Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201932 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 330 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/...
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AS OF 330 PM SUNDAY... TONIGHT... A MODERATELY MOIST AIR MASS IS IN PLACE WITH PRECIP WATER VALUES RANGING FROM 1.5 INCHES IN THE WESTERN PIEDMONT TO AROUND 1.8 INCHES IN THE COASTAL PLAIN. A MID-UPPER LEVEL L/W TROUGH WAS POSITIONED OVER THE TN VALLEY-DEEP SOUTH THIS AFTERNOON WITH A SERIES OF S/WS ROUNDING THE BASE OF THE TROUGH NEAR THE GULF COAST THEN LIFTING NEWD ACROSS GA AND THE CAROLINAS. A WEAK SHEAR AXIS ALSO STRETCHES ACROSS SE VA-EASTERN NC. WATER VAPOR IMAGERY DEPICTS A WELL-DEFINED VORT MAX CROSSING SE AL AT 18Z. MODEL GUIDANCE HAS BEEN HANDLING THIS SYSTEM FAIRLY CONSISTENT...LIFTING THE SYSTEM NEWD TO THE VICINITY OF GSP/CAE BY 06Z. FOR THE REST OF THE AFTERNOON...SUBSIDENCE IN THE WAKE OF A DEPARTING VORT MAX WILL AID TO DIMINISH SOME OF THE CLOUD COVER. THE ADDED INSOLATION WILL AID TO DESTABILIZE THE ATMOSPHERE...LEADING TO THE DEVELOPMENT OF SCATTERED CONVECTION...ESPECIALLY IN VICINITY OF THE LINGERING MID LEVEL SHEAR AXIS OVER THE COASTAL PLAIN. SEVERE STORM PARAMETERS ARE MARGINAL AT BEST AT THIS TIME SO NOT ANTICIPATING MUCH IN THE WAY OF SEVERE WEATHER. HOWEVER THE HEAVIER SHOWERS AND STORMS WILL PRODUCE LOCALLY HEAVY RAINFALL AS THE AIR MASS HAS BECOME ALMOST TROPICAL-LIKE AND STEERING FLOW IS WEAK. BULK OF SHOWERS WILL DIMINISHING WITH LOSS OF HEATING. AS THE S/W OVER SE AL GETS CLOSER TO OUR REGION LATER TONIGHT...EXPECT AN INCREASE IN SHOWER COVERAGE OVER OUR FAR SOUTHERN COUNTIES. MIN TEMPS TONIGHT SHOULD BE NO LOWER THAN THE UPPER 60S TO AROUND 70.
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&& .SHORT TERM /MONDAY AND MONDAY NIGHT/...
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AS OF 330 PM SUNDAY... MONDAY...SOUTH CAROLINA S/W PROJECTED TO LIFT E-NE INTO SE NC BY EARLY AFTERNOON THEN OFFSHORE BY EARLY EVENING. THIS FEATURE INTERACTING WITH THE AVAILABLE MOISTURE AND SLIGHTLY FAVORABLE DIVERGENCE ALOFT SHOULD TRIGGER/SUSTAIN SCATTERED-NUMEROUS SHOWERS AND A FEW THUNDERSTORMS...ESPECIALLY DURING THE AFTERNOON HOURS. EXPECT BULK OF PRECIP TO OCCUR OVER THE SOUTHERN AND EASTERN SECTIONS OF THE FORECAST AREA. A LINGERING SFC RIDGE OVER THE NORTHERN-NORTHWEST PIEDMONT MAY SUPPRESS CONVECTIVE DEVELOPMENT. PLAN TO VARY POPS FROM CHANCE ACROSS THE FAR NORTH-NW TO LIKELY ACROSS THE SE THIRD. SIMILAR TO TODAY...CLOUDS AND SCATTERED SHOWERS WILL RESULT IN TEMPS SEVERAL DEGREES BELOW NORMAL. WITH CONVECTION EXPECTED TO FIRE BY LATE MORNING/EARLY AFTERNOON DUE TO CLOSE PROXIMITY OF THE S/W...FAVOR MAX TEMPS ON THE COOLER SIDE OF MOS GUIDANCE (LOWER 80S). IF CONVECTION ABSENT AT EARLY AFTERNOON...TEMPS MAY END UP REACHING THE MID 80S. MONDAY NIGHT... SCATTERED-NUMEROUS SHOWERS WILL GRADUALLY DIMINISH AS THE S/W LIFTS OFFSHORE AND ATMOSPHERE BEGINS TO STABILIZE WITH LOSS OF HEATING. STILL COULD SEE A FEW SHOWERS PERSIST OR RE- GENERATE AS ADDITIONAL MINOR LIFT NEWD. POPS CAPPED AT 30-40 PERCENT FOR NOW. MIN TEMPS UPPER 60S-LOWER 70S.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/... 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. && .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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