Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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361
FXUS62 KRAH 170604
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
204 AM EDT SUN MAY 17 2015

.SYNOPSIS...A SURFACE TROUGH WILL STRENGTHEN OVER THE PIEDMONT OF VA
AND THE CAROLINAS THROUGH TUESDAY. SUB-TROPICAL HIGH WILL OTHERWISE
REMAIN OVER THE SOUTHEASTERN U.S. UNTIL A COLD FRONT CROSSES OUR
REGION TUESDAY NIGHT.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
AS OF 910 PM SATURDAY...

RIDGE IN PLACE KEEPING CONVECTION CONFINED TO THE NORTH AND WEST OF
THE FORECAST AREA THIS EVENING. DRY CONDITIONS EXPECTED OVERNIGHT
AND RH CROSS SECTIONS AND SREF CEILING PROBABILITIES INDICATE THAT
WE SHOULD NOT HAVE ANY PROBLEMS WITH LOW STRATUS SUNDAY MORNING AS
WE HAVE HAD THE PAST COUPLE OF MORNINGS. LOWS IN THE LOWER 60S.
-ELLIS

SUNDAY...MID-UPPER LEVEL RIDGE MAINTAINS ITS PRESENCE ALOFT WHILE
THE SFC RIDGE WEAKENS A TAD. CIRCULATION AROUND THE RIDGE WILL
GRADUALLY ADVECT AND MORE MOIST AIR MASS INTO CENTRAL NC. BY LATE
SUNDAY INTO SUNDAY EVENING...PRECIPITABLE WATER VALUES PROJECTED TO
BE IN THE 1.5-1.75 INCH RANGE. A WEAK MID LEVEL SHEAR AXIS ROUNDS
THE TOP OF THE UPPER RIDGE LATE SUNDAY INTO SUNDAY. THIS FEATURE
INTERACTING WITH THE AVAILABLE MOISTURE AND SLIGHT INSTABILITY MAY
TRIGGER AN ISOLATED SHOWER OR STORM LATE SUNDAY-EARLY SUNDAY
EVENING...MAINLY ACROSS OUR FAR NORTH-NW COUNTIES.

THE MODIFYING AIR MASS SHOULD YIELD MAX TEMPS SUNDAY 2-3 DEGREES
WARMER THAN TODAY`S HIGH TEMPS. MAX TEMPS SUNDAY SOLIDLY IN THE MID
80S.

SUNDAY NIGHT...MINOR SHEAR AXIS AND ACCOMPANYING SFC TROUGH MOVES
INTO CENTRAL NC OVERNIGHT. WHILE FORCING ALONG THIS FEATURE ANEMIC
AT BEST...THE MODERATELY MOIST AIR MASS IN PLACE MAY BE SUFFICIENT
TO SUPPORT AN ISOLATED SHOWER OR TWO OVERNIGHT. MIN TEMPS A FEW
DEGREES WARNER THAN PREVIOUS NIGHTS DUE TO THE WETTER ATMOSPHERE.
MIN TEMPS UPPER 60S TO NEAR 70. -WSS

&&

.SHORT TERM /MONDAY AND TUESDAY/...
AS OF 255 PM SATURDAY...

MONDAY INTO TUESDAY...A S/W CROSSING THE UPPER MIDWEST INTO THE
GREAT LAKES WILL GRADUALLY KNOCK DOWN THE UPPER RIDGE OVER THE MID
ATLANTIC AND THE CAROLINAS...WITH THE MORE SIGNIFICANT HEIGHT FALLS
OCCURRING ON TUESDAY. APPEARS THAT THE UPPER LEVEL RIDGE WILL
MAINTAIN ENOUGH OF PRESENCE TO KEEP CHANCES OF CONVECTION NO WORSE
THAN SLIGHT-SMALL CHANCE. BULK OF THE CONVECTION WILL BE OF THE AIR
MASS/PULSE-TYPE VARIETY THOUGH A SLIGHTER BETTER CONCENTRATION
EXPECTED OVER THE NW PIEDMONT WHERE CONVECTION THAT FORMS OVER THE
HIGHER TERRAIN WILL HAVE A BETTER CHANCE OF ADVANCING OFF THE RIDGES
AND INTO THE FOOTHILLS/NW PIEDMONT. LINGERING OUTFLOWS FROM THIS
CONVECTION IN CONJUNCTION WITH A WEAK SFC TROUGH OVER THE AREA WILL
SUPPORT SLIGHT CHANCE POPS MONDAY NIGHT.

A SFC FRONT ATTENDANT WITH THE S/W CROSSING THE GREAT LAKES WILL
GLIDE SEWD AND CROSS CENTRAL NC TUESDAY NIGHT. WHILE THE ATMOSPHERE
PROJECTED TO BE SLIGHTLY UNSTABLE...BULK SHEAR IS WEAK AND WLY FLOW
IN THE 850-700MB RANGE USUALLY IS A PREDICTOR OF LESS THAN NORMAL
CONVECTIVE COVERAGE. THUS WILL MAINTAIN POPS NO HIGHER THAN 30-50
PERCENT LATE TUESDAY INTO TUESDAY EVENING ACROSS THE REGION.

PRESENCE OF MID-UPPER LEVEL RIDGE MONDAY WILL CONTINUE TO MODERATE
THE LOW LEVEL AIR MASS...REFLECTIVE OF MONDAY AFTERNOON 850MB TEMPS
16-17 DEGREE C OVER THE AREA. THICKNESSES AROUND 1418M SUPPORTIVE OF
AFTERNOON TEMPS WELL INTO THE 80S TO NEAR 90. MORE CLOUD COVERAGE
AND EARLIER ONSET OF CONVECTION SUGGEST MAX TEMPS TUESDAY AFTERNOON
A FEW DEGREES COOLER.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 255 PM SATURDAY...

THE COLD FRONT IS PROGGED TO BE EAST OF I-95 BY EARLY WEDNESDAY
MORNING...QUICKLY MOVING OFFSHORE AROUND SUNRISE. IN IT`S WAKE DRIER
AIR WILL MOVE IN...SHUTTING OFF THE RAIN BEFORE SUNRISE AND
RESULTING IN FAIR WEATHER FOR THE REST OF THE DAY. CAA WILL ENSUE
BEHIND THE FRONT...AND FORECAST THICKNESSES SUGGEST HIGHS RANGING
FROM THE LOWER 80S NORTH TO UPPER 80S SOUTH. FAIR WEATHER WILL
CONTINUE INTO WED NIGHT...BUT CLOUDS WILL INCREASE FROM THE WEST IN
ADVANCE OF A SHORT WAVE CROSSING THE MISS AND TN VALLEYS. LOWS IN
THE MID-UPR 50S.

THE AFOREMENTIONED SHORT WAVE WILL CROSS CENTRAL NC DURING THE
DAYTIME THU...BUT MOISTURE DOES NOT APPEAR TO BE SUFFICIENT FOR A
WIDESPREAD RAIN CHANCE. AS SUCH...LOOK FOR MAINLY DRY WX ON THU.
MORE NOTABLE WILL BE THE COOLER AIRMASS USHERED IN BY NW FLOW.
THICKNESSES...WHICH WILL BE ABOUT 30M BELOW NORMAL...SUPPORT HIGHS
IN THE UPPER 70S. LOWS THURSDAY NIGHT AROUND 60.

ANOTHER FAST-MOVING SHORT WAVE EMBEDDED IN THE BROAD TROUGH OVER THE
SOUTHEAST STATES WILL MOVE ACROSS CENTRAL NC ON FRIDAY. CURRENT
TIMING SUGGESTS THAT A FEW SHOWERS WILL BE POSSIBLE DURING THE PRE-
DAWN HOURS FRIDAY...BUT THE RISK FOR THESE SHOWERS MAY CONTINUE
THROUGH THE DAY. MODEST MOISTURE ASSOC WITH THIS SYSTEM SUGGESTS A
LOW-POP EVENT...WITH ANY RAINFALL BEING FAIRLY LIGHT AND FAVORING
THE EASTERN HALF OF OUR CWA GIVEN THE WESTERLY FLOW ALOFT. RAIN
CHANCES SHOULD DIMINISH BY SATURDAY WITH A WEAK RIDGE BUILDING
ACROSS THE AREA. TEMPS WILL GRADUALLY MODERATE TO NEAR OR ABOVE
NORMAL IN THE FRI-SAT TIME FRAME (NORMAL HIGHS THIS TIME OF YEAR ARE
AROUND 80 AND NORMAL LOWS IN THE MID 50S).

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 200 AM SUNDAY...

SUB-TROPICAL RIDGING WILL RESULT IN GENERALLY VFR CONDITIONS AND
LIGHT SSW FLOW THROUGH THE TAF PERIOD. THE ONE EXCEPTION WILL BE A
LOW-MEDIUM CHANCE OF A BRIEF OCCURRENCE OF FOG AT RWI AROUND
DAYBREAK. INITIALLY SCT TO BKN CIRRUS THIS MORNING WILL BE JOINED BY
DIURNAL CUMULUS CLOUDS WITH BASES BETWEEN 3500-6000 FT BY MIDDAY-
EARLY AFTERNOON.

OUTLOOK: ASIDE FROM A LOW PROBABILITY OF BRIEF LOW STRATUS OR FOG
EACH MORNING THROUGH TUE...MAINLY AT FAY AND RWI...THE ONLY OTHER
POSSIBLE INTERRUPTION TO VFR CONDITIONS WILL BE IN SCATTERED SHOWERS
AND STORMS...WITH THE RELATIVE GREATEST CHANCE TUE AFTERNOON AT RWI
AND FAY...WITH CHANCES GENERALLY ONLY 25 PERCENT OR LESS ELSEWHERE
AND OTHERWISE.

&&

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

&&

$$

SYNOPSIS...26
NEAR TERM...ELLIS/WSS
SHORT TERM...WSS
LONG TERM...RAH
AVIATION...26



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