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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 201843
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
243 PM EDT MON MAY 20 2013

.SYNOPSIS...
A SHORTWAVE TROUGH WILL CONTINUE TO WORK THROUGH THE AREA THIS
AFTERNOON BRINGING UNSETTLED WEATHER THROUGH THIS EVENING. THE
TROUGH WILL MEANDER NORTHEASTWARD TUESDAY BEFORE MORE SETTLED
WEATHER RETURNS FOR WEDNESDAY.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 215 PM MONDAY...

...LOCALLY HEAVY RAIN TODAY INTO THE EVENING...

TODAY: WIDESPREAD SHOWERS AND THUNDERSTORMS HAVE BROKEN OUT IN A
SERIES OF LINES ACROSS THE CWA THIS AFTERNOON IN ASSOCIATION WITH A
SHORTWAVE IMPULSE PASSING THROUGH SOUTHERN VA. FOR THE MOST
PART...THUNDER HAS BEEN LIMITED TO A SELECT FEW CELLS WITH HEAVY
SHOWERS BEING THE PRIMARY MODE OF CONVECTION. THERE ARE SEVERAL WEAK
BOUNDARIES THAT HAVE SET UP THIS AFTERNOON. THE FIRST HAS LIFTED
NORTHEAST OF THE CWA...A SECOND ALONG THE HIGHWAY 1 CORRIDOR AND A
THIRD THROUGH THE TRIAD JUST EAST OF THE I-85 CORRIDOR. THESE TWO
LINES WILL GRADUALLY PUSH EASTWARD THIS AFTERNOON BRINGING MORE
HEAVY RAIN TO AN AREA ALREADY RECEIVING 2-3 INCHES OF RAIN IN SOME
LOCATIONS. THAT BEING SAID...RAIN RATES HAVE BEEN LOW ENOUGH AND
ENOUGH TIME HAS PASSED SINCE THE LAST RAINFALL THAT FLOODING SHOULD
NOT BE A WIDESPREAD PROBLEM THIS AFTERNOON. MORE LOCALIZED FLOODING
IS POSSIBLE WITH HEAVIER SHOWERS ESPECIALLY IN URBAN AREAS AND IN
THE NORMALLY FLASHY SMALLER CREEKS. RAINFALL TOTALS THIS AFTERNOON
WILL RANGE FROM A TENTH TO A QUARTER OF AN INCH OR SO WITH LOCALLY
HEAVIER AMOUNTS IN STRONGER STORMS. TRAINING OF STORMS SHOULD NOT BE
AS BIG OF A PROBLEM THIS AFTERNOON AND EVENING AS IT WAS EARLIER
THIS MORNING.

DESPITE THE SHORTWAVE ENERGY SEVERE POTENTIAL THIS AFTERNOON STILL
LOOKS EXTREMELY LIMITED. BOTH LOW AND MID-LEVEL LAPSE RATES ARE VERY
WEAK...AS IS THE EFFECTIVE SHEAR WHICH IS LESS THAN 15 KNOTS IN ALL
LOCATIONS. ML CAPE VALUES REMAIN BETWEEN 500-1000...LIMITED BY THE
CONTINUED BROKEN TO OVERCAST SKIES THIS AFTERNOON. THAT BEING SAID A
FEW CELL MERGERS HAVE ALLOWED SOME SHOWERS TO GROW TO A LEVEL
SUPPORTIVE OF VERY SMALL HAIL AND LIGHTNING. OTHERWISE HEAVY RAIN
AND MINOR FLOODING WILL CONTINUE TO BE THE MAIN THREAT OF THE DAY.

EXPECT WINDS THIS AFTERNOON TO GENERALLY BE SOUTHWESTERLY AT 5-10
KNOTS WITH THE OCCASIONAL GUST TO 15-20 KNOTS IN SHOWERS. HIGH
TEMPERATURES TODAY WILL MOST LIKELY VARY DEPENDING ON LOCATION WITH
A FEW BREAKS IN THE CLOUDS SUPPORTIVE OF HIGHS NEAR 80 WITH THOSE
LOCATIONS MAINTAINING OVERCAST SKIES TO TOP OUT IN THE MID TO UPPER
70S.

TONIGHT: HIGH RESOLUTION CONVECTIVE ALLOWING MODELS SUPPORT SHOWER
AND THUNDERSTORM ACTIVITY ENDING IN THE WEST AFTER 00Z AND
CONTINUING THROUGH 3Z IN THE EAST. THE ACCURACY OF THESE
MODELS...ESPECIALLY THE HRRR WAS BETTER EARLIER IN THE DAY THAN IT
IS NOW BUT THE SOLUTION STILL SEEMS REASONABLE GIVEN THE LOCATION OF
THE SHORTWAVE TO THE NORTH. AFTER CONVECTION ENDS EXPECT ISSUES WITH
FOG/LOW CEILINGS AND SUB-VFR VISIBILITIES AT ALL SITES OVERNIGHT.
THIS WILL CONTINUE THROUGH SUNRISE TUESDAY. LOWS WILL BE IN THE
LOWER TO MID 60S NW TO SE.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 215 PM MONDAY...

TUESDAY STILL SHOWS THE UPPER LEVEL TROUGH LINGERING AT LEAST OVER
THE NORTHEASTERN PART OF THE STATE WITH A SURFACE HIGH OVER THE
SOUTHWESTERN ATLANTIC. THE BEST MOISTURE TRANSPORT AND PRECIPITABLE
WATER VALUES WILL SHIFT TO THE EASTERN HALF OF THE STATE TOMORROW
BUT WILL STILL HAVE THE CHANCE FOR SHOWERS AND THUNDERSTORMS TO
DEVELOP WITH DIURNAL HEATING. ONCE AGAIN THE SEVERE THREAT WILL BE
SEVERELY HINDERED BY LACK OF GOOD LAPSE RATES...SHEAR...AND
INSTABILITY IN THE MOISTURE CONVERGENCE ZONE. THE BEST INSTABILITY
WILL BE ACROSS THE TRIAD...WHERE CLOUD COVER SHOULD BE
DECREASED...BUT ALSO WHERE THE LOW LEVELS WILL BE A BIT DRIER. IF WE
CAN GET A STORM TO FORM...THE BEST CHANCE FOR SEVERE STORMS WOULD BE
BACK ACROSS THE NORTHWEST LATE TOMORROW AFTERNOON WITH DAMAGING
WINDS THE PRIMARY THREAT...BUT ONCE AGAIN THIS IS A VERY SMALL
THREAT AND NOT EXPECTING THIS TO HAPPEN AT THIS TIME.

MODELS HAVE COME INTO A BIT BETTER AGREEMENT ON TEMPERATURES FOR
TOMORROW WITH HIGHS IN THE MID 80S EXPECTED ACROSS THE CWA AND
PERHAPS A FEW DEGREES WARMER IN THE TRIAD WHERE THERE WILL BE
GREATER INSOLATION.

TUESDAY NIGHT THINGS WILL BEGIN TO DRY OUT AS THE MESO LOW PUSHES
OFF TO THE NORTHEAST AND WEAK UPPER LEVEL RIDGING TAKES OVER.
SURFACE DEWPOINTS WILL REMAIN IN THE LOWER TO MID 60S AND LOW FOG
AND/OR STRATUS COULD ONCE AGAIN BE A PROBLEM TUESDAY NIGHT INTO
WEDNESDAY MORNING. EXPECT LOWS IN THE MIDDLE 60S TUESDAY NIGHT.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
AS OF 240 PM MONDAY...

FOR WEDNESDAY...WEAK SHORTWAVE RIDGING WILL BUILD OVER THE AREA...
WHILE AT THE SURFACE...THE BERMUDA HIGH WILL RIDGE WESTWARD INTO THE
CAROLINAS. ALL OF THIS WILL TRANSLATE TO AN EVEN FURTHER DECREASE IN
PRECIP COVERAGE. HOWEVER...SUFFICIENT MOISTURE WILL STILL BE IN
PLACE OVER THE REGION...WITH PWAT VALUES HOVERING NEAR 1.5 INCHES OR
SO. THEREFORE...AM STILL EXPECTING TO SEE WIDELY SCATTERED TO
SCATTERED DIURNALLY DRIVEN CONVECTION...WITH THE HIGHEST CHANCES
BEING ACROSS THE WESTERN PORTIONS OF THE FORECAST AREA. HIGHS ONCE
AGAIN SHOULD BE IN THE MID/UPPER 80S...WITH OVERNIGHT LOWS IN THE
MID/UPPER 60S.

SHOWER AND THUNDERSTORM COVERAGE SHOULD BEGIN TO INCREASE ONCE AGAIN
BY THE END OF THE WORK WEEK AS THE MID/UPPER LEVEL RIDGE SHIFTS
OFFSHORE AHEAD OF OUR NEXT MID/UPPER LEVEL TROUGH AND ASSOCIATED
COLD FRONT. MODELS REMAIN IN GENERAL AGREEMENT WITH BRINGING THE
FRONT THROUGH THE FORECAST AREA LATE THURSDAY NIGHT/EARLY FRIDAY.
THEREFORE...WILL SHOW POPS HIGHEST POPS CONCENTRATED DURING THE
THURSDAY/EARLY FRIDAY TIME FRAME...THEN DECREASING FROM WEST TO EAST
THROUGHOUT THE DAY ON FRIDAY. BULK SHEAR VALUES WILL INCREASE TO
AROUND 25 KNOTS OR SO...THEREFORE BETTER STORM ORGANIZATION IS
EXPECTED...HOWEVER THE BEST UPPER LEVEL FORCING WILL PASS WELL TO
OUR NORTH. THEREFORE...EVEN THOUGH AN ISOLATED SEVERE STORM CANNOT
BE COMPLETELY RULED OUT...THE OVERALL THREAT REMAINS LOW AT THIS
TIME. WITH THE INCREASED PRECIP CHANCES/CLOUDS ON THURSDAY AND
FRIDAY...TEMPS WILL MOSTLY BE IN THE LOW/MID 80S.

IT STILL APPEARS THE WEEKEND AND INTO EARLY NEXT WEEK WILL BE DRY AS
HIGH PRESSURE BUILDS IN BEHIND THE DEPARTING FRONT. SLIGHTLY COOLER
TEMPS ARE EXPECTED DURING THIS TIME FRAME...GENERALLY THE UPPER 70S
TO LOWER 80S...WITH OVERNIGHT LOWS IN THE 50S.
-- End Changed Discussion --

&&

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

24 HOUR TAF PERIOD:

WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL PREVAIL THIS
AFTERNOON ACROSS THE CWA AT ALL TERMINALS. CURRENTLY RADAR SHOWS
SHORTWAVE CURRENTLY MOVING ACROSS THE TRIAD WITH STRONGER CELLS ON
THE EASTERN SIDE WITH LINGERING SHOWERS TO THE WEST. FOR THE TRIAD
STRONGEST SHOWERS AND THUNDERSTORMS MOST LIKELY MOVING THROUGH NOW
THROUGH THE NEXT COUPLE OF HOURS AND DOWN TRENDING TO MOSTLY LIGHT
SHOWERS THEREAFTER. FURTHER TO THE EAST CONDITIONS SHOULD REMAIN
MORE FAVORABLE FOR HEAVIER SHOWERS AND THUNDERSTORMS THROUGH EARLY
EVENING. EXPECT CEILINGS TO BOUNCE BETWEEN VFR AND MVFR AND SINKING
OCCASIONALLY TO IFR IN THE STRONGER CELLS. WILL COVER THIS WITH A
TEMPO GROUP IN THE TAFS WITH VFR/MVFR PREVAILING. WINDS WILL REMAIN
GENERALLY SOUTHWESTERLY AT 5-10 KNOTS WITH OCCASIONAL GUSTS OF 15-20
IN HEAVY SHOWERS.

AFTER PRECIPITATION WINDS DOWN TONIGHT EXPECT SOME LOW
CEILINGS/VISIBILITIES...GENERALLY AFTER 3Z. EXPECT SOME FOG IN THE
WEST WITH MORE OF A LOW STRATUS SITUATION FURTHER TO THE EAST.
CONDITIONS SHOULD REMAIN SUB VFR EVERYWHERE UNTIL 15Z WHEN VFR
CEILINGS AND VISIBILITIES SHOULD RETURN. ALTHOUGH CONDITIONS WILL BE
IMPROVING AND GENERALLY DRYING...THE MESO-LOW WILL LINGER OVERHEAD
KEEPING THE CHANCE FOR SHOWERS ALIVE THROUGH THE END OF THE TAF
PERIOD.

LONG TERM:

LOW STRATUS AND FOG ARE EXPECTED TO RETURN TUESDAY NIGHT INTO
WEDNESDAY. WEDNESDAY WILL BE THE DRIEST DAY BUT WILL STILL HAVE THE
CHANCE FOR DIURNAL SHOWERS AND STORMS. THURSDAY AND THURSDAY NIGHT
WILL FEATURE THE PASSAGE OF A COLD FRONT AND A RETURN TO SUB-VFR
CONDITIONS. VFR CONDITIONS WILL GRADUALLY RETURN TO THE AREA ON
FRIDAY.

&&

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

&&

$$

SYNOPSIS...ELLIS
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...KRR
AVIATION...ELLIS