MESOSCALE PRECIPITATION DISCUSSION 0716
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 AM EST MON DEC 28 2015
 
AREAS AFFECTED...CENTRAL AND EASTERN AR...CENTRAL AND EASTERN
MO...FAR SOUTHWEST IL...WESTERN TN...NORTHWEST MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 280900Z - 281500Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP
AND LIFT NORTHEAST THIS MORNING AHEAD OF A DEEPENING CYCLONE OVER
THE ARKLATEX REGION.

DISCUSSION...A STRONG MID LEVEL LOW CENTER AND AN OCCLUDING
SURFACE LOW WILL BE MOVING ACROSS THE ARKLATEX REGION OVER THE
NEXT FEW HOURS AND THIS WILL CONTINUE TO HELP FOCUS WIDESPREAD
SHOWERS AND THUNDERSTORMS ACROSS THE LOWER MS AND ESPECIALLY THE
MID MS VALLEY THROUGH MID-MORNING ALONG WITH PARTS OF THE LOWER OH
VALLEY.

STRONG MOISTURE TRANSPORT AND AT LEAST A MODEST AMOUNT OF
INSTABILITY CONTINUES TO LIFT NORTH AHEAD OF THE LOW CENTER AND
ASSOCIATED COLD FRONT. MUCAPE VALUES ARE ONLY ON THE ORDER OF 500
TO 1000 J/KG OVER SOUTHERN AR AND INTO EASTERN LA AND MS...BUT
THERE IS A 50 KT LOW LEVEL JET AS PER VWP DATA TRANSPORTING AN
ANOMALOUSLY DEEP POOL OF SUBTROPICAL MOISTURE NORTHWARD. A RIBBON
OF 1.6 TO 1.8 INCH PWS ARE NOSING NORTH FROM LA INTO
CENTRAL/SOUTHERN AR AHEAD OF THE SURFACE LOW...AND THIS AXIS OF
DEEPER MOISTURE WILL BE TRANSPORTED GRADUALLY NORTHEAST TOWARD THE
MID MS AND LOWER OH VALLEYS THROUGH THE MORNING HOURS.
MEANWHILE...ENHANCED UPPER LEVEL JET DYNAMICS ASSOCIATED WITH A
WELL-DEFINED 250 MB JET COUPLET LIFTING FROM THE ARKLATEX ACROSS
NORTHERN AR AND SOUTHEAST MO THIS MORNING WILL PROVIDE STRONG DEEP
LAYER ASCENT/FORCING THAT WILL TAKE ADVANTAGE OF THE DEEP MOISTURE
AND AVAILABLE INSTABILITY TO SUSTAIN THE WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY.

THE PW ANOMALIES ARE UPWARDS OF 3 TO 4 STD DEV ABOVE NORMAL
LOCALLY AND WILL CONTINUE TO FACILITATE INTENSE RAINFALL RATES OF
1 TO 2 INCHES/HR AT LEAST LOCALLY WHERE SOME OF THE STRONGER
CONVECTIVE CORES SET UP.

CONSECUTIVE RUNS OF THE HRRR...COUPLED WITH THE 00Z ARW AND 00Z
NMMB HIRES GUIDANCE SUGGESTS AN AXIS OF HEAVY RAINFALL BECOME A
BIT MORE FOCUSED THROUGH MID MORNING FROM CENTRAL AND NORTHEAST AR
NORTHWARD INTO PARTS OF CENTRAL AND ESPECIALLY EASTERN MO AS THE
UPPER JET COUPLE ARRIVES. EXPECT ADDITIONAL RAINFALL AMOUNTS OF AS
MUCH AS 2 TO 4 INCHES THROUGH 15Z FOR THESE AREAS...AND THEN A
GRADUAL TREND FOR IMPROVEMENT THEREAFTER AS A MID LEVEL DRY SLOT
ARRIVES AND BEGINS ERODING THE PRECIPITATION SHIELD.
HOWEVER...MANY OF THESE AREAS HAVE BEEN COMPLETELY INUNDATED BY
HEAVY RAINFALL OVER THE LAST 24 HOURS...AND ANY ADDITIONAL RAINS
WILL SIMPLY EXACERBATE ONGOING RUNOFF PROBLEMS AND FLASH FLOODING
CONCERNS. 

FARTHER SOUTHEAST INTO WESTERN TN AND NORTHERN MS...LOCALLY STRONG
CONVECTION FOCUSED ALONG THE COLD FRONT WILL FOSTER SOME 1 TO 3
INCH AMOUNTS. THE CONCERN FOR RUNOFF PROBLEMS HERE WILL BE
SOMEWHAT LOWER THOUGH AS THE COLD FRONT BEGINS TO ACCELERATE OFF
TO THE EAST...AND THIS WILL LIMIT THE DURATION OF ADDITIONAL RAINS.

ORRISON

ATTN...WFO...JAN...LSX...LZK...MEG...PAH...SGF...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...

LAT...LON   38979160 38979073 38188959 36848918 35218907 
            34428939 33889006 33669105 33849194 34369232 
            35099271 35739299 37179311 38029274 38649227