AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
310 PM EST SAT FEB 28 2015

.SYNOPSIS...COLD HIGH PRESSURE REMAINS OVER THE REGION THROUGH 
SUNDAY. INCREASING MOISTURE WILL HELP PROVIDE FOR UNSETTLED WEATHER 
SUNDAY. A COLD FRONT MOVES THROUGH THE AREA MONDAY...FOLLOWED BY 
HIGH PRESSURE AGAIN FOR TUESDAY...BEFORE ANOTHER COLD FRONT MOVES 
INTO THE REGION WEDNESDAY.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
AS OF 310 PM SATURDAY... 

...LIGHT ICING EVENT LIKELY FOR THE NC PIEDMONT AND WRN 
SANDHILLS LATE TONIGHT INTO SUNDAY...

OVERVIEW: WINTER IS MOST CERTAINLY NOT OVER YET. MORE WINTRY 
PRECIP... DRIVEN PRIMARILY BY INCREASING MOIST ISENTROPIC UPGLIDE 
ATOP THE COLD WEDGING SURFACE HIGH CENTERED TO OUR NE... APPEARS 
LIKELY TO DEVELOP AND ENTER SOUTH-CENTRAL NC LATE TONIGHT BEFORE 
INCREASING IN COVERAGE AND SPREADING NORTHWARD OVER THE REMAINDER OF 
THE PIEDMONT ON SUNDAY. 

SYNOPTIC PATTERN: WE'LL MAINTAIN A FAST MID LEVEL FLOW FROM THE WSW 
(TRENDING TO BE FROM THE WEST) OVER NC. AT THE SURFACE... THE PARENT 
HIGH PROVIDING THE CHILLY AIR WILL SHIFT OFF THE NORTHEAST COAST 
LATE TONIGHT... ALLOWING THE INVERTED TROUGH ALONG THE SE COAST AND 
COASTAL NC TO SHARPEN. THIS WILL CULMINATE IN A RESIDUAL STABLE COLD 
POOL (AND MESOHIGH) OVER THE FAR WRN PIEDMONT/FOOTHILLS OF NC/SC 
LATE SUN INTO SUN NIGHT. AT 850 MB... A WEAK WAVE WILL TRACK FROM 
NRN FL TO THE NORTH... RESULTING IN STRENGTHENING FLOW JUST ALOFT 
AND AN INCREASINGLY PRONOUNCED WARM NOSE IN CENTRAL NC THERMAL 
PROFILES. THIS WAVE WILL TRACK TO OUR NE SUN EVENING/SUN NIGHT... 
LEADING TO AN EVENTUAL END TO PRECIP FROM WEST TO EAST. 

PRECIP TIMING AND AMOUNTS: HAVE MAINLY FOLLOWED A BLEND OF THE HIGH-
RESOLUTION WRF-NMM/WRF-ARW... THE HRRR... AND DOWNSCALED NAM QPF AND 
TIMING. EXPECT PATCHY LIGHT PRECIP TO MOVE INTO THE SRN PIEDMONT AND 
SANDHILLS AFTER MIDNIGHT TONIGHT... WITH LOW COVERAGE AND JUST TRACE 
AMOUNTS. THEN AS THE MOIST UPGLIDE DEEPENS AND STRENGTHENS... EXPECT 
PRECIP TO INCREASE TO AT LEAST 50-60% COVERAGE (AND THIS MAY NEED TO 
BE RAISED IF LATER MODEL RUNS ARE CONSISTENT) OVER THE PIEDMONT 
SUNDAY MORNING... SPREADING EAST OVER THE REST OF THE CWA DURING THE 
AFTERNOON... BEFORE ENDING WEST TO EAST SUN NIGHT. MODELS DEPICT A 
FAIRLY LIGHT QPF... ESPECIALLY INITIALLY OVER THE SANDHILLS UP 
THROUGH THE EASTERN PIEDMONT WHERE THERE WILL BE SOME MINOR DRY 
POCKETS ALOFT. THIS IS REASONABLE CONSIDERING THE RELATIVELY SHALLOW 
NATURE OF THE LIFT. EXPECT TOTAL QPF GENERALLY FROM 0.25 TO 0.40... 
WITH LOWER AMOUNTS IN THE SE CWA TRENDING TO THE HIGHER AMOUNTS IN 
THE NW CWA. 

PRECIP TYPE: FOLLOWING THE TOP-DOWN PTYPE METHODOLOGY... EXPECT ANY 
INITIAL PRECIP TO BE SOME VERY LIGHT FREEZING DRIZZLE (DUE TO 
SOMEWHAT DRY AIR ALOFT LIMITING ICE IN THE CLOUD)... TRENDING TO 
MAINLY LIGHT FREEZING RAIN OVER NRN/WRN CWA. THE ENCROACHING WARMER 
SURFACE AIR (AS THE COLD DOME THINS ON THE EDGES) WILL RESULT IN AN 
HOUR-BY-HOUR TRANSITION TO LIGHT RAIN FROM SE TO NW... WITH THE 
FREEZING RAIN THREAT LAST DEPARTING FROM THE TRIAD/ROXBORO AREAS 
LATE IN THE AFTERNOON AS WET BULBS THERE RISE TO AROUND FREEZING. AS 
THE SURFACE HIGH WILL BE RETREATING NE AWAY FROM THE AREA... IT WILL 
SLOWLY LOSE ITS GRIP ON OUR AREA AND CEASE TO PROVIDE A STEADY 
SOURCE OF LOW LEVEL DRY AIR THAT MIGHT ENSURE CONTINUED GLAZE BUILD-
UP. SO WITH TIME... LATENT HEAT RELEASE WILL SERVE TO LIMIT ICE 
ACCRUAL... SUCH THAT SOME OF THE QPF IN THE LATTER HOURS OF THE 
EVENT WILL SIMPLY RUN OFF. THAT SAID HOWEVER... BASED ON FORECAST 
SURFACE WET BULB TEMPS AND BUFR SOUNDINGS... IT APPEARS THAT THERE 
WILL BE A DEEP ENOUGH SURFACE COLD LAYER TO SUPPORT A LIGHT GLAZING 
OVER MUCH OF THE WESTERN TWO-THIRDS OF THE CWA... WITH THE GREATER 
AMOUNTS (PERHAPS AT OR JUST OVER A TENTH OF AN INCH) OVER THE 
CLIMATOLOGICALLY-FAVORED NW CWA. 

TEMPERATURES: READINGS WILL FOLLOW AN ATYPICAL TREND THROUGH SUNDAY 
NIGHT. EXPECT LOWS TONIGHT OF 23-33... HIGHS SUNDAY OF 32-39 WEST OF 
I-95 AND MAINLY 40S EAST OF I-95... AND LOWS SUN NIGHT 32-44... 
ALTHOUGH TEMPS SUN EVENING/NIGHT SHOULD BE STEADY OR PERHAPS RISE A 
COUPLE OF DEGREES OVERNIGHT AS THE RESIDUAL COOL POOL STARTS TO MIX 
OUT IN THE FACE OF INCREASING WSW FLOW ALOFT LATE. -GIH 

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/... 
AS OF 220 PM SATURDAY...

THE APPROACHING UPPER LEVEL TROUGH WEAKENS AS IT MOVES THROUGH 
CENTRAL NC ON MONDAY. LATEST MODEL RUNS INDICATE MONDAY WILL BE 
MOSTLY DRY...WITH A SLIGHT CHANCE OF SOME LIGHT PRECIPITATION EARLY 
IN THE DAY...DRYING INTO THE AFTERNOON AS THE RAINFALL ALONG THE 
FRONT DISSIPATES OVER THE MOUNTAINS. THE COLD FRONT WILL TILT TO A 
MORE WEST TO EAST ORIENTATION AND SLIDE THROUGH THE AREA BY MONDAY 
EVENING. SURFACE HIGH PRESSURE WILL BUILD IN THEREAFTER AND REMAIN 
THROUGH MONDAY NIGHT. ALTHOUGH TEMPERATURES SHOULD RISE DURING THE 
DAY GIVEN GRADUALLY CLEARING SKIES AND THUS GOOD SUNSHINE...THE 
INCREASES WILL BE GREATEST ACROSS THE SOUTH WHERE THE FROPA HAPPENS 
LATER. HIGHS WILL RANGE FROM UPPER 40S ACROSS THE NORTH TO UPPER 50S 
IN THE SOUTH...ALTHOUGH THEY ARE HIGHLY DEPENDENT ON THE TIMING OF 
THE FRONT. OVERNIGHT LOWS SHOULD BE IN TEH UPPER 20S NORTH TO UPPER 
30S SOUTH.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/... 
AS OF 300 PM SATURDAY...

TUESDAY THROUGH THURSDAY NIGHT: THE UPPER LEVEL TROUGH ASSOCIATED 
WITH AN UPPER LEVEL LOW OVER CENTRAL CANADA ON TUESDAY WILL EXTEND 
SOUTHWEST THROUGH THE INTERMOUNTAIN WEST AND INTO THE DESERT 
SOUTHWEST. AT THE SURFACE...THE COLORADO LOW THAT DEVELOPS ON MONDAY 
WILL BEGIN ITS TREK EASTWARD THROUGH THE MIDWEST MONDAY NIGHT... 
SLIDING NORTHEAST INTO THE GREAT LAKES ON TUESDAY. THE ASSOCIATED 
COLD FRONT THAT DEVELOPS WILL EXTEND FROM APPROX THE CENTRAL GREAT 
LAKES TO THE ARKLATEX BY LATE TUESDAY. 

ACROSS CENTRAL NC...THE CAD WEDGE THAT SET UP MONDAY NIGHT WILL 
LINGER THROUGH THE DAY TUESDAY. THE FORECAST PROBLEM FOR THIS PART 
OF THE FORECAST CONTINUES TO BE HIGH UNCERTAINTY IN TEMPERATURES DUE 
TO THE LINGERING WEDGE AND THE WARM FRONT RETREATING NORTHWARD. THE 
MODELS HAVE A TENDENCY TO ERODE THE WEDGE TOO QUICKLY...ESPECIALLY 
IF THERE IS PRECIPITATION FALLING INTO IT...SO CURRENTLY INDICATE 
THE WEDGE STICKING AROUND A BIT LONGER...WITH A LARGE SPREAD IN 
TEMPS FROM NW TO SE ACROSS THE AREA TUESDAY AND WEDNESDAY. 
CONFIDENCE REMAINS LOW WITH RESPECT TO TEMPS...AS ANY CHANGES TO THE 
WEDGE EROSION AND TIMING/POSITION OF THE WARM FRONT AS IT RETREATS 
NORTHWARD WILL HIGHLY IMPACT TEMPERATURES. THEY WILL HOWEVER 
INCREASE GRADUALLY FROM MIDNIGHT WEDNESDAY THROUGH AROUND MIDNIGHT 
THURSDAY AS THE WARM FRONT RETREATS NORTHWARD. SHOULD THE WEDGE BE 
LOCKED IN LONGER OR ERODE EARLIER CURRENT FORECAST TEMPS WOULD BE 
WAY OFF. TEMPS: LOW 40S NW TO MID 50S SE TUESDAYS...INCREASING TO 
LOW 60S NW TO LOW 70S SE ON WEDNESDAY. A NORMAL DIURNAL TEMPERATURE 
CURVE SHOULD RETURN WEDNESDAY NIGHT. LOWS IN THE LOW 40S NW TO LOW 
50S SE. HIGHS THURSDAY MID 40S NW TO MID 50S SE.

PRECIPITATION: SOME LIGHT RAIN COULD FALL INTO THE WEDGE ON TUESDAY 
AS WARM MOIST AIR FROM THE SOUTH ADVECTS IN OVER THE COLD AIR 
TRAPPED AT THE SURFACE. THIS WOULD ACT TO THEN LOCK THE WEDGE IN 
LONGER. THERE WILL BE A SLIGHT CHANCE TO CHANCE OF PRECIP ACROSS THE 
WEST/NORTHWEST PORTIONS OF THE AREA THROUGH WEDNESDAY MORNING... 
EVEN THOUGH THE MAIN PRE-FRONTAL CONVECTIVE RAINFALL REMAINS LARGELY 
WEST OF THE APPALACHIANS. THE LATEST 12Z ECMWF AND GFS MODEL RUNS 
ARE IN BETTER AGREEMENT WITH THE TIMING OF THE FROPA AND THE 
ASSOCIATED RAINFALL AS IT MOVES THROUGH THE AREA. THE LATEST RUNS 
SUGGEST THAT RAIN WILL BE LIKELY ACROSS THE WEST BEGINNING WEDNESDAY 
AFTERNOON...PROGRESSING THROUGH CENTRAL NC WEDNESDAY NIGHT AND 
THURSDAY...AND ENDING AROUND MIDNIGHT FRIDAY. THIS IS ANOTHER CASE 
OF THE COLD AIR CHASING THE PRECIP...AND FOR NOW EXPECT ALL PRECIP 
TO FALL AS RAIN...BUT THAT WILL CONTINUE TO BE MONITORED WITH 
SUBSEQUENT FORECAST UPDATES AS THAT PERIOD APPROACHES.

FRIDAY THROUGH SATURDAY: HIGH PRESSURE WILL BUILD IN BEHIND THE 
FROPA THURSDAY NIGHT...REMAINING OVER THE REGION INTO THE WEEKEND. 
EXPECT A DRY FORECAST PERIOD FOR NOW...WITH HIGHS IN THE LOW TO MID 
40S FRIDAY...INCREASING INTO THE 50S SATURDAY. LOWS FRIDAY NIGHT IN 
THE 20S.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 1235 PM SATURDAY...

PRIMARY AVIATION CONCERNS NEXT 24 HRS: CIGS DROPPING TO MVFR AND IFR 
STARTING LATE THIS EVENING (SOUTH) INTO THE EARLY OVERNIGHT HOURS 
(NORTH)... WITH POTENTIAL LOW LEVEL WIND SHEAR DEVELOPING.

SURFACE HIGH PRESSURE CENTERED TO OUR NORTH NEAR BALTIMORE WILL 
CONTINUE TO NOSE SOUTHWARD INTO CENTRAL/WRN NC THROUGH THIS EVENING. 
EXPECT NO MORE THAN A DECK OF VFR MID CLOUDINESS THROUGH THE 03Z 
(FAY) TO 06Z (RDU/RWI) TIME FRAME... WITH VFR VSBYS. A DEVELOPING 
INVERTED TROUGH NEAR THE COAST COMBINED WITH A SURGE OF MOISTURE 
FROM NRN FL SPREADING NORTHWARD INTO WRN/CNTRL NC OVERNIGHT WILL 
BRING A GROWING RISK OF PRECIP LATE... SPREADING IN FROM SOUTH TO 
NORTH... WITH LIGHT PRECIP AFFECTING FAY FIRST THEN MOVING INTO 
INT/GSO/RDU AREAS LATE TONIGHT. RWI MAY NOT SEE MUCH IF ANY PRECIP 
UNTIL NEAR 18Z SUNDAY OR LATER. CIGS WILL LOWER TO MVFR THEN RAPIDLY 
TO IFR LATE TONIGHT INTO EARLY SUN MORNING... WITH A GOOD CHANCE OF 
LOW LEVEL WIND SHEAR ESPECIALLY AT FAY STARTING AS EARLY AS 09Z. 
CONFIDENCE IS HIGH IN IFR OR LIFR CIGS AFTER 10Z-12Z SUNDAY. 
FREEZING RAIN IS THE MOST LIKELY PRECIP TYPE AT INT/GSO LATE TONIGHT 
THROUGH SUNDAY... WITH FREEZING RAIN CHANGING TO RAIN AT RDU... AND 
BRIEF FREEZING RAIN CHANGING EARLY TO RAIN AT FAY. GLAZING OF ICE IS 
MOST LIKELY AT INT/GSO... LESS SO AT RDU/FAY. 

LOOKING BEYOND 18Z SUNDAY... IFR/LIFR CONDITIONS WILL HOLD THROUGH 
THE REST OF SUNDAY WITH PRECIP SPREADING ENE INTO RWI. EVEN IF LLWS 
CRITERIA ARE NOT STRICTLY MET... WINDS AT ALL SITES WILL BE 
INCREASING WITH HEIGHT FROM THE SW THROUGH THE LOWEST 2-3 KFT... 
MAKING HANDLING OF SOME AIRCRAFT CHALLENGING. PRECIP ENDS EARLY 
SUNDAY EVENING BUT LIFR CLOUDS EXPECTED TO LINGER THROUGH SUNDAY 
NIGHT... THEN ERODE FROM THE TOP MONDAY AS A COLD FRONT SWEEPS 
THROUGH FROM NW TO SE. HIGH PRESSURE BUILDS IN FROM THE NORTH LATE 
MON THROUGH MON NIGHT... THEN ANOTHER APPROACHING STORM SYSTEM WILL 
BRING A GOOD CHANCE OF SUB-VFR CIGS EARLY TUE THROUGH TUE NIGHT. MAY 
SEE A BREAK TO MVFR OR VFR CIGS WED... BUT YET ANOTHER STORM SYSTEM 
IS POISED TO BRING INCREASING WINDS WED THEN MORE SUB-VFR CONDITIONS 
AND PRECIP WED NIGHT/THU. -GIH

&&

.RAH WATCHES/WARNINGS/ADVISORIES... 
WINTER WEATHER ADVISORY FROM 4 AM TO NOON EST SUNDAY FOR 
NCZ008>010-024>026-040-041-073>076.
WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST SUNDAY FOR 
NCZ077-083>086-088.
WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST SUNDAY FOR 
NCZ007-021>023-038-039.

&&

$$

SYNOPSIS...DJF 
NEAR TERM...HARTFIELD 
SHORT TERM...KC 
LONG TERM...KC 
AVIATION...HARTFIELD



National Weather Service Glossary of Abbreviations
Back to forecast page
Expanded Version (without abbreviations)

Units: English | Metric

Find the Weather for any City, State or Zipcode, or Country:

U.S. State List | Severe Weather | Tropical Storms | Ski Conditions
United States | Canada | Central America | South America | Asia | Europe | Australia | Africa | Islands

Weather Underground Copyright© 2015
Weather Underground, Inc.

Questions or Comments? Contact Us