724  
FXUS62 KCAE 271852  
AFDCAE  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE COLUMBIA SC  
252 PM EDT WED OCT 27 2021  
   
SYNOPSIS
 
 
SEASONABLE TEMPERATURES ARE EXPECTED TODAY AS AIR MASS REMAINS  
DRY. A STRONG LOW PRESSURE SYSTEM WILL DEVELOP OVER THE  
SOUTHEASTERN STATES THURSDAY WITH WIDESPREAD SHOWERS AND A FEW  
THUNDERSTORMS THROUGH THURSDAY NIGHT. SOME STRONG  
SHOWERS/STORMS ARE POSSIBLE, BUT WIDESPREAD SEVERE WEATHER IS  
NOT EXPECTED AT THIS TIME. CONDITIONS WILL SLOWLY IMPROVE OVER  
THE WEEKEND BUT TEMPERATURES WILL REMAIN BELOW NORMAL.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AREA REMAINS UNDER THE INFLUENCE OF TRANSITORY RIDGE OF HIGH  
PRESSURE BOTH AT THE SURFACE AND ALOFT IN A VERY AMPLIFIED  
PATTERN WITH STRONG UPPER LOW PRESSURE OFF THE COAST OF NEW  
ENGLAND AND A DEEP TROUGH OVER THE SOUTHERN PLAINS. BIT DRIER  
AIRMASS IN PLACE THAN MODELS INDICATED WITH DEW POINTS IN THE  
MID TO UPPER 30S ACROSS THE FORECAST AREA. WITH WEAK FLOW OVER  
THE AREA, TEMPERATURES WILL BE A FEW DEGREES COOLER AS WE LOSE  
OUT ON DOWNSLOPE WINDS WE HAD YESTERDAY. TONIGHT, THE UPPER  
RIDGE AXIS WILL BEGIN TO SHIFT OFFSHORE WITH DEEPER SW  
DEVELOPING. WITH SUCH DRY AIR IN PLACE, IT WILL TAKE SOME TIME  
FOR ATMOSPHERE TO MOISTEN, AND AS A RESULT LIGHT WINDS AND CLEAR  
SKIES EARLY WILL LEAD TO FAVORABLE RADIATIONAL COOLING  
CONDITIONS BEFORE CLOUDS BEGIN TO INCREASE AROUND 10KFT AND  
ABOVE, FIRST IN THE CSRA AND THEN IN THE REST OF THE FORECAST  
AREA. LOWS DROP INTO THE MID 40S IN THE NORTHERN FORECAST AREA  
TO NEAR 50 IN THE CSRA AS CLOUDS INTERFERE WITH RADIATIONAL  
COOLING. WITH MOISTURE LACKING BELOW 10KFT, NO PRECIPITATION IS  
EXPECTED TONIGHT.  
 

 
   
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
 
 
SUMMARY: A POTENT UPPER LEVEL SYSTEM AND ASSOCIATED COLD FRONT  
WILL MOVE THROUGH THE AREA THURSDAY. WIDESPREAD MODERATE-HEAVY  
IS EXPECTED THROUGHOUT THE DAY THURSDAY AND THURSDAY NIGHT.  
CONFIDENCE IN THE SEVERE RISK REMAINS RELATIVELY LOW, WITH  
EXTREMELY IMPRESSIVE WIND PROFILES BUT UNFAVORABLE  
THERMODYNAMICS. THE EASTERN CWA REMAINS MOST FAVORABLE IF SEVERE  
WEATHER DOES DEVELOP. SOME SHOWERS ARE POSSIBLE AGAIN FRIDAY AS  
THE UPPER LOW MOVES OVERHEAD. THERE IS OVERALL LITTLE CHANGE IN  
THE FORECAST FOR THE SYSTEM THURSDAY. THE MOST RECENT SUITES OF  
HI- RES MODELS ARE IN REASONABLE AGREEMENT WITH A COMPLEX AND  
INHERENTLY TRICKY SETUP.  
 
THURSDAY MORNING: THE CWA WILL QUICKLY COME UNDER THE FORCING  
OF THE DEEP UPPER LOW BY EARLY THURSDAY AS MID LEVEL HEIGHTS  
FALL AND BROAD DIVERGENCE ALOFT BEGINS. THE CORRESPONDING  
OCCLUDING SURFACE LOW WILL STILL BE POSITIONED OVER ARKANSAS BY  
THIS TIME BUT THE SURFACE OCCLUDED/COLD FRONT WILL BE QUICKLY  
PUSHING THROUGH MS AND AL BY THURSDAY MORNING. A SECONDARY  
OCCLUDED LOW CENTER WILL FORM ALONG THE FRONTAL BOUNDARY  
THROUGHOUT THURSDAY WHICH ADDS TO THE COMPLEXITY OF THE EVENT.  
STRONG ISENTROPIC LIFT WILL BEGIN BY THE LATE MORNING THURSDAY  
AS WARM ADVECTION AHEAD OF THE SECONDARY LOW AND WARM FRONT  
RAMPS OUT. PWATS BY THIS TIME WILL HAVE REBOUNDED TO OVER 1.5"  
SO COMBINED WITH THE STRONG ISENTROPIC LIFT, THIS IS EXPECTED TO  
PRODUCE A BROAD AREA OF MODERATE SHOWERS AND SOME ISOLATED  
THUNDERSTORMS BY THE EARLY AFTERNOON.  
 
THURSDAY AFTERNOON/EVENING: SEVERE POTENTIAL INCREASES IN THE  
AFTERNOON AS THE BEST KINEMATICS WILL BE OVERSPREADING THE AREA, A  
100+ KNOT 250MB JET OVERHEAD, RAPIDLY FALLING MID-LEVEL HEIGHTS  
AND PVA, AND 45+ KNOT 850MB SOUTHERLY FLOW. THE SECONDARY LOW  
DEVELOPMENT WILL HELP BACK SURFACE FLOW AND KEEP BOUNDARY LAYER  
WINDS FROM THE EAST- SOUTHEAST. THIS ALL COMBINES FOR IMPRESSIVE  
HODOGRAPHS WITH SUBSTANTIAL SPEED AND DIRECTIONAL SHEAR IN THE  
LOW LEVEL LAYERS, 0-1KM BULK SHEAR OVER 30+ KNOTS AND 50+ KNOTS  
OF 0-3 BULK SHEAR. SO KINEMATICS ARE EASILY SUPPORTIVE OF  
SEVERE HAZARDS. THE THERMODYNAMICS REMAIN THE LIMITING FACTOR  
WITH PERSISTENT MORNING CLOUD COVER AND PRECIP THAT WILL LIMIT  
THE NORTHWARD EXPANSION OF THE WARM SECTOR. SO ONLY VERY WEAK  
SURFACE AND/OR MIXED LAYER INSTABILITY IS EXPECTED TO DEVELOP,  
WITH GOOD AGREEMENT ACROSS THE HI-RES SUITE IN THIS. THE INTENSE  
WARM ADVECTION ALOFT WILL ONLY ADD TO THE UNFAVORABLE LOW LEVEL  
THERMODYNAMICS, ACTING AS A WEAK CAP FROM 850-700MB. SO  
COMBINING EVERYTHING, THE EASTERN HALF OF THE CWA CONTINUES TO  
REMAIN THE MOST FAVORABLE FOR SEVERE WEATHER SINCE LATE  
AFTERNOON THERMODYNAMICS WILL BE MOST FAVORABLE THERE, TO GO  
ALONG WITH IMPRESSIVE KINEMATICS. SPC HAS EXPANDED THE SLIGHT  
AND MARGINAL RISKS TO INCLUDE MOST OF THE CWA NOW, FOR SEVERE  
WIND AND TORNADOES.  
 
THE MAIN AREAS OF UNCERTAINTIES ARE RELATED TO THE  
THERMODYNAMIC SETUP (AS THE KINEMATICS ARE MUCH MORE CONFIDENT):  
WHERE DOES THE OCCLUDED LOW EXACTLY TRACK?, HOW DOES THE WARM  
SECTOR DEVELOP?, AND HOW WIDESPREAD IS THE MORNING GULF COAST  
CONVECTION?.  
 
DRIER AIR FILLS IN BEHIND THE FRONTAL PASSAGE LATE THURSDAY AND  
INTO FRIDAY. THE UPPER LOW WILL MOVE OVER THE CWA FRIDAY AND, COMBINED  
WITH THE ENHANCED LOW-MID LAPSE RATES AND SOME DIURNAL HEATING,  
ISOLATED SHOWERS ARE EXPECTED THROUGHOUT THE AFTERNOON. HIGH  
TEMPS WILL REMAIN IN THE UPPER 60S ACROSS THE AREA THANKS TO  
WEAK COLD ADVECTION.  
 

 
   
LONG TERM /SATURDAY THROUGH TUESDAY/
 
 
GOOD AGREEMENT ACROSS GUIDANCE THAT THE SLIGHT CHANCE OF  
SHOWERS CONTINUES ON SATURDAY AS THE UPPER LOW WILL FINALLY  
LIFT TO OUR NORTHEAST. A NORTHWEST FLOW REGIME THEN DEVELOPS  
AND USHERS IN A MUCH DRIER AND SEASONAL PERIOD FOR THE REMAINDER  
OF THE LONG TERM. BLEND AND ENSEMBLES ARE IN REASONABLE  
AGREEMENT, NEAR AVERAGE TEMPERATURES WITH ZONAL FLOW ALOFT AND  
LITTLE CHANCE FOR PRECIP UNTIL LATER NEXT WEEK.  
 

 
   
AVIATION /18Z WEDNESDAY THROUGH SUNDAY/
 
 
HIGH PRESSURE OVER THE AREA WITH VFR CONDITIONS AT ALL TERMINALS  
WITH PASSING HIGH CLOUDS AND LIGHTER WINDS, GENERALLY OUT OF  
THE NW AROUND 5 KNOTS. WINDS DECREASE TONIGHT, BECOMING LIGHT  
AND VARIABLE WITH INCREASING MOISTURE. BY TOMORROW MORNING  
EXPECT AN OVERCAST DECK AROUND 8KFT AND SOUTHEASTERLY WINDS  
BETWEEN 5 TO 10 KNOTS AS LOW PRESSURE APPROACHES FROM THE WEST.  
MAY GET SOME LOWER CLOUDS TO DEVELOP LATE IN THE TAF PERIOD BUT  
CONFIDENCE IN RESTRICTIONS BEFORE 18Z IS LOW. PRECIPITATION  
CHANCES WILL ALSO BE HIGHEST AFTER 18Z AS WELL, ALTHOUGH CAN'T  
COMPLETELY RULE OUT CHANCES, ESPECIALLY AT AGS/DNL.  
 
EXTENDED AVIATION OUTLOOK... EXPECT INCREASING MOISTURE  
THURSDAY AFTERNOON WITH RAIN AND ASSOCIATED RESTRICTIONS AS A  
STRONG LOW PRESSURE SYSTEM MOVES INTO THE REGION. CHANCE OF  
SHOWERS AND ASSOCIATED RESTRICTIONS FRI/SAT DUE TO UPPER LEVEL  
LOW OVER THE AREA. UPPER LOW MOVING NORTHEAST OF THE AREA SUNDAY  
WITH IMPROVING CONDITIONS INTO EARLY NEXT WEEK.  
 

 
   
CAE WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...NONE.  
 

 
 

 
 
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