000
FXUS62 KRAH 262358
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
658 PM EST WED NOV 26 2014

.SYNOPSIS...AN UPPER LEVEL DISTURBANCE AND ATTENDANT SURFACE LOW
PRESSURE SYSTEM WILL TRACK EAST ACROSS THE REGION OVERNIGHT. DRY
HIGH PRESSURE WILL BUILD INTO THE CAROLINAS FROM THE WEST ON
THURSDAY AND FRIDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 315 PM WEDNESDAY...

THE COASTAL LOW CURRENTLY SITS JUST OFF THE NRN OUTER BANKS OF NC...
MOVING STEADILY NORTHWARD. THE MID LEVEL VORTICITY MAX RIDING NE ON
THE SW SIDE OF THE BROAD RIDGE ALOFT CONTINUES TO SHEAR AND WEAKEN
AS IT MOVES THROUGH CENTRAL NC/VA... AND THIS DWINDLING FORCING FOR
ASCENT COUPLED WITH WANING UPPER DIVERGENCE AND LOWER PW FROM WEST
TO EAST ARE RESPONSIBLE FOR THE DOWNTURN IN BOTH COVERAGE AND
INTENSITY OF RAINFALL... AS WELL AS THE INCREASING SUNSHINE ACROSS
THE WRN AND SRN CWA. THIS TREND SHOULD CONTINUE... WITH RAIN CHANCES
DECREASING RAPIDLY OVER THE NEXT FEW HOURS... YIELDING LITTLE OR NO
RAIN CHANCES IN CENTRAL NC AFTER 6 PM OR 7 PM OR SO. BUT ATTENTION
IMMEDIATELY TURNS TO THE POTENT SHORTWAVE TROUGH NOW MOVING RAPIDLY
THROUGH THE MID MISS VALLEY... EXPECTED TO MOVE EAST THROUGH THE
CAROLINAS TONIGHT THROUGH MIDDAY THU... ACCOMPANIED BY SURFACE LOW
PRESSURE EXPECTED TO MOVE EASTWARD ACROSS CENTRAL/SRN NC. LATEST
SHORT-RANGE HI-RES MODEL GUIDANCE HAS SPED UP THE ONSET OF LIGHT
RAIN OVER OUR FORECAST AREA...AND BASED ON EXTRAPOLATION OF UPSTREAM
PRECIP...THIS LOOKS VERY REASONABLE. WILL BRING IN SLIGHT CHANCES OF
LIGHT SHOWERS OVER THE WRN PIEDMONT BY MID-LATE EVENING...THEN
FOLLOWING THE CONSENSUS OF LATEST MODEL OUTPUT...WILL SPREAD 20-50%
RAIN CHANCES ACROSS THE NRN PIEDMONT AND NRN COASTAL PLAIN LATER
TONIGHT... CONTINUING THROUGH THU MORNING... FOLLOWED BY AN EXIT OF
THE PRECIP OUT OF THE NORTHEAST CWA DURING THE EARLY AFTERNOON
HOURS. THIS PRECIP SHOULD BE MOSTLY SHOWERY IN NATURE...GIVEN THE
POTENTIAL FOR WEAK INSTABILITY ALOFT AS 850-500 MB LAPSE RATES ARE
STILL PROJECTED TO BE 7.0-7.5 C/KM. AS SUCH...WOULDN`T BE SURPRISED
TO SEE A FEW LIGHTNING STRIKES...ESPECIALLY GIVEN THE DYNAMIC
CONTRIBUTION TO LIFT FROM THE INCOMING VORTICITY MAX AND IMPROVING
UPPER DIVERGENCE DUE TO WIND ACCELERATION OVER SC AND SRN NC. TOTAL
RAINFALL AMOUNTS WITH THIS SYSTEM SHOULD BE SMALL... GENERALLY A
TENTH OF AN INCH OR LESS... ALTHOUGH TRENDS WOULD SUGGEST THAT THE
VA BORDER COUNTIES COULD SEE A COUPLE TENTHS... AS FORECAST
SOUNDINGS SHOW GREATER SATURATION IN THE LOW LEVELS AS COMPARED TO
YESTERDAY. CONSENSUS OF STATISTICAL GUIDANCE SUPPORTS LOWS TONIGHT
OF 34-37. THERE IS STILL A SMALL CHANCE THAT WE COULD SEE A FEW WET
SNOWFLAKES LATE TONIGHT INTO THU MORNING MAINLY NEAR THE VA
BORDER... BUT FORECAST SOUNDINGS AND SREF PLUMES AT DANVILLE SUGGEST
A THREAT TOO LOW TO MENTION... AND ANYTHING THAT FELL WOULD GENERATE
NO IMPACT. EXPECT IMPROVING SUNSHINE LATE IN THE DAY... WITH MORE
OVERALL INSOLATION SOUTH THAN NORTH... BUT STILL ANTICIPATE COOL
HIGHS RANGING FROM 48 NORTH TO 55 FAR SOUTH. -GIH

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 320 PM WEDNESDAY...

THU NIGHT: THE VORTICITY MAX AND ACCOMPANYING SURFACE LOW SHOULD BE
HEADING EAST OFF THE COAST BY THU EVENING... AS HIGH PRESSURE BEGINS
TO BUILD IN FROM THE WEST... WITH GRADUALLY RISING HEIGHTS OVERNIGHT
AS THE SHORTWAVE TROUGH LIFTS OUT. EXPECT CLEARING SKIES EARLY WITH
DECREASING WINDS. LOWS AT THE MID RANGE OF GUIDANCE... 25-30... WITH
GOOD RADIATIONAL COOLING CONDITIONS EXPECTED. -GIH

FRIDAY AND FRIDAY NIGHT: SURFACE HIGH PRESSURE WILL BUILD IN FROM
THE DEEP SOUTH ON FRIDAY AS THE UPPER LEVEL TROUGH MOVES OFF OF THE
COAST. FOR THE FIRST PART OF THE DAY...CENTRAL NC WILL REMAIN ON THE
EAST SIDE OF THE HIGH...IN WEAK NORTHERLY FLOW BUT BY LATE AFTERNOON
THE HIGH WILL MOVE DIRECTLY OVERHEAD...CALMING ANY REMAINING WIND.
CLOUD COVER LEFT OVER FROM THE DEPARTING SYSTEM WILL FILTER OUT TO
THE NORTHEAST. THUS EXPECT LOWEST TEMPS IN THE NE AND HIGHEST IN THE
SW. COOLEST DAY OF THE WEEK WITH HIGHS IN THE MID 40S TO NEAR 50
DEGREES. FRIDAY NIGHT WILL SEE TEMPERATURES DROP INTO THE MID TO
UPPER 20S WITH FEW CLOUDS AND CALM WINDS. -ELLIS

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 245 PM WEDNESDAY...

SATURDAY THROUGH MONDAY NIGHT: THE FIRST PART OF THE LONG TERM WILL
FEATURE A SIGNIFICANT WARMING TREND AS SURFACE HIGH PRESSURE MOVES
EAST OF THE AREA SETTING UP RETURN FLOW OVER CENTRAL NC. THIS WILL
BE THE MAIN DRIVER AS UPPER LEVEL FLOW REMAINS VERY ZONAL. ALTHOUGH
BOTH THE GFS AND THE ECMWF AGREE THAT IT WILL BE WARMER...THE
QUESTION REMAINS HOW MUCH? WITH FEW TO SCATTERED CLOUDS OVER THE
AREA...RISING THICKNESSES AND WARM AIR ADVECTION THROUGH
SOUTHWESTERLY FLOW...CANT SEE HOW TEMPERATURES WONT RISE
SIGNIFICANTLY. THEREFORE HAVE GONE TO THE HIGH SIDE OF GUIDANCE
WHICH IN THIS CASE IS MORE IN LINE WITH THE LONG RANGE ECMWF NUMBERS
FOR MAX TEMPS THROUGH MONDAY. SPECIFICALLY MID TO UPPER 50S
SATURDAY...MID TO UPPER 60S SUNDAY...AND UPPER 60S TO LOWER 70S
MONDAY. LOWS WILL ALSO WARM THROUGH THE WEEKEND BUT MORE
MODESTLY...UPPER 30S INCREASING TO MID 40S SUNDAY NIGHT BEFORE
FALLING SLIGHTLY BACK INTO THE LOWER 40S ON TUESDAY AHEAD OF A COLD
FRONT DRAPED TO OUR NORTHWEST.

TUESDAY THROUGH WEDNESDAY: THE LAST PART OF THE LONG TERM INTRODUCES
A FAIR AMOUNT OF UNCERTAINTY IN THE HANDLING OF THE AFOREMENTIONED
COLD FRONT AS THE PARENT LOW IS IS QUICKLY HAULED AWAY TO THE
NORTHEAST BY THE NORTHERN STREAM JET...LEAVING A WEAKLY DEFINED
FRONTAL ZONE JUST TO THE NORTHWEST OF THE CWA. ANY PRECIPITATION
ASSOCIATED WITH TEH FRONT SHOULD HOLD OFF UNTIL TUESDAY MORNING WHEN
A FAIRLY STRONG 1040 MB HIGH PRESSURE SYSTEM MOVES THROUGH QUEBEC.
THIS LOCATION IS FURTHER NORTH THAN THE PREVIOUS MODEL RUNS AND IS
NOT QUITE AS IDEAL FOR A CLASSICAL/HYBRID COLD AIR DAMMING EVENT AS
IT WAS YESTERDAY. STILL THINK SOME FORM OF A WEAK CAD IS POSSIBLE
AND THUS KEEPING HIGHS ON TUESDAY FAIRLY LOW AS WE SHOULD BE
OVERCAST WITH NORTHEASTERLY WINDS. MAX TEMPS IN THE LOW TO UPPER 50S
BUT STILL COULD BE LOWER IN THE TRIAD IF WEDGE DEVELOPS. THIS HIGH
WILL NOT REMAIN IN PLACE FOR VERY LONG AS IT IS QUICKLY MOVES OUT TO
SEA BY A DEVELOPING LOW OVER NORTHERN ONTARIO AND A DEEPENING UPPER
LEVEL TROUGH OVER THE MIDWEST. THIS WILL SET UP A SLIGHTLY WARMER
DAY ON WEDNESDAY IN THE WARM AIR ADVECTION REGIME AHEAD OF THE FRONT
AS LONG AS THE WEDGE DISSIPATES. MID 50S TO MID 60S NW TO SE. PRECIP
CHANCES AND AMOUNTS STILL FAIRLY UNCERTAIN AT THIS POINT BUT WILL
CARRY SLIGHT CHANCE POPS TUESDAY AND WEDNESDAY. LOWS DURING THIS
TIME IN THE UPPER 30S TO LOWER 40S.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 700 PM WEDNESDAY...

24-HR TAF PERIOD: VFR CONDITIONS HAVE RETURNED TO THE MAJORITY OF
CENTRAL NC AS OF 00Z THIS EVENING. HOWEVER...A POTENT UPPER LEVEL
DISTURBANCE AND ASSOCIATED SFC LOW PRESSURE SYSTEM WILL RAPIDLY
APPROACH FROM THE WEST THIS EVENING...PROGRESSING EAST ACROSS
NORTHERN NC AND SOUTHERN VA OVERNIGHT/EARLY THU MORNING. A PERIOD OF
SHOWERS AND MVFR/IFR CEILINGS CAN BE EXPECTED BETWEEN 06-12Z THU AT
THE INT/GSO TERMINALS. THOUGH PRECIPITATION WILL BE LESS LIKELY AT
THE RDU/RWI TERMINALS...MVFR/IFR CEILINGS ARE EXPECTED BETWEEN 09-
15Z THU. FURTHER SOUTH OF THE APPROACHING DISTURBANCE AT THE FAY
TERMINAL...VFR CONDITIONS ARE EXPECTED TO PREVAIL. CALM OR LIGHT/
VARIABLE WINDS AT ALL TERMINALS OVERNIGHT WILL BECOME WNW/NW AT 10-
15 KT BETWEEN 15-18Z THU AS THE DISTURBANCE MOVES OFFSHORE AND HIGH
PRESSURE BUILDS INTO THE REGION FROM THE WEST.

LOOKING AHEAD: VFR CONDITIONS WILL PREVAIL THU AFTERNOON THROUGH SAT
NIGHT AS DRY HIGH PRESSURE SETTLES OVER THE REGION. EXPECT AN
INCREASING POTENTIAL FOR ADVERSE AVIATION CONDITIONS SUN NIGHT
THROUGH EARLY NEXT WEEK AS HIGH PRESSURE MOVES OFFSHORE AND THE NEXT
IN A SERIES OF UPPER LEVEL DISTURBANCES APPROACHES THE REGION FROM
THE WEST. -VINCENT

&&

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

&&

$$

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

NWS RAH Office Area Forecast Discussion