Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 020349
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1023 PM EDT MON SEP 1 2014

.SYNOPSIS...AN AREA OF HIGH PRESSURE WILL EXTEND OVER THE REGION
THROUGH TUESDAY. A WEAK SURFACE FRONT WILL SETTLE SOUTHWARD ACROSS
CENTRAL NC ON WEDNESDAY. HIGH PRESSURE WILL BUILD BACK OVER THE AREA
FOR THE REMAINDER OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1010 PM MONDAY...

MID LEVEL RIDGE... CENTERED TO THE SSW OF CENTRAL NC OVER THE DEEP
SOUTH... WILL EXTEND INTO OUR REGION TONIGHT. HOWEVER... WEAK
DISTURBANCES IN THE WESTERLY MID LEVEL FLOW WILL HELP TO KEEP SKIES
PARTLY CLOUDY AT TIMES. THE LATEST HI-RES GUIDANCES CONTINUES TO
KEEP DRY CONDITIONS OVER CENTRAL NC THOUGH. THUS... WILL CONTINUE A
DRY FORECAST FOR TONIGHT WITH MOSTLY CLEAR TO PARTLY CLOUDY SKIES.
LOWS TUESDAY MORNING ARE EXPECTED TO BE NEAR 70/LOWER 70S TO MID 70S
SE.

WILL LIKELY SEE PATCHES OF FOG DEVELOP AFTER MIDNIGHT...MAINLY OVER
THE COASTAL PLAIN..SANDHILLS AND EASTERN PIEDMONT. HOWEVER DENSE FOG
WILL BE RARE WITH BULK OF THE VISIBILITIES AT OR ABOVE 1-2 MILES.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 305 PM MONDAY...

TUESDAY AND TUESDAY NIGHT... MID-UPPER LEVEL RIDGE PROJECTED TO
SLOWLY WEAKEN THIS PERIOD. THIS MAY ALLOW A FEW MORE T-STORMS TO
DEVELOP IN THE SLIGHT-MODERATELY UNSTABLE AIR MASS TUESDAY AFTERNOON-
EVENING. IN ADDITION...A S/W RESPONSIBLE FOR TRIGGERING THE
CONVECTION ACROSS PARTS OF THE MISSOURI VALLEY/OZARKS THIS AFTERNOON-
EVENING WILL APPROACH CENTRAL NC FROM THE NW LATE IN THE DAY. THIS
FEATURE MAY TRIGGER ADDITIONAL ISOLATED-SCATTERED CONVECTION TUESDAY
EVENING ACROSS THE NW PIEDMONT...AND OVERNIGHT TUESDAY INTO EARLY
WEDNESDAY OVER THE REMAINDER OF CENTRAL NC. WHILE FORCING IS BETTER
COMPARED TO THE PAST FEW DAYS...LIFT IS STILL CONSIDERED WEAK-
MARGINAL AT BEST. THUS WILL LIMIT POPS TO NO HIGHER THAN LOW CHANCE.

ANOTHER HOT DAY IN STORE FOR THE REGION. AFTERNOON THICKNESSES WILL
REMAIN 20-25M ABOVE NORMAL...SUPPORTIVE OF HIGH TEMPS IN THE LOW-MID
90S UNDER FULL SUN CONDITIONS. WHEN THE HUMIDITY IS FACTORED
IN...HEAT INDEX VALUES NEAR 100-104 WILL BE COMMON WITH THE HIGHEST
H.I.VALUES IN THE SOUTHERN COASTAL PLAIN AND SANDHILLS. MIN TEMPS
TUESDAY NIGHT GENERALLY IN THE LOWER 70S. -WSS

FOR WED/WED NIGHT: THE WEAK SURFACE REFLECTION THAT REMAINS FROM THE
COLD FRONT APPROACHING CENTRAL NC WILL BECOME EVEN MORE WASHED OUT
AS IT SHIFTS INTO THE LEE TROUGH OVER CENTRAL NC. MODELS SHOW A VERY
WEAK VORTICITY LOBE ASSOCIATED WITH THIS FRONT PUSHING ESE THROUGH
NC EARLY WED... AND ITS APPROACH ALONG WITH LINGERING STRONG LOW
LEVEL MOISTURE TRANSPORT OVER ERN NC SHOULD SUPPORT AN AREA OF
ATYPICAL MORNING SHOWERS/STORMS OVER THE ERN AND ESPECIALLY SE CWA
WED MORNING. THE DEPARTURE AND DAMPENING OF THE MEAN MID LEVEL
TROUGH WELL TO OUR NE WILL RESULT IN MODEST RISING HEIGHTS (15-25 M)
WITHIN THE FLAT (W-E ORIENTED) MID LEVEL RIDGE ACROSS NC THROUGH WED
NIGHT. THE LATEST NAM RUN IS CONSISTENT WITH PREVIOUS RUNS IN
BRINGING LOWER PW (UNDER 1.5") INTO MUCH OF THE CWA FROM THE NW WITH
A BIT STRONGER 850-700 MB NW WIND AS COMPARED TO THE GFS... WHICH
KEEPS PW VALUES UP TO 1.7-1.9". GIVEN THE FACT THAT THE MID LEVEL
TROUGH WILL BE DAMPENING WITH LITTLE REASON TO SUPPORT A STRONG PUSH
OF DRY AIR PAST THE MOUNTAINS... THE GFS`S MORE SUBDUED TROUGH
INFLUENCE APPEARS MORE LIKELY... BASED ON THE PERSISTENCE OF THE
STRONG RIDGE. MODERATE INSTABILITY IS EXPECTED OVER ALL BUT PERHAPS
THE FAR NW... WITH THE GFS SHOWING MUCAPE PEAKING AT 1000-2500 J/KG.
WILL STAY CLOSE TO THE GFS/ECMWF SOLUTION WITH SCATTERED AFTERNOON
THROUGH EVENING STORMS... WITH BEST COVERAGE ACROSS THE SOUTHERN CWA
AND ALONG/EAST OF THE PERSISTENT LEE TROUGH... AS WELL AS ALONG THE
INLAND-TRACKING SEA BREEZE. WITH ABOVE-NORMAL PW AND WEAK MID LEVEL
FLOW... SLOW-MOVERS AND HEAVY-RAINERS ARE POSSIBLE. WITH THICKNESSES
A TAD LOWER THAN TUE BUT REMAINING 12-20 M ABOVE NORMAL... EXPECT
WARM AND STICKY HIGHS OF 91-95... DESPITE A GOOD CHANCE OF DEBRIS
CLOUD COVER THROUGH THE DAY. CONVECTION CHANCES SHOULD RECEDE WED
NIGHT BUT THE GFS INDICATES PLENTY OF ELEVATED BUOYANCY POTENTIAL
OVERNIGHT... INCLUDING MLCAPE OF 500-1000 J/KG RESULTING FROM VERY
WARM 960-920 MB TEMPS. WILL HOLD ONTO CHANCE POPS MAINLY SOUTH HALF
OVERNIGHT. MUGGY LOWS IN THE LOW-MID 70S. -GIH

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 230 PM MONDAY...

FOR THU/FRI: CONTINUED ABOVE-NORMAL WARMTH WITH ONLY MINOR CHANGES
IN AIR MASS. AT THE SURFACE... THE WEAK LEE TROUGH HOLDS THROUGH
CENTRAL NC... ALONG WITH A HUMID AND SOMEWHAT STAGNANT AIR MASS. A
POSITIVELY TILTED TROUGH SHIFTS THROUGH THE PACIFIC NORTHWEST AND SW
CANADA INTO THE DAKOTAS THU... RESULTING IN BUILDING HEIGHTS AND
GRADUAL MID LEVEL WARMING OVER THE SOUTHEAST STATES. THIS POLAR
STREAM TROUGH THEN SHIFTS INTO ERN CANADA... WHILE THE FLAT RIDGE
HOLDS ACROSS NC. WITH PLENTY OF LOW LEVEL MOISTURE POOLING...
ISOLATED TO SCATTERED STORMS FOCUSED ALONG A SEA BREEZE OR SOME
OTHER SUBTLE BOUNDARY REMAIN A GOOD BET... DESPITE THE WARMING TEMPS
ALOFT. WILL RETAIN AFTERNOON AND EVENING STORM CHANCES BOTH DAYS...
WITH TEMPS HOLDING ABOUT A CATEGORY ABOVE NORMAL AS THICKNESSES STAY
10-15 M ABOVE NORMAL.

FOR SAT THROUGH MON: A PATTERN TRANSITION IS LIKELY NEXT WEEKEND.
THE INITIAL MID LEVEL TROUGH CONTINUES HEADING EASTWARD OVER ERN
CANADA EARLY SAT... HOWEVER A SLUG OF STRONG VORTICITY EMANATING
FROM A STRONG COLD VORTEX OVER THE BEAUFORT SEA WILL PUSH EASTWARD
CLOSE ON ITS HEELS... TAKING A COLD FRONT TO NEW ENGLAND AND THE OH
VALLEY BY EARLY SAT. THE RESULTING TROUGH OVER ERN NOAM SUNDAY
SHOULD HELP PUSH THE FRONT SOUTHWARD INTO NC... AFTER WHICH TIME IT
IS APT TO LAY WEST/EAST AND STALL OVER THE CAROLINAS FOR LATE SUN
THROUGH MON. THE GFS HAS A STRONGER/FASTER TIME FRAME THAN THE
ECMWF... WITH THE FORMER MODEL SOLUTION TAKING THICKNESSES MUCH
COLDER... UP TO 25 M BELOW NORMAL AS OPPOSED TO THE ECMWF WHICH IS
BARELY 5 M BELOW NORMAL. TOUGH TO RESOLVE SUCH DIFFERENCES BUT GIVEN
THE STRENGTH OF THE SRN CONUS RIDGE... AND THE FAR-NORTH TRACK OF
THE POLAR LOW... I REMAIN SKEPTICAL ABOUT A STRONG COLD FRONTAL
PASSAGE THROUGH NC. WILL STAY ON THE CONSERVATIVE SIDE OF THE TEMP
TREND... WITH HIGHS/LOWS INITIALLY AROUND 90/AROUND 70 SAT...
SLIPPING TO LOW-MID 80S/UPPER 60S BY MON. PRECIP CHANCES AND
PATTERNS ARE LIKELY TO CHANGE LITTLE THROUGH SUN... PERHAPS
INCREASING IN COVERAGE AS THE FRONT APPROACHES WITH FALLING HEIGHTS
ALOFT... STRENGTHENING (YET STILL SOMEWHAT WEAK) MID LEVEL FLOW...
AND A PERSISTENT CONFLUENT INFLUX OF GULF AND ATLANTIC MOISTURE IN
THE LOW LEVELS. WILL MAINTAIN SCATTERED SHOWERS AND STORMS FOCUSED
ON -- BUT NOT RESTRICTED TO -- AFTERNOON AND EVENING HOURS. WILL
KEEP A CLIMO CHANCE POP ON MON... WITH LOWER THAN USUAL CONFIDENCE
AS CONVECTION WILL GREATLY DEPEND ON WHETHER THE FRONT HOLDS UP
ACROSS NC OR SHIFTS TO OUR SOUTH. -GIH

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 800 PM MONDAY...

MOSTLY VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGHOUT THE CURRENT
TAF PERIOD. THE EXCEPTION WILL A BRIEF PERIOD OF LOW STRATUS/FOG
TOWARDS DAYBREAK ON TUESDAY...MOST LIKELY ACROSS THE EASTERN HALF OF
THE FORECAST AREA AND WITH KRWI HAVING THE HIGHEST PROBABILITY (GIVEN
THE PERSISTENT AIR MASS IN PLACE). AFTER ALMOST CALM WINDS
OVERNIGHT...MOSTLY LIGHT (UNDER 10 KNOTS) SOUTHWESTERLY WINDS WILL
PREVAIL. ISOLATED STORMS ARE EXPECTED TUESDAY AFTERNOON/EVENING.

OUTLOOK...TYPICAL SUMMERTIME CONDITIONS ARE EXPECTED TO PERSIST
THROUGH THE PERIOD...FEATURING DIURNAL CONVECTION EACH
AFTERNOON/EVENING AND PATCHY FOG/LOW CLOUDS DURING THE PRE-DAWN
MORNING HOURS.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...WSS
NEAR TERM...BSD/WSS
SHORT TERM...WSS/HARTFIELD
LONG TERM...HARTFIELD
AVIATION...KRD


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