Area Forecast Discussion
Issued by NWS Memphis, TN

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000
FXUS64 KMEG 232354
AFDMEG

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
654 PM CDT WED APR 23 2014

.UPDATE...
UPDATED TO ADD 00Z AVIATION DISCUSSION.

&&

.PREV DISCUSSION... /ISSUED 359 PM CDT WED APR 23 2014/

DISCUSSION...

SURFACE HIGH PRESSURE OVER THE MID SOUTH THIS EVENING WILL MOVE
EAST OVERNIGHT. THIS WILL KEEP MOSTLY CLEAR SKIES...DRY
CONDITIONS...AND ALLOW FOR LOW TEMPERATURES TO DROP INTO THE
MIDDLE 40S TO LOWER 50S...EXCEPT MIDDLE 50S IN DOWNTOWN MEMPHIS
DUE TO URBAN HEAT ISLAND EFFECTS.

A POTENT MID AND UPPER LEVEL SHORTWAVE OVER THE WESTERN HIGH
PLAINS THIS AFTERNOON WILL MOVE QUICKLY EAST AND TAKE ON A
SLIGHTLY NEGATIVE TILT. THIS SHORTWAVE WILL MOVE ACROSS THE MID
SOUTH THURSDAY AFTERNOON AND EVENING. THE LOW LEVEL FLOW WILL VEER
QUICKLY SOUTH BY THURSDAY MORNING AND ADVECT AND SEASONABLY MOIST
AIRMASS...CHARACTERIZED BY LOWER 60S DEWPOINTS...INTO THE REGION
BY THURSDAY AFTERNOON. STRONG SURFACE HEATING IN ADVANCE OF THE
APPROACHING TROUGH SHOULD PUSH TEMPERATURES INTO THE UPPER 70S TO
LOWER 80S BY MID AFTERNOON. AS MID LEVEL HEIGHTS BEGIN TO
FALL...THE ATMOSPHERE WILL DESTABILIZE WITH SBCAPE VALUES RANGING
FROM 800-1500 J/KG BY LATE AFTERNOON ACROSS AREAS MAINLY ALONG
AND WEST OF THE MISSISSIPPI RIVER. STEEP MID LEVEL LAPSE RATES
LESS THAN 7.0 C/KM SHOULD ALSO BE IN PLACE ACROSS THESE AREAS. IN
ADDITION...DEEP LAYER SHEAR SHOULD INTENSIFY AS A POTENT 50-60 KT
CYCLONICALLY CURVED MID LEVEL JET OVERSPREADS THE MID SOUTH FROM
THE WEST AND LOW LEVEL FLOW INCREASES TO IN EXCESS OF 40 KTS
AROUND 5 KFT. THE DIRECTIONAL WIND FLOW AT ALL LEVELS BECOME
RATHER UNIDIRECTIONAL BY EVENING. THIS UNIDIRECTIONAL FLOW
COMBINED WITH STRONGER FORCING FROM ALOFT SHOULD FAVOR A LINEAR
STORM MODE WITH STORMS LIKELY QUICKLY ORGANIZING INTO A QUASI
LINEAR CONVECTIVE SYSTEM WITH THE POTENTIAL FOR BOWING SEGMENTS
AND EMBEDDED BOOKEND VORTICES. ALTHOUGH AN ISOLATED TORNADO CANNOT
BE RULED OUT...THE PRIMARY THREATS SHOULD REMAIN DAMAGING WINDS
AND LARGE HAIL. THERE IS A SLIGHT RISK FOR SEVERE STORMS FOR AREAS
ALONG AND WEST OF THE MISSISSIPPI RIVER THURSDAY AFTERNOON AND
EVENING. THUNDERSTORMS SHOULD SLOWLY WEAKEN WITH EASTWARD EXTENT
WITH THE LOSS OF HEATING AND AS STORMS BEGIN TO OUTRUN THE MORE
FAVORABLE LOW LEVEL MOIST AXIS AND BETTER INSTABILITY.

SHOWERS AND THUNDERSTORMS SHOULD END FROM WEST TO EAST LATE
THURSDAY EVENING AS A COLD FRONT MOVES THROUGH THE REGION. THIS
FRONT SHOULD STALL ALONG THE NORTHERN GULF COAST STATES ON FRIDAY.
HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST ON FRIDAY WITH A RETURN
TO DRY WEATHER AND LOWER HUMIDITY LEVELS. THE DRY AIRMASS SHOULD
STILL ALLOW TEMPERATURES TO CLIMB BACK INTO THE MIDDLE 70S TO
LOWER 80S. THE STALLED FRONT SHOULD QUICKLY LIFT BACK TO THE NORTH
AS A WARM FRONT LATE FRIDAY NIGHT AND SATURDAY...BECOMING
POSITIONED ALONG THE OHIO RIVER VALLEY BY SATURDAY EVENING. THIS
FRONT SHOULD PASS THROUGH DRY AS UPPER LEVEL RIDGING BUILDS OVER
THE AREA. TEMPERATURES SHOULD BE QUITE WARM ON SATURDAY WITH HIGHS
IN THE LOWER TO MIDDLE 80S ALONG WITH A SIGNIFICANT INCREASE IN
DEWPOINTS/HUMIDITY LEVELS BEHIND THE WARM FRONTAL PASSAGE.

A SIGNIFICANT UPPER LEVEL LOW PRESSURE SYSTEM MOVING INTO THE
WESTERN STATES OVER THE WEEKEND WILL MOVE NORTHEAST INTO THE
CENTRAL PLAINS BY LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK. A
SERIES OF POTENT SHORTWAVE DISTURBANCES ROTATING THROUGH THE BASE
OF THE INCREASINGLY NEGATIVELY TILTED TROUGH SHOULD SET THE STAGE
FOR A MORE SIGNIFICANT SEVERE WEATHER THREAT ACROSS THE SOUTHERN
PLAINS INTO THE LOWER MISSISSIPPI VALLEY FROM SUNDAY INTO MONDAY.
AN EXPANSIVE MOIST WARM SECTOR SHOULD BE IN PLACE ACROSS THE
ENTIRE AREA THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK.
DEWPOINTS OVER THE MID SOUTH SHOULD SURGE INTO THE MIDDLE AND
UPPER 60S DURING THIS TIME PERIOD. A LEAD SHORTWAVE LIFTING ACROSS
WESTERN PORTIONS OF THE REGION BY SUNDAY AFTERNOON AND EVENING MAY
RESULT IN AN INITIAL ROUND OF THUNDERSTORMS WITH THE POTENTIAL FOR
SEVERE THUNDERSTORMS. DEPENDING UPON HOW THIS INITIAL CONVECTION
EVOLVES AND IMPACTS THE AIRMASS IN PLACE...THERE IS THE POTENTIAL
FOR THE ATMOSPHERE TO RECOVER ON MONDAY AND SET THE STAGE FOR
ANOTHER ROUND OF POTENTIALLY SEVERE THUNDERSTORMS BY MONDAY
AFTERNOON AS ANOTHER POTENT SHORTWAVE EJECTS ACROSS THE REGION.
THERE ARE PLENTY OF DETAILS THAT STILL NEED TO BE WORKED
OUT...BUT THE POTENTIAL EXISTS FOR A MORE SIGNIFICANT SEVERE
WEATHER EPISODE LATE THIS WEEKEND AND INTO EARLY NEXT WEEK.

ADDITIONAL SHOWERS AND THUNDERSTORMS MAY REDEVELOP ON TUESDAY
AHEAD OF A SURFACE LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT
MOVING ACROSS THE AREA. MUCH COOLER TEMPERATURES SHOULD DEVELOP BY
NEXT WEDNESDAY AS THE UPPER LEVEL LOW PRESSURE MOVES OVER THE AREA
AND CONTINUES THE THREAT FOR SHOWERS OVER THE REGION.

JLH


&&

.AVIATION...
00Z TAF CYCLE

VFR CONDITIONS EXPECTED TO CONTINUE THROUGH MUCH OF THE PERIOD.
SHOWERS AND THUNDERSTORMS ARE ANTICIPATED TO DEVELOP AROUND OR
AFTER 21Z AT MEM/JBR AND MKL BY 23Z AS A SHORTWAVE TROUGH MOVES
THROUGH THE LOWER MISSISSIPPI VALLEY THURSDAY NIGHT. HAVE ONLY
MENTIONED VCTS AT THIS TIME...BUT MAY CONSIDER ADDING TEMPOS TO
THE ABOVE MENTIONED SITES FOR THE 06Z TAF SET WITH PERHAPS A
2 HOUR TEMPO SOMETIME BETWEEN 23-03Z AT MEM. LIGHT E/SE WINDS
TONIGHT WILL VEER SOUTH AND INCREASE BY EARLY AFTERNOON TO
BETWEEN 12-17 KTS WITH GUSTS UP TO 25-27 KTS...ESPECIALLY AT
MEM/JBR.

CJC
&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&

$$







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