Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 272028
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
330 PM EST SAT DEC 27 2014

.SYNOPSIS...HIGH PRESSURE NEAR THE CAROLINA COAST THIS AFTERNOON
WILL MOVE OFFSHORE TONIGHT. A COLD FRONT WILL APPROACH THE REGION
FROM THE NORTHWEST ON SUNDAY... AND GRADUALLY MOVE THROUGH THE
REGION ON MONDAY. HIGH PRESSURE WILL BUILD INTO THE SOUTHEAST
FOR THE MIDDLE TO END OF THE WORK WEEK.
&&

.NEAR TERM /TONIGHT THROUGH SUNDAY/...
AS OF 255 PM SATURDAY..

LATEST SURFACE ANALYSIS SHOWS AN AREA OF SURFACE HIGH PRESSURE
CENTERED NEAR THE NC/SC COAST ALONG THE COASTAL CAROLINAS AND
VIRGINIA. A POSITIVELY TILTED DEAMPLIFYING UPPER TROUGH ACROSS THE
WESTERN PLAINS AT MIDDAY TODAY WILL CONTINUE TO SHIFT SLOWLY EAST
TODAY AND TONIGHT. THE NORTHERN PORTION OF THE TROUGH ASSOCIATED
WITH THE NORTHERN JET STREAM WILL SHEAR EAST INTO THE EASTERN GREAT
LAKES WHILE BY LATE SUNDAY AFTERNOON. THE SOUTHERN EXTENT OF THE
TROUGH IS SHARPER AND MOVES SLOWLY EAST REACHING THE ARKLATEX BY
SUNDAY EVENING. THE ASSOCIATED COLD FRONT WHICH EXTENDS FROM
MICHIGAN SOUTHWEST TO EASTERN TX AT MIDDAY TODAY WILL MOVE EAST
REACHING EASTERN PA AND NORTHWEST GA BY LATE SUNDAY AFTERNOON.

MAINLY CLEAR SKIES ACROSS CENTRAL NC THIS AFTERNOON WILL GIVE WAY TO
INCREASING HIGH AND MID CLOUDINESS THIS EVENING AS MOISTURE BEGINS
TO INCREASE AHEAD OF THE FRONT. WHILE HIGH AND MID LEVEL CLOUDINESS
WILL THICKEN OVERNIGHT... NAM/GFS/SREF BUFR SOUNDINGS ALL NOTE THAT
THE LOWER THIRD OF THE TROPOSPHERE IS SLOW TO MOISTEN OVERNIGHT
UNTIL LOW LEVEL MOISTURE SURGES INTO THE REGION FROM THE SOUTHWEST
TOWARD DAYBREAK SUNDAY. THE PRECIPITATION IS LARGELY DRIVEN BY
ISENTROPIC LIFT AROUND THE 295K SURFACE WITH THE BEST SURGE OF LIFT
SKIRTING ACROSS THE NORTHWESTERN EDGE OF CENTRAL NC AND WILL
ADVERTISE LOW CATEGORICAL POPS THERE. FORCING FOR ASCENT DECREASES
TO THE SOUTH AND EAST ON SUNDAY WITH LOW CHANCE POPS ADVERTISED FOR
THE SANDHILLS AND SOUTHERN COASTAL PLAIN. SO SUNDAY WILL FEATURE
CLOUDY SKIES ACROSS CENTRAL NC IT WONT BE WASHOUT FOR EVERYONE.
MAINLY SPOTTY LIGHT RAIN IS EXPECTED TO THE SOUTH AND SOUTHEAST OF
RALEIGH WITH THE MOST WIDESPREAD RAIN EXPECTED NEAR AND ESPECIALLY
TO THE NORTHWEST OF INTERSTATE 85.

TEMPERATURES WILL BE A LITTLE TRICKY AS THEY WILL TEND TO FALL
QUICKLY THIS EVENING AFTER SUNSET BUT THE OVERNIGHT TREND WILL BE
COMPLICATED BY THE INCREASING MID AND HIGH CLOUDS AND THE LIGHT
SOUTHERLY STIRRING AHEAD OF THE APPROACHING COLD FRONT. WILL
FORECAST LOWS IN THE MID 40S WEST TO LOWER 40S EAST. HIGHS ON SUNDAY
WILL BE COMPLICATED BY TE PRECIPITATION WHICH SHOULD KEEP HIGHS IN
THE MID 50S ACROSS THE NORTHWEST PIEDMONT WITH MID 60S ACROSS THE
SANDHILLS AND SOUTHERN COASTAL PLAIN WHERE THE RAIN WILL BE MORE
SCATTERED. -BLAES
&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 330 PM SATURDAY...

SUNDAY NIGHT...DEEP SW FLOW WILL MAINTAIN A MOIST AIR MASS ACROSS
CENTRAL NC SUNDAY NIGHT INTO MONDAY MORNING. A STOUT DISTURBANCE
ALOFT WILL APPROACH IN THE SW FLOW LATE SUNDAY AND CROSS OUR REGION
EARLY MONDAY. MEANWHILE CENTRAL NC WILL BE IN THE RIGHT ENTRANCE
REGION OF A 130-150KT JET. THE ENHANCED LIFT SUPPLIED BY BOTH THE
JET AND THE APPROACHING DISTURBANCE INTERACTING WITH AN ABNORMALLY
MOIST AIR MASS (PRECIP WATER VALUES PROJECTED TO BE 1-1.2 INCHES)
WILL CAUSE RAIN TO BECOME WIDESPREAD LATE SUNDAY NIGHT INTO EARLY
MONDAY. MIN TEMPS UPPER 40S FAR NORTH TO THE LOW-MID 50S FAR SOUTH.

MONDAY... WIDESPREAD RAIN WILL DIMINISH IN COVERAGE AND INTENSITY BY
MID DAY-EARLY AFTERNOON AS THE UPPER LEVEL DISTURBANCE AND THE JET
DEPART OUR REGION. WHILE THE MID-UPPER LEVELS OF THE ATMOSPHERE WILL
DRY OUT...SW FLOW IN THE 925-850MB LAYER WILL MAINTAIN SATURATION
RESULTING IN OVERCAST SKIES WITH SPOTS OF RAIN AND/OR DRIZZLE.

SURFACE COLD FRONT WILL DRAG SOUTHWARD ACROSS THE REGION AS THE
UPPER DISTURBANCE PULLS OUT TO THE EAST-NE. A SHALLOW COLD AIR AIR
MASS WILL INFILTRATE OUR REGION FROM THE NORTH. THIS SHOULD LEAD TO
FALLING TEMPS BY LATE MORNING ACROSS THE NORTH...AND THE AFTERNOON
ACROSS THE SOUTH.

MONDAY NIGHT INTO TUESDAY...850MB TROUGH PROJECTED TO REMAIN WEST OF
OUR REGION UNTIL MID DAY TUESDAY. THIS SUGGEST A CONTINUATION IN
EXTENSIVE CLOUDINESS AND PATCHY LIGHT RAIN/DRIZZLE THROUGH THE
MAJORITY OF MONDAY NIGHT. PASSAGE OF 850MB TROUGH AND ENSUING W-NW
FLOW IN ITS WAKE ALONG WITH SUBSIDENCE WILL AID TO DISSIPATE CLOUD
COVERAGE WEST-TO-EAST TUESDAY AFTERNOON. LOW LEVEL COLD AIR
ADVECTION WILL RESULT IN A SMALLER THAN NORMAL DIURNAL TEMP
RECOVERY. MIN TEMPS MID-UPPER 40S NORTH TO LOWER 40S SOUTH. MAX
TEMPS TUESDAY MID 40S NORTH TO NEAR 50 SOUTH.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 330 PM SATURDAY...

WEDNESDAY THROUGH SATURDAY... A BROAD UPPER LEVEL TROUGH WILL COVER
THE BULK OF THE U.S. THIS PERIOD WITH A CLOSED UPPER LEVEL LOW
PROJECTED TO EDGE SLOWLY EAST ACROSS THE SW U.S-SOUTHERN ROCKIES.
MODEL GUIDANCE TRADITIONALLY HAVE TROUBLE TIMING THE MOVEMENT OF
THESE CLOSED LOWS INT EH SW. USUALLY...SLOWER IS BETTER.

FOR CENTRAL NC...EXPECT DRY CONDITIONS THROUGH AT LEAST FRIDAY AND
POSSIBLY INTO SATURDAY WITH TEMPS BELOW NORMAL AT MID
WEEK...MODERATING TO NEAR NORMAL LEVELS BY THE WEEKEND. A S/W WILL
CROSS THE MID ATLANTIC LATE WEDNESDAY-WEDNESDAY NIGHT...ACCOMPANIED
BY A DRY SFC FRONT PASSAGE. FLOW BEHIND THIS FEATURE WILL REINFORCE
THE COOL AIR IN PLACE. MAX TEMPS WILL AVERAGE 4-6 DEGREES BELOW
NORMAL WEDNESDAY-FRIDAY WHILE OVERNIGHT LOWS IN THE 20S WILL BE
COMMON.

TIMING DIFFERENCES IN THE MODELS BY NEXT WEEKEND PLAY HAVOC WITH
PRECIP CHANCES AND TEMP FORECAST. PERSISTENT WLY FLOW SHOULD LEAD TO
MODIFICATION OF THE AIR MASS...LEADING TO TEMPS AT OR ABOVE NORMAL.
IF PRECIP DELAYED UNTIL LATE SATURDAY OR SATURDAY NIGHT...POTENTIAL
FOR TEMPS TO BE WELL ABOVE NORMAL.


&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 1250 PM SATURDAY...

...HIGH CONFIDENCE OF VFR CONDITIONS THROUGH MIDNIGHT TONIGHT WITH
ADVERSE AVIATION CONDITIONS SPREADING INTO MUCH OF CENTRAL NC EARLY
SUNDAY... VFR CONDITIONS ARE EXPECTED ACROSS CENTRAL NC THIS
AFTERNOON AND EVENING AS HIGH AND MID LEVEL CLOUDINESS INCREASES
LATE. AN AREA OF SHOWERS ACROSS UPSTATE GA/SC WILL MOVE INTO WESTERN
NC VERY LATE THIS AFTERNOON BUT THIS PRECIPITATION SHOULD LARGELY
DISSIPATE. IF SOMEHOW IT MAKES IT INTO THE WESTERN PIEDMONT IT WOULD
OCCUR AS A VFR RAIN SHOWER WITH A HIGH CEILING AND LIMITED
VISIBILITY REDUCTION.

MORE SIGNIFICANT WEATHER ARRIVES WELL AFTER MIDNIGHT AS DEEPER
MOISTURE IS DRAWN INTO CENTRAL NC AHEAD OF AN APPROACHING COLD
FRONT. RAIN WILL SPREAD INTO THE WESTERN PIEDMONT FROM THE SOUTHWEST
BETWEEN 10-14Z INCLUDING THE KINT AND KGSO TERMINALS AND THEN MOVE
EAST ARRIVING AROUND 13-17Z AT KRDU AND KRWI WITH SEVERAL HOURS OF
RAIN EXPECTED IN THE TRIAD. SPOTTIER RAIN IS EXPECTED NEAR KFAY
OCCURRING FROM 15-22Z. THE BEST SUPPORT FOR PRECIPITATION WILL OCCUR
ACROSS NORTHWESTERN NC WITH THE AMOUNT...DURATION AND LIKELIHOOD OF
PRECIPITATION DECREASING TOWARD THE SOUTHEAST. IN THE TRIAD CEILINGS
SHOULD FALL INTO THE IFR TO POSSIBLY LIFR RANGE AFTER PRECIPITATION
BEGINS WITH VSBYS IN THE MVR/IFR RANGE...CONDITIONS ESPECIALLY CIGS
WILL LIKELY BE A LITTLE BETTER BUT STILL REDUCED TO THE EAST AT KRDU
AND KRWI AND SHOULD BE BETTER FURTHER SOUTH AND EAST AT KFAY. LIGHT
SOUTH-SOUTHWEST WINDS AT 190-250 DEG AT LESS THAN 10KTS WILL
CONTINUE THROUGH THE 24 HOUR TAF PERIOD.

LOOKING AHEAD...THE AREA OF PRECIPITATION ON SUNDAY SHOULD MOVE OUT
OF THE AREA BY SUNSET BEFORE ANOTHER AREA OF RAIN ASSOCIATED WITH
THE COLD FRONT AND A SURFACE WAVE MOVES ACROSS THE AREA LATE SUNDAY
NIGHT AND MONDAY. LINGERING LOW CLOUDS AND DRIZZLE WILL CONTINUE
MONDAY NIGHT INTO TUESDAY BEFORE CONDITIONS IMPROVE LATER TUESDAY
WITH FAIR WEATHER EXPECTED ON WEDNESDAY. -BLAES
&&

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

&&

$$

SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM....WSS
LONG TERM...WSS
AVIATION...BLAES


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