-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 180219
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1015 PM EDT MON JUN 17 2013

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE NORTHWEST TUESDAY MOVE ACROSS
OUR REGION TUESDAY NIGHT INTO WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1015 PM MONDAY...

AN MCV CONTINUES TO MOVE EASTWARD ACROSS THE SOUTHERN TIER OF OUR
COUNTIES. MUCH OF THE LEAD STRONGER CONVECTION HAS WEAKENED LEAVING
A CLUSTER OF LOCALLY HEAVY SHOWERS AND ISOLATED THUNDERSTORMS
SPREADING OUT INTO A LARGE STRATIFORM RAIN AREA. LIGHT TO MODERATE
RAIN WILL CONTINUE ACROSS THE SOUTHERN AND SOUTHEASTERN ZONES
THROUGH 100 TO 200 AM... BEFORE THE MCV MOVES OFFSHORE. POPS WILL
SHOW THIS TREND WITH POP DROPPING BACK TO 20 PERCENT ACROSS THESE
REGIONS AFTER 200 AM. ELSEWHERE... GIVEN THE CURRENT SET UP... WITH
VERY MOIST AND CONDITIONALLY UNSTABLE CONDITIONS... AN ISOLATED
STORM MAY DEVELOP JUST ABOUT ANYWHERE OVERNIGHT. HOWEVER...
ORGANIZED CONVECTION SHOULD HOLD OFF UNTIL THE APPROACH OF THE
STRONG UPPER LEVEL SYSTEM FROM THE WEST ON TUESDAY.

PATCHY STRATUS AND FOG ARE LIKELY LATER TONIGHT. SEE THE AVIATION
DISCUSSION BELOW. OTHERWISE... PARTLY TO MOSTLY CLOUDY... WARM AND
HUMID. LOWS 68-73.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 240 PM MONDAY...

TUESDAY:
MAIN S/W TROUGH AND ASSOCIATED WEAK COLD FRONT ARE EXPECTED TO
APPROACH THE REGION ON TUESDAY... WITH MOST MODELS NOW SHOWING THE
FEATURES CROSSING THE REGION BEYOND THE NEAR TERM FORECAST TIME
FRAME. HAVE TRENDED THE FORECAST TOWARDS A BLEND OF THE 12Z/17TH
NAM AND 00Z/17TH ECMWF FOR TIMING AND STRENGTH OF THE NEXT SYSTEM
(WHICH HOLDS THE SYSTEM TO THE WEST OF THE AREA THROUGH 00Z/19TH)...
WHICH IS IN LINE WITH THE ABOVE THINKING. THUS... HAVE LOWERED POPS
A BIT FOR TUESDAY. HOWEVER... STILL HAVE LIKELY POPS... AND EXPECT
AT LEAST SCATTERED SHOWERS AND STORMS ASSOCIATED WITH CONTINUED WEAK
DISTURBANCES CROSSING THE AREA IN THE INCREASINGLY CYCLONIC FLOW
ALOFT (WEST-SOUTHWESTERLY MID LEVEL FLOW) AND MOIST ATMO. THIS WILL
HELP TO SHARPEN UP A PRE-FRONTAL TROUGH TUESDAY AFTERNOON. EXPECT WE
WILL AGAIN HAVE A MARGINAL SVR THREAT... WITH STRONG TO DAMAGING
WINDS THE MAIN THREAT. DEEP LAYER SHEAR IS EXPECTED TO BE IN THE 20
TO 30 KT RANGE... WITH MLCAPE VALUES AGAIN AROUND 1000 J/KG. WITH
THE EXPECTED INCREASE IN CONVECTIVE COVERAGE... WE WILL NEED TO KEEP
AN EYE ON URBAN AREAS THAT RECEIVE ANY HEAVY RAIN FROM THE SHOWERS
AND STORMS (FLASH FLOODING THREAT). EXPECT HIGH TEMPS WILL AGAIN BE
HAMPERED BY CLOUD COVER. THUS... WILL GO WITH HIGHS RANGING FROM THE
LOWER TO MID 80S... WITH PERHAPS SOME UPPER 80S ACROSS OUR FAR EAST
AND SOUTH.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...
MODEL GUIDANCE CONTINUES TO OFFER VARYING TIMING SCENARIOS
CONCERNING THE MID LEVEL S/W AND ATTENDANT SFC FRONT WHICH IS
EXPECTED TO EFFECT OUR REGION TUESDAY NIGHT INTO WEDNESDAY. THE
12Z/17TH GFS HAS TRENDED SLIGHTLY SHARPER AND FASTER WITH THE
TROUGH. THE 12Z CANADIAN/12Z NAM AND 00Z ECMWF FAVOR A SLOWER (6-12
HOURS SLOWER) SOLUTION. FAVORING MODEL CONSENSUS WOULD SUGGEST
PAINTING THE HIGHEST POPS OVERNIGHT TUESDAY NIGHT THROUGH WEDNESDAY
MORNING WITH RAIN CHANCES DECREASING FROM THE WEST-NW WEDNESDAY
AFTERNOON. THE SHORT TERM MODEL GUIDANCE DEPICT A SFC WAVE CROSSING
CENTRAL NC LATE TUESDAY NIGHT INTO WEDNESDAY MORNING. THIS FEATURE
SHOULD ENHANCE LOW LEVEL HELICITY WHICH IS DEPICTED NICELY (BUT ONLY
FOR AN HOUR OR TWO) BY BUFKIT HODOGRAPHS DISPLAY WITH AN ARCHING
HODOGRAPH IN THE SFC-3KM RANGE. WOULD PREFER A SLIGHTLY STRONGER
WIND PROFILE PLUS AIR MASS MORE THAN MARGINALLY UNSTABLE BEFORE
HIGHLIGHTING SEVERE STORM THREAT IN THE HWO.

FOR NOW WILL INTRODUCE A TREND OF INCREASING POPS LATE TUESDAY NIGHT
THROUGH EARLY AFTERNOON WEDNESDAY THEN DECREASING POPS MID AFTERNOON
WEDNESDAY THROUGH EARLY WEDNESDAY EVENING.

HIGH TEMPS WEDNESDAY WILL BE HELD BACK BY EXTENSIVE CLOUDINESS AND
SCATTERED-NUMEROUS SHOWERS AND THUNDERSTORMS. PLAN TO MAINTAIN MAX
TEMPS NEAR 80-LOWER 80S. MIN TEMPS TUESDAY NIGHT WILL BE WARM IN THE
HUMID AIR MASS (UPPER 60S TO LOWER 70S) WHILE TEMPS OVERNIGHT
WEDNESDAY NIGHT SHOULD BE 3-5 DEGREES COOLER (LOW-MID 60S) BEHIND
THE SFC FRONT.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 3 PM MONDAY...

THURSDAY THROUGH FRIDAY NIGHT...SFC HIGH PRESSURE WILL EXTEND ACROSS
CENTRAL NC THU-FRI BEHIND THE EXITING MID LEVEL S/W. LOW LEVEL NE
FLOW WILL SPREAD AND MAINTAIN A DRY STABLE AIR MASS OVER CENTRAL NC.
THIS WILL LIMIT/INHIBIT CONVECTIVE DEVELOPMENT. LOW LEVEL
THICKNESSES AVERAGE 10M BELOW NORMAL. THIS TRANSLATES TO HIGH TEMPS
IN THE LOW-MID 80S. OVERNIGHT TEMPS GENERALLY IN THE LOW-MID 60S.

SATURDAY THROUGH MONDAY...A NARROW UPPER RIDGE WILL STRETCH FROM THE
SOUTHERN PLAINS INTO THE CENTRAL APPALACHIANS AND MID ATLANTIC
SATURDAY THROUGH MONDAY. ATTENDANT SFC RIDGE WILL GRADUALLY WEAKEN
THROUGH THE WEEKEND. THIS WILL CAUSE THE LOW LEVEL FLOW TO GRADUALLY
VEER FROM E-NE ON SATURDAY TO A S-SE FLOW LATE SUNDAY INTO MONDAY.
THIS SLY FLOW REGIME WILL RESULT IN AN UPTICK IN HUMIDITY LEVELS
SUNDAY INTO MONDAY. AT THIS TIME...CHANCES FOR AFTERNOON-EVENING
CONVECTION APPEAR TOO SMALL TO MENTION IN FORECAST.

PRESENCE OF UPPER LEVEL RIDGE WILL CAUSE AIR MASS TO MODIFY AS
WELL...YIELDING LOW LEVEL THICKNESSES ABOUT 10M ABOVE NORMAL BY
EARLY NEXT WEEK. THUS EXPECT HIGH TEMPS IN THE MID-UPPER 80S
SATURDAY...WARMING INTO THE UPPER 80S TO LOWER 90S ON MONDAY.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AS OF 740 PM MONDAY...

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS SOUTHERN NC
THIS EVENING. MVFR/IFR CIGS/VSBYS CONDITIONS POSSIBLE ALONG WITH
GUSTY WINDS TO 35-40 MPH WITH THE STRONGEST STORMS MAINLY SOUTH OF
KFAY.

A VERY MOIST AIR MASS WILL BE FAVORABLE FOR PATCHY FOG AND IFR/LIFR
CEILINGS OVERNIGHT... AND ADDITIONAL SCATTERED SHOWERS ARE POSSIBLE.

TUESDAY... MVFR TO IFR CIGS AND VSBYS CAN BE EXPECTED WITH SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS... MAINLY IN THE AFTERNOON AND
EVENING HOURS.

ADDITIONAL DISTURBANCES WILL BE CROSSING THE AREA ALONG WITH A WEAK
COLD FRONT TUESDAY NIGHT INTO WEDNESDAY...WITH PERIODS OF SHOWERS
AND STORMS PRODUCING SUB-VFR CONDITIONS.

VFR CONDITIONS ARE GENERALLY EXPECTED FROM THURSDAY ONWARD...
OUTSIDE OF POSSIBLY SOME EARLY MORNING STRATUS AND OR FOG DURING THE
PRE-DAWN HOURS OF EACH MORNING.

&&

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

&&

$$

SYNOPSIS...BSD
NEAR TERM...BADGETT/BSD
SHORT TERM...WSS
LONG TERM...WSS
AVIATION...BADGETT/BSD