Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 170355
AFDOUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
1055 PM CDT THU APR 16 2015

.DISCUSSION...
THE 06Z AVIATION DISCUSSION FOLLOWS....

&&

.AVIATION...
A LARGE CUTOFF UPPER-LEVEL LOW SPINNING OVER THE FOUR CORNERS
REGION WILL CAUSE SPORADIC TSRA AND CLUSTERS OF TSRA OVER OK/N TX
THROUGH TOMORROW NIGHT. IT IS EXTREMELY DIFFICULT TO TIME THE
STORMS...SINCE THERE IS NO SINGLE FOCUS THAT WE CAN TRACK.
SO...THE TAFS ARE BASED MAINLY ON THE CONSENSUS OF MODEL
OUTPUT...WHICH IS ADMITTEDLY NOT VERY ACCURATE. THESE SAME MODELS
SUGGEST LOW CLOUDS AND PERHAPS FOG WILL SPREAD NW ACROSS THE
REGION TOWARD SUNRISE...AND WHILE THIS SCENARIO IS BELIEVABLE...IT
IS UNLIKELY THAT CONDITIONS WILL BE QUITE AS BAD AS THE MODELS
SUGGEST. GULF STRATUS LAYERS TYPICALLY HAVE BASES AROUND 1500 FT
OVER MOST OF OK/N TX THIS TIME OF YEAR...WHICH IS WHAT WE HAVE IN
THE PRELIMINARY TAFS.

SOME IF CONDITIONS WARRANT...SOME CHANGES TO THIS FORECAST MAY BE
MADE BEFORE THE ACTUAL TAF ISSUANCE AT ABOUT 0530Z.

&&

.PREV DISCUSSION... /ISSUED 924 PM CDT THU APR 16 2015/

DISCUSSION...
A COMPLEX OF THUNDERSTORMS HAD DEVELOPED OVER NORTHWEST
OKLAHOMA BY LATE THIS EVENING. A WAKE LOW APPEARS TO BE DEVELOPING
WITHIN THE COMPLEX...LEADING TO RATHER STRONG WINDS IN ELLIS
COUNTY. THESE WINDS MAY EXPAND OR CONTINUE TO SHIFT TO THE SOUTH
WITH TIME. THEY ARE TOO SMALL-SCALE TO REPRESENT IN A REASONABLE
WAY IN THE FORECAST.

SHORT-RANGE MODELS SHOW A GENERAL TENDENCY OF THE EXISTING STORM
COMPLEX TO START SHIFTING EAST WITH TIME...REACHING CENTRAL AND/OR
NORTH-CENTRAL OKLAHOMA SEVERAL HOURS AFTER MIDNIGHT. DETAILS
REMAIN SKETCHY...BUT THE OVERALL CONCEPT IS CONSISTENT AND IS
REASONABLE...GIVEN THE CURRENT SITUATION.

THE FORECAST WAS UPDATED EARLIER TO ACCOUNT FOR RAIN TRENDS AND
THEIR LARGE-SCALE EFFECTS. WE WILL CONTINUE TO UPDATE AS NEEDED TO
KEEP UP-TO-DATE WITH THE STORM SYSTEM AS IT EVOLVES TONIGHT.

PREV DISCUSSION... /ISSUED 626 PM CDT THU APR 16 2015/

DISCUSSION...
THE 00Z AVIATION DISCUSSION FOLLOWS....

AVIATION...
SCT TSRA...A FEW STRONG/SEVERE...WILL OCCUR OVER W OK/N TX W/KSPS
THIS EVENING. TAFS MENTION TSRA ONLY WHERE PROBABILITY IS GREATER
THAN 50 PERCENT THIS EVENING. A SMALL STORM COMPLEX MAY FORM
AROUND MIDNIGHT FROM EXISTING STORMS...AND SPEED E ALONG THE KS/OK
BORDER. IF THIS HAPPENS...STRONG W WINDS WILL OCCUR AT KPNC. THE
KPNC TAF INCLUDES THIS EVENT...BUT NOT AS STRONG AS IT MIGHT BE.
TOMORROW MORNING...GUIDANCE SUGGESTS WIDESPREAD IFR
CEILINGS/VISIBILITIES. ALTHOUGH CERTAINLY POSSIBLE...IT SEEMS
UNLIKELY TO BE THAT BAD. CLOUD BASES SHOULD RISE SLOWLY THROUGH
THE DAY...AND THERE WILL BE CHANCES OF TSRA ALL DAY...BUT MAINLY
IN THE AFTERNOON AND EARLY EVENING.

PREV DISCUSSION... /ISSUED 334 PM CDT THU APR 16 2015/

DISCUSSION...
THIS DISCUSSION WILL REMAIN FOCUSED ON THE SHORT TERM...
THUNDERSTORM AND PRECIPITATION CHANCES FROM THIS EVENING THROUGH
FRIDAY MORNING...

OVERALL... GUIDANCE HAS DONE A POOR JOB IN HANDLING THE BKN/OVC
LOW/MID STRATUS ACROSS THE BULK OF WRN AND CENTRAL OK AND WRN N TX.
THROUGH 20Z... SOME SCATTERED CLEARING HAS FINALLY STARTED AS MORE
STRATOCU/CLOUD STREETS HAVE DEVELOPED. THIS CLOUD COVER WILL
CONTINUE TO PROMOTE A LACK OF INSTABILITY/BL MIXING ACROSS MOST OF
WRN OK AND WRN N TX... BUT WITH THE RECENT TRANSITION TO STRATOCU...
MIXING MAY FINALLY BE PICKING UP. THE EARLY AFTN CONVECTION ACROSS
FAR NW OK AND INTO THE PANHANDLES APPEARED TO BE DRIVEN BY A FOCUSED
REGION OF ISENTROPIC ASCENT... SUPPORTED BY A NARROW REGION OF 1500
J/KG INSTABILITY AND DIVERGENCE ALOFT GIVEN THE ORIENTATION OF THE
UPPER LVL JET MAX ASSOCIATED WITH THE H500 LOW... WHICH CONTINUES TO
SETTLE OVER THE FOUR CORNERS REGION. THE RECENT SEVERE CONVECTION IN
THE PANHANDLES THAT DEVELOPED OVER THE PAST 1 TO 2 HOURS IS
PRIMARILY FOCUSED ON THE DRYLINE/PSUEDO-FRONTAL BOUNDARY THAT
DEVELOPED EARLIER.

AT THE MOMENT... HOW CONVECTION WILL EVOLVE THROUGH THIS EVENING
REMAINS A CHALLENGE. TRADITIONAL GUIDANCE CONTINUES TO STRUGGLE WITH
HOW TO EVOLVE THE UPPER LOW AND CONVECTION. RECENT MESOSCALE
GUIDANCE IS ABLE TO CATCH ON IN SPURTS... BUT IT STRUGGLES AS WELL.
OVERALL... EXPECT CONVECTION ACROSS THE PANHANDLES TO CONTINUE TO
TRANSITION EASTWARD... HOWEVER... RECENT OBS THROUGH 20Z SUGGEST THE
DRYLINE MAY BE STARTING ITS GRADUAL RETREAT TO THE WEST. WITH THIS
SAID... EXPECT THE SFC TROUGH/FRONT (IF WE CAN CALL IT THAT)... WILL
CONTINUE TO LIFT E/NE INTO WRN OK THIS EVENING... WITH STORMS MOVING
INTO NWRN OK AROUND 5 TO 7PM CDT. THE OVERALL EVOLUTION OF STORMS
APPEAR TO HAVE BEEN CAPTURED ON THE RECENT HRRR (18Z RUN)... BUT THE
TIMING MAY BE LATE... THE 12Z TTU WRF SEEMS TO HAVE A DECENT HANDLE
ON TIMING... AS DOES THE WRF-NMM. NOT TO FOCUS SOLELY ON THE WRN
ACTIVITY... STRONG CONVECTION HAS DEVELOPED ACROSS WEST CENTRAL TX
THIS AFTN. CURRENT THOUGHTS HAVE THIS ACTIVITY LIFTING N/NE INTO WRN
N TX AND THE RED RIVER VALLEY. RECENT MESOSCALE GUIDANCE SEEMS TO
SUGGEST THIS ACTIVITY WILL LESSEN AFTER SUNSET AS IT REMAINS DRIVEN
BY DIURNAL HEATING/INSTABILITY.

AS FOR SEVERE STORMS THIS AFTN/EVENING ACROSS WRN OK/WRN N TX...
STORMS THAT ARE ABLE TO MOVE IN OR DEVELOP WILL RESIDE WITHIN AN
ENVIRONMENT SUPPORTIVE OF LARGE HAIL (GOLF BALLS) AND DAMAGING WINDS
(60-70MPH). SEVERE POTENTIAL WILL WANE WITH ANY SCATTERED CONVECTION
THAT PERSISTS INTO THE OVERNIGHT HOURS EASTWARD INTO CENTRAL OK BY
FRIDAY MORNING. THE TORNADO THREAT OVER THE TX PANHANDLE WILL
DIMINISH AS STORMS MOVE OFF THE DRYLINE AND INTO WRN OK... 0-1KM
HELICITY DECREASES AND THE LACK OF A FOCUSING BOUNDARY DOES NOT BODE
WELL FOR TORNADIC DEVELOPMENT ACROSS WRN OK AT THE MOMENT.

JTK

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  59  74  59  77 /  40  50  60  30
HOBART OK         57  75  55  77 /  60  50  50  20
WICHITA FALLS TX  60  77  58  80 /  40  50  50  20
GAGE OK           54  74  51  76 /  90  50  50  20
PONCA CITY OK     58  74  58  75 /  40  60  70  50
DURANT OK         61  77  62  78 /  30  50  60  30

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&

$$

03/23/23



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