196  
FXUS62 KRAH 241818  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
118 PM EST TUE JAN 24 2017  
   
SYNOPSIS
 
 
MILD HIGH PRESSURE WILL BUILD INTO THE AREA IN THE WAKE OF THE DEEP  
LOW PRESSURE SYSTEM LIFT NORTHEAST UP THE NORTHERN MID ATLANTIC  
COAST. A COLD FRONT WILL PUSH EAST ACROSS CENTRAL NC ON THURSDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1030 AM TUESDAY...  
 
ONLY CHANGE TO THE FORECAST THIS MORNING WAS TO RAISE TEMPS A  
DEGREE OR TWO IN THE SOUTHWEST GIVEN LATEST GUIDANCE AND MORNING  
TRENDS, WHICH TEND TO AFFIRM THE WEAKENING OF COLD ADVECTION  
FROM SOUTHWEST TO NORTHEAST BEHIND THE DEPARTING LOW.  
OTHERWISE, NW WIND GUSTS TO 25KT OR SO OBSERVED IN THE TRIAD  
WILL SPREAD EAST THROUGH OUT THE DAY UNDER CLEAR SKIES AND HIGHS  
RANGING FROM 58 TO 64 NW TO SE.  
 
GOOD RADIATIONAL CONDITIONS TONIGHT WILL SUPPORT LOWS IN THE  
MID 30S NORTH/NORTHWEST TO LOWER 40S ELSEWHERE.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/
 
 
AS OF 305 AM TUESDAY...  
 
RIDGING OVER THE AREA TO START THE DAY ON WEDNESDAY WILL SHIFT EAST  
AND OFFSHORE DURING THE LATER HALF OF THE AFTERNOON, IN ADVANCE OF A  
LEAD POSITIVELY TILTED SHORTWAVE TROUGH EJECTING EASTWARD THROUGH  
THE CENTRAL PLAIN AND MS VALLEY, WITH ATTENDANT COLD FRONT PROGGED  
TO REACH THE CENTRAL AND SOUTHERN APPALACHIANS AROUND MIDNIGHT  
WEDNESDAY NIGHT. TEMPERATURES AHEAD OF THE FRONT ON WEDNESDAY WILL  
WARM WELL INTO THE 60S ACROSS ALL OF CENTRAL NC, AND WILL FLIRT WITH  
70 ACROSS THE SOUTHERN HALF. ADDITIONALLY, WITH THE APPROACH OF THE  
FRONT, WE WILL ALSO SEE SOME BREEZY SWLY WINDS MATERIALIZE BY THE  
LATE AFTERNOON, BUT CERTAINLY BY THE EVENING, GUSTING INTO THE UPPER  
TEENS.  
 
A 50 TO 60KT LLJ RACING OUT AHEAD OF THE SYSTEM AND UNDERNEATH THE  
ENTRANCE REGION OF A 125-135KT JET STREAK MOVING INTO THE MID-  
ATLANTIC REGION WILL LEAD TO RAPID 1000-700MB MOISTENING WEDNESDAY  
EVENING/NIGHT, AND BRINGING A QUICK MOVING BAND OF LOW TOPPED  
SHOWERS INTO THE AREA AFTER MIDNIGHT. DUE TO FAST-PROGRESSIVE NATURE  
OF THE SYSTEM, QPF AMOUNTS WILL BE LIGHT, GENERALLY A TENTH OF AN OR  
LESS. LOWS WEDNESDAY NIGHT RANGING FROM MID TO UPPER 40S NW TO  
LOWER/MID 50 EAST.  
 

 
   
LONG TERM /THURSDAY THROUGH TUESDAY/
 
 
AS OF 400 AM TUESDAY...  
 
THURSDAY: LIGHT RAIN ASSOCIATED WITH LOW-MID LEVEL FRONTOGENESIS  
ALONG AND BEHIND A COLD FRONT PROGRESSING ACROSS CENTRAL NC IS  
EXPECTED TO END FROM WEST-EAST THURSDAY MORNING AS THE FRONT TRACKS  
EAST OF CENTRAL NC/OFFSHORE AND THE PARENT SHORTWAVE/SFC CYCLONE  
LIFT NE THROUGH NEW ENGLAND TOWARD THE CANADIAN MARITIMES. A RAPID  
CLEARING TREND IS EXPECTED IN THE WAKE OF THE FRONT IN ASSOC/W  
STRONG LOW-LEVEL COLD ADVECTION. FORECAST SOUNDINGS SHOW LOW-LEVEL  
LAPSE RATES RAPIDLY STEEPENING (BECOMING DRY ADIABATIC FROM THE SFC-  
H85) AS CAA COINCIDES WITH PEAK HEATING THU AFTERNOON, A FAVORABLE  
SETUP FOR STRONG W/WNW WINDS. 00Z GFS/NAM/ECMWF GUIDANCE DIFFER WITH  
REGARD TO THE PRECISE EVOLUTION OF THE PARENT CYCLONE IN NEW ENGLAND  
DURING THE DAY THU. THE GFS SOLUTION INDICATES A STRONGER CYCLONE  
AND TIGHTER MSLP/HEIGHT GRADIENT OVER THE MID-ATLANTIC/CAROLINAS  
THAN THE NAM, WHILE THE ECMWF IS SOMEWHERE IN-BETWEEN. ALTHOUGH THE  
DIFFERENCE IN THE SYNOPTIC PATTERN IS RELATIVELY SUBTLE, THE  
DIFFERENCE IS SUFFICIENT ENOUGH THAT WESTERLY FLOW WITHIN THE MIXED  
LAYER IS ~10 KNOTS STRONGER ON THE GFS IN COMPARISON TO THE NAM. AT  
A BLEND BETWEEN THE GFS/NAM SUGGESTS THAT W/WNW WINDS WILL BECOME  
SUSTAINED AT 15-25 MPH WITH FREQUENT GUSTS TO 30-35 MPH DURING THE  
STRONGEST PRESSURE RISES (6-8MB/6-HR BETWEEN 18-00Z) THURSDAY  
AFTERNOON. ADDITIONALLY, ALTHOUGH LESS LIKELY AT THIS TIME, 40+ MPH  
CONVECTIVE GUSTS COULD ACCOMPANY SHOWER ACTIVITY IN VICINITY OF THE  
FRONT ALONG/EAST OF I-95 LATE THU MORNING OR EARLY THU AFTERNOON.  
EXPECT HIGHS IN THE MID/UPPER 50S TO NEAR 60F (WARMEST NEAR SC  
BORDER). LOWS THU NIGHT IN THE LOWER TO MID 30S.  
 
FRI-SUN: LONG RANGE GUIDANCE CONTINUES TO INDICATE DRY CONDITIONS,  
BELOW NORMAL TEMPERATURES AND A BRISK W/WNW BREEZE DURING THE  
AFTERNOON HOURS FRI-SUN.  
 
SUNDAY NIGHT-MONDAY: THE LATEST 00Z GUIDANCE SUGGESTS THAT CANADIAN  
SHORTWAVE ENERGY DIGGING SOUTHWARD THROUGH THE UPPER GREAT LAKES AND  
WESTERN OHIO VALLEY ON SUNDAY MAY DIG FURTHER SOUTH/WEST THAN IN  
PREVIOUS RUNS. AS A RESULT, LIGHT PRECIPITATION (AND PTYPE ISSUES)  
MAY ACCOMPANY THE DEEPER /MORE AMPLIFIED/ UPPER LEVEL WAVE PROGGED  
TO TRACK ACROSS THE REGION SUNDAY NIGHT/MONDAY. -VINCENT  
 

 
   
AVIATION /18Z TUESDAY THROUGH SUNDAY/
 
 
AS OF 115 PM TUESDAY...  
 
NORTHWESTERLY WINDS AROUND 15KT, GUSTING TO AROUND 25KT, WILL  
CONTINUE THIS AFTERNOON AND THEN DIMINISH AS BY 00Z AS HIGH  
PRESSURES EDGES INTO THE REGION. WINDS OVERNIGHT WILL BE LIGHT  
AND SOUTHWESTERLY, OR CALM, WITH CLEAR SKIES AND VFR. VFR WILL  
CONTINUE ON WEDNESDAY WHILE A 5-10KT SOUTHWESTERLY WIND  
DEVELOPS.  
 
LOOKING AHEAD: VFR CONDITIONS ARE EXPECTED THROUGH WEDNESDAY. A  
COLD FRONT WILL CROSS THE REGION LATE WEDNESDAY NIGHT/EARLY  
THURSDAY, BRINGING WITH A CHANCE OF RAINS AND WHAT AREAS TO BE  
MAINLY MVFR/IFR CEILINGS TO THE AREA. VFR CONDITIONS SHOULD  
RETURN LATE THURSDAY AFTERNOON/EVENING.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...CBL  
NEAR TERM...SMITH/CBL  
SHORT TERM...CBL  
LONG TERM...VINCENT  
AVIATION...SMITH  
 
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