Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 230226
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1026 PM EDT MON SEP 22 2014

.SYNOPSIS...AN UPPER LEVEL LOW WILL DEVELOP OVER THE CAROLINAS
TONIGHT...AND WILL SLOWLY WEAKEN OVER THE REGION THROUGH MID-WEEK.
MEANWHILE...AT THE SURFACE...A STALLED FRONT WILL LINGER ALONG THE
SOUTHEAST COAST AS HIGH PRESSURE EXTENDS INTO THE AREA FROM THE
NORTH.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 1020 PM MONDAY...

TONIGHT: A SHORTWAVE TROUGH THAT PRODUCED 70 METER H5 HEIGHT FALLS
AT FFC THIS EVENING WILL CONTINUE TO EVOLVE INTO A CUT-OFF LOW OVER
THE CAROLINAS THROUGH THE NEXT 36-48 HOURS. SPRINKLES OR BARELY
MEASURABLE LIGHT RAIN...ONES FALLING FROM MID LEVEL CEILINGS...WILL
RESULT THROUGH SUNRISE FROM THE SOUTHERN PIEDMONT AND SANDHILLS TO
THE SOUTHERN AND CENTRAL COASTAL PLAIN. CONSIDERABLE MID-HIGH
CLOUDINESS WILL PREVAIL OTHERWISE AND ELSEWHERE TONIGHT. WHILE BOTH
PROXIMITY RAOB AND VWP DATA INDICATE LOW LEVEL FLOW HAS MAINTAINED A
NORTHERLY COMPONENT THIS AFTERNOON AND EVENING...THESE WINDS ARE
FORECAST TO ASSUME AN EASTERLY COMPONENT EARLY TUE...AT WHICH TIME
LOWER LEVEL MOISTURE FORCING WILL SUPPORT A GOOD TO LIKELY
PROBABILITY OF RAIN ACROSS THE FAR SOUTHEASTERN RAH CWFA.


PREVIOUS NEAR TERM DISCUSSION...

STRONG SHORTWAVE DIVING SE OVER THE SOUTHERN APPALACHIANS WILL
DECELERATE AND WILL CLOSE AND EVENTUALLY BECOME CUT-OFF OVER THE
CAROLINAS TONIGHT THROUGH TUESDAY NIGHT...GRADUALLY SHEARING  DURING
THE PERIOD. IN RESPONSE...SURFACE COLD FRONT WILL STALL OUT ALONG
THE COAST AS HIGH PRESSURE TO OUR NORTH NOSES SOUTH INTO THE
CAROLINAS.

EVEN THE NEAR TERM PERIOD HAS SLIDE TO UNAVOIDABLE OBSCURITY AS
MODEL SPREAD REMAINS HIGH BEGINNING AS EARLY AS LATE TONIGHT-
TUESDAY. THE GFS WHICH HAD BEEN CONSISTENTLY ON THE DRIER SIDE OF
THE MODEL SPECTRUM...IS NOW THE WETTER/MORE AMPLIFIED SOLUTION.
GIVEN THAT THE ECMWF REMAINS THE MOST CONSISTENT SOLUTION OVER THE
LAST COUPLE OF DAYS...THE EC WILL BE RELIED ON HEAVILY FOR THE NEAR
TERM FORECAST.

RAIN CHANCES:  RAIN WILL ATTEMPT TO SPREAD INLAND ACROSS THE
SOUTHERN COASTAL PLAIN (SAMPSON/WAYNE COUNTIES)LATE TONIGHT... AND
THROUGH THE DAY ON TUESDAY...BUT EVEN MORE SO TUESDAY NIGHT VIA
STRENGTHENING LOW-LEVEL EASTERLY MOISTURE TRANSPORT IN RESPONSE TO
WEAK WAVE DEVELOPMENT ALONG THE COASTAL INVERTED TROUGH AND UNDER
THE  INCREASING UPPER DIFFLUENCE MAXIMA ON THE EAST SIDE OF THE
UPPER LOW. IF THE GFS IS CORRECT...PRECIP COULD DEVELOP WELL INLAND
AND MUCH FASTER THAN FORECAST REFLECTS...BUT FOR NOW WILL GO WITH
THE SLOWER TIMING OF THE EC.

TEMPERATURES: LOW TEMPERATURES THE NEXT TWO NIGHTS WILL NOT BE QUITE
AS COOL AS ORIGINALLY THOUGHT OWING TO THE RETURN OF CLOUDS. LOWS
RANGING FROM LOWER 50S N/NW PIEDMONT TO UPPER 50S/NEAR 60 SOUTHEAST.
HIGHS TUESDAY NEAR 70.


&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 230 PM MONDAY...

FORECAST CONFIDENCE REMAINS SOMEWHAT BELOW NORMAL FOR THE MIDDLE OF
THE WEEK AS THERE CONTINUES TO BE SOME DISAGREEMENT AMONG THE
MODELS...ALTHOUGH THERE IS SOME MODEL CONVERGENCE TOWARDS A MORE
UNSETTLED PERIOD. THE LOW LEVEL FLOW AROUND THE HIGH WILL INCREASE
AND BEGIN TO GRADUALLY TAKE ON MORE OF AN EAST OF NORTHERLY
COMPONENT (AS HIGH PRESSURE SHIFTS OFF THE NORTHEAST COAST) ALLOWING
MOISTURE TO RETURN TO THE AREA. IN ADDITION...MODELS CONTINUE TO
HINT AT A WEAKNESS ALOFT AND ASSOCIATED INVERTED TROUGH DEVELOPING
NEAR THE SOUTHEAST COAST (ALTHOUGH TO VARYING DEGREES AMONG THE
MODELS). THIS WOULD INCREASE CLOUDS AND PRECIP CHANCES (ESPECIALLY
ACROSS EASTERN NC). THE MORE CONSISTENT ECMWF SHOWS A CLOSED LOW
ALOFT ACROSS THE SOUTHEAST WHICH IN TURN RESULTS IN A STRONGER
INVERTED TROUGH AND THEREFORE MORE ENHANCED PRECIP/CLOUD COVER. THE
GFS NOW ALSO SHOWS A CLOSED LOW ALOFT OVER THE AREA...BUT IT IS
FURTHER OFFSHORE (AND MORE PROGRESSIVE) WITH THE INVERTED
TROUGH...THUS IT IS STILL THE DRIER SOLUTION. WILL CONTINUE TO
FOLLOW MORE CLOSELY TO THE MORE CONSISTENT ECMWF (AND EC ENSEMBLE
MEAN). REGARDLESS...CLOUDY AND COOLER CONDITIONS WILL PERSIST...
WITH RAIN CHANCES INCREASING (ESPECIALLY ACROSS THE EAST). HIGHS ARE
EXPECTED TO STAY IN THE LOW TO MID 70S (WITH SOME UPPER 60S
POSSIBLE) AND OVERNIGHT LOWS MOSTLY IN THE MID/UPPER 50S TO LOWER
60S.

&&

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

SOME DRYING IS EXPECTED BEGINNING FRIDAY...BUT ESPECIALLY INTO THE
WEEKEND AS THE UPPER LOW FILLS IN WHILE RIDGING TRIES TO BUILD EAST.
THIS WILL CAUSE THE INVERTED TROUGH TO WEAKEN/DISSIPATE. HOWEVER...
WILL NOT REMOVE POPS ALTOGETHER AS THERE WILL BE STILL BE A WEAKNESS
ALOFT OVER THE AREA AND MOISTURE WILL NOT DECREASE SIGNIFICANTLY.
WITH THE ABOVE IN MIND...TEMPS WILL UNDERGO SOME MODERATION...AND
ARE EXPECTED TO RETURN TO NEAR NORMAL VALUES. OUR NEXT SYSTEM MAY
APPROACH THE AREA EARLY NEXT WEEK...BUT AS CAN BE EXPECTED (GIVEN
THE LOW CONFIDENCE IN THE MEDIUM RANGE FORECAST)...THERE IS A LOT OF
UNCERTAINTY IN THE EXTENDED RANGE.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 730 PM MONDAY...

VFR CONDITIONS ARE LIKELY TO DOMINATE AT ALL CENTRAL NC TERMINAL
FORECAST SITES THROUGH TUE. A STALLED FRONTAL ZONE JUST SOUTHEAST OF
CENTRAL NC... COMBINED WITH AN UPPER LEVEL LOW PRESSURE AREA
DEVELOPING OVERHEAD... WILL PROVIDE A FOCUS FOR BOUTS OF LIGHT RAIN
NEAR FAY... PRIMARILY THIS EVENING AND AGAIN TOWARD DAYBREAK TUE.
VSBYS MAY BRIEFLY DIP TO MVFR WITHIN THIS LIGHT RAIN... HOWEVER THE
VAST MAJORITY OF THE TIME... BOTH CIGS AND VSBYS AT FAY WILL STAY
VFR... DESPITE THE LIGHT RAIN. OTHERWISE... AT INT/GSO/RDU/RWI...
COOL HIGH PRESSURE RIDGING IN FROM THE NORTH WILL PROVIDE ENOUGH OF
A PUSH OF LOW LEVEL DRY AIR TO HOLD ANY PRECIP AND SUB-VFR
CLOUDS/VSBYS OUT OF THESE TAF SITES THROUGH TUE AFTERNOON. EXPECT
SURFACE WINDS TO HOLD OUT OF THE NORTHEAST UNDER 8 KTS TONIGHT AND 8-
12 KTS ON TUE.

LOOKING BEYOND 00Z WED... UNCERTAINTY GROWS STARTING TUE EVENING...
AS IT IS NOT CLEAR HOW FAR INLAND THE COASTAL RAINFALL WILL MOVE.
BUT THE MOST LIKELY SCENARIO IS FOR SOME INLAND PENETRATION OF LIGHT
RAIN OVER THE FAY/RWI/RDU AREAS TUE NIGHT THROUGH WED. MVFR CIGS ARE
POSSIBLE AT FAY TUE NIGHT/WED... BUT ARE MUCH LESS LIKELY AT
RDU/RWI. THERE IS A MUCH BETTER CHANCE OF MVFR OR IFR CIGS WED
EVENING/NIGHT AS NEAR-SURFACE MOISTURE INCREASES. CIGS SHOULD
REBOUND TO VFR THU... DOMINATING THROUGH SAT AS THE UPPER LEVEL LOW
OVER THE REGION WEAKENS AND LIFTS TO OUR NORTHEAST. -GIH

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...MWS/CBL
SHORT TERM...KRD
LONG TERM...KRD
AVIATION...HARTFIELD



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