Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201849 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 250 PM EDT SUN JUL 20 2014 .SYNOPSIS...AN INCREASINGLY MOIST AND SLIGHTLY UNSTABLE AIR MASS COUPLED WITH AN AREA OF LOW PRESSURE OVER THE TENNESSEE VALLEY WILL CAUSE SCATTERED SHOWERS AND A FEW THUNDERSTORMS TO OCCUR ACROSS CENTRAL NORTH CAROLINA THROUGH MID WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1040 AM SUNDAY... A MINOR S/W WHICH CAN BE TRACED BACK ON WATER VAPOR IMAGERY TO THE MISSOURI OZARKS YESTERDAY MORNING WAS INTERACTING WITH A MODERATELY MOIST AIR MASS ACROSS CENTRAL NC...TRIGGERING SCATTERED SHOWERS. THESE SHOWERS WERE EXITING THE EASTERN PIEDMONT LATE THIS MORNING AND SHOULD EXIT THE NORTHERN COASTAL PLAIN COUNTIES BY EARLY AFTERNOON. WEAK SUBSIDENCE IN THE WAKE OF THE DEPARTING S/W WILL LIKELY HINDER CONVECTIVE DEVELOPMENT THROUGH MID AFTERNOON ACROSS MOST OF CENTRAL NC. AFTER 20-21Z...MAY SEE AN INCREASE IN CONVECTIVE COVERAGE...MAINLY IN THE SOUTHERN COASTAL PLAIN WHERE A DIFFERENTIAL HEATING BOUNDARY MAY EXIST...AND IN THE WESTERN PIEDMONT AS WEAK BUT STEADY WLY FLOW WILL STEER ANY CONVECTION THAT FORMS IN THE HIGHER TERRAIN EASTWARD INTO THE PIEDMONT. AFTERNOON TEMPS A CHALLENGE. MORNING SHOWERS KEEPING TEMPS DOWN IN THE TRIANGLE AREA WHILE LOW OVERCAST/LIMITED INSOLATION IS RESULTING IN LATE MORNING TEMPS NEAR 70/LOWER 70S ACROSS THE REST OF THE PIEDMONT. OVER THE SANDHILLS AND SOUTHERN COASTAL PLAIN...BRIEF PEEKS OF SUN HAVE PUSHED TEMPS WELL INTO THE 70S. PRESENT INDICATIONS ARE THAT THE MAX TEMPS OVER SECTIONS OF THE EASTERN PIEDMONT AND NORTHERN COASTAL PLAIN WILL NEED TO BE LOWERED A FEW DEGREES WHILE MAX TEMP FORECAST ALONG OUR WESTERN AND SOUTHERN PERIPHERY APPEARS TO BE ON TARGET. -WSS THREAT OF SCATTERED SHOWERS AND THUNDERSTORMS CONTINUES TONIGHT ...ESPECIALLY ACROSS THE EAST AND SOUTHEAST. THE GFS...NAM AND ECMWF ALL DEPICT THE POTENTIAL FOR A LARGE AREA OF CONVECTION ACROSS SC LATE TONIGHT WHICH COULD ADJUST THE MASS FIELDS AND ALTER THE AMOUNT OF CONVECTION IN NC. FOR NOW WILL HIGHLIGHT THE SOUTH AND SOUTHEAST WITH POPS IN THE MID 30S AND MID 20S TO THE NORTH. LOWS SHOULD RANGE WITHIN A FEW DEGREES OF 70. -BLAES && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 240 AM SUNDAY... A PERSISTENT UPPER LEVEL TROUGH IS EXPECTED TO EXTEND FROM THE SOUTHERN APPALACHIANS INTO THE NORTHERN GULF COAST ON MONDAY AND MONDAY NIGHT. THIS WILL PLACE CENTRAL NC IN A FAVORED REGION FOR UNSETTLED WEATHER AS DISTURBANCES ROTATE AROUND THE TROUGH AND MOVE NEAR CENTRAL NC. PRECIPITABLE WATER VALUES ARE PROGGED TO INCREASE FURTHER ON MONDAY AND RANGE FROM 1.7 TO 2.1 INCHES. FORECAST SOUNDINGS DEPICT A VERY MOIST AIR MASS WITH LIMITED INSTABILITY AND RATHER MEAGER LAPSE RATES. CONVECTION THAT DEVELOPS WILL LIKELY BE SLOW MOVING AND POTENTIALLY PRODUCE SOME VERY HEAVY RAIN. WILL HIGHLIGHT THE SOUTHERN PIEDMONT AND COASTAL PLAIN AS THE MOST FAVORED LOCATIONS FOR PRECIPITATION ON MONDAY AND MONDAY NIGHT WITH POPS AROUND 45 PERCENT AND DECREASE THEM TO THE NORTHWEST. HIGHS ON MONDAY SHOULD RANGE BETWEEN 83 AND 86 DEGREES WITH OVERNIGHT LOWS IN THE UPPER 60S. -BLAES && .LONG TERM /TUESDAY THROUGH SUNDAY/...
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AS OF 250 PM SUNDAY... TUESDAY: CENTRAL NC WILL BE POSITIONED BETWEEN A CLOSED UPR LOW OVER THE DEEP SOUTH AND THE RIDGE OFF THE SE COAST...WITH A WEAK SHEAR AXIS ELONGATED ACROSS OUR SOUTHERN ZONES. MEANWHILE...INVERTED TROUGH IS PROGGED TO REMAIN NEAR THE COAST. FORECAST SOUNDINGS CONTINUE TO SHOW PLENTY OF PWAT (AOA 2 INCHES) ACROSS OUR CWA...BUT FORECAST CAPE STILL AOB 1000 J/KG AND VERY WEAK DEEP LAYER FLOW. AS SUCH...LOOK FOR SCATTERED MAINLY AFTERNOON/EVENING SHOWERS AND TSTMS...WITH THE MAIN CONCERN BEING LOCALIZED SLOW-MOVING HEAVY DOWNPOURS WHICH MAY RESULT IN SOME POOR DRAINAGE FLOODING. OTHERWISE...NOT MUCH OF A CONCERN FOR DAMAGING WIND OR HAIL GIVEN MODEST INSTABILITY AND SHEAR. AIRMASS SHOULD SUPPORT NEAR-NORMAL HIGHS AROUND 90 IF SOME SUNSHINE CAN BREAK THROUGH THE CLOUDS. LOWS TUESDAY NIGHT AROUND 70. WEDNESDAY: WE`LL SEE A CHANGE TO A MORE TYPICAL WEATHER PATTERN WITH THE PIEDMONT SFC TROUGH SETTING UP AS MID LEVEL WESTERLY FLOW INCREASES AHEAD OF AN APPROACHING SHORT WAVE TROUGH THAT WILL BE MOVING ACROS THE GREAT LAKES REGION. LOOK FOR BETTER COVERAGE OF SCATTERED AFTERNOON AND EVENING SHOWERS/TSTMS. FORECAST SOUNDINGS INDICATE CAPE INCREASING TO 1500 J/KG NEAR AND EAST OF THE TRIANGLE...BUT 0-6KM BULK SHEAR EXPECTED TO REMAIN AOB 20KT. THUS...THE STRONGER STORMS MAY BE CAPABLE OF PRODUCING SOME STRONG WIND GUSTS AND/OR SOME HAIL...BUT THE MAIN CONCERN WILL ONCE AGAIN BE HEAVY DOWNPOURS AND POOR DRAINAGE FLOODING WITH PWAT STILL AROUND 2 INCHES. HIGHS IN THE LOWER 90S AND LOWS IN THE LOWER 70S. THURSDAY AND FRIDAY: DECENT MODEL AGREEMENT THAT THE COLD FRONT WILL MOVE INTO OUR CWA LATER IN THE DAY THURSDAY AND STALL ACROSS OUR EASTERN/SOUTHERN ZONES ON FRIDAY. AS SUCH...POPS WILL TREND FROM HIGHEST NORTHWEST TO LOWEST SOUTHEAST ON THURSDAY...THEN FLIPPING TO HIGHEST SOUTH/EAST TO LOWEST NORTHWEST ON FRIDAY. TEMPS ON THURSDAY STILL ABOVE NORMAL (HIGHS IN THE MID 90S AND LOWS IN THE LOWER 70S) GIVEN THE LATE ARRIVAL OF THE FRONT...THEN COOLING BACK TO NEAR NORMAL FOR FRIDAY WITH THE FRONT ACROSS OR JUST EAST OF OUR AREA. NEXT WEEKEND: AT THIS POINT IT LOOKS LIKE THE AFOREMENTIONED BOUNDARY WILL BE WEAKENED OR DISSIPATED TO OUR SOUTH AND EAST. EXPECT A MORE TYPICAL SUMMER PATTERN DURING THIS TIME WITH SCATTERED AFTERNOON/EVENING SHOWERS AND TSTMS AND TEMPS NEAR 90 FOR HIGHS AND NEAR 70 FOR LOWS.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... AS OF 115 PM SUNDAY... AN INCREASINGLY MOIST AND SLIGHTLY UNSTABLE AIR MASS WILL SUPPORT THE DEVELOPMENT OF SCATTERED SHOWERS AND A FEW THUNDERSTORMS THIS AFTERNOON THROUGH THE MIDDLE OF THE WORK WEEK. THE SHOWERS AND STORMS WILL BE MOST LIKELY DURING THE AFTERNOON AND EVENING HOURS. IN VICINITY OF THE HEAVIER SHOWERS EXPECT MVFR/IFR CONDITIONS. AT THIS TIME...TUESDAY IS SHAPING UP TO THE BE THE MOST CONVECTIVELY ACTIVE DAY. A COLD FRONT APPROACHING FROM THE NORTHWEST WILL ALSO ENHANCE THE PROBABILITY OF SHOWERS AND STORMS ON THURSDAY. THE THREAT FOR EARLY MORNING LOW CLOUDS AND FOG WILL ALSO BECOME MORE LIKELY THROUGH THURSDAY. THIS PERIOD OF SUB VFR CONDITIONS WILL BE MOST LIKELY BETWEEN THE HOURS OF 08Z-14Z. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS/BLAES SHORT TERM...BLAES LONG TERM...NP AVIATION...WSS

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