624  
FXUS64 KJAN 172040  
AFDJAN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE JACKSON MS  
340 PM CDT WED OCT 17 2018  
   
DISCUSSION
 
 
THIS EVENING THROUGH TOMORROW:  
 
THROUGH THIS AFTERNOON, A FEW LIGHT RAIN SHOWERS WILL BE POSSIBLE  
AS MID-LEVEL MOISTURE IS LIFTED OVER THE COOLER SURFACE AIRMASS.  
DRIER AIR WILL CONTINUE TO SLOWLY WORK SOUTHWARD INTO OUR FORECAST  
AREA, FURTHER ERODING THE LOW STRATUS ACROSS THE REGION AND  
ENDING RAIN CHANCES. BREAKS IN THE CLOUDS ARE ALREADY APPARENT AS  
FAR SOUTH AS INTERSTATE 20. EXPECT TONIGHT'S LOW TEMPERATURES TO  
RANGE FROM THE LOWER 50S IN OUR NORTH TO THE UPPER 50S IN THE PINE  
BELT. TEMPERATURES WILL REBOUND SOME TOMORROW WITH BROKEN CLOUD  
COVER AND INCREASED DAYTIME HEATING. NO PRECIPITATION IS EXPECTED  
TOMORROW. /NF/  
 
TOMORROW NIGHT THROUGH WEDNESDAY:  
 
A SEASONABLY ACTIVE FALL WEATHER PATTERN WILL CONTINUE THROUGH  
THE PERIOD WITH THE PASSAGE OF ANOTHER COLD FRONT FOLLOWED BY A  
COUPLE SOUTHERN STREAM DISTURBANCES. BY TOMORROW NIGHT, THE CUTOFF  
LOW OVER THE DESERT SOUTHWEST WILL BEGIN TO FILL AS IT LIFTS TO  
THE NORTHEAST AND BECOMES ABSORBED INTO THE NORTHERN STREAM. SUB-  
TROPICAL RIDGING WILL ALSO EXTEND FROM THE GULF COAST STATES TO  
JUST NORTH OF THE BAHAMAS. CYCLONIC ROSSBY WAVE BREAKING OVER THE  
GULF OF ALASKA WILL HELP ESTABLISH A BRIEF DIPOLE BLOCKING PATTERN  
OVER THE WEST COAST ON FRIDAY WHICH WILL AMPLIFY A DIGGING TROUGH  
DIVING INTO THE NORTHERN PLAINS. THIS TROUGH WILL SUPPRESS THE  
SUB-TROPICAL RIDGING AND WILL SEND A COLD FRONT THROUGH THE GREAT  
PLAINS TOWARDS THE ARKLAMISS REGION. HOWEVER, TEMPERATURES WILL  
BE WARM ON FRIDAY BEFORE THE RIDGE IS ABLE TO GET FULLY DISPLACED,  
WITH THE WARMEST HIGHS IN THE LOW 80S EXPECTED SOUTHEAST OF THE  
NATCHEZ TRACE CORRIDOR. SOUTHWESTERLY FLOW AROUND THE WESTERN EDGE  
OF THE RETREATING RIDGE WILL HELP FOSTER SCATTERED SHOWERS ACROSS  
THE AREA, ESPECIALLY IN THE VICINITY OF THE APPROACHING FRONTAL  
BOUNDARY. THE COLD FRONT WILL MAKE ITS WAY THROUGH THE AREA FRIDAY  
NIGHT THROUGH SATURDAY WITH MAINLY SCATTERED SHOWERS EXPECTED AS  
THE BEST FORCING AND UPPER DYNAMICS FROM THE PARENT TROUGH REMAIN  
DISPLACED TO THE NORTH.  
 
THE BULK OF THE COOLER AND DRIER AIR WILL MOVE IN SATURDAY NIGHT  
WITH COLD AIR ADVECTION RAMPING UP AS A MODIFIED CONTINENTAL POLAR  
AIRMASS ORIGINATING FROM THE CANADIAN YUKON DROPS THROUGH THE PLAINS  
AND INTO THE MISSISSIPPI RIVER VALLEY. THE COLDEST MORNING OF THE  
SEASON SO FAR WILL LIKELY BE ON MONDAY AS THE SURFACE RIDGE AXIS  
BECOMES CENTERED FROM THE MID-ATLANTIC INTO THE DEEP SOUTH. THIS  
WILL RELAX THE SURFACE PRESSURE GRADIENT WITH LIGHT TO CALM WINDS  
AND DRY AIR WITH SURFACE DEWPOINTS IN THE LOW 40S TO UPPER 30S  
CONDUCTIVE FOR EFFICIENT RADIATIONAL COOLING. THE MAIN LIMITING  
FACTOR WILL BE UNCERTAINTY REGARDING CLOUD COVER FROM CIRRUS AS A  
PERTURBATION EMBEDDED IN THE WESTERLY SOUTHERN STREAM FLOW  
APPROACHES THE ARKLAMISS. HOWEVER, LATEST GLOBAL MODELS HAVE SLOWED  
DOWN THE TIMING OF THIS FEATURE AND CLOUD COVER LOOKS TO HOLD OFF  
UNTIL LATE ENOUGH ON MONDAY MORNING TO NOT OVERLY HINDER RADIATIONAL  
COOLING POTENTIAL. WITH THAT BEING SAID, LOW TEMPERATURES ARE  
PROGGED TO DROP INTO THE UPPER 30S TO MID 40S ACROSS THE REGION.  
 
HEADING INTO EARLY NEXT WORK WEEK, THERE ARE INDICATIONS THAT  
SEVERAL SOUTHERN STREAM DISTURBANCES COULD INTERACT WITH THE  
NORTHERN GULF BAROCLINIC ZONE AND HELP INDUCE SEVERAL SURFACE WAVES.  
THE FIRST OF THESE DISTURBANCES IS PROGGED TO REMAIN SUPPRESSED  
BENEATH SHORTWAVE RIDGING ON TUESDAY WITH HEAVY RAINFALL ALONG AND  
JUST OFF THE GULF COAST. HOWEVER, A MORE PRONOUNCED SHORTWAVE TROUGH  
IS EXPECTED TO MOVE OUT OF NORTHERN MEXICO INTO SOUTHERN TEXAS AND  
COULD BRING INCREASED RAIN CHANCES TO THE ARKLAMISS REGION BY THE  
MIDDLE OF NEXT WEEK. /TW/  
 

 
   
AVIATION
 
 
18Z TAF DISCUSSION:  
VFR CONDITIONS WILL PREVAIL AT KGLH, GWO, AND KGTR THROUGH THE  
PERIOD. TAF SITES THROUGH CENTRAL AND SOUTHERN MISSISSIPPI WILL  
BEGIN THE PERIOD WITH IFR CEILINGS DUE TO A PERSISTENT LOW STRATUS  
DECK. THESE CEILINGS ARE EXPECTED TO LIFT TO MVFR HEIGHTS BY 21Z  
AT THOSE TAF SITES, AND IMPROVE TO VFR CONDITIONS BY 00Z THURSDAY.  
LIGHT RAIN SHOWERS WILL CONTINUE AROUND THE REGION BEFORE 00Z,  
CAUSING BRIEF PERIODS OF REDUCED VISIBILITY SHOULD THEY IMPACT ANY  
TAF SITE. /NF/  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
JACKSON 56 71 56 81 / 5 2 0 7  
MERIDIAN 54 72 55 82 / 5 1 0 6  
VICKSBURG 55 70 54 78 / 5 1 0 8  
HATTIESBURG 59 76 59 85 / 5 0 0 18  
NATCHEZ 57 72 58 82 / 5 3 0 11  
GREENVILLE 51 66 51 70 / 5 1 0 16  
GREENWOOD 51 67 52 74 / 5 1 0 11  
 

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

 
 

 
 
TW/NF  
 
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