782  
FXUS62 KRAH 300827  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
427 AM EDT THU MAR 30 2017  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE WILL EXTEND ACROSS EASTERN NC THROUGH THURSDAY.  
AN AREA OF LOW PRESSURE WILL BRING UNSETTLED WEATHER TO THE AREA  
THURSDAY NIGHT AND FRIDAY.  
 

 
   
NEAR TERM /THROUGH TODAY/
 
 
AS OF 425 AM THURSDAY...  
 
THE SOUTHERN EDGE OF A SURFACE HIGH EXTENDING DOWN INTO THE AREA  
FROM THE NORTH IS BRINGING EASTERLY FLOW TO THE AREA BUT  
SOUTHEASTERLY FLOW ALONG THE APPALACHIANS AND AS A RESULT A GROWING  
AREA OF MVFR STRATUS IS STARTING TO BUILD IN ACROSS THE NORTHWEST  
PIEDMONT. THIS FEATURE WILL BE INFLUENTIAL ON TODAY'S WEATHER WHEN  
IT COMES TO SKY COVER, PRECIPITATION AND ULTIMATELY TEMPERATURES.  
LATER THIS MORNING DRIZZLE OR EVEN LIGHT RAIN WILL BE POSSIBLE  
ACROSS THE NORTHWEST PIEDMONT AS MORE MOISTURE FLOWS INTO THE AREA.  
DEPENDING UPON HOW THICK THE STRATUS BECOMES, AND MODEL SOUNDINGS  
SHOW A SIGNIFICANT CLOUD DECK ABOUT 8 KFT THICK, HIGH TEMPERATURES  
UNDER THE STRATUS COULD BE OVERDONE. AS A RESULT HAVE SLASHED  
TEMPERATURES ACROSS THE NORTH TO BELOW GUIDANCE WITH UPPER 50S IN  
THE TRIAD BUT A FAIRLY TIGHT GRADIENT WITH LOWER 70S ACROSS THE  
SOUTHERN COUNTIES. THE TRIANGLE WILL BE A MAJOR GAMBLE TODAY WITH  
ANYTHING FROM LOWER TO UPPER 60S POSSIBLE. FOR NOW HAVE CHOSEN TO GO  
ON THE LOWER END BUT A SAFE BET WILL BE THE MIDDLE 60S.  
 

 
   
SHORT TERM /THURSDAY NIGHT AND FRIDAY/
 
 
AS OF 420 AM THURSDAY...  
 
ATTENTION WILL TURN TO THE SOUTHWEST ON THURSDAY NIGHT AS A WARM  
FRONT SURGES IN AND TEMPERATURES SHOULD ACTUALLY BEGIN TO RISE  
OVERNIGHT AT MOST LOCATIONS. GOOD ISENTROPIC LIFT IN THE WEST WILL  
BEGIN TO ENCOURAGE PRECIPITATION OVER THE WESTERN PORTION OF THE CWA  
BETWEEN 0-6Z FRIDAY. MODEL FORECAST SOUNDINGS ARE VIRTUALLY  
SATURATED THROUGHOUT THE COLUMN WITH PW VALUES NEAR 1.3 INCHES. THE  
LOW LEVEL JET STRUCTURE IS FAIRLY UNORGANIZED EARLY FRIDAY MORNING  
AND THERE ARE SEVERAL SMALL DISTURBANCES IN THE FLOW SO EXPECT  
SEVERAL SMALLER WAVES OF PRECIPITATION WHICH COULD BE SCATTERED IN  
NATURE AT TIMES. AS THE PRECIPITATION PUSHES EASTWARD IT COULD  
BECOME A BIT MORE ORGANIZED INTO MORE MULTICELLULAR OR BROKEN LINES  
BUT SHEAR WILL BE DECREASING AT THIS TIME PARTICULARLY IN THE LOWER  
LEVELS AS WINDS BECOME SOUTHWESTERLY AND MORE UNIDIRECTIONAL WITH  
HEIGHT. INSTABILITY WILL INCREASE SLIGHTLY WITH PEAK HEATING AND A  
DYNAMIC PUSH FROM THE LEFT EXIT REGION OF A 500 MB JET COULD CAUSE A  
STORM OR TWO TO BECOME SEVERE. SPC HAS THE EASTERN HALF OF THE AREA  
IN A MARGINAL RISK FOR SEVERE WX WITH DAMAGING WINDS THE MOST LIKELY  
THREAT. WITH DECENT MOISTURE IN THIS SYSTEM EXPECT RAINFALL TOTALS  
ANYWHERE FROM A HALF OF AN INCH ON THE LOW END TO ABOUT AN INCH ON  
THE HIGH END.  
 
TEMPERATURES WILL BE TRICKY ON FRIDAY GIVEN THE CONVECTION BUT WITH  
CENTRAL NC IN THE WARM SECTOR FOR MUCH OF THE DAY EXPECT HIGHS IN  
THE LOW TO MID 70S IN MOST LOCATIONS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
 
 
AS OF 405 AM THURSDAY...  
 
AN ENERGETIC PACIFIC JET WILL SEND A SERIES OF SIGNIFICANT  
SHORTWAVE PERTURBATIONS INTO THE WEST-CENTRAL U.S., WHERE THE  
MODELS INDICATE THEY WILL AMPLIFY TOWARD THE FOUR CORNERS/SRN  
PLAINS REGION AND INTERACT WITH AN EQUALLY ENERGETIC SOUTHERN  
STREAM. THAT INTERACTION WILL ULTIMATELY SHEAR THE  
PERTURBATIONS ENEWD INTO THE MIDDLE ATLANTIC STATES, WITH  
ASSOCIATED EPISODES OF PRECIPITATION/CONVECTION, ABOUT EVERY 72  
HOURS IN CENTRAL NC. THIS A RELATIVELY PERSISTENT PATTERN FROM  
RECENT DAYS, WHICH INCLUDED THE ROUND OF CONVECTION FROM THIS  
PAST MON NIGHT, AND WHICH WILL LIKELY RESULT IN ANOTHER ONE  
LATER TONIGHT (HIGHLIGHTED IN THE SHORT TERM DISCUSSION ABOVE).  
 
FRI NIGHT: THE MODELS ARE NOW IN GOOD AGREEMENT WITH THE  
PROGRESSION OF THE UPPER LOW INITIALLY OVER THE CENTRAL PLAINS,  
TO THE NRN MIDDLE ATLANTIC COAST BY LATE FRI NIGHT. AN  
ACCOMPANYING SURFACE TROUGH AXIS/SECONDARY FRONT WILL CROSS THE  
NE PIEDMONT/NRN COASTAL PLAIN WITH A LINGERING CHANCE OF  
SHOWERS AND A STORM OR TWO FRI EVENING. OTHERWISE, CLEARING AND  
COOLING WILL OCCUR, WITH LOWS IN THE LOWER TO MIDDLE 50S.  
 
SAT-SUN: BENEATH LONGWAVE RIDGING BULGING NWD FROM THE CARIBBEAN  
TO CENTRAL CANADA, THE WEEKEND IS EXPECTED TO BE DRY, AND MILD,  
WITH A REINFORCING DRY FRONTAL PASSAGE (THE LEADING EDGE OF A  
PACIFIC HIGH) SAT NIGHT. PERIODS OF STRATOCUMULUS MAY BUBBLE  
BENEATH A STRONG, 5 K FT SUBSIDENCE INVERSION, BUT NOT WITH  
ENOUGH COVERAGE TO SIGNIFICANTLY IMPACT TEMPERATURES THROUGH THE  
PERIOD. HIGHS IN THE UPPER 60S TO 70S, WARMEST AHEAD OF THE  
REINFORCING FRONT ON SAT. LOWS, COOLEST SUN MORNING IN THE 40S,  
AND ABOUT A CATEGORY HIGHER IN RETURN SELY FLOW AND INCREASING  
DEEP MOISTURE BY MON MORNING.  
 
THE NEXT COUPLE OF STRONG SHORTWAVE PERTURBATIONS WILL FOLLOW  
ON SCHEDULE AND CROSS CENTRAL NC LATE MON-MON NIGHT AND AGAIN  
JUST BEYOND THIS FORECAST PERIOD (THU). THE RESULT WILL BE  
ANOTHER LIKELY PROBABILITY OF SHOWERS AND STORMS LATE MON-MON  
NIGHT, PRECEDED BY POSSIBLE WEAK IN-SITU CAD DURING THE DAY  
MON. IT WILL OTHERWISE BE MILD THROUGH THE PERIOD, WITH  
TEMPERATURES MOSTLY IN THE 70S AND 50S FOR HIGHS AND LOWS,  
RESPECTIVELY.  
 

 
   
AVIATION /06Z THURSDAY THROUGH MONDAY/
 
 
AS OF 200 AM THURSDAY...  
 
24 HOUR TAF PERIOD: SOUTHEASTERLY FLOW BEGINNING TO DAM UP AGAINST  
THE MOUNTAINS IS STARTING TO PRODUCE A SHIELD OF STRATUS OVER  
SOUTHWEST VA WHICH IS EXPANDING SOUTHWARD. EXPECT THIS CLOUD COVER  
TO BEGIN TO MOVE INTO THE TRIAD OVER THE NEXT COUPLE OF HOURS BUT IT  
MAY BE A WHILE LONGER BEFORE IT BEGINS TO LOWER TO MVFR LEVELS.  
RIGHT NOW THE LOWEST OBS OUT OF VA ARE ALL NEAR 5 KFT. EVENTUALLY  
EXPECT CLOUD BASES TO SETTLE NEAR 1500 FEET. BETWEEN 9-12Z MVFR  
CONDITIONS MAY REACH KRDU BUT DONT EXPECT THEM TO REACH KRWI OR KFAY  
BEFORE LIFTING. CONTINUED SOUTHEASTERLY FLOW MAY KEEP MVFR  
CONDITIONS LOCKED INTO THE TRIAD FOR THE ENTIRETY OF THE TAF PERIOD.  
SOME LIGHT PRECIPITATION IS ALSO POSSIBLE LATER THIS MORNING IN THE  
TRIAD. LATER IN THE TAF PERIOD SOME MORE SIGNIFICANT SHOWERS  
ASSOCIATED WITH A WARM FRONT WILL MOVE THROUGH THE TRIAD AND KFAY  
BEFORE MOVING THROUGH KRDU AND EVENTUALLY KRWI. MVFR OR POSSIBLY  
EVEN IFR CONDITIONS COULD BE ASSOCIATED WITH THIS WAVE OF CONVECTION.  
 
LONG TERM: AFTER THE WARM FRONT ROLLS THROUGH THE AREA AT THE END OF  
THE TAF PERIOD, A COLD FRONT WILL FOLLOW ON ITS HEELS ON FRIDAY  
SPARKING ANOTHER ROUND OF CONVECTION. THIS WILL CLEAR OUT ON FRIDAY  
NIGHT AND GIVE WAY TO QUIET CONDITIONS UNTIL MONDAY WHEN ANOTHER  
STRONG LOW PRESSURE SYSTEM IS PROGGED TO CROSS CENTRAL NC CAUSING  
POTENTIALLY ADVERSE AVIATION CONDITIONS.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
 
SYNOPSIS...WSS  
NEAR TERM...ELLIS  
SHORT TERM...ELLIS  
LONG TERM...MWS  
AVIATION...ELLIS  
 
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