIDANCE IS FOR A MORE SOUTHERLY SWATH
OF PRECIPITATION...WHICH WOULD LIMIT SNOWFALL TOTALS. BUT A TRACK
JUST ONE COUNTY (30 MILES) TO THE NORTH OR SOUTH COULD MAKE THE
DIFFERENCE BETWEEN NEGLIGIBLE ACCUMULATIONS AND MESOSCALE-ENHANCED
TOTALS IN EXCESS OF 3 INCHES. THE WRF SUITE WAS FAVORING A MORE
NORTHERLY TRACK...BUT CONFIDENCE IN THESE SOLUTIONS DECLINED WITH
THE LATEST TTU WRF AND REMARKABLY DRY RAP. THE TIME FRAME OF THE
EVENT WILL BE CAPTURED BY ADDITIONAL MESOSCALE GUIDANCE AVAILABLE
THIS EVENING...AND THE TRACK OF HEAVIEST PRECIPITATION AND
RESULTING SNOWFALL AMOUNTS MAY NEED TO BE ADJUSTED.

EVEN WHERE SIGNIFICANT SNOWFALL OCCURS...TEMPERATURES WILL RISE
ABOVE FREEZING WEDNESDAY AFTERNOON...RESULTING IN EFFICIENT
MELTING OF THE WET SNOW. THE AFTERNOON BUS RIDE AND THE EVENING
COMMUTE SHOULD BE LARGELY FREE OF IMPACTS.

&&

.SYNOPSIS...
RAIN WILL INVADE FROM THE SOUTHWEST LATE THIS EVENING...WITH
PRECIPITATION SPREADING ACROSS MUCH OF NORTH AND CENTRAL TEXAS
AFTER MIDNIGHT. INITIALLY RAIN...A TRANSITION TO SNOW OR A
RAIN/SNOW MIX WILL BEGIN DURING THE PREDAWN HOURS WEDNESDAY. RAIN
AND SNOW WILL BEGIN SHIFTING EASTWARD AFTER DAYBREAK...EXITING THE
REGION BY EARLY AFTERNOON. SNOWFALL TOTALS ARE EXPECTED TO EXCEED
1/2 INCH WITHIN THE ADVISORY AREA...WITH LESSER BUT POTENTIALLY
ACCUMULATING SNOWFALL POSSIBLE TO THE SOUTH. THE AXIS OF GREATEST
SNOWFALL IS STILL EXPECTED NEAR THE I-20 AND I-30 CORRIDORS...
WHERE AMOUNTS WILL GENERALLY BE 1 TO 3 INCHES. ISOLATED HIGHER
AMOUNTS WILL BE POSSIBLE...PARTICULARLY EAST AND NORTHEAST OF THE
DALLAS/FORT WORTH METROPLEX.

&&


.SHORT TERM...
DESPITE TEMPERATURES REMAINING BELOW FREEZING INTO THE AFTERNOON
HOURS...AND LINGERING CLOUD COVER...RESIDUAL ICE ON ROADWAYS HAS
EFFECTIVELY MELTED TODAY. IN ADDITION TO SUBLIMATION FROM THE TOP
OF THE ICE LAYER...DIFFUSE SUNLIGHT HAS BEEN SUFFICIENT TO WARM
THE PAVEMENT AND MELT THE ICE FROM BELOW. WITH TEMPERATURES ABOVE
FREEZING THIS EVENING...A REFREEZE OF ANY MELTWATER IS NOT
EXPECTED. THUS...ANY IMPACTS TO TRAVEL LATE TONIGHT AND WEDNESDAY
MORNING WILL BE A RESULT OF NEW PRECIPITATION.

AN UPPER LOW...RESPONSIBLE FOR THE THUNDERSTORMS IN THE MOUNTAINS
OF CENTRAL ARIZONA...WILL RACE INTO WEST TEXAS THIS EVENING.
GUIDANCE REMAINS IN EXCELLENT AGREEMENT WITH RESPECT TO THE TIMING
OF ITS PASSAGE THROUGH NORTH AND CENTRAL TEXAS. HOWEVER...THE
CRUCIAL DISPARITY AMONG OPERATIONAL SOLUTIONS WITH THE TRACK OF
THE FEATURE REMAINS...MAINTAINING A LEVEL OF UNCERTAINTY IN THE
EVOLUTION OF THE PRECIPITATION TONIGHT AND WEDNESDAY.

UNDETERRED BY THE CONSENSUS...THE 18Z NAM CONTINUES TO BE BULLISH
ON SNOW. THIS IS LARGELY A FACTOR OF ITS BOWLING BALL LOW IN THE
MID-LEVELS THAT TAKES A TRACK BETWEEN I-20 AND THE RED RIVER. WITH
SUFFICIENT COLD AIR...THIS IS ONE OF THE MOST FAVORABLE SETUPS FOR
SIGNIFICANT SNOWFALL IN THIS REGION. THE SCENARIO BEARS SOME
SIMILARITY TO THE SNOW EVENT OF FEBRUARY 3-4 OF 2011...WHICH WAS
THE SECOND OF A TRIO OF WINTER WEATHER EVENTS IN AN OTHERWISE
PLACID WINTER SEASON. WHILE THAT EVENT RESULTED IN SNOWFALL
AMOUNTS EXCEEDING WARNING CRITERIA FROM DALLAS TO SULPHUR
SPRINGS...THE ARE SOME MITIGATING FACTORS WITH THIS EVENT.

MITIGATING FACTORS
- SURFACE TEMPERATURES ARE 10-15 DEGREES WARMER THAN THE DAY THAT
  PRECEDED THE FEBRUARY 2011 EVENT. NO LOW-LEVEL COLD ADVECTION
  IS EXPECTED...AND DYNAMIC COOLING ALONE IS UNLIKELY TO RESULT
  IN SUB-FREEZING TEMPERATURES THROUGHOUT THE PRECIPITATION
  EVENT.
- THIS SYSTEM WILL SWING THROUGH MUCH FASTER...LIMITING
  THE DURATION OF THE PRECIPITATION...ONLY A PORTION OF WHICH
  WILL BE SNOW.
- IN ADDITION...THE CONSENSUS (GFS/ECMWF/CANADIAN) FAVORS AN
  OPENING RATHER THAN DEEPENING WAVE...LIMITING THE SCALE OF THE
  ASSOCIATED LIFT.

THERMAL PROFILES SUGGEST THE PRECIPITATION WILL BEGIN AS RAIN. AS
THE UPPER LOW APPROACHES...DYNAMIC COOLING OF THE COLUMN WILL
GRADUALLY RESULT IN A TRANSITION TO SNOW OR A RAIN/SNOW MIX. ITS
PASSAGE AT THE DIURNAL MINIMUM OF TEMPERATURE WILL AID IN THIS
TRANSITION TO FROZEN PRECIPITATION. THIS TRANSITION MAY NOT OCCUR
IN SOUTHERN ZONES (OUTSIDE OF THE ADVISORY AREA) UNTIL DAYBREAK.
SURFACE TEMPERATURES WILL BE NEAR OR ABOVE FREEZING WHEN THIS
TRANSITION OCCURS...LIMITING THE EVENTUAL ACCUMULATIONS.
HOWEVER...THIS WET SNOW SHOULD COOL THE SURFACE LAYER A FEW
DEGREES...AND IN THE BAND OF HEAVIEST PRECIPITATION...THE SNOWFALL
RATES ALONE SHOULD ASSURE SOME ACCUMULATIONS ARE REALIZED. THE
RESULT WILL BE SHORT DURATION EVENT OF MODERATE IMPACT...BUT ONE
THAT DIRECTLY IMPACTS MORNING COMMUTE TIME

THE CONSENSUS OF SYNOPTIC GUIDANCE IS FOR A MORE SOUTHERLY SWATH
OF PRECIPITATION...WHICH WOULD LIMIT SNOWFALL TOTALS. BUT A TRACK
JUST ONE COUNTY (30 MILES) TO THE NORTH OR SOUTH COULD MAKE THE
DIFFERENCE BETWEEN NEGLIGIBLE ACCUMULATIONS AND MESOSCALE-ENHANCED
TOTALS IN EXCESS OF 3 INCHES. THE WRF SUITE WAS FAVORING A MORE
NORTHERLY TRACK...BUT CONFIDENCE IN THESE SOLUTIONS DECLINED WITH
THE LATEST TTU WRF AND REMARKABLY DRY RAP. THE TIME FRAME OF THE
EVENT WILL BE CAPTURED BY ADDITIONAL MESOSCALE GUIDANCE AVAILABLE
THIS EVENING...AND THE TRACK OF HEAVIEST PRECIPITATION AND
RESULTING SNOWFALL AMOUNTS MAY NEED TO BE ADJUSTED.

EVEN WHERE SIGNIFICANT SNOWFALL OCCURS...TEMPERATURES WILL RISE
ABOVE FREEZING WEDNESDAY AFTERNOON...RESULTING IN EFFICIENT
MELTING OF THE WET SNOW. THE AFTERNOON BUS RIDE AND THE EVENING
COMMUTE SHOULD BE LARGELY FREE OF IMPACTS.

&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  30  46  31  43  26 /  80  80   5  10   5
WACO, TX              32  50  30  47  28 /  70  60   5   5  10
PARIS, TX             28  37  29  41  23 /  60  80   5  10  10
DENTON, TX            29  47  28  42  23 /  80  70   5  10   5
MCKINNEY, TX          29  43  26  41  24 /  80  80   5  10  10
DALLAS, TX            30  45  32  43  27 /  80  80   5  10   5
TERRELL, TX           30  41  31  44  27 /  80  80   5  10  10
CORSICANA, TX         31  45  31  45  28 /  80  80   5  10  10
TEMPLE, TX            32  53  31  50  28 /  60  50   5   5  10
MINERAL WELLS, TX     29  53  29  43  22 /  80  50   5  10   5

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST
WEDNESDAY FOR TXZ091>095-100>107-115>123-129>135-141>148-157-159-
161.


&&

$$

82/58



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