WPC Met Watch |
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Mesoscale Precipitation Discussion: #0677 (2017) |
(Issued at 158 AM EDT SUN AUG 13 2017
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MPD Selection |
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MESOSCALE PRECIPITATION DISCUSSION 0677
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EDT SUN AUG 13 2017
AREAS AFFECTED...NORTHERN TX...SOUTHEAST OK...SOUTHWEST AR...FAR
NORTHWEST LA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 130600Z - 131200Z
SUMMARY...MORE ORGANIZED COVERAGE OF HEAVY SHOWERS AND
THUNDERSTORMS IS EXPECTED OVERNIGHT AND THROUGH THE EARLY MORNING
HOURS. SLOW CELL MOTION AND INTENSE RAINFALL RATES ARE LIKELY TO
CAUSE FLASH FLOODING.
DISCUSSION...THE LATEST GOES WV IMAGERY SHOWS AN UPPER LEVEL
SHORTWAVE TROUGH MOVING GRADUALLY EAST ACROSS WEST-CENTRAL TX AND
THIS ENERGY WILL BE INTERACTING WITH A WAVY QUASI-STATIONARY FRONT
ACROSS PARTS OF CENTRAL AND NORTHERN TX. ALREADY THERE IS SOME
RATHER CONCENTRATED AREAS OF COLD-TOPPED CONVECTION WITH HEAVY
SHOWER AND THUNDERSTORM ACTIVITY NOTED ALONG AND SOUTH OF THE RED
RIVER...AND GENERALLY NORTH OF THE FRONT.
OVER THE NEXT SEVERAL HOURS...THE APPROACHING SHORTWAVE ENERGY IS
EXPECTED TO HELP DEVELOP A WAVE OF LOW PRESSURE ALONG THE FRONT
OVER NORTH-CENTRAL TX WHICH COUPLED WITH AN INCREASING S/SW LOW
LEVEL JET SHOULD HELP FOCUS GREATER MOISTURE AND INSTABILITY ALONG
THE FRONT AND ALSO IN A MORE ELEVATED FASHION NORTH OF IT ACROSS
THE RED RIVER GIVEN A STRENGTHENING WARM ADVECTION/ISENTROPIC LIFT
SIGNAL. THE RESULT SHOULD BE AN INCREASE IN CONVECTIVE
COVERAGE/INTENSITY WITH NUMEROUS SLOW-MOVING CLUSTERS OF HEAVY
SHOWERS AND THUNDERSTORMS FOCUSING ALONG AND NORTH OF THE FRONT
OVER AREAS OF NORTHERN AND EVENTUALLY NORTHEAST TX...AND ALSO
ACROSS THE RED RIVER INTO ADJACENT AREAS OF SOUTHEAST OK. AREAS
OF SOUTHWEST AR AND POTENTIALLY EVEN FAR NORTHWEST LA MAY SEE
CONVECTION ARRIVING TOWARD DAWN AS THE ENERGY UPSTREAM GRADUALLY
SHIFTS OFF TO THE EAST.
THE LATEST RAP FORECASTS THE LOW LEVEL JET TO INCREASE TO NEAR 40
KTS ALONG WITH PWATS REACHING OVER 2.25 INCHES. THE 03Z CIRA-LPW
DATA SHOWED A NOTABLE CONCENTRATION OF MOISTURE UP IN THE 500/300
MB LAYER WITH THE APPROACHING SHORTWAVE TROUGH...AND THIS WILL
HELP FACILITATE MORE EFFICIENT RAINFALL PROCESSES FOR ENHANCED
RAINFALL RATES IN THE 06Z TO 12Z TIME PERIOD AS CONVECTION
ORGANIZES FURTHER. RAINFALL AMOUNTS OF AS MUCH AS 3 INCHES/HR WILL
BE POSSIBLE.
THE LATEST THINKING IS THAT THE HEAVIEST AMOUNTS OF RAIN WILL BE
BASICALLY ALONG THE RED RIVER OVERNIGHT...WITH THE LATEST HRRRX
GUIDANCE APPEARING TO HAVE THE BEST HANDLE ON THE CURRENT
ACTIVITY. IT SUGGESTS AS MUCH AS 4 TO 6 INCHES OF ADDITIONAL RAIN
THROUGH 12Z...AND THIS SEEMS REASONABLE GIVEN THE FAVORABLE
THERMODYNAMICS...LOW LEVEL JET AND UPSTREAM SHORTWAVE AXIS. SOME
ISOLATED HEAVIER AMOUNTS OVER 6 INCHES CANNOT BE RULED OUT. FLASH
FLOODING IS LIKELY...AND ESPECIALLY IN VICINITY OF THE MORE
URBANIZED CORRIDORS WHICH INCLUDES THE DALLAS-FORT WORTH
METROPOLITAN AREA.
ORRISON
ATTN...WFO...FWD...LZK...OUN...SHV...TSA...
ATTN...RFC...ABRFC...LMRFC...WGRFC...
LAT...LON 34619503 34089370 33309327 32559356 32369418
32489510 32439650 32209757 32339826 32839841
33499787 34369680
Last Updated: 158 AM EDT SUN AUG 13 2017
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