Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KRAH 022003
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
303 PM EST MON MAR 2 2015

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH
THIS AFTERNOON THROUGH TONIGHT...IN THE WAKE OF A COLD FRONTAL
PASSAGE THIS MORNING. HIGH PRESSURE WILL SHIFT OFFSHORE DURING THE
DAY TUESDAY AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE
CENTRAL PLAINS INTO THE GREAT LAKES.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 1000 AM MONDAY...

TODAY:

SFC COLD FRONT STARTING TO PROGRESS E-SEWD INTO THE TRIAD...AND
LOOKS TO BE ON SCHEDULE...EXPECTED TO CLEAR THE FORECAST AREA AOA
18Z.  PRECEDING DRYING ALOFT ASSOCIATED WITH BRISK 35-40KT LOW-LEVEL
WESTERLY DOWNSLOPE FLOW EAST OF THE MOUNTAINS...IS HELPING TO MIX
OUT THE LOW CLOUDS/FOG IN ADVANCE OF THE FRONT...WITH NOTABLE BREAKS
IN CLOUD COVER ALREADY SHOWING UP AS FAR EAST AS THE TRIANGLE.
HOWEVER...FULL CLEARING IS NOT EXPECTED UNTIL THE DRIER/COOLER
AIRMASS ADVECTS IN BEHIND THE FRONT THIS AFTERNOON...AND EVEN THIS
WILL BE SHORT-LIVED BEFORE LOW CLOUDS/MOISTURE RUSHES BACK IN
OVERNIGHT. EXPECT HIGHS TO RANGE FROM LOWER 50S NORTH TO
MID/UPPER 50S SOUTH.

TONIGHT: THOUGH DECREASED CLOUD COVER SHOULD BE PRESENT FOR A PERIOD
THIS EVENING...LOW CEILINGS WILL RE-DEVELOP AFTER MIDNIGHT IN
ASSOC/W SOUTHERLY RETURN FLOW /WARM ADVECTION/ AS THE LOW-LEVEL
RIDGE SHIFTS QUICKLY OFFSHORE. IN ADDITION TO STRENGTHENING WARM
ADVECTION...DPVA IN THE FORM OF FAST-MOVING/SMALL AMPLITUDE
SHORTWAVE ENERGY IS EXPECTED TO BE PRESENT BETWEEN 06-12Z TUE... AND
LIGHT PRECIP WILL BE POSSIBLE IN THE WESTERN PIEDMONT AND WESTERN
PORTIONS OF THE SANDHILLS BY SUNRISE TUE. DUE TO THE PROGRESSIVE
NATURE OF THE HIGH BUILDING INTO THE REGION LATER TODAY...THE
AIRMASS IN PLACE TUE MORNING WILL BE LESS CAPABLE OF SUPPORTING
MIXED PTYPE THAN IN THE PREVIOUS EVENT. NEVERTHELESS...A NUISANCE
PERIOD OF LIGHT PL/FZRA CANNOT BE RULED OUT ALONG AND WEST OF
THE HWY 1 CORRIDOR AROUND SUNRISE TUE MORNING. GIVEN ABOVE NORMAL
UNCERTAINTY WITH REGARD TO THE QUALITY OF THE ANTECEDENT AIRMASS AND
EVOLUTION OF PRECIPITATION EARLY TUE MORNING...THE FORECAST WILL
SIMPLE REFLECT A CHANCE OF LIGHT RAIN BETWEEN MIDNIGHT-SUNRISE FROM
THE TRIANGLE WESTWARD. EXPECT LOWS IN THE LOWER TO MID 30S. -VINCENT

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 300 PM MONDAY...

THE FORECAST PROBLEM FOR THIS PART OF THE FORECAST CONTINUES TO BE
THE UNCERTAINTY IN TEMPERATURES DUE TO THE POTENTIALLY LINGERING
WEDGE AND THE TIMING AND EXTENT TO WHICH THE WARM FRONT RETREATS
NORTHWARD. GIVEN THAT THE MODELS HAVE A TENDENCY TO ERODE THE WEDGE
TOO QUICKLY...ESPECIALLY IF THERE IS PRECIPITATION FALLING INTO
IT...CURRENTLY FORECAST THE WEDGE STICKING AROUND INTO WEDNESDAY
AFTERNOON IN THE FAR NW PIEDMONT...WITH A LARGE SPREAD IN TEMPS FROM
NW TO SE ACROSS THE AREA. CONFIDENCE REMAINS SOMEWHAT LOW WITH
RESPECT TO TEMPS...AS ANY CHANGES TO THE TIMING AND POSITION OF THE
WEDGE/WARM FRONT AS THEY ERODE/RETREAT NORTHWARD WILL HIGHLY IMPACT
TEMPERATURES. THEY WILL HOWEVER INCREASE GRADUALLY THROUGH AROUND
MIDNIGHT THURSDAY BEFORE THE COLD FRONT BEGINS MOVING INTO THE NW.
KEEPING IN MIND THE POTENTIAL MARGIN FOR ERRORS...FORECAST HIGH
TEMPS IN THE MID 60S NW TO MID 70S SE ON WEDNESDAY. A NORMAL DIURNAL
TEMPERATURE CURVE SHOULD RETURN WEDNESDAY NIGHT...ALTHOUGH THE
TEMPERATURE GRADIENT WILL BE QUITE LARGE AND WILL DEPEND ON THE
TIMING AND POSITION OF THE COLD FRONT...EXPECT LOWS IN THE UPPER 30S
NORTH TO LOW 50S SOUTH WEDNESDAY NIGHT AND HIGHS IN THE LOW 40S
NORTH TO MID 50S SOUTH ON THURSDAY AND DECREASING BEHIND THE FRONT.

PRECIPITATION: THERE WILL BE A SLIGHT CHANCE OF PRECIP...MAINLY
ACROSS THE WESTERN PORTIONS OF THE AREA WEDNESDAY...EVEN THOUGH THE
MAIN PRE-FRONTAL CONVECTIVE RAINFALL REMAINS LARGELY ALONG OR WEST
OF THE APPALACHIANS UNTIL WEDNESDAY AFT/EVE. SOUTHWESTERLY WINDS
WILL BE QUITE STRONG ON WEDNESDAY AFT/EVE AS THE GRADIENT TIGHTENS
AHEAD OF THE FRONT. LATE WEDNESDAY AFTERNOON IS STARTING TO SHAPE UP
AS A HIGH SHEAR/LOW CAPE EVENT. FORECAST SOUNDINGS INDICATE 200-300
JOULES OF CAPE AND 0-3 KM SHEAR VALUES AROUND 35 KTS...MAINLY ALONG
AND EAST OF I-95 AT THIS TIME. WITH SURFACE TEMPS EXPECTED IN THE
MID 70S AND DEWPOINTS AROUND 60 DEGREES...THUNDERSTORMS WILL BE
POSSIBLE WEDNESDAY AFTERNOON...THUS WILL INTRODUCE A SLIGHT CHANCE
ACROSS THE EAST WITH THIS AFTERNOON`S FORECAST. THE LATEST 12Z ECMWF
AND GFS MODEL RUNS ARE IN BETTER AGREEMENT WITH THE TIMING OF THE
FROPA AND THE ASSOCIATED RAINFALL AS IT MOVES THROUGH THE AREA. THE
LATEST RUNS SUGGEST THAT RAIN WILL BE LIKELY WEDNESDAY NIGHT...
PROGRESSING NW TO SE THROUGH CENTRAL NC THROUGH MIDNIGHT FRIDAY.
THIS REMAINS CASE OF THE COLD AIR CHASING THE PRECIP...BUT FOR NOW
STILL EXPECT ALL PRECIP TO FALL AS RAIN...HOWEVER THERE IS A SMALL
CHANCE THAT A FEW SNOWFLAKES COULD MIX IN ON THE TAIL END OF THE
EVENT.


&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 300 PM MONDAY...

FRIDAY THROUGH SATURDAY: HIGH PRESSURE WILL BUILD IN BEHIND THE
FRONT THURSDAY NIGHT...REMAINING OVER THE REGION INTO THE WEEKEND.
EXPECT A DRY FORECAST FRIDAY THROUGH SATURDAY...WITH HIGHS IN THE
UPPER 30S TO LOW 40S FRIDAY...INCREASING THROUGH THE WEEKEND AND
INTO THE UPPER 50S TO LOW 60S BY MONDAY. LOWS WILL SEE A SIMILAR
TREND...INCREASING FROM MAINLY LOW 20S LOW 20S THU AND FRI NIGHTS TO
THE LOW TO MID 30S BY SAT AND SUN NIGHTS. THERE IS SOME MODEL
DISAGREEMENT TOWARD THE END OF THE PERIOD WITH REGARD TO PRECIP
CHANCES...AS THE ECMWF BRINGS PRECIP IN FROM THE SOUTHWEST SUNDAY
NIGHT AND THE GFS IS COMPLETELY DRY. WILL FORECAST A SLIGHT CHANCE
FOR RAIN SUN NIGHT/MONDAY...ALTHOUGH CONFIDENCE IS LOW AT THIS TIME.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 115 PM MONDAY...

24-HR TAF PERIOD:

A STRONG BUT TRANSIENT +1030MB SURFACE HIGH WILL BUILD EAST ACROSS
THE AREA THIS AFTERNOON AND TONIGHT IN THE WAKE OF THE COLD FRONT
PASSAGE EARLIER TODAY. DRY AIR ADVECTION ALONG AND BEHIND THE FRONT
HAS RESULTED IN VFR CONDITIONS ACROSS THE AREA. WILL SEE NWLY WIND
GUSTS INTO THE UPPER TEENS IMMEDIATELY BEHIND THE FRONT...BECOMING
LIGHT THIS EVENING FROM THE EAST-NORTHEAST.

AVIATION CONDITIONS WILL QUICKLY DETERIORATE TONIGHT...ESPECIALLY
ACROSS THE WESTERN PIEDMONT(KINT AND KGSO)WITH MVFR/IFR CEILINGS
RETURNING BETWEEN MIDNIGHT AND SUNRISE TUE MORNING AS THE SFC HIGH
MOVES QUICKLY OFFSHORE...ALLOWING LOW-LEVEL SOUTHERLY RETURN FLOW TO
DEVELOP WITH PATCHY LIGHT RAIN/DZ. ITS POSSIBLE THAT AREAS ALONG AND
NEAR THE NC/VA BORDER MAY SEE A BRIEF PERIOD OF FREEZING
RAIN/DRIZZLE TUESDAY MORNING...BEFORE CHANGING OVER TO A COLD RAIN
THEREAFTER AS TEMPERATURES WARM INTO THE LOWER/MID 30S.

CONFIDENCE IS MUCH LOWER AT KRDU...KRWI...KFAY...WHERE THERE IS A
LARGE SPREAD IN THE MODEL GUIDANCE. SOME MODEL GUIDANCE SUGGESTS
SOME THAT THE EAST-NORTHEASTERLY FLOW COULD SPREAD STRATUS INTO THE
AREA  BETWEEN 00-06Z. OTHER MODELS INDICATE THAT CEILINGS WILL
REMAIN IN THE LOW END VFR RANGE OVERNIGHT(4-5KT)....EVENTUALLY
BECOMING SUB-VFR NEAR THE END OF THE TAF PERIOD IN ASSOCIATION WITH
COLD AIR DAMMING AS THE WARM MOIST ADVECTION SPREADS EASTWARD
AS THE HIGH SHIFTS OFFSHORE.

LOOKING AHEAD: ADVERSE AVIATION CONDITIONS (IFR TO MVFR /LIFR
CEILINGS AND RAIN) ASSOC/W A PRONOUNCED COLD AIR DAMMING WEDGE WILL
PREVAIL TUESDAY AFTERNOON ... WITH SOME IMPROVEMENT IN CEILINGS
POSSIBLE AT SOUTHERN TERMINALS LATE TUE NIGHT AS A WARM FRONT LIFTS
NORTHWARD THROUGH THE CAROLINAS. ADVERSE AVIATION CONDITIONS ARE
LIKELY TO PREVAIL THE REMAINDER OF THE WEEK. -VINCENT

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...CBL/VINCENT
SHORT TERM...KC
LONG TERM...KC
AVIATION...CBL/VINCENT


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.