913  
FXUS64 KJAN 171516 AAA  
AFDJAN  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE JACKSON MS  
916 AM CST SUN DEC 17 2017  
   
UPDATE
 
 
UPDATED FOR MORNING DISCUSSION.  
 

 
   
DISCUSSION
 
 
THE SYSTEM CONTINUES TO PROGRESS FASTER THAN EXPECTED. LOCAL  
RADARS SHOW THE BACK EDGE OF RAIN NEARING INTERSTATE 55 AND THIS  
EDGE WILL SHIFT EAST OF OUR CWA DURING THE AFTERNOON. DRIER AIR  
WILL MOVE ACROSS THE NORTHWEST HALF OF OUR CWA THIS AFTERNOON BUT  
DEEPER MOISTURE WILL CONTINUE ACROSS OUR SOUTHEAST INTO THIS  
EVENING. WITH A FEW SUBTLE DISTURBANCES IN THE SOUTHWEST FLOW  
ALOFT, LIGHT PRECIPITATION WILL BE HARD TO RULE OUT OVER OUR  
SOUTHEAST GOING INTO THIS EVENING. /22/  
 
PRIOR DISCUSSION BELOW:  
AS ANTICIPATED, A LARGE AREA OF RAIN AND EMBEDDED THUNDERSTORMS  
IS MOVING ACROSS THE ARKLAMISS EARLY THIS MORNING IN ASSOCIATION  
WITH A QUICK-MOVING SHORTWAVE TROUGH. ANOMALOUS PRECIPITABLE WATER  
IN EXCESS OF 1.5 INCHES IS SUPPORTING HEAVY DOWNPOURS, AND AT  
LEAST A FEW LOCATIONS WILL RECEIVE OVER AN INCH OF RAINFALL IN  
SPITE OF THE PROGRESSIVE NATURE OF THE SYSTEM. GUIDANCE HAS SPED  
UP SOME WITH THE EXIT OF THE BETTER LARGE SCALE ASCENT BY THIS  
AFTERNOON, AND HAVE ADJUSTED THE FORECAST ACCORDINGLY. HOWEVER,  
EXPECT PERIODS OF RAINFALL TO BE POSSIBLE FROM LATER TONIGHT INTO  
MONDAY AS MOISTURE CONVERGENCE AND SUBTLE PERTURBATIONS IN THE  
LARGE SCALE FLOW HELP TO REINITIATE SHOWER/TSTM ACTIVITY,  
ESPECIALLY FOR LOCATIONS ALONG/SOUTH OF THE I-20 CORRIDOR.  
OTHERWISE, MILDER TEMPERATURES CAN BE EXPECTED, ESPECIALLY TONIGHT  
WHEN LOWS SHOULD BE NEAR 15 DEGREES ABOVE NORMAL. /EC/  
 
AN ACTIVE LATE DECEMBER WEATHER PATTERN WILL CONTINUE TO DIVULGE  
THROUGH THE MID AND LONG TERM PORTIONS OF THE FORECAST. THIS NEXT  
SEVEN DAYS COULD BE THE WETTEST WE'VE EXPERIENCED IN QUITE SOME TIME  
IN THE ARKLAMISS. WPC 7 DAY QPF TOTALS ARE IN EXCESS OF 6" IN  
PORTIONS OF THE DELTA AND RANGE FROM 2" UPWARDS ELSEWHERE. IF THIS  
FORECAST HOLDS TRUE, IT WILL UNDOUBTEDLY PUT A SIGNIFICANT DENT IN  
OUR CURRENT DROUGHT AND HELP ERASE SOME OF THE YEARLY RAINFALL  
DEFICITS AT SOME SITES AND ADD TO THE SURPLUS AT OTHERS BEFORE THE  
YEAR ENDS.  
 
A VERY MOIST AIRMASS WILL EXIST OVER THE ARKLAMISS ON MONDAY THROUGH  
TUESDAY AS THE PERSISTENT UPPER LEVEL SW FLOW PATTERN AND LOW LEVEL  
SOUTHERLY FLOW RESULT IN PWATS NEAR THEIR CLIMATOLOGICAL MAXES.  
SIGNIFICANT RAIN CHANCES WILL PERSIST THROUGH THE EARLY WEEK PERIOD.  
THE BEST CHANCES FOR STORMS WILL EXIST ON TUESDAY THROUGH EARLY  
WEDNESDAY AS A SURFACE FRONT THAT IS ASSOCIATED WITH A CLOSED UPPER  
LOW THAT WILL BEGIN TO CROSS THE SOUTHERN PLAINS AND APPROACH OUR  
REGION, SWINGS THROUGH THE REGION. SOUTHERLY FLOW WILL INCREASE  
AHEAD OF THIS FRONTAL PASSAGE AND THE GFS IS PRETTY AGGRESSIVE WITH  
ATMOSPHERIC DESTABILIZATION AHEAD OF THE FRONT, DEPICTING CAPE  
VALUES RANGING FROM 400-1200 J/KG TUESDAY AFTERNOON THROUGH  
WEDNESDAY MORNING. A FEW STRONG STORMS COULD BE POSSIBLE DURING THIS  
PERIOD BUT IT WILL DEPEND HEAVILY ON CLEARING AHEAD OF AND THE  
TIMING OF THE FRONTAL PASSAGE. DRIER AIR WILL BEGIN TO FILTER INTO  
THE REGION BY LATE WEDNESDAY AFTER THE FRONT HAS SWEPT THROUGH THE  
AREA. ANOTHER, DEEPER, CUTOFF LOW WILL APPROACH THE REGION LATER IN  
THE WORK WEEK, PUSHING ANOTHER FRONT THROUGH THE REGION, WHICH  
WILL ONCE AGAIN LEAD TO INCREASED RAINFALL CHANCES ON FRIDAY INTO  
SATURDAY.  
 
ALTHOUGH MODEL SIMILITUDE BEGINS TO DECREASE AS WE GET CLOSER TO THE  
WEEKEND, THEY HAVE COME INTO BETTER AGREEMENT THAN PREVIOUS RUNS, AS  
THEY CONTINUE TO DEPICT A WEATHER SITUATION OVER THE HOLIDAY PERIOD  
THAT DEFINITELY WARRANTS COGNIZANCE. CONFIDENCE IS STILL TOO LOW TO  
MENTION ANY SOLUTIONS JUST YET, BUT HOPEFULLY WE WILL BE ABLE TO  
BETTER GAUGE SOLUTIONS OR POSSIBLE IMPACTS IN SUBSEQUENT  
FORECASTS. /JPM3/  
 

 
   
AVIATION
 
 
12Z TAF DISCUSSION:  
AVIATION WEATHER WILL BE POOR FOR MOST OF THIS FORECAST PERIOD  
FROM TODAY THROUGH TONIGHT. WIDESPREAD RA/SHRA WILL BE MOVING  
ACROSS THE FORECAST AREA THIS MORNING BEFORE EXITING TO THE EAST  
BY EARLY AFTERNOON. MVFR TO IFR CEILINGS WILL ACCOMPANY THE RAIN,  
BUT EXPECT CEILINGS TO LOWER FURTHER TO POTENTIALLY LIFR CATEGORY  
WHEN THE RAIN ENDS, ESPECIALLY ALONG/EAST OF THE GWO TO HKS/JAN  
CORRIDOR. FOG IS LOOKING MORE LIKELY AS WELL TONIGHT ALONG THE  
GTR/MEI/HBG CORRIDOR DUE TO LITTLE MIXING OF THE MOIST AIRMASS  
FOLLOWING THIS SYSTEM COMBINED WITH THE RELATIVELY COLD GROUND.  
/EC/  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
JACKSON 66 50 65 58 / 43 22 52 42  
MERIDIAN 58 48 62 55 / 85 35 43 41  
VICKSBURG 65 50 66 58 / 10 20 58 55  
HATTIESBURG 64 56 66 59 / 89 42 66 41  
NATCHEZ 67 54 66 60 / 12 35 68 42  
GREENVILLE 58 44 62 55 / 10 6 12 57  
GREENWOOD 59 46 64 54 / 14 7 15 53  
 

 
   
JAN WATCHES/WARNINGS/ADVISORIES
 
 
MS...NONE.  
LA...NONE.  
AR...NONE.  
 

 
 

 
 
JPM3/22/EC  
 
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