Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 251720
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
120 PM EDT SAT APR 25 2015

.SYNOPSIS...A WARM FRONT WILL STALL ACROSS CENTRAL NC THIS AFTERNOON
AND REMAIN STATIONARY OVERNIGHT AS AN AREA OF LOW PRESSURE TRAVERSES
WEST-TO-EAST ACROSS THE REGION. A COLD FRONT WILL CROSS THE AREA ON
SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM SATURDAY...

JUST MINOR ADJUSTMENTS MADE TO THE NEAR TERM FORECAST. MAINLY TO
BRING THE RAIN IN JUST A TOUCH FASTER ACROSS THE SW THIRD AND SOME
TWEAKS TO HOURLY TEMP TREND BASED ON RAIN ARRIVAL.

LOW LEVEL SWLY FLOW AHEAD OF A S/W IN THE MID/UPPER LEVELS WILL
INCREASE ISENTROPIC UPGLIDE LATE THIS MORNING THROUGH THE AFTERNOON.
RAIN SHIELD NOW ENCROACHING UPON THE SOUTHERN PIEDMONT AT 14Z WILL
CONTINUE TO SPREAD NE...MOVING INTO THE TRIANGLE REGION BY MIDDAY...
AND MOST OF CENTRAL NC BY EARLY AFTERNOON. 12Z GSO SOUNDING DEPICTS
A FAIRLY DRY SUB CLOUD LAYER. THIS SUGGEST A DECENT POTENTIAL FOR
EVAPORATIVE COOLING ONCE RAIN SATURATES THE COLUMN. HAVE ADJUSTED
HOURLY TEMPS TO TRY TO CAPTURE THE TREND OF TEMPS COOLING A FEW
DEGREES ONCE THE RAIN SETS IN. BASED ON EXPECTED RAIN COVERAGE EARLY
THIS AFTERNOON...MOST PLACES SHOULD BE IN THE 50S WITH THE LOWER
TEMPS ACROSS THE NORTHERN PIEDMONT (LOW-MID 50S) AND 55-60 ACROSS
THE SOUTH-SE.

BASED ON THE LATEST NEAR TERM MODELS...SHOULD SEE RAIN SHIELD
DIMINISH FROM THE SW LATE THIS AFTERNOON (AROUND 21Z) AS DRIER AIR
ALOFT ADVECTS INTO THE REGION.

WILL RETAIN MENTION OF THUNDER THIS EVENING ACROSS THE FAR SOUTH
WITH POTENTIAL FOR STRONG CONVECTION OVER THE TN VALLEY TO DRIFT
INTO OUR SOUTHERN COUNTIES AFTER 00Z. WHILE SHEAR MORE THAN
SUFFICIENT TO SUPPORT ORGANIZED CONVECTION...LOW LEVEL INSTABILITY
APPEARS TO BE SORELY LACKING OVER OUR REGION THIS EVENING WHICH
WOULD LIMIT STRONG/SEVERE POTENTIAL. WILL CONTINUE TO MONITOR
UPSTREAM CONDITIONS THROUGH THE AFTERNOON.


&&

.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 /18Z SATURDAY THROUGH THURSDAY/...
AS OF 120 PM SATURDAY...

HIGH LIKELIHOOD THAT AVIATION CONDITIONS WILL DETERIORATE TO
IFR/LIFR CEILINGS BY LATE THIS AFTERNOON...PERSISTING THROUGH EARLY
SUNDAY MORNING. AREAS OF RAIN WILL DIMINISH FROM THE WEST THIS
AFTERNOON WITH PATCHES OF FOG AND/OR DRIZZLE IN ITS WAKE.

THERE IS LESS THAN A 1-IN-5 CHANCE OF A THUNDERSTORM THIS EVENING
THROUGH THE OVERNIGHT HOURS ACROSS THE SOUTHERN COUNTIES. THIS
CHANCE APPEARS BEST (BUT STILL NO MORE THAN 1:5) NEAR OR SOUTH OF
KFAY.

AVIATION CONDITIONS WILL BE SLOW TO IMPROVE SUNDAY WITH WIDESPREAD
IFR/MVFR CEILINGS AND THE POSSIBILITY OF A FEW SHOWERS IN THE
AFTERNOON-EARLY EVENING...MAINLY ACROSS THE NORTHERN COUNTIES
INCLUDING KRWI...KRDU...AND THE TRIAD TERMINALS.

CONDITIONS SHOULD IMPROVE SUNDAY NIGHT INTO MONDAY AS A DRIER MORE
STABLE AIR MASS INFILTRATES THE REGION. THE VFR CONDITIONS SHOULD
PERSIST INTO TUESDAY. A LOW PRESSURE SYSTEM APPROACHING FROM THE SW
WILL BRING THE NEXT CHANCE FOR SUB VFR CONDITIONS TO CENTRAL NC
WEDNESDAY INTO THURSDAY.

&&


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

&&

$$

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



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