Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 251045
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EDT SAT APR 25 2015

.SYNOPSIS...A WARM FRONT WILL MOVE INTO THE AREA AND STALL TODAY.
AN AREA OF LOW PRESSURE WILL APPROACH FROM THE WEST THIS EVENING AND
CROSS THE AREA OVERNIGHT...FOLLOWED BY A COLD FRONT ON SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 340 AM SATURDAY...

HIGH CLOUDS CONTINUE TO THICKEN ACROSS THE AREA THIS MORNING AHEAD
OF A SHORTWAVE AND ASSOCIATED LOW PRESSURE MOVING INTO THE MID-
MISSISSIPPI VALLEY REGION.  AN AREA OF RAIN DRIVEN BY WARM ADVECTION
IS MOVING THROUGH THE LOWER TENNESSEE VALLEY REGION AND WILL ENCROACH
UPON THE WESTERN PIEDMONT AFTER SUNRISE...THOUGH THE ATMOSPHERE OVER
CENTRAL IS VERY DRY WITH PW AROUND A QUARTER OF AN INCH ON THE 00Z
KGSO RAOB.  VIRGA SHOULD GIVE WAY TO A WIDESPREAD LIGHT RAIN IN THE
WEST BY MID-MORNING AND CONTINUE TO THE EAST THROUGH EARLY
AFTERNOON.   THE CHANCE OF THUNDER LOOKS PRETTY LOW WITH THE INITIAL
BAND OF PRECIP DUE TO WEAK LAPSE RATES AND LIMITED HEATING.  A WARM
FRONT WORKING NORTH THROUGH SC THIS AFTERNOON SHOULD END UP
SOMEWHERE ACROSS SOUTHERN NC THIS EVENING...WITH ITS NORTHWARD PUSH
HAMPERED BY THE LIGHT RAIN AND RESULTING COOL POOL OVER THE
PIEDMONT.

MEANWHILE...A DRY SLOT WILL SPREAD ACROSS THE REGION...BRINGING THE
INITIAL PRECIP TO AN END BUT ALSO CREATING SOME POTENTIAL
INSTABILITY WHICH WOULD HELP STEEPEN MID-LEVEL LAPSE RATES THIS
EVENING AS THE REMNANTS OF THE AFOREMENTIONED SHORTWAVE AND
ASSOCIATED 60-80M HEIGHT FALLS CROSS THE AREA.    FORECAST SOUNDINGS
SHOW THE INCREASE IN AT LEAST SOME WEAK MUCAPE ACROSS SOUTHERN NC BY
00Z.  WITH STRONG WESTERLIES ALOFT AND 50-60KT OF BULK SHEAR...THE
BIGGEST QUESTION WILL THEN BE THE COVERAGE OF CONVECTION APPROACHING
FROM THE NORTHWEST AND WHETHER OR NOT WILL CAN BECOME SURFACE
BASED...AND LATEST MODEL GUIDANCE SUGGESTS SBCAPE WILL BE
NEGLIGIBLE. CURRENTLY...FORECAST CONFIDENCE IS LOW REGARDING SEVERE
WEATHER...BUT THERE APPEARS TO BE ENOUGH POTENTIAL TO ADD A CHANCE
OF THUNDER ACROSS THE SOUTH AND ADD SOME WORDING TO THE HWO.
LATEST MODEL RUNS SHOW A LITTLE BETTER AGREEMENT REGARDING
QPF...WITH THE BETTER POTENTIAL FOR A THIRD TO A HALF INCH ACROSS
THE SOUTH IN CLOSER PROXIMITY TO THE WARM FRONT.

AS FOR TEMPS...THE CURRENT FORECAST LOOKS PRETTY GOOD IN SHOWING A
STRONG GRADIENT FROM WEST TO EAST BASED OF THE TIMING OF PRECIP AND
ANTICIPATED IN-SITU DAMMING....WITH LOW/MID 50S WEST AND LOW/MID 60S
EAST.  TEMPS WILL ONLY FALL A FEW DEGREES TONIGHT AS MOST OF THE
AREA REMAINS SOCKED IN WITH ABUNDANT LOW CLOUDS AND SOME AREAS OF
FOG...UPPER 40S NORTH TO MID 50S SOUTH.


&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
AS OF 340 AM SATURDAY...

THE DEAMPLIFYING SHORTWAVE FROM SATURDAY NIGHT AND THE ASSOCIATED
SURFACE LOW WILL MOVE EAST OF THE AREA ALONG WITH EARLY SUNDAY BUT
WILL BE FOLLOWED BY ANOTHER WAVE ROUNDING THE UPPER LOW WOBBLING
EAST ACROSS NEW ENGLAND.  A STRONG 850MB FRONT DRAPED ACROSS THE
OHIO VALLEY AND MID-ATLANTIC STATES WILL PUSH SOUTH ACROSS NC SUNDAY
AFTERNOON...WHICH SHOULD HELP TO ERODE THE LINGER DAMMING COOL POOL
AND LOW CLOUDS...BUT IT MAY NOT BE EARLY ENOUGH TO ALLOW FOR MUCH
HEATING BEFORE SUNSET.  THUS...HIGHS ARE EXPECTED TO AGAIN BE WELL
BELOW NORMAL IN THE UPPER 50S AND 60S FOR MUCH OF THE AREA...WITH
SOME 70S POSSIBLE ACROSS THE FAR SOUTH. WILL MAINTAIN A CHANCE OF
SHOWERS WITH THE FRONT ON SUNDAY...ENDING SUNDAY EVENING.  LOWS
SUNDAY NIGHT IN THE 40S.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 405 AM SATURDAY...

A DEEP...EAST TO WEST-ELONGATED CLOSED LOW WILL MOVE SLOWLY AWAY
FROM THE NEW ENGLAND AND SOUTHEAST CANADA COAST...WHILE INDIVIDUAL
SHORTWAVES ROTATE AROUND THE LOW IN THE MEAN...ONE OF WHICH WILL
PIVOT ACROSS THE MIDDLE ATLANTIC STATES MON-MON NIGHT. THE MODELS
GENERALLY SUPPORT THIS SOLUTION OF GLANCING FORCING FOR ASCENT AND
STEEPENING MID-LEVEL LAPSE RATES (TO AROUND 6-6.5 C/KM) IN
ASSOCIATION WITH THE COLDER MID LEVEL TEMPERATURES ACCOMPANYING THE
SHORTWAVE TROUGH...ACROSS CENTRAL AND ESPECIALLY NE NC. WHILE
SHOWERS OR SPRINKLES WILL BE POSSIBLE IN ASSOCIATION WITH THE
PASSING WAVE OVER CENTRAL-EASTERN VA AND NE NC...IT IS LIKELY THAT
THE AFFECT OVER CENTRAL NC WILL SIMPLY BE A PERIOD OF ENHANCED (SCT-
BKN) CUMULUS MON AFTERNOON-EVE...WITH RELATIVE GREATEST COVERAGE AND
DEPTH OVER THE NE HALF OF THE CWFA. OTHERWISE...THE FLOW IN THE LOW
LEVELS WILL BE GENERALLY NE THROUGH TUE...AS HIGH PRESSURE RIDGES
EAST FROM THE OH VALLEY - SUPPORTIVE OF BELOW AVERAGE TEMPERATURES
IN THE MIDDLE 60S TO LOWER 70S BY DAY AND 40S BY NIGHT.

SIGNIFICANT FORECAST UNCERTAINTY REMAINS FOR MID-LATE WEEK...OWING
TO THE INTERACTION OF THE AFOREMENTIONED VORTEX MOVING SLOWLY AWAY
FROM NEW ENGLAND -AND ASSOCIATED TRAILING CONFLUENT FLOW BENEATH
HIGHER LATITUDE BLOCKING- WITH A SOUTHERN STREAM UPPER LOW
APPROACHING FROM THE SW US AND PROBABLE NORTHERN STREAM
INFLUENCE/AMPLIFICATION FROM SOUTHERN CANADA. THE OVERALL PATTERN
WILL FAVOR A SOUTHWARD-SUPPRESSED STORM TRACK/CYCLOGENESIS AND
ASSOCIATED FOCUS FOR PRECIPITATION ACROSS THE SOUTHEAST STATES TUE-
THU...WITH THE RELATIVE HIGHEST PROBABILITY OF RAIN IN CENTRAL NC
LATE WED THROUGH EARLY THU.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 645 AM SATURDAY...

VFR CONDITIONS CURRENTLY AS MID AND HIGH BLOUDS INCREASE AND A FEW
SPRINLES MOVE WEST TOE AST ACROSS CENTRAL NC. AN AREA OF RAIN
ASSOCIATED WITH WARM ADVECTION ACROSS  THE LOWER TENNESSEE VALLEY
REGION WILL MOVE INTO THE WESTERN PIEDMONT BETWEEN 12Z AND
15Z...THOUGH THE RAIN SHOULD BE LIGHT INITIALLY GIVEN HOW DRY THE
AIRMASS IS OVER CENTRAL NC THIS MORNING. CEILINGS WILL STEADILY
LOWER TO MVFR FROM WEST TO EAST BY LATE MORNING AND EARLY
AFTERNOON...FOLLOWED BY IFR CONDITIONS AS THE RAIN BECOMES MORE
WIDESPREAD.  A WARM FRONT IS FORECAST TO LIFT INTO THE SOUTHERN
PORTIONS OF THE AREA...POSSIBLY APPROACHING KFAY DURING THE
AFTERNOON.  THIS MAY OFFER SOME SUPPORT FOR AN ISOLATED THUNDERSTORM
FROM KRCZ TO KFAY DURING THE LATE AFTERNOON AND EVENING HOURS.  THE
PROBABILITY OF THUNDERSTORMS IS MUCH LOWER TO THE NORTH.  WINDS WILL
GENERALLY BE LIGHT AND VARIABLE FROM KRDU TO KGSO/KINT...WITH A MORE
SOUTHERLY COMPONENT EXPECT AT KFAY AND KRWI THIS AFTERNOON.

POOR AVIATION CONDITIONS WILL CONTINUE OVERNIGHT AS CEILINGS ARE
LIKELY TO LOWER TO LIFR AND SOME AREAS OF FOG DEVELOP

OUTLOOK... ADVERSE AVIATION CONDITIONS ARE EXPECTED TO CONTINUE INTO
LATE SUNDAY BEFORE IMPROVING BY MONDAY.  THE NEXT CHANCE OF SUB-VFR
CONDITIONS WILL BE MIDWEEK.

&&


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

&&

$$

SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22
LONG TERM...RAH
AVIATION...22


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