Flash Flood Warning 1, NWS Memphis, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
635 AM CST SAT JAN 3 2015

.UPDATE...

UPDATED TO SHIFT SLIGHT RISK FOR SEVERE STORMS FURTHER EAST THAN
WAS EARLIER ADVERTISED.

&&

.DISCUSSION...

NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO ADVANCE MORE
QUICKLY EASTWARD THAN MUCH OF THE MODEL GUIDANCE SUGGESTED
EARLIER. THIS SHOULD SERVE TO LIMIT INSTABILITY LEVELS AND
THEREFORE THE SEVERE WEATHER THREAT ACROSS ALL BUT PORTIONS OF
NORTHEAST MISSISSIPPI TODAY. PORTIONS OF NORTHEAST MISSISSIPPI
SHOULD STILL DESTABILIZE SUFFICIENTLY...SBCAPES UP TO 500
J/KG...TO SUPPORT A FEW SEVERE STORMS CAPABLE OF A FEW SEVERE
STRAIGHT LINE WIND GUSTS AND ISOLATED TORNADOES.

THE LATEST PUBLIC FORECAST AND HAZARDOUS WEATHER OUTLOOK REFLECTS
THE LATEST TRENDS AND HAVE BEEN ISSUED.

JLH

&&

.PREV DISCUSSION... /ISSUED 405 AM CST SAT JAN 3 2015/

DISCUSSION...

A POWERFUL UPPER LEVEL LOW PRESSURE SYSTEM WILL BE LIFTING
NORTHEAST OUT OF TEXAS AND INTO THE MIDDLE MISSISSIPPI VALLEY BY
LATER THIS EVENING. THIS UPPER LOW SHOULD OPEN UP AND TAKE ON AN
INCREASINGLY NEGATIVE TILT AS IT PASSES OFF TO OUR NORTHWEST. AT
THE SURFACE...LOW PRESSURE IS CURRENTLY TAKING SHAPE ACROSS
SOUTHWEST ARKANSAS ALONG A PREFRONTAL SURFACE TROUGH. THIS
SURFACE LOW WILL LIFT NORTHEASTWARD ACROSS ARKANSAS TODAY AND
SLOWLY DEEPEN. AS THIS OCCURS...STRENGTHENING SOUTHERLY FLOW IN
ADVANCE OF THE LOW PRESSURE SYSTEM WILL DRAW A SURFACE WARM FRONT
NORTHWARD INTO THE MID SOUTH WITH LOWER 60S DEWPOINTS ADVECTING
INTO MUCH OF EASTERN ARKANSAS AND NORTHERN MISSISSIPPI BY EARLY
AFTERNOON. THE ATMOSPHERE SHOULD SLOWLY DESTABILIZE ACROSS THESE
AREAS BY LATE MORNING AND REMAIN MODESTLY UNSTABLE THROUGH THE
AFTERNOON AS TEMPERATURES RISE INTO THE UPPER 60S. THIS SHOULD
ALLOW SBCAPE VALUES TO RISE AS HIGH AS 500 J/KG ACROSS SOUTHERN
PORTIONS OF THE FORECAST AREA THIS AFTERNOON. ALSO OF NOTE...SOME
OF THE LATEST 4KM WRF RUNS NOTE EVEN GREATER INSTABILITY OVER
THESE AREAS. THIS MAY BE A BIT OVERDONE BUT SOMETHING TO WATCH. IN
ADDITION...A STRENGTHENING LOW LEVEL JET...WITH 850 MB FLOW
INCREASING TO IN EXCESS OF 50 KTS...SHOULD OVERSPREAD THE MID
SOUTH LATER THIS MORNING THROUGH THE AFTERNOON. SURFACE WINDS
SHOULD ALSO REMAIN BACKED FROM THE SOUTHEAST AHEAD OF THE SURFACE
LOW WHICH WILL LEAD TO 0-1 KM SRH VALUES IN EXCESS OF 200 M2/S2.

AS THE SURFACE LOW LIFTS NORTHEAST...THUNDERSTORMS SHOULD CONTINUE
TO DEVELOP ALONG THE TRAILING PREFRONTAL SURFACE TROUGH AS IT
MOVES EAST INTO WESTERN PORTIONS OF THE FORECAST AREA BY LATE
MORNING. STORMS SHOULD THEN INTENSIFY SOME AS THEY MOVE EAST OF
THE MISSISSIPPI RIVER INTO THE HIGHER INSTABILITY AXIS THAT WILL
RESIDE ACROSS MUCH OF NORTH MISSISSIPPI. A FEW OF THESE STORMS MAY
BECOME SEVERE AND POSE A THREAT FOR SOME DAMAGING STRAIGHT LINE
WINDS AS WELL AS ISOLATED TORNADOES WITH ANY EMBEDDED CIRCULATIONS
WITHIN THE QUASI LINEAR CONVECTIVE SYSTEM (QLCS). NUMEROUS
THUNDERSTORMS ARE ALSO EXPECTED FURTHER NORTH INTO NORTHEAST
ARKANSAS...THE MISSOURI BOOTHEEL...AS WELL AS WEST TENNESSEE
TODAY...BUT WITH LIMITED INSTABILITY ANY STORMS SHOULD REMAIN
BELOW SEVERE LIMITS ACROSS THESE AREAS. PWAT VALUES DO SURGE
TOWARDS THE 99TH PERCENTILE FOR THIS TIME OF YEAR ACROSS THE
ENTIRE MID SOUTH...SO HEAVY RAINFALL WILL ALSO BE A THREAT
AREAWIDE WITH POSSIBLE FLASH FLOODING. A FLASH FLOOD WATCH REMAINS
IN EFFECT ACROSS THE AREA INTO THIS EVENING WITH A GENERAL 2 TO 3
INCH RAINFALL POSSIBLE...WITH LOCALIZED HIGHER AMOUNTS.

THE UPPER LEVEL TROUGH AND SURFACE LOW PRESSURE SYSTEM WILL LIFT
WELL NORTHEAST OF THE MID SOUTH BY LATE THIS EVENING AS THE
TRAILING PREFRONTAL TROUGH MOVES ACROSS EASTERN AREAS. ONCE THIS
TROUGH SWEEPS EAST AFTER MIDNIGHT...THERE SHOULD BE AN ABRUPT END
TO THE RAIN AND THUNDERSTORMS FROM WEST TO EAST. TEMPERATURES
SHOULD COOL INTO THE UPPER 30S TO MIDDLE 40S BEFORE SUNRISE ON
SUNDAY MORNING.

A STRONGER COLD FRONT WILL MOVE ACROSS THE MID SOUTH ON SUNDAY
WITH A FEW ISOLATED SHOWERS POSSIBLE ACROSS PORTIONS OF NORTHWEST
TENNESSEE. THIS FRONT SHOULD USHER IN COLDER TEMPERATURES FOR THE
FIRST PART OF NEXT WEEK. IN FACT...TEMPERATURES SHOULD BEGIN TO
FALL SUNDAY AFTERNOON BEHIND THE FRONTAL PASSAGE. HIGH
TEMPERATURES SHOULD REMAIN BELOW NORMAL THROUGH NEXT TUESDAY.

AN ARCTIC COLD FRONT IS PROGGED TO PASS ACROSS THE MID SOUTH BY
THE MIDDLE OF NEXT WEEK WITH A 1050+ MB SURFACE HIGH BUILDING
SOUTH ACROSS THE PLAINS. THIS SHOULD RESULT IN SOME OF THE COLDEST
TEMPERATURES ACROSS THE AREA SO FAR THIS WINTER SEASON. HIGH
TEMPERATURES WILL LIKELY REMAIN BELOW FREEZING IN MOST AREAS BOTH
WEDNESDAY AND THURSDAY OF NEXT WEEK WITH LOWS RANGING FROM THE
SINGLE DIGITS NORTH TO MIDDLE TEENS SOUTH. THIS VERY COLD AIRMASS
WILL SLOWLY MODIFY TOWARDS THE END OF NEXT WEEK BUT REMAIN BELOW
SEASONAL AVERAGES. THE NEXT STORM SYSTEM SHOULD APPROACH BY NEXT
WEEKEND WITH RENEWED PRECIPITATION CHANCES.

JLH

&&

.AVIATION...
12Z TAFS

IFR / OCNL LIFR CONDITIONS TO CONTINUE THROUGHOUT THE DAY. A
STRONG LOW PRESSURE SYSTEM WILL DEEPEN AND MOVE QUICKLY ACROSS THE
MID-SOUTH THIS MORNING AND INTO THIS AFTERNOON. HEAVY SHOWERS AND
THUNDERSTORMS ARE EXPECTED AT ALL SITES AS A COLD FRONT PUSHES
THROUGH. LLWS WILL PEAK THIS MORNING AT JBR AND MEM AROUND 15Z
WITH TUP AND MKL JUST AFTER. CEILINGS AND VISBYS ARE EXPECTED TO
IMPROVE AT ALL SITES AFTER 04/10Z.

SURFACE WINDS WILL INITIALLY BE FROM THE SOUTH 12-16 KTS GUSTING
TO AROUND 25 KTS...SHIFTING TO THE WEST AND DIMINISHING TO AROUND
10 KTS AFTER 04/00Z WITH FRONTAL PASSAGE.

AC3

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR CLAY-CRAIGHEAD-
     CRITTENDEN-CROSS-GREENE-LAWRENCE-LEE AR-MISSISSIPPI-
     PHILLIPS-POINSETT-RANDOLPH-ST. FRANCIS.

MO...FLASH FLOOD WATCH UNTIL 6 PM CST THIS EVENING FOR DUNKLIN-
     PEMISCOT.

MS...FLASH FLOOD WATCH THROUGH THIS EVENING FOR ALCORN-BENTON MS-
     CALHOUN-CHICKASAW-COAHOMA-DESOTO-ITAWAMBA-LAFAYETTE-LEE MS-
     MARSHALL-MONROE-PANOLA-PONTOTOC-PRENTISS-QUITMAN-
     TALLAHATCHIE-TATE-TIPPAH-TISHOMINGO-TUNICA-UNION-YALOBUSHA.

TN...FLASH FLOOD WATCH THROUGH THIS EVENING FOR BENTON TN-CARROLL-
     CHESTER-CROCKETT-DECATUR-DYER-FAYETTE-GIBSON-HARDEMAN-
     HARDIN-HAYWOOD-HENDERSON-HENRY-LAKE-LAUDERDALE-MADISON-
     MCNAIRY-OBION-SHELBY-TIPTON-WEAKLEY.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MEMPHIS TN
617 AM CST SAT JAN 3 2015

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>022-048>055-088>092-041430-
ALCORN-BENTON MS-BENTON TN-CALHOUN-CARROLL-CHESTER-CHICKASAW-CLAY-
COAHOMA-CRAIGHEAD-CRITTENDEN-CROCKETT-CROSS-DESOTO-DECATUR-
DUNKLIN-DYER-FAYETTE-GIBSON-GREENE-HARDEMAN-HARDIN-HAYWOOD-
HENDERSON-HENRY-ITAWAMBA-LAFAYETTE-LAKE-LAUDERDALE-LAWRENCE-
LEE AR-LEE MS-MADISON-MARSHALL-MCNAIRY-MISSISSIPPI-MONROE-OBION-
PANOLA-PEMISCOT-PHILLIPS-POINSETT-PONTOTOC-PRENTISS-QUITMAN-
RANDOLPH-SHELBY-ST. FRANCIS-TALLAHATCHIE-TATE-TIPPAH-TIPTON-
TISHOMINGO-TUNICA-UNION-WEAKLEY-YALOBUSHA-
617 AM CST SAT JAN 3 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST ARKANSAS...
THE MISSOURI BOOTHEEL...NORTH MISSISSIPPI...AND WEST TENNESSEE.

.DAY ONE...TODAY AND TONIGHT

A FLASH FLOOD WATCH IS IN EFFECT FOR THE MID SOUTH TODAY INTO THIS
EVENING. HEAVY RAINFALL...WITH AMOUNTS BETWEEN 2 AND 3 INCHES WILL
BE COMMON...WITH LOCALIZED HEAVIER AMOUNTS.

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHEAST MISSISSIPPI TODAY. THE POTENTIAL WILL EXIST FOR
DAMAGING STRAIGHT LINE WIND GUSTS AND ISOLATED TORNADOES WITH ANY
STORMS THAT BECOME SEVERE. THE GREATEST SEVERE WEATHER RISK SHOULD
RESIDE SOUTHEAST OF A LINE FROM CORINTH MISSISSIPPI TO COFFEEVILLE
MISSISSIPPI.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

AN ARCTIC COLD FRONT WILL MOVE ACROSS THE MID SOUTH BY THE MIDDLE
OF NEXT WEEK BRINGING VERY COLD TEMPERATURES AND THE POTENTIAL FOR
DANGEROUS WIND CHILL VALUES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED ACROSS PORTIONS NORTHEAST MISSISSIPPI
TODAY.

JLH