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

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000
FXUS64 KFWD 181441
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
941 AM CDT SAT APR 18 2015

.UPDATE...
MORNING UPPER AIR DATA AND SHORT-TERM MODEL GUIDANCE HAS
IDENTIFIED A SHORTWAVE TROUGH THAT IS PIVOTING AROUND THE UPPER
LOW OVER COLORADO. THIS SHORTWAVE WILL TRACK THROUGH TEXAS THIS
AFTERNOON AND EVENING. A DRY LINE IS FORECAST TO SET UP JUST WEST
OF THE CWA BORDER THIS AFTERNOON AND WILL BECOME THE FOCUS FOR
SCATTERED CONVECTION WHEN FORCING FROM THE SHORTWAVE TROUGH
ARRIVES. CONVECTIVE INITIATION SHOULD START AFTER 3 PM JUST WEST
OF THE CWA...WITH THESE STORMS MOVING/DEVELOPING GRADUALLY
NORTHEASTWARD INTO AND THROUGH THE CWA DURING THE LATE AFTERNOON
AND EVENING HOURS. GIVEN THE EXPECTED TIMING...HAVE LOWERED THE
POPS ALONG AND EAST OF I-35 FOR THE TODAY PERIOD AS ANY
RAIN/STORMS SHOULD HOLD OFF UNTIL THIS EVENING FOR THESE AREAS.

THERE IS A LACK OF LOW LEVEL WIND FLOW EVIDENT IN THE MORNING
DATA AND THE AIRMASS HAS BEEN FAIRLY WORKED OVER BY THE CONVECTION
FROM YESTERDAY AND LAST NIGHT. HOWEVER THE APPROACH OF THE
SHORTWAVE TROUGH WILL HELP TURN WINDS TO THE SOUTH BY THE
AFTERNOON...THEREBY INCREASING MOISTURE/THETA-E ADVECTION AND BULK
SHEAR VALUES ACROSS NORTH TEXAS. TEMPERATURES WILL ALSO WARM INTO
THE UPPER 70S AND LOWER 80S OVER NORTH TEXAS TODAY...WHICH WILL
YIELD GENERALLY 1000-2000 J/KG OF SURFACE BASED CAPE. THUS THE
AIRMASS SHOULD BE RECHARGED JUST ENOUGH TO SUPPORT SCATTERED
CONVECTION WITH A POTENTIAL FOR SEVERE WIND AND HAIL...ESPECIALLY
WEST OF I-35 IN THE LATE AFTERNOON HOURS. THE SEVERE THREAT WILL
DIMINISH AS THE STORMS HEAD EAST OF I-35 DUE TO THE LOSS OF
HEATING AND INCREASING CINH.

TR.92

&&

.AVIATION...
/ISSUED 707 AM CDT SAT APR 18 2015/
/12Z TAFS/

PREVIOUS RAINFALL AND LIGHT WINDS HAVE MADE THE TAFS QUITE
CHALLENGING THROUGH THE FIRST 3-6 HRS OF THE FORECAST. TO ADD TO
THE MIX...SUBSIDENCE AND SOME PARTIAL BREAKS IN THE MULTIPLE
LAYERS OF CLOUDS ARE CAUSING VSBYSO FLUCTUATE FROM P6SM TO 1/4SM
IN FOG FROM THE TAF SITES AND AREAS TO THE WEST. WILL CARRY
PREVAILING MVFR VSBYS W/TEMPO IFR-VLIFR VSBYS IN SHALLOW GROUND
FOG THROUGH LATE MORNING. AS WARMING TEMPERATURES AND STRONGER SE
WINDS ARRIVE BY MIDDAY...LOOK FOR VFR CIGS TO PREVAIL.

AN UPPER LOW OVER COLORADO WILL DRIFT OVER THE HIGH PLAINS OF
WESTERN KS BY TONIGHT. ANOTHER STORM CLUSTER WILL FORM OFF THE
WEST TX DRYLINE LATE THIS AFTERNOON AND MIGRATE EWD TOWARD I-35
AND THE TAF SITES IN THE 23Z-04Z TIME FRAME ONCE AGAIN. HAVE
BROUGHT STORMS IN AN HOUR SOONER AT AFW/FTW...BUT OTHERWISE WILL
CARRY A 2-HR TEMPO GROUP FOR THE HIGHEST CONFIDENCE TIMING FOR
TSRA WITH MVFR CIGS/CB. WITH THE UPPER LOW FURTHER EAST COMPARED
TO THE SAME TIME LAST NIGHT...WE DO NOT EXPECT THE CONVECTIVE
COMPLEX TO HANG AROUND QUITE AS LONG THROUGH 06Z LIKE FRIDAY
EVENING.

WE EXPECT LIGHT N/NE TO VRB SURFACE WINDS UNDER 5 KTS THROUGH
MID-LATE MORNING. THE ENVIRONMENTAL FLOW SHOULD TAKES OVER WITH
S/SE WINDS NEAR 10 KTS DURING AFTERNOON...BECOMING SOUTHERLY 5-10
KTS OVERNIGHT. IT/S HIGHLY POSSIBLE THAT THIS FLOW WILL BE DISTURBED
BY CONVECTIVE OUTFLOW ONCE AGAIN WITH DIFFERING DIRECTIONS AND
SPEEDS...BUT THAT WILL NEED TO BE ADDRESSED ON LATER TAFS WHEN
CONFIDENCE IS HIGHER.

MORE MVFR/IFR CONDITIONS MAY RETURN SUNDAY MORNING...BUT SHOULD
OCCUR MAINLY AFTER 12Z AND BEYOND THIS TAF CYCLE.

05/


&&



.PREV DISCUSSION... /ISSUED 415 AM CDT SAT APR 18 2015/
THE UPPER LOW THAT HAS BEEN PARKED OVER THE FOUR CORNERS IS
BEGINNING TO DISLODGE...AND BY THIS TIME SUNDAY MORNING IT WILL BE
OVER THE HIGH PLAINS NEAR THE COLORADO/KANSAS BORDER. THIS WILL
STEADILY VEER THE 700MB FLOW ACROSS WEST TEXAS TODAY...HELPING TO
NUDGE THE DRYLINE FARTHER EAST THAN IN RECENT DAYS. ALTHOUGH
WITHIN THE FIRST 24 HOURS OF THE LATEST GUIDANCE...OPERATIONAL
SOLUTIONS VARY WIDELY ON THE LATE AFTERNOON POSITION. ALTHOUGH THE
NAM IS AMONG THE FARTHEST WEST...WHICH IS UNUSUAL IN THIS
SCENARIO...THE CONSENSUS AMONG THE MESOSCALE GUIDANCE IS FOR THE
BOUNDARY TO REACH A VERNON-SAN ANGELO LINE NEAR PEAK HEATING. OUR
FORECAST WILL FAVOR THIS POSITION. BASED ON THE MID-LEVEL FLOW...
THERE SHOULD BE A BULGE NEAR THE RED RIVER. THE RAP AND TTU WRF
SHOW THIS CLEARLY...ADDING TO THE CONFIDENCE IN THEIR EVOLUTION OF
THE BOUNDARY TODAY.

THE ATMOSPHERE ACROSS NORTH TEXAS HAS BEEN WELL WORKED OVER. THIS
STABILITY...COUPLED WITH SUBSIDENCE IN THE WAKE OF A DEPARTING
DISTURBANCE...SHOULD PRECLUDE MUCH ADDITIONAL PRECIPITATION THIS
MORNING. WEAK LOW-LEVEL FLOW WILL RESULT IN NEGLIGIBLE MOIST
ADVECTION TODAY...AND DESTABILIZATION THIS AFTERNOON WILL BE
PRIMARILY GOVERNED BY SURFACE HEATING. ALTHOUGH THE I-35 CORRIDOR
WILL BE SLOW TO CLEAR TODAY...WESTERN NORTH TEXAS WILL SEE
SUFFICIENT SUNSHINE. EXPECT THUNDERSTORMS TO DEVELOP ALONG THE
DRYLINE MID TO LATE AFTERNOON. THOUGH RELATIVELY WEAK...THE
STEERING FLOW ALOFT SHOULD GUIDE THE ACTIVITY EAST THROUGH NORTH
TEXAS THIS EVENING. EVEN THOUGH THE SURFACE LAYER WILL BE
STEADILY STABILIZING AT THAT TIME...THE COLD POOL ASSOCIATED WITH
AN ORGANIZED MCS SHOULD PROLONG THE LIFESPAN OF ITS UPDRAFTS. THIS
WILL MAINTAIN A HAIL THREAT WELL INTO THE EVENING. THIS IS NOT THE
TYPICAL SETUP FOR A SQUALL LINE...BUT A WELL ORGANIZED COMPLEX
COULD POSE A WIND THREAT AS WELL. THE SPEED SHOULD BE SUFFICIENT
TO AVOID SIGNIFICANT FLOODING CONCERNS IN MOST AREAS...BUT WHERE
HEAVY RAIN HAS FALLEN RECENTLY...ADDITIONAL RAINFALL COULD
REAGGRAVATE FLOODING ISSUES.

AS THE UPPER LOW EJECTS THROUGH THE CENTRAL PLAINS...IT WILL SURGE
A COLD FRONT THROUGH THE REGION. WITH WIDESPREAD ACTIVITY THIS
EVENING...LARGE-SCALE SUBSIDENCE INVADING...AND VEERING LOW-LEVEL
FLOW EARLY SUNDAY...THE ATMOSPHERE SHOULD BE UNABLE TO PRODUCE ANY
FRONTAL PRECIPITATION. THE EXCEPTION WOULD BE EAST TEXAS...WHERE
THE MOISTURE PROFILE WILL BE MORE FAVORABLE...AND THE FRONT WILL
ARRIVE DURING THE WARM AFTERNOON HOURS. ABUNDANT APRIL SUNSHINE
AND A PRONOUNCED DOWNSLOPE WIND SHOULD OFFSET ANY COLD ADVECTION
BEHIND THE FRONT...AND TEMPERATURES SHOULD REACH THE 80S IN MANY
AREAS SUNDAY AFTERNOON. THE COOL AIR WILL ARRIVE SUNDAY NIGHT...
AND RURAL AREAS IN THE NORTHERN HALF OF THE CWA WILL LIKELY DIP
INTO THE 40S MONDAY AND TUESDAY MORNING.

ZONAL FLOW WILL PREVAIL MUCH OF THE UPCOMING WEEK. THE NEXT WAVE
EMBEDDED IN THIS WESTERLY FLOW WILL ARRIVE AROUND TUESDAY...BUT
AT THAT TIME...BOUNDARY LAYER MOISTURE MAY NOT HAVE BEEN ABLE TO
SUFFICIENTLY RECOVER. ADDITIONAL RIPPLES WILL FOLLOW...MAINTAINING
RAIN CHANCES. HOWEVER...POPS ARE NOTHING MORE THAN CLIMATOLOGY.
EXTENDED GUIDANCE IS IN REMARKABLY GOOD AGREEMENT WITH
UNSEASONABLE STRONG SHORTWAVE RIDGING AS THE NEXT UPPER LOW ENTERS
THE DESERT SOUTHWEST. GFS MOS TEMPS FOR THURSDAY AND FRIDAY ARE
NEAR 90 DEGREES. WITH PERFECT PROG 850MB TEMPS AROUND 20C...THIS
IS NOT OUT OF THE QUESTION. A BIT CONCERNED THAT CLOUD COVER MAY
PUT A DAMPER ON THE SPRING FEVER...AND FOR NOW...WILL KEEP
TEMPERATURES CLOSER TO CLIMATOLOGY.

25



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  79  60  80  53  73 /  20  50  10   5   5
WACO, TX              80  60  83  53  75 /  20  50  10   5   5
PARIS, TX             75  58  77  50  70 /  20  40  20   5   0
DENTON, TX            77  57  79  49  72 /  30  50  10   5   5
MCKINNEY, TX          78  58  79  51  73 /  20  50  10   5   0
DALLAS, TX            80  62  81  54  74 /  20  50  10   5   5
TERRELL, TX           78  60  80  52  74 /  20  50  10   5   5
CORSICANA, TX         79  61  82  52  75 /  20  50  20   5   5
TEMPLE, TX            79  60  84  53  74 /  20  50  10   5   5
MINERAL WELLS, TX     81  55  79  48  74 /  40  50  10   5   5

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$


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