AP-TX--FTW-TX N Area Forecast Discussion, TX

000

FXUS64 KFWD 151103

AFDFWD

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE FORT WORTH TX

603 AM CDT WED JUL 15 2015

.AVIATION...

VFR CONDITIONS WILL PERSIST THOUGH THE TAF PERIOD UNDER A STRONG

UPPER LEVEL RIDGE. SOUTHERLY WINDS WILL REMAIN AROUND 10 KNOTS

THROUGH THURSDAY AFTERNOON.

78.JG

&&

.PREV DISCUSSION... /ISSUED 321 AM CDT WED JUL 15 2015/

EARLY MORNING WATER VAPOR SATELLITE IMAGERY CONTINUED TO SHOW A

LARGE AREA OF HIGH PRESSURE ALOFT CENTERED OVER NORTH CENTRAL

TEXAS. THIS FEATURE IS EXPECTED TO REMAIN THE DOMINANT PLAYER IN

CONTROL OF THE LOCAL AREA WEATHER PATTERN THROUGH EARLY NEXT WEEK.

TYPICALLY UNDER A RIDGE OF HIGH PRESSURE IN THE SUMMER ACROSS THE

SOUTHERN PLAINS...THE LONGER THE RIDGE HOLDS IN PLACE...THE MORE

THE HEAT BUILDS UP. THAT HAS NOT BEEN THE CASE THUS FAR UNDER THIS

UPPER LEVEL RIDGE THAT HAS HELD STEADY FOR NEARLY A WEEK NOW. THE

PRIMARY REASON THAT THE TEMPERATURES HAVE NOT BEEN ON A SLOW AND

STEADY RISE ALL WEEK IS LIKELY DUE TO PERSISTENT SOUTHERLY FLOW

FROM THE SURFACE UP TO ABOUT 1 MILE ABOVE GROUND LEVEL (AROUND 850

MB). EVEN THOUGH IT MAY NOT FEEL COOLER ALONG THE GULF COAST THIS

TIME OF YEAR...TEMPERATURES ALONG THE GULF COAST AND OVER THE

WESTERN GULF OF MEXICO ARE TYPICALLY 10 DEGREES COOLER THAN

TEMPERATURES FARTHER INLAND DUE TO THE FACT THAT WATER DOES NOT

HEAT OR COOL AS QUICKLY AS LAND. AS A RESULT...LOW-LEVEL SOUTHERLY

FLOW REPRESENTS A WEAK COLD AIR ADVECTION PATTERN. IF OUR LOW-

LEVEL WINDS WERE SIMPLY VEERED BY 20 TO 30 DEGREES TOWARDS THE

WEST...TEMPERATURE ADVECTION WOULD BE NEUTRAL FAVORING A BUILD UP

OF HEAT UNDER OUR DOME OF HIGH PRESSURE ALOFT. AS LONG AS OUR LOW

LEVEL FLOW REMAINS MORE SOUTHERLY THAN SOUTHWESTERLY...DAILY HIGH

TEMPERATURES WILL LIKELY HOLD STEADY IN THE UPPER 90S FOR MOST

LOCATIONS.

FOR TODAY...HEAT INDEX VALUES ARE EXPECTED TO CLIMB TO AROUND 100

DEGREES FOR MOST LOCATIONS...WHICH WOULD BE A FEW DEGREES COOLER

THAN THE PAST COUPLE OF DAYS. HEAT INDICES OF 100 DEGREES ARE NOT

COOL BY ANY STRETCH...HOWEVER THERE IS REASON TO BELIEVE IT WILL

NOT FEEL QUITE AS HUMID AND SWAMPY OUTSIDE THIS AFTERNOON. 08Z/3AM

DEW POINT VALUES WERE RUNNING ABOUT 3 DEGREES LOWER/DRIER THAN

YESTERDAY AT THIS TIME. AS A RESULT...THINK THAT AFTERNOON

HUMIDITY VALUES ARE LIKELY TO BE LOWER TODAY...MAKING OUR UPPER

90S TEMPERATURES A LITTLE MORE COMFORTABLE THIS AFTERNOON.

FOR THE REMAINDER OF THE WEEK...MAINTAINED HIGHS IN THE UPPER 90S

FOR MOST LOCATIONS AS MODEL GUIDANCE SUGGESTS THAT OUR WEATHER

PATTERN WILL REMAIN FAIRLY CONSISTENT. PERSISTENT SOUTHERLY FLOW

MAY CAUSE HUMIDITY VALUES TO RISE AGAIN AS WE HEAD INTO THE

WEEKEND...SO MAX HEAT INDEX VALUES ARE LIKELY TO REMAIN IN THE

100 TO 105 DEGREE RANGE FOR THE NEXT SEVERAL DAYS. NO HEAT

ADVISORY IS PLANNED AT THIS TIME WITH HEAT INDEX VALUES EXPECTED

TO HOLD JUST BELOW 105 DEGREES.

THIS WEEKEND...MODELS CONTINUE TO STRENGTHEN THE UPPER LEVEL RIDGE

OVER THE REGION. IF THIS OCCURS...IT IS POSSIBLE FOR HIGH

TEMPERATURES TO CLIMB A FEW DEGREES...BRING HIGHS FROM THE UPPER

90S TO RIGHT AROUND OR JUST ABOVE 100 DEGREES. FOR NOW KEPT HIGHS

A DEGREE OR TWO BELOW 100 SIMPLY BECAUSE THE LOW-LEVEL WINDS DO

NOT REALLY CHANGE DIRECTION IN MODEL GUIDANCE. THE BUILD UP OF

HEAT AND THE STRENGTH OF AN UPPER LEVEL RIDGE CAN BE DEPENDENT

UPON ONE ANOTHER.

THERE IS A POSITIVE FEEDBACK LOOP IN WHICH THE UPPER RIDGE CAUSES

CLEAR SKIES WHICH ALLOWS US TO HEAT UP QUITE A BIT EACH DAY. THE

BUILD UP OF HEAT IN TURN RESULTS IN A TROPOSPHERIC RESPONSE TO

EXPAND IN THICKNESS CAUSING THE UPPER LEVEL RIDGE TO STRENGTHEN.

WHEN SOME FACTOR INTERRUPTS THIS POSITIVE FEEDBACK LOOP...I.E.

PERSISTENT WEAK LOW-LEVEL WARM AIR ADVECTION...MODELS CAN

OVERESTIMATE THE STRENGTH OF HEATING AND RIDGING ALOFT.

AT ANY RATE...IT WILL FEEL HOT EITHER WAY... IT IS REALLY JUST A

MATTER OF WILL WE FEEL HOT BECAUSE THE AIR TEMPERATURE WILL SLOWLY

CLIMB...OR BECAUSE THE HUMIDITY WILL REMAIN HIGH WHILE

TEMPERATURES REMAIN IN THE UPPER 90S? EITHER WAY...HEAT INDEX

VALUES WILL HOLD IN THE 100 TO 105 DEGREE RANGE AND ANYONE WITH

OUTDOOR PLANS SHOULD PLAN TO MITIGATE THE IMPACTS OF THE HEAT.

FOR EARLY NEXT WEEK...MODELS INDICATE THAT A STRONG SHORTWAVE

TROUGH WILL MOVE OVER THE CENTRAL PLAINS FLATTENING OUT OUR

PERSISTENT UPPER LEVEL RIDGE...AND BRINGING A WEAK COLD FRONT

SOUTH JUST ACROSS THE RED RIVER ON TUESDAY. IF THIS VERIFIES...

MONDAY WILL PROBABLY BE HOT AS LOW-LEVEL WINDS WILL VEER AROUND TO

THE SOUTHWEST OUT AHEAD OF THE COLD FRONT. WE WOULD VERY LIKELY

CLIMB ABOVE 100 DEGREES IF THE UPPER LEVEL RIDGE STARTS TO FLATTEN

OUT ON MONDAY AS A RESULT. TUESDAY AND WEDNESDAY WOULD BE A FEW

DEGREES COOLER SIMPLY DUE TO THE PRESENCE OF SOME UPPER LEVEL

CLOUDS AND WEAKER RIDGING ALOFT. IF THE FRONT ACTUALLY MOVE SOUTH

OF THE RED RIVER...SCATTERED THUNDERSTORMS WOULD LIKELY DEVELOP

TUESDAY AND POSSIBLY WEDNESDAY AFTERNOON NORTH OF INTERSTATE 20 TO

THE RED RIVER.

FOR NOW...RAISED TEMPERATURES ON MONDAY A DEGREE OR TWO...AND

PLACED SOME 10 POPS IN ACROSS THE NORTHERN CWA TUESDAY AND

WEDNESDAY AFTERNOON WITHOUT MENTIONING THUNDER IN THE FORECAST AT

THIS TIME. IF THE COLD FRONT GETS HERE...POPS WILL NEED TO BE

RAISED. DID NOT COMPLETELY BUY IN ON A COLD FRONT SINKING SOUTH OF

THE RED RIVER AT THIS TIME BECAUSE CLIMATOLOGY DICTATES THAT THIS

DOES NOT HAPPEN VERY OFTEN IN MID TO LATE JULY. ADDITIONALLY...

ONLY YESTERDAY THE CONSENSUS OF GUIDANCE WAS TO KEEP THE UPPER

LEVEL RIDGE IN PLACE AND KEEP ALL COLD FRONTS WELL NORTH INTO THE

CENTRAL PLAINS. WOULD LIKE TO SEE MORE RUN TO RUN/DAY TO DAY

CONSISTENCY OUT OF MODEL GUIDANCE BEFORE JUMPING ON A SOLUTION

THAT IS SOMEWHAT UNUSUAL FOR THIS TIME OF YEAR.

CAVANAUGH

&&

.PRELIMINARY POINT TEMPS/POPS...

DALLAS-FT. WORTH, TX 97 77 97 78 97 / 0 0 0 0 5

WACO, TX 95 74 96 76 97 / 0 0 0 5 5

PARIS, TX 96 74 95 76 95 / 0 0 0 0 5

DENTON, TX 98 75 97 77 96 / 0 0 0 0 5

MCKINNEY, TX 96 75 96 77 96 / 0 0 0 0 5

DALLAS, TX 98 78 98 79 97 / 0 0 0 0 5

TERRELL, TX 95 75 96 76 97 / 0 0 0 0 5

CORSICANA, TX 95 74 95 76 97 / 0 0 0 5 5

TEMPLE, TX 95 74 96 75 96 / 0 0 0 5 5

MINERAL WELLS, TX 95 73 97 75 98 / 0 0 0 0 5

&&

.FWD WATCHES/WARNINGS/ADVISORIES...

NONE.

&&

$$

78

Delivered by Weather Underground Inc. Wed Jul 15 2015 7:03AM EDT