Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 281110
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
710 AM EDT TUE APR 28 2015

.SYNOPSIS...HIGH PRESSURE WILL EXTEND INTO THE AREA FROM THE
NORTHWEST TODAY AND TONIGHT. MEANWHILE... LOW PRESSURE STRENGTHENING
ALONG THE GULF COAST TODAY WILL TRACK EAST THEN NORTHEAST OVER THE
SOUTHEAST STATES LATE TONIGHT THROUGH WEDNESDAY NIGHT... THEN SLOWLY
PULL OFF THE CAROLINA COAST THURSDAY.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
AS OF 320 AM TUESDAY...

TODAY: HIGH CONFIDENCE IN A MOSTLY SUNNY AND QUIET DAY. A SURFACE
FRONTAL ZONE CONTINUES TO SINK TO OUR SOUTH.... AS HIGH PRESSURE
CENTERED WELL TO OUR NW BUILDS INTO THE AREA. DEEP DRY AND SINKING
AIR WILL ENSURE DRY CONDITIONS... AND LITTLE IN THE WAY OF
SUBSTANTIAL CLOUD COVER DESPITE A LOBE OF VORTICITY DROPPING DOWN
THE MIDATLANTIC COAST AND ERN NC... ON THE SE SIDE OF THE LARGE
VORTEX OVER THE NW ATLANTIC. HOWEVER... DO ANTICIPATE SOME HIGH THIN
CLOUDS... MAINLY IN THE SOUTH... AS CIRRUS SPREADS OUT FROM A
CONVECTIVE COMPLEX OVER THE NORTH CENTRAL GULF. THE LIGHT BREEZE
FROM THE NORTH AND NE AND THICKNESSES THAT ARE EXPECTED TO BE UP TO
40 M BELOW NORMAL WILL EQUATE TO WELL BELOW NORMAL TEMPS... IN THE
MID-UPPER 60S... DESPITE THE MILKY SUNSHINE.

TONIGHT: CLOUDS SHOULD BE ON THE INCREASE AS THE POTENT MID LEVEL
LOW SITTING OVER NRN TX BEGINS TO OPEN UP AND TRACK TO THE EAST...
MOVING TO AL/WRN GA BY DAYBREAK WED. DPVA WILL SPREAD INTO OUR AREA
FROM THE SW TONIGHT... LEADING TO THICKENING AND LOWERING CLOUD
BASES OVERNIGHT. BUT ANY DYNAMIC FORCING FOR ASCENT OVER CENTRAL NC
WILL BE BRIEF AND WEAK... AND MODELS ARE QUITE DRY BELOW 700 MB... A
REFLECTION OF THE EXPANSIVE SURFACE HIGH STILL NOSING IN FROM THE
WNW. REGARDING THE SURFACE LOW NOW CENTERED NEAR THE CONVECTIVE
COMPLEX OVER THE NORTH CENTRAL GULF... THE LATEST MODEL RUNS ARE
SUPPRESSING THE TRACK OF THIS LOW WELL TO OUR SOUTH THROUGH DAYBREAK
WED... ACROSS NRN FL... AND AS A RESULT THEY HOLD VIRTUALLY ALL
MEASURABLE PRECIP ALONG AND SOUTH OF THE NC/SC BORDER THROUGH 12Z.
FOLLOWING THIS... HAVE KEPT THE FORECAST DRY THROUGH TONIGHT...
SHOWING A TREND TOWARD INCREASING RAIN CHANCES IN THE FAR SOUTH BY
WED MORNING. THE THICKENING CLOUDS SHOULD LIMIT INSOLATION
ESPECIALLY SOUTH... YIELDING SEASONABLE LOWS IN THE UPPER 40S TO
AROUND 50 DESPITE THE COOL AIR IN PLACE. -GIH

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM MONDAY...

FOR WED/WED NIGHT: AS NOTED ABOVE... MODELS HAVE TRENDED TOWARD A
MORE SOUTHERN TRACK TO THE SURFACE LOW ACROSS THE SOUTHEAST
STATES... REASONABLE GIVEN THE DAMPENING OF THE MID LEVEL SHORTWAVE
TROUGH AS HEIGHTS WILL TEND TO RISE BETWEEN THE LARGE VORTEX OVER
THE NORTHWEST ATLANTIC AND THE STRONG POLAR STREAM MID LEVEL LOW
THAT WILL DROP SOUTHWARD THROUGH THE GREAT LAKES REGION TOWARD THE
OHIO VALLEY LATE WED INTO WED NIGHT. THE ECMWF REMAINS THE WETTEST
AND STRONGEST WITH THE SOUTHEAST LOW AND ALSO TAKES IT FARTHER NORTH
THAN THE NAM/GFS. PRECIP WATER VALUES ARE PROJECTED TO ONLY BE
SUBSTANTIALLY ABOVE NORMAL ACROSS THE SOUTHEAST AND EXTREME SRN
CWA... WITH NEAR NORMAL VALUES IN THE NORTHERN FORECAST AREA. LIFT
MECHANISMS WILL BE HARD TO COME BY... GIVEN THE WEAK LOW LEVEL WIND
FIELD NOT CONDUCIVE TO MASS CONVERGENCE... THE WANING DPVA... AND
THE VERY WEAK OR ABSENT LOW LEVEL MOIST ISENTROPIC UPGLIDE. THERE IS
EVIDENCE OF A PERIOD OF GOOD UPPER DIVERGENCE IN THE LEFT EXIT
REGION OF THE 130+ KT SUBTROPICAL JET ACROSS THE CENTRAL GULF COAST
INTO SRN GA... BUT IT MAY BE TOO LITTLE TO INDUCE ENOUGH LIFT TO
OVERCOME THE DRIER LOW LEVELS. AS SUCH... AND WITH A CLEAR MODEL
TREND... HAVE TRIMMED BACK POPS TO NO GREATER THAN CHANCE ACROSS THE
NORTH (N OF HWY 64)... KEEPING LIKELY TO LOW-END CATEGORICAL POPS IN
THE EXTREME SOUTH/SE WHERE MOISTURE WILL BE DEEPER WITH BETTER LIFT
POTENTIAL... BUT WITH REDUCED QPF. WHAT UPPER LEVEL FORCING FOR
ASCENT THERE IS APPEARS TO MAXIMIZE WED AFTERNOON THEN DEPART WED
EVENING... FOLLOWED BY A BRIEF REBOUND LATE WED NIGHT IN POSSIBLE
FORCING AS THE POLAR WAVE/LOW DROPS INTO THE OH VALLEY. WILL TREND
POPS DOWN TO LOW CHANCE MAINLY SE WED NIGHT. IF THIS TREND
PERSISTS... WE MAY BE ABLE TO CUT BACK POPS FURTHER WED NIGHT ACROSS
WRN/NRN PARTS OF THE FORECAST AREA. EXPECT HIGHS WED FROM THE LOW
60S SOUTH (THICKER CLOUD COVER) TO UPPER 60S NORTH... IN LINE WITH
STATISTICAL GUIDANCE. LOWS WED NIGHT IN THE UPPER 40S WEST AND LOWER
50S EAST. -GIH

THURSDAY AND THURSDAY NIGHT: CERTAINLY A SHIFT IN MODEL GUIDANCE
THIS EVENING AS THE INITIAL COASTAL LOW IS MORE SUPPRESSED TO THE
SOUTHEAST AND THE UPPER LOW MOVING IN FROM THE NORTH IS ABLE TO PUSH
SOUTHWARD UNIMPEDED. THE RESULT FOR THURSDAY IS UNCERTAIN WHEN IT
COMES TO PRECIPITATION BUT CHANCES HAVE CERTAINLY DECREASED IN THE
EAST WHERE IT IS POSSIBLE THAT PLACES MAY SEE VERY LITTLE RAIN ON
THURSDAY IN BETWEEN THE COASTAL AND UPPER LOWS. QPF VALUES HAVE ALSO
DROPPED SIGNIFICANTLY ACROSS THE REST OF THE CWA FROM PRIOR
SIMULATIONS. AS THE UPPER TROUGH DIGS SOUTHWARD THERE WILL BE PLENTY
OF FORCING WITH IT AS BULK SHEAR VALUES CLIMB TO NEAR 60 KTS...BUT
MUCH OF THIS BEING IN THE UPPER BOUNDS NEAR 5-6 KM. THIS IS ABOVE
THE MEAGER INSTABILITY THAT MAY SHOW UP BY THURSDAY NIGHT BUT EVEN
IN THE MID-LEVELS THERE COULD BE AS MUCH AS 30 KTS OF SHEAR TO WORK
WITH. AT THIS POINT NOT CONFIDENT ENOUGH TO INTRODUCE THUNDER INTO
THE FORECAST...WOULD EXPECT MAINLY CONVECTIVE SHOWERS ASSOCIATED
WITH THIS FEATURE AT THIS POINT. WITH THE COASTAL LOW FURTHER TO THE
SOUTHEAST...THERE WILL BE LESS OVERRUNNING PRECIP TO LOCK IN THE IN-
SITU DAMMING AND THUS TEMPERATURES ON THURSDAY COULD END UP BEING
HIGHER THAN EXPECTED. WILL RAISE A COUPLE DEGREES FOR NOW MAINLY
HIGHS IN THE MID 60S WITH LOWS IN THE UPPER 40S ON THURSDAY NIGHT. -
ELLIS

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 310 AM TUESDAY...

DEPENDING ON WHERE THE UPPER LOW ENDS UP AND HOW LONG IT LINGERS
OVER NC WILL DETERMINE IF PRECIPITATION LINGERS INTO FRIDAY.
REGARDLESS...QPF VALUES SHOULD BE LIGHT. EVENTUALLY THE LOW WILL
PUSH OFF TO THE EAST BUT REGARDLESS FRIDAY WILL BE THE START OF A
WARMING TREND THAT WILL START HIGHS ON FRIDAY NEAR 70 DEGREES AN END
UP NEAR 80 DEGREES BY MONDAY AFTERNOON. WITH A SURFACE HIGH FINALLY
MOVING INTO A MORE SUMMER-LIKE POSITION OVER THE WESTERN
ATLANTIC...SOUTHERLY RETURN FLOW OVER CENTRAL NC WILL KEEP
TEMPERATURES WARM AND DRY DESPITE ADVECTING A GRADUALLY MOISTENING
AIRMASS WITH PW VALUES GOING FROM A HALF OF AN INCH ON FRIDAY TO
CLOSER TO AN INCH ON MONDAY. LOWS WILL MODERATE THROUGH THIS PERIOD
FROM THE UPPER 40S TO THE UPPER 50S.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 710 AM TUESDAY...

VFR CONDITIONS ARE LIKELY ACROSS CENTRAL NC THROUGH 12Z WED MORNING.
SPRAWLING HIGH PRESSURE WILL EXTEND INTO THE FORECAST AREA FROM THE
NORTHWEST TODAY INTO TONIGHT...  BRINGING FAIRLY DRY AIR NEAR THE
SURFACE... ENSURING UNRESTRICTED VSBYS. WE WILL SEE SOME HIGH CLOUDS
STREAMING IN FROM THE SW THROUGH THE PERIOD... ESPECIALLY TONIGHT...
AS LOW PRESSURE FORMING OVER THE CENTRAL GULF COAST STARTS TO TRACK
SLOWLY TO THE EAST-NORTHEAST... WHILE UPPER LEVEL LOW PRESSURE
APPROACHES FROM THE WEST. WE`LL ALSO HAVE A FEW MID CLOUDS THIS
MORNING... MAINLY OVER THE NRN/ERN TERMINALS (RDU/RWI/FAY)...
RESULTING FROM AN UPPER DISTURBANCE DROPPING SOUTHWARD ALONG THE
MIDATLANTIC COAST. ANY CIGS WILL BE VFR... ABOVE 10 000 FT AGL. HIGH
CLOUDS WILL THICKEN AND LOWER LATE TONIGHT AS THE LOW PRESSURE MOVES
INTO THE SOUTHEAST STATES... AND CLOUDS BASED AROUND 4000 FT AGL ARE
LIKELY TO MOVE IN FROM THE SW LATE TONIGHT... HOWEVER CIGS WILL
REMAIN VFR THROUGH DAYBREAK WED. WINDS WILL BE LIGHT AND MAINLY FROM
THE NORTH AND NE.

LOOKING BEYOND 12Z WED MORNING... THE COMBINATION OF APPROACHING LOW
PRESSURE TROUGH ALOFT FROM THE WEST AND THE SURFACE LOW CROSSING THE
SOUTHEAST STATES WILL LEAD TO LOWERING CIGS AND INCREASING RAIN
CHANCES FROM THE SOUTHWEST WED... LASTING INTO THU. SUB-VFR CIGS ARE
POSSIBLE LATE WED INTO THU... HOWEVER CONFIDENCE IS NOT HIGH... AS
THE WORST AVIATION CONDITIONS MAY HOLD TO OUR SOUTH DURING THIS
PERIOD. AVIATION INTERESTS SHOULD MONITOR LATER FORECASTS AND
CONDITIONS. THE CHANCE OF IFR CONDITIONS INCREASES LATE THU NIGHT
INTO FRI AS UPPER LEVEL LOW PRESSURE MOVES IN FROM THE NW. THE
DEPARTURE OF THE LOW PRESSURE TO OUR EAST LATE FRI WILL BRING
IMPROVING CONDITIONS BACK TO VFR LATE FRI THROUGH SAT AS HIGH
PRESSURE BUILDS IN FROM THE WEST. -GIH

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD/ELLIS
LONG TERM...ELLIS
AVIATION...HARTFIELD



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