Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 191530
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1130 AM EDT SUN APR 19 2015

.SYNOPSIS...A STALLED FRONTAL ZONE OVER CENTRAL NORTH CAROLINA WILL
LIFT NORTHWARD INTO VIRGINIA AS A WARM FRONT LATE THIS AFTERNOON AND
EVENING...AS A DEVELOPING LOW PRESSURE SYSTEM TRACKS NORTHEAST INTO
THE OHIO VALLEY. AN ASSOCIATED COLD FRONT WILL APPROACH THE
MOUNTAINS FROM THE WEST ON MONDAY...THEN TRACK EAST TO THE CAROLINA
COAST MONDAY NIGHT.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 1130 AM SUNDAY...

NOT A GREAT DEAL OF CHANGES TO THE PREVIOUS FORECAST WARRANTED WITH
TWO ROUNDS OF PRECIPITATION EXPECTED ACROSS CENTRAL NC THIS
AFTERNOON AND TONIGHT. REGIONAL RADAR IMAGERY SHOWS A LARGE AREA OF
RAIN WITH EMBEDDED HEAVIER ELEMENTS MOVING NORTHEAST FROM WESTERN NC
AND NORTHERN SC TOWARD CENTRAL NC. THE ARRIVAL OF THIS APPEARS
SLOWER THAN EXPECTED SO WEVE ADJUSTED THE POPS ACCORDINGLY. WHILE
THE RAIN COULD BE LOCALLY HEAVY...THE AMOUNTS AND DURATION APPEAR
SHORT ENOUGH TO AVOID MAJOR FALASH FLOODING ISSUES ALTHOUGH SOME
FLOODING PROBLEMS IN THE TYPICAL SUSCEPTIBLE URBAN LOCATIONS IN THE
TRIAD MAY BE HARD TO AVOID.

A LULL IN PRECIPITATION IS LIKELY TO OCCUR LATE THIS AFTERNOON AND
EARLY EVENING BEFORE THE NEXT ROUND OF PRECIPITATION SWEEPS
NORTHEAST. THIS AREA OF PRECIPITATION MAY BE MORE SHOWERY AND
CONVECTIVE IN NATURE AND THERE COULD BE A FEW RUMBLES OF THUNDER
WITH IT AS DRY AIR ALOFT ARRIVES ALONG WITH A SLIGHT STEPENING OF
MID LEVEL LAPSES RATES.

WIDESPREAD CLOUDINESS AND THE ARRIVAL OF PRECIPITATION SHOULD
PRECLUDE MUCH DIURNAL CHANGE IN TEMPERATURES TODAY AND TONIGHT WITH
TEMPERATURES RELATIVELY STEADY IN THE 60S TO LOWER 70S.

PREVIOUS AFD...
PRECIPITATION: EXPECT NEAR 100% CHANCES FOR
PRECIPITATION TODAY... IN ASSOC/W DPVA ATTENDANT INCREASINGLY
NUMEROUS SMALL AMPLITUDE WAVES EMBEDDED WITHIN STRENGTHENING SW FLOW
ALOFT AND LOW-LEVEL CONVERGENCE ATTENDANT A WEAK WARM FRONT /LOW-
LEVEL TROUGH/ PROGRESSING SW-NE OR SSW-NNE ACROSS CENTRAL NC IN THE
PRESENCE OF A VERY MOIST (PWAT ~1.75") ALBEIT MARGINALLY UNSTABLE
AIRMASS. EXPECT PRECIP INCREASING IN COVERAGE/INTENSITY FROM SW-NE
AFTER ~12Z THIS MORNING...REACHING THE TRIANGLE BY LATE MORNING
(~15Z) AND FAR NE COASTAL PLAIN (I.E. HALIFAX COUNTY) BY EARLY
AFTERNOON (16-18Z). EXPECT THE HEAVIEST PRECIPITATION TO FALL
ALONG/WEST OF THE YADKIN RIVER...IN CLOSER VICINITY TO STRONGER DPVA
/ATTENDANT SFC CYCLONE/
TRACKING NE THROUGH THE TN VALLEY AND WHERE FORCING WILL BE LOCALLY
AUGMENTED BY CONVERGENCE /OROGRAPHIC ASCENT/ ASSOCIATED WITH A
STRENGTHENING SOUTHEASTERLY LLJ BETWEEN 15-21Z. PRECIP CHANCES WILL
DECREASE FROM SW-NE OR SSW-NNE ACROSS CENTRAL NC LATE THIS EVENING
(00-04) AS THE LOW-LEVEL TROUGH /WARM FRONT/ LIFTS NORTHWARD INTO
THE DELMARVA AND A DRIER MID-LEVEL AIRMASS ADVECTS INTO THE REGION
FROM THE SW/WSW. AS COVERAGE BEGINS TO DECREASE...INTENSIFICATION OF
LINGERING CONVECTION WILL BE POSSIBLE...PRIMARILY IN THE 00-06Z TIME
FRAME AS MID-LEVEL LAPSE RATES STEEPEN IN ADVANCE OF MORE POTENT
SHORTWAVE ENERGY TRACKING INTO THE REGION FROM THE SOUTHWEST. PRECIP
CHANCES WILL RAPIDLY DIMINISH IN THE 06-12Z TIME FRAME AS SUBSIDENCE
COMMENCES IN THE WAKE OF THE SHORTWAVE.

TEMPS: HIGHS WILL BE LIMITED BY PRECIPITATION (WEST) AND PERVASIVE
CLOUD COVER FOLLOWED BY PRECIP (EAST)...RANGING FROM THE MID/UPPER
60S FAR NW PIEDMONT TO LOWER 70S ELSEWHERE. GIVEN A SOUTHERLY BREEZE
AND LITTLE CHANGE IN AIRMASS...EXPECT LOWS TONIGHT IN THE LOW TO MID
60S.

SEVERE: SEVERE WEATHER IS NOT ANTICIPATED TODAY (12-00Z) WITH UPPER
LEVEL FORCING ON THE MARGINAL END OF THE SPECTRUM AND DIURNAL
DESTABILIZATION SIGNIFICANTLY HAMPERED BY WEAK/MOIST-ADIABATIC MID-
LEVEL LAPSE RATES AND PERVASIVE CLOUD COVER. A PERIOD OF CONVECTIVE
INTENSIFICATION WILL BE POSSIBLE BETWEEN 00-06Z WHEN STRONGER DPVA
ARRIVES IN THE PRESENCE OF STEEPENING MID-LEVEL LAPSE RATES. SHOULD
DISCRETE INTENSIFICATION OCCUR...A BRIEF/LOW-END TORNADO OR WIND
THREAT COULD NOT BE RULED OUT THIS EVENING...LOW AS THE PROBABILITY
MAY BE.

FLOODING: GIVEN DEEP MOISTURE (PWAT ~1.75") AND A GOOD ~6-9 HR
PERIOD OF MODERATE TO HEAVY PRECIPITATION EXPECTED IN WESTERN
PORTIONS OF THE STATE...ISOLD FLASH FLOODING WILL BE POSSIBLE...
PARTICULARLY IN URBAN AND FLOOD PRONE AREAS ACROSS THE TRIAD. GIVEN
THAT THE HEAVIEST PRECIPITATION 9AND GREATEST COVERAGE THEREOF) IS
EXPECTED TO FALL WEST OF THE YADKIN RIVER (WEST OF NWS RALEIGH CWA)
AND THAT THE WESTERN PIEDMONT HAS EXPERIENCED BELOW NORMAL
PRECIPITATION DURING THE PAST 6 MONTHS...A FLASH FLOOD WATCH WILL
NOT BE NECESSARY EAST OF THE YADKIN. -VINCENT

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 400 AM SUNDAY...

EXPECT A CLEARING TREND MONDAY MORNING THROUGH EARLY AFTERNOON AS
LINGERING LOW STRATUS LIFTS AND BECOMES CU/TCU WITH BASES OF 3-4 KFT
BY EARLY AFTERNOON. A MODIFIED ELEVATED MIXED LAYER CHARACTERIZED BY
H7-H5 LAPSE RATES ON THE ORDER OF 7 C/KM IS PROGGED TO ADVECT INTO
THE REGION LATE TONIGHT...MAINTAINED BY WSW/SW FLOW ALOFT DURING THE
DAY MONDAY. LOW-LEVEL MOISTURE (SFC DWPT UPPER 50S TO LOWER 60S)
WILL PERSIST THROUGHOUT THE DAY...WITHIN AN INCREASINGLY WELL-MIXED
WARM SECTOR DOWNSTREAM OF A COLD FRONT APPROACHING THE MOUNTAINS
FROM THE WEST DURING THE LATE AFT/EVE. GIVEN STRONG DIURNAL HEATING
AND STEEP MID-LEVEL LAPSE RATES ATOP SEASONABLY IMPRESSIVE LOW-LEVEL
MOISTURE...MODERATE DESTABILIZATION IS EXPECTED WITH MLCAPE VALUES
SOLIDLY IN THE 1500-2500 J/KG RANGE. THOUGH LITTLE IN THE WAY OF A
CAP IS PRESENT MON AFTERNOON PER THE LATEST GUIDANCE/FORECAST
SOUNDINGS...CONVECTION IS UNLIKELY TO DEVELOP BEYOND THE `TURKEY
TOWER` STAGE THROUGH MID AFTERNOON (~21Z) GIVEN SUCH A DRY AIRMASS
ALOFT...AN INSUFFICIENT FOCUS...AND AN OVERAL LACK OF DEEPER ASCENT.

BY LATE AFTERNOON (~21Z)...MODERATE/UNTAPPED INSTABILITY AND AN
ABSENCE OF CONVECTIVE INHIBITION ARE EXPECTED TO ALLOW RAPID
CONVECTIVE DEVELOPMENT ALONG THE COLD FRONT /PRE-FRONTAL TROUGH/
PROGRESSING INTO THE FOOTHILLS...GROWING UPSCALE INTO A SQUALL LINE
BETWEEN 21-00Z AS ADDITIONAL CONVECTION DEVELOPS ALONG OUTFLOW IN AN
ENVIRONMENT CHARACTERIZED BY WESTERLY LOW-LEVEL SHEAR AND MODERATE/
HIGH DCAPE. WILL INDICATE A 50% CHANCE OF SHOWERS/STORMS MOVING WEST-
EAST ACROSS CENTRAL NC BETWEEN 21-03Z.

SEVERE THREAT: WITH THE ABOVE ENVIRONMENT IN MIND...ANY STORMS THAT
DEVELOP COULD BECOME SEVERE...WITH A PRIMARY THREAT OF DAMAGING
WINDS. QUARTER TO GOLFBALL SIZE HAIL WOULD BE POSSIBLE IN ASSOC/W
ROTATING UPDRAFTS...PARTICULARLY DISCRETE UPDRAFTS (I.E. INITIALLY
IN WESTERN PIEDMONT). AN ENHANCED THREAT OF DAMAGING WINDS WILL BE
PRESENT ALONG/EAST OF HWY 1 IF UPSCALE GROWTH INTO A MATURE MCS
OCCURS WITHIN THE ENVIRONMENT PROGGED BY GUIDANCE. -VINCENT

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 100 AM SUNDAY...

...DRIER CONDITIONS FOR MUCH OF THE UPCOMING WEEK...

THE MAIN COLD FRONT WILL BE OFFSHORE BY 12Z/TUE. COOL AND DRY
ADVECTION WILL OVERSPREAD CENTRAL AND EASTERN NORTH CAROLINA
TUESDAY AS THE SURFACE HIGH SHIFTS EAST ALONG THE GULF COAST
STATES. HIGHS SHOULD STILL REACH 70-75 IN MOST AREAS EXCEPT UPPER
60S IN THE NORTHWEST PIEDMONT INCLUDING WINSTON-SALEM AND
GREENSBORO. BREEZY W-NW WINDS AT 10-20 MPH ARE EXPECTED FROM MID
MORNING THROUGH THE AFTERNOON... DIMINISHING LATE AFTERNOON.

THE SURFACE HIGH PRESSURE WILL PUSH EAST ALONG THE SE STATES THEN
OFFSHORE TUESDAY NIGHT AND WEDNESDAY. THIS OCCURS AS A DRY COLD
FRONT IS FORECAST TO APPROACH THE REGION WEDNESDAY AFTERNOON DRIVEN
BY THE NW FLOW ALOFT. A RETURN SW SURFACE FLOW SHOULD COMMENCE
FROM THE TENNESSEE VALLEY NORTHEAST ACROSS THE CENTRAL
APPALACHIANS AND NW NC TUESDAY NIGHT. THE SW RETURN FLOW WILL
ARRIVE OVER THE REST OF NORTH CAROLINA WEDNESDAY. THERE WILL BE
LITTLE TO NO GULF MOISTURE RETURN OUT AHEAD OF THIS FRONT WITH ONLY
SOME MID AND HIGH CLOUDINESS EXPECTED. THEREFORE... EXPECT PARTLY
CLOUDY SKIES TUESDAY NIGHT AND PARTLY SUNNY WEDNESDAY. LOWS IN THE
MID 40S. HIGHS IN THE LOWER TO MID 70S WEDNESDAY.

THE COLD FRONT IS EXPECTED TO STALL JUST TO OUR SOUTH ON WEDNESDAY
NIGHT AND THURSDAY BEFORE THE NEXT SURGE OF ENERGY IN THE WNW FLOW
ALOFT EVENTUALLY DRIVES ANOTHER COLD FRONT TOWARD THE AREA LATE
THURSDAY. THE GULF AND ATLANTIC APPEAR TO BE CUT OFF DURING THIS
TIME IN THE PREDOMINATELY WESTERLY FLOW - HOWEVER HARD TO TIME
ENERGY ALOFT MAY BRING A SMALL CHANCE OF LIGHT SHOWERS LATE WED
NIGHT AND THURSDAY. WE WILL ONLY CARRY A SLIGHT CHANCE AT THE
CURRENT TIME DUE TO THE LACK OF AVAILABLE MOISTURE EXPECTED.
LOWS AND HIGHS SHOULD RETURN TO NORMAL (LOWER TO MID 50S/LOWER TO
MID 70S) INTO THURSDAY.

FRIDAY AND SATURDAY... DRY CONDITIONS SHOULD CONTINUE THROUGH LATE
WEEK BEHIND THE COLD FRONT THURSDAY. HOWEVER... LOW CONFIDENCE OF
TIMING AND STRENGTH OF A POTENTIAL SOUTHERN BRANCH SYSTEM
TOWARD THE WEEKEND INCREASING THE CHANCE OF SHOWERS BY SATURDAY.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 150 AM SUNDAY...

24 HOUR PERIOD: CIGS WILL DROP TO MVFR... THEN IFR... AT KINT AND
KGSO BETWEEN 09Z AND 12Z... AND PROGRESS NORTHEAST THROUGH THE
MORNING AS RAIN AND EMBEDDED HEAVY RAIN SHOWERS OVERSPREAD THE AREA
AHEAD OF A WARM FRONT. THE HEAVIEST RAIN WITH ISOLATED THUNDERSTORMS
WILL LIKELY OCCUR BETWEEN 21Z/SUN AND 03Z/MON WHEN LIFR CIGS/VSBYS
CAN BE EXPECTED.

THE HEAVY RAIN WILL PUSH NORTH OF THE REGION BETWEEN 03Z-07Z/MON...
LEAVING WIDESPREAD IFR/MVFR CEILINGS THROUGH 12Z/MON.

VFR CONDITIONS ARE EXPECTED MONDAY. HOWEVER... A COLD FRONT WILL
BRING MVFR CIGS DURING THE MID TO LATE AFTERNOON. SW WINDS 15-25KT
WILL PRECEDE THE FRONT... SHIFTING TO THE WEST DURING THE EVENING AT
10KT. SCATTERED CIGS/VSBYS OF IFR TO MVFR WILL OCCUR IN SHOWERS AND
THUNDERSTORMS MONDAY AFTERNOON AND EVENING UNTIL THE FRONT PASSES.

A RETURN TO VFR CONDITIONS ARE FORECAST FOR LATE MONDAY NIGHT
THROUGH THURSDAY AS HIGH PRESSURE BUILDS IN.

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...BLAES/VINCENT
SHORT TERM...VINCENT
LONG TERM...BADGETT
AVIATION..BADGETT



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