163 
FXUS64 KFWD 111004
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
404 AM CST FRI DEC 11 2015

.DISCUSSION...

09 SUBJECTIVE SURFACE ANALYSIS SHOWED A STATIONARY FRONT DRAPED
ROUGHLY NORTH TO SOUTH ACROSS NORTH TEXAS LOCATED JUST EAST OF THE
INTERSTATE 35/35E CORRIDOR. ALONG AND WEST OF THIS FRONT...
TEMPERATURES WERE IN THE LOWER TO MID 40S WITH LIGHT WINDS AND
ONLY CIRRUS ALOFT. TO THE EAST OF THE FRONT...TEMPERATURES RANGED
FROM THE LOW 50S NEAR THE FRONT...TO THE MID 60S 50 MILES OR SO
EAST OF THE FRONT. THE MID-60S AIR WAS REPRESENTATIVE OF A
TYPICAL SPRING TIME WARM SECTOR AIR MASS WITH DEW POINTS IN THE
LOW 60S AND LOW STRATUS IN PLACE. CLOSER TO THE BOUNDARY... THIS
RICH LOW LEVEL MOISTURE INTERACTING WITH COOLER AIR NEAR THE FRONT
RESULTED IN A NARROW CORRIDOR OF DENSE FOG...EXTENDING FROM PARIS
TEXAS SOUTHWEST OVER ROCKWALL AND TERRELL. WENT AHEAD WITH A DENSE
FOG ADVISORY FOR THESE LOCATIONS EARLY THIS MORNING AS THE FRONT
IS UNLIKELY TO MOVE MUCH THROUGH SUNRISE WHEN IT HAS NOT MOVED
MUCH AT ALL OVERNIGHT.

TODAY...EARLY MORNING WATER VAPOR SATELLITE IMAGERY SHOWED A LARGE
UPPER TROUGH OVER THE NORTHWESTERN CONUS. THIS TROUGH IS EXPECTED
TO MOVE SOUTH-SOUTHEAST OVER THE SOUTHWESTERN CONUS OVER THE NEXT
24 HOURS SPREADING STRONG/JET STREAM WINDS OVER THE SOUTHERN AND
CENTRAL CONUS ROCKIES. THIS FLOW WILL HELP INDUCE LEE SIDE
CYCLOGENESIS TODAY...RESULTING IN THE STALLED OUT FRONTAL BOUNDARY
LIFTING NORTH ACROSS THE REGION THIS AFTERNOON. THIS WILL ALLOW
UNSEASONABLY WARM MOIST AIR TO FLOW NORTH ACROSS NORTH AND CENTRAL
TEXAS TODAY...RESULTING IN NEAR RECORD HIGHS FOR THE DFW AREA AND
WACO. KEPT FORECAST HIGHS JUST BELOW RECORD LEVELS TODAY PRIMARILY
DUE TO THE ABUNDANCE OF LOW-LEVEL MOISTURE IN PLACE JUST SOUTHEAST
OF THE FRONT'S CURRENT POSITION. THIS MOISTURE IS INITIALLY
SHALLOW IN NATURE...BUT THINK THAT THERE WILL BE A BIT MORE CLOUD
COVER THAN STATISTICAL GUIDANCE INDICATES DUE TO HOW CLOSE THE
DEEPER MOISTURE IS TO THE CWA ALREADY. THESE CLOUDS WILL PROBABLY
DEVELOP DURING THE PEAK HEATING HOURS OF THE DAY...SHAVING A
DEGREE OR TWO OFF MOS GUIDANCE HIGHS. REGARDLESS OF WHETHER RECORD
HIGHS ARE SET TODAY OR NOT...EXPECTING A WARM AND PLEASANT DAY
ACROSS THE REGION. KEPT THE FORECAST DRY FOR TODAY DESPITE THE
SURGE OF MOISTURE ACROSS THE REGION DUE TO A LACK OF STRONG LIFT.

TONIGHT/SATURDAY MORNING...MODEL GUIDANCE IS FAIRLY CONSISTENT IN
ADVERTISING A 40-45 KT LOW-LEVEL JET DEVELOPING OVER THE REGION AS
LEE-SIDE CYCLOGENESIS CONTINUES TO RAMP UP. THIS SPRING LIKE LOW-
LEVEL JET IS EXPECTED TO TRANSPORT DEEP LOW-LEVEL MOISTURE INTO
PLACE BELOW A FAIRLY STOUT INVERSION NEAR THE 850 MB LEVEL. THIS
STRONG LOW- LEVEL JET ONLY REPRESENTS WEAK LIFT AS WARM AIR
ADVECTION WILL BE FAIRLY CONSISTENT WITHIN THE WARM SECTOR OF THIS
STORM SYSTEM. AS A RESULT...THINK THAT THE DEEP MOISTURE AND
STRONG LOW-LEVEL JET WILL ONLY RESULT IN AREAS OF DRIZZLE ACROSS
NORTH AND CENTRAL TEXAS FROM LATE TONIGHT THROUGH TOMORROW
MORNING. BETTER RAIN CHANCES WILL ARRIVE LATER IN THE DAY ON
SATURDAY...BUT DO NOT SEE MUCH MORE THAN DRIZZLE OR VERY LIGHT
RAIN THROUGH LATE SATURDAY MORNING WITH PERSISTENT WEAK LIFT
CONTAINED UNDER THE INVERSION ALOFT. HAVE 20-30 POPS WITH DRIZZLE
OR LIGHT RAIN MENTIONED IN THE FORECAST AS A RESULT. DESPITE THE
DRIZZLE...MORNING LOWS ARE EXPECTED TO BE QUITE WARM WITH LOWS IN
THE MID 60S. THE RECORD HIGH LOW TEMPERATURE AT DFW ON DECEMBER 12
IS 64 AND 66 AT WACO...THE FORECAST LOW IS 65 FOR TONIGHT/SATURDAY
MORNING FOR BOTH LOCATIONS.

SATURDAY AND SATURDAY NIGHT...THE LARGE UPPER TROUGH IS EXPECTED
TO CONTINUE TO MOVE EAST SPREADING LARGE SCALE FORCING FOR ASCENT
OVER THE REGION. THIS IS A LARGE AND DYNAMIC STORM SYSTEM...AND
THE ANALYSIS OF LATEST MODEL GUIDANCE SUGGESTS THAT THIS STORM
SYSTEM WILL BRING TWO ROUNDS OF THUNDERSTORMS ACROSS NORTH AND
CENTRAL TEXAS FROM SATURDAY AFTERNOON THROUGH SATURDAY NIGHT.

THE FIRST ROUND OF THUNDERSTORMS IS EXPECTED TO BE PRIMARILY
LOCATED EAST OF INTERSTATE 35 FROM SATURDAY AFTERNOON THROUGH
SATURDAY EVENING. THIS CONVECTION IS EXPECTED TO BE WIDESPREAD AND
POSSIBLY ORGANIZED...HOWEVER PROBABLY NOT ORGANIZED IN TERMS OF
PROVIDING A SIGNIFICANT SEVERE WEATHER THREAT. THE INITIAL ROUND
OF STORMS EAST OF INTERSTATE 35 MAY PROVIDE A MARGINAL SEVERE
WEATHER THREAT...BUT LOOKS MOST LIKELY TO PRODUCE ORGANIZED AREAS
OF HEAVY RAINFALL AND POSSIBLY FLASH FLOODING. ISOLATED TO
SCATTERED THUNDERSTORMS MAY DEVELOP WEST OF INTERSTATE 35 LATE
SATURDAY AFTERNOON OR SATURDAY EVENING. IF THESE STORMS
DEVELOP...THEY HAVE A BETTER CHANCE AT PRODUCING SEVERE WEATHER.
THIS IS BROKEN DOWN BELOW:

FOR STORMS EAST OF INTERSTATE 35...CONFIDENCE IS HIGHEST THAT
THESE STORMS WILL DEVELOP FROM SATURDAY AFTERNOON THROUGH
EVENING...SO BUMPED POPS UP TO 80 TO 100 PERCENT AS A RESULT. DEEP
LAYER SHEAR IS CERTAINLY SUPPORTIVE OF SEVERE OR ORGANIZED
STORMS...HOWEVER INSTABILITY APPEARS TO BE LACKING. MORNING
DRIZZLE COMBINED WITH MEAGER MID-LEVEL LAPSE RATES DUE TO THE COLD
CORE OF THE UPPER TROUGH ALOFT REMAINING OUT WEST SATURDAY
AFTERNOON SEEMS TO REALLY REDUCE THE CHANCE OF ORGANIZED SEVERE
STORMS EAST OF INTERSTATE 35 THROUGH SATURDAY EVENING. THE
HEAVY RAIN THREAT COULD BE QUITE HIGH HOWEVER. 

FORECAST PWAT VALUES EAST OF INTERSTATE 35 ARE 1.75 TO 1.80"...IF
THIS VERIFIES IT WOULD EASILY EXCEED THE RECORD MEASURED PWAT FOR
THE REGION IN DECEMBER BY AT LEAST A TENTH OF AN INCH. THIS MAY
NOT SOUND VERY IMPRESSIVE...BUT IT REPRESENTS A NEARLY TROPICAL
AIRMASS IN MID DECEMBER! WINDS ALOFT ARE QUITE STRONG EAST OF
INTERSTATE 35 RESULTING IN A STORM MOTION TO THE NORTHWEST AT
50-55 KTS. THIS STORM MOTION WOULD NORMALLY PRECLUDE A SIGNIFICANT
FLOODING THREAT...HOWEVER LOOKING AT THE CONVECTION AS A SYSTEM AS
OPPOSED TO INDIVIDUAL STORMS YIELDS A VERY DIFFERENT ANALYSIS.
CORFIDI VECTORS INDICATE A CONVECTION SYSTEM MOTION OF ONLY 5 TO
10 KTS FROM 21Z TO 03Z SATURDAY AFTERNOON/EVENING. THIS STRONGLY
SUPPORTS TRAINING OF CONVECTION...ENHANCING THE THREAT OF HEAVY
RAINFALL AND FLOODING. HELD OFF ON A FLASH FLOOD WATCH FOR NOW AS
THERE ARE MODEL INCONSISTENCIES AS TO WHERE THIS BATCH OF TRAINING
CONVECTION WILL SET UP...NAMELY...HOW FAR EAST OF INTERSTATE 35
WILL THIS OCCUR? ASSUMING MODELS CONTINUE TO ADVERTISE THIS
THREAT...ONCE CONFIDENCE IN THE EXACT POSITION OF THIS TRAINING
CONVECTION IS HIGHER...A FLASH FLOOD WATCH MAY BE NEEDED ALONG AND
EAST OF THE INTERSTATE 35/35E CORRIDOR. 

FOR SATURDAY LATE AFTERNOON TO EVENING OUT WEST AND NORTHWEST...IF
STORMS DEVELOP HERE...THEY ARE MORE LIKELY TO BE ISOLATED TO
SCATTERED IN NATURE...AND WILL HAVE MORE CAPE DUE TO DIFFERENTIAL
COOLING ALOFT ASSOCIATED WITH UPPER LEVEL HEIGHT FALLS AND
PERSISTENT LOW-LEVEL WARM AIR ADVECTION. THE FORECAST INSTABILITY
IS STILL SOMEWHAT MARGINAL...BUT LIKELY SUFFICIENT FOR LOW-TOPPED
SUPERCELLS WEST OF INTERSTATE 35 AND NORTH OF INTERSTATE 20. THE
ISOLATED STORM MODE MAY BE DIFFICULT TO MAINTAIN...SO THERE MAY
ONLY BE A 3-4 HOUR WINDOW FOR SUPERCELL THUNDERSTORMS IN THIS AREA
TOMORROW. AS STRONG FORCING FOR ASCENT CONTINUES TO SPREAD
EAST...CONVECTIVE MERGERS ARE MUCH MORE LIKELY...SUPPORTING A
TRANSITION TO A LINEAR OR MULTI-CELL STORM MODE BY LATE SATURDAY
EVENING.

FINALLY...THE SECOND ROUND OF THUNDERSTORMS. IT IS UNCLEAR IF
ROUND 2 WILL DEVELOP FROM SUPERCELL STORM MERGERS AS DISCUSSED
ABOVE...OR SIMPLY STRONG CONVECTION DEVELOPING ALONG A NORTH TO
SOUTH ORIENTED LINE ASSOCIATED WITH A PACIFIC FRONT DRIVEN EAST BY
THE UPPER TROUGH DYNAMICS ALOFT. THE MOISTURE IS DEEP ENOUGH THAT
A LINE OF STORMS IS VERY LIKELY TO DEVELOP AND MOVE QUICKLY EAST
ACROSS NORTH AND CENTRAL TEXAS AFTER MIDNIGHT SATURDAY NIGHT/EARLY
SUNDAY MORNING. WENT AHEAD WITH 80 TO 90 POPS ACROSS THE REGION AS
A RESULT. THIS LINE OF STORMS WILL PROBABLY BE MOVING TOO FAST TO
SUPPORT A SIGNIFICANT FLOODING THREAT ALL BY ITSELF...HOWEVER IF
FLOODING OCCURS EAST OF INTERSTATE 35 BY SATURDAY EVENING...ANY
ADDITIONAL RAINFALL MAY EXACERBATE ONGOING FLOODING ISSUES. EVEN
THOUGH IT SEEMS STRANGE...THE MOST WIDESPREAD SEVERE WEATHER
THREAT FOR NORTH AND CENTRAL TEXAS PROBABLY EXISTS WITH THIS
OVERNIGHT SQUALL LINE.

THE DEEP MOISTURE IN PLACE WILL KEEP LOW-LEVEL LAPSE RATES NEAR
THE MOIST ADIABATIC LAPSE RATE OF AROUND 5.5 DEG C PER KM. THE
MID-LEVEL LAPSE RATES VERY NEAR THE LINE WILL BE STEEPENING DUE TO
DYNAMIC COOLING ALOFT FROM THE UPPER TROUGH. THE LOW-LEVEL SHEAR
PROFILE WILL BE VERY STRONG...WITH 0-3 KM SHEAR MAGNITUDES ON THE
ORDER OF 50 KTS. THESE 3 COMPONENTS FALL WITHIN THE FAVORABLE
PARAMETER SPACE FOR THE RECENTLY DEVELOPED SEVERE HAZARDS IN
ENVIRONMENTS WITH REDUCED BUOYANCY /SHERB/ INDEX WHICH WAS
DEVELOPED TO HIGHLIGHT ENVIRONMENTS FAVORABLE FOR SEVERE WEATHER
WHEN CAPE IS LOW BUT SHEAR IS HIGH. THE ENVIRONMENT IS SUPPORTIVE
OF SEVERE WEATHER BASED ON THIS RESEARCH...WITH DAMAGING WINDS THE
MOST LIKELY HAZARD. BRIEF MESO- VORTEX TORNADOES WOULD BE POSSIBLE
AS WELL. THIS LINE SHOULD MOVE FROM WEST TO EAST ACROSS THE AREA
QUICKLY SATURDAY NIGHT...RESULTING IN A DRY FORECAST FOR MOST
LOCATIONS ON SUNDAY.

SUNDAY THROUGH MONDAY...MAINTAINED A DRY AND COOLER FORECAST WITH
SUBSIDENCE ALOFT AND DRY AIR ADVECTION BEHIND THE PACIFIC FRONT
AND SQUALL LINE SUNDAY MORNING.

TUESDAY THROUGH THURSDAY...ANOTHER UPPER LEVEL STORM SYSTEM
APPROACHES THE REGION. THE ECMWF IS GENERALLY DRIER WITH THIS NEXT
SYSTEM AND THE CURRENT FORECAST SIDES WITH THE ECMWF. THE GFS
INDICATES QUITE A BIT OF PRECIPITATION ON WEDNESDAY DUE TO LIFT
OVER A COOL FRONTAL BOUNDARY. DISCOUNTED THE GFS SOLUTION FOR NOW
AS THE MODEL OUTPUT FOR QPF GENERATES QPF EXTREMELY FAST WITH
LIMITED TIME FOR MOISTURE ADVECTION OR STRONG LIFT BEHIND THE
FRONTAL BOUNDARY. WILL CONTINUE TO WATCH THE EVOLUTION OF THIS MID
WEEK STORM SYSTEM IN LATER FORECASTS.

CAVANAUGH

&&

.AVIATION...
/ISSUED 1155 PM CST THU DEC 10 2015/
/06Z TAFS/

CONCERNS...FOG POTENTIAL OVERNIGHT. OTHERWISE...VFR WITH CIRRUS.

AT MIDNIGHT...A WEAK FRONTAL BOUNDARY IS JUST EAST OF TAF SITES.
FOG HAS DEVELOPED IN THE HUMID AIR EAST OF THE BOUNDARY. ALTHOUGH
THE BOUNDARY IS BECOMING INCREASINGLY DIFFUSE...WINDS AT TAF SITES
SHOULD MAINTAIN A WESTERLY COMPONENT...KEEPING THE FOG TO THE
EAST. WITH LEE TROUGHING DEVELOPING...WINDS WILL STEADILY BACK
OVERNIGHT...BECOMING SOUTHERLY BY DAYBREAK FRIDAY. THE WESTERN
EDGE OF THE FOG BOUNDARY MAY APPROACH LOVE FIELD...BUT CONFIDENCE
IS LOW AT THIS TIME...AND NO FOG IS MENTIONED IN THE TAFS.

WIND SPEEDS WILL INCREASE ON FRIDAY...WITH SOME GUSTS ABOVE 20KTS
FROM MIDDAY INTO THE AFTERNOON AND EVENING HOURS. MVFR CEILINGS
WILL ARRIVE FRIDAY EVENING AND PERSIST INTO SATURDAY MORNING.

EXTENDED...
THUNDERSTORMS MAY IMPACT TAF SITES LATE SATURDAY AND SATURDAY
NIGHT.

WACO...
WINDS HAVE BECOME NORTHWESTERLY BUT SHOULD GRADUALLY BACK THROUGH
DAYBREAK. BY THE TIME SIGNIFICANT MOIST ADVECTION BEGINS...THE
UNSEASONABLY WARM WEATHER SHOULD PREVENT LOW CEILINGS. HOWEVER...
A FEW CUMULUS CLOUDS WILL BE POSSIBLE FRIDAY AFTERNOON.

25


&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  78  65  72  54  61 /   0  20  50  90  40 
WACO, TX              78  65  73  54  62 /   0  20  60  90  40 
PARIS, TX             74  64  72  57  60 /   5  20  80  90  80 
DENTON, TX            78  63  71  52  60 /   0  20  50  90  40 
MCKINNEY, TX          76  64  71  54  59 /   0  20  60  90  50 
DALLAS, TX            78  65  72  55  61 /   0  20  60  90  50 
TERRELL, TX           75  65  72  55  61 /   0  20  80  90  60 
CORSICANA, TX         78  66  74  56  62 /   5  20  80  90  60 
TEMPLE, TX            79  66  72  55  62 /   0  20  60  90  40 
MINERAL WELLS, TX     81  62  71  51  59 /   0  10  40  80  20 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR TXZ094-095-
105>107-120>123.

&&

$$