Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260214 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1014 PM EDT WED MAR 25 2015 .SYNOPSIS...A FRONT WILL REMAIN QUASI-STATIONARY OVER CENTRAL NC TONIGHT...THEN LIFT NORTH OF THE AREA ON THU. MEANWHILE...A COLD FRONT WILL APPROACH FROM THE WEST AND CROSS OUR REGION THU NIGHT...FOLLOWED BY THE PASSAGE OF AN UPPER LEVEL DISTURBANCE FRI AND FRI NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1014 PM WEDNESDAY... EXPECT THE INFLUX OF ATLANTIC MOISTURE TO CONTINUE ADVECTING INTO THE REGION...MAINLY OVER THE SANDHILLS AND COASTAL PLAIN... INCREASING DEWPOINTS AND CONVECTIVE RAINFALL CHANCES. STILL EXPECT THE SOUTHERLY LLJ TO INCREASE TO 30-40 KTS OVERNIGHT...DESCENT MID LEVEL LAPSE RATES...AND GRADUALLY INCREASING ELEVATED INSTABILITY OVER THE SOUTHEASTERN PORTIONS OF THE AREA. THIS WILL SUPPORT SCATTERED TO NUMEROUS SHOWERS...AND POSSIBLY A RUMBLE OR TWO OF THUNDER. STILL ANTICIPATE LIMITED SEVERE POTENTIAL AT THIS TIME. LOWS TONIGHT SHOULD BE NEAR STEADY...GENERALLY MID 50S NW TO MID 60S SE. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 335 PM WEDNESDAY... THURSDAY: OWING TO THE SLOWER ARRIVAL OF THE FRONT INTO THE AREA...NOW DELAYED UNTIL AFTER 00Z FRIDAY...ONCE CONVECTION EXITS THE COASTAL PLAIN THURSDAY MORNING...THURSDAY LOOKS TO BE MOSTLY DRY ACROSS CENTRAL NC. IT WILL BE MUCH WARMER AS WELL. AS LOW-LEVEL FLOWS TO VEER AROUND A MORE SWLY COMPONENT...DRIER AIR WILL ADVECT INTO THE AREA FROM THE SW WHICH WILL HELP TO SCOUR LINGERING LOW CLOUDS/MOISTURE AND YIELD PARTLY TO MOSTLY SUNNY CONDITIONS THURSDAY AFTERNOON. WARM SECTOR TEMPERATURES WILL RISE WELL INTO THE 70S ACROSS THE AREA...APPROACHING NEAR 80 ACROSS THE FAR SE ZONES. THURSDAY NIGHT: COLD FRONT WILL CROSS THE AREA FROM WEST TO EAST BETWEEN 03 TO 12Z THURSDAY NIGHT/EARLY FRIDAY MORNING. CHANCE OF THUNDER LOOKS LOW APPEARS QUESTIONABLE GIVEN UNFAVORABLE DIURNAL TIMING AND LACK OF SUPPORT ALOFT AS THE AMPLIFYING UPPER LEVEL TROUGH IS PROGGED TO LAG BEHIND THE COLD FRONT. HOWEVER...BOTH THE GFS AND EC INDICATE THE POTENTIAL FOR WEAK DISTURBANCES IN ADVANCE OF THE MAIN TROUGH THAT COULD ENHANCE FORCING BETWEEN 00 TO 06Z ACROSS THE AREA WITH LINGERING STEEP MID-LEVEL LAPSE RATES AROUND 7.0 DEG/KM ACROSS THE WESTERN PIEDMONT. WILL INCLUDE A SLIGHT CHANCE OF THUNDER ACROSS THE NW PIEDMONT...WITH SHOWERS ELSEWHERE DUE TO WANING INSTABILITY AS THE FRONT CROSSES THE AREA. ANAFRONTAL PRECIP WILL THEN FILL IN BEHIND THE FRONT WITH THE APPROACH OF THE AMPLIFYING TROUGH INTO THE SOUTHERN APPALACHIANS AND ENSUING STRONG LOW-LEVEL CAA. LOWS RANGING FROM UPPER 40S/LOWER 50S NW TO NEAR 60S ACROSS THE SE DEPENDING ON THE EXACT TIMING OF THE COLD FRONT. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 340 PM WEDNESDAY... THE SURFACE COLD FRONT AND PRIMARY AREA OF SHOWERS ARE EXPECTED TO BE JUST EAST OF THE CWA BY 12Z FRIDAY....WHILE THE MAIN TROUGH AXIS LAGS WEST OF THE MOUNTAINS UNTIL FRIDAY EVENING. IN BETWEEN...LINGERING MOISTURE AND CONTINUED HEIGHT FALLS APPEAR TO BE ENOUGH FOR SOME ADDITIONAL ANAFRONTAL PRECIP THROUGH EARLY AFTERNOON...BEFORE MORE RESPECTABLE DRYING ALOFT MOVES IN FROM WEST TO EAST. LOW CONFIDENCE TEMP FORECAST AS TEMPS SHOULD INITIALLY BE FALLING THROUGH THE MORNING HOURS...WITH THE STRONGEST WARMING OVER THE WESTERN PIEDMONT DURING THE AFTERNOON IF CLOUDS CAN BREAK WITH THE DRYING ALOFT. USING A BLEND OF GUIDANCE GENERALLY YIELDS LOW TO MID 50S. THE PRIMARY TROUGH AXIS AND ASSOCIATED VORT CENTER WILL CROSS THE AREA FRIDAY NIGHT. AS TEMPS FALL THROUGH THE 40S AND INTO THE UPPER 30S...GFS FORECAST SOUNDINGS SHOW A BRIEF PERIOD OF STRONG OMEGA AND SUFFICIENT RESATURATION OF THE ICE-NUCLEATION ZONE FOR SHOWERS AFTER MIDNIGHT....FOCUSED MAINLY EAST OF THE TRIANGLE. SREF SOUNDINGS SHOW A WIDE VARIETY OF PROFILES AND THE ECMWF DOESNT HAVE MOISTURE QUITE A DEEP OVER THE COASTAL PLAIN. WITH A RELATIVELY SHALLOW ABOVE FREEZING LAYER NEAR THE SURFACE...ABOUT 2500 FT PER GFS SOUNDINGS...ITS POSSIBLE THAT RAIN SHOWERS COULD MIX WITH SOME SNOW AFTER MIDNIGHT...BUT WOULD LIKE TO SEE A LITTLE BETTER AGREEMENT IN MOISTURE PROFILES BEFORE INCLUDING ANY MENTION IN THE OFFICIAL FORECAST. LOWS IN THE LOWER 30S WEST TO UPPER 30S EAST. THE UPPER TROUGH WILL MOVE EAST AND HIGH PRESSURE BEGINS TO BUILD IN ON SATURDAY AND 1000-850MB THICKNESSES BOTTOM OUT IN THE 1270 TO 1280M RANGE. THE SURFACE HIGH IS FORECAST TO REMAIN JUST WEST OF THE MOUNTAINS...SO ONLY THE WESTERN PIEDMONT LOOKS TO HAVE A GOOD CHANCE OF DECOUPLING BY SUNDAY MORNING. THICKNESSES WOULD SUPPORT SUB-FREEZING LOWS FOR THE ENTIRE AREA AND EVEN MID 20S GIVEN MULTIPLE HOURS OF IDEAL RADIATIONAL COOLING. A WARMING TREND WILL THEN COMMENCE SUNDAY ONWARD AS HEIGHT BEGIN TO BUILD ALOFT AGAIN AND HIGH PRESSURE MOVES OFFSHORE. TEMPS ARE EXPECTED TO REBOUND BACK TO AND ABOVE NORMAL FOR THE FIRST HALF FO THE WEEK. ANOTHER COLD FRONT IS EXPECTED ON MONDAY...THOUGH WITH LIMITED MOISTURE AND ONLY A BRIEF COOL DOWN BEHIND IT. && .AVIATION /00Z THURSDAY THROUGH SUNDAY/... AS OF 845 PM WEDNESDAY... THE PRESENCE OF A QUASI-STATIONARY FRONT BETWEEN GSO AND RDU WILL RESULT IN POOR AVIATION CONDITIONS OVER CENTRAL NC THROUGH MID- MORNING TO MIDDAY THU. INITIALLY MVFR-VFR CEILINGS THIS EVENING WILL STEADILY LOWER INTO LIFR-IFR RANGE BY THU MORNING...WITH THE RELATIVE HIGHEST PROBABILITY AND LONGEST DURATION OF OCCURRENCE WEST OF THE STATIONARY FRONT - AT INT/GSO...WHILE CONDITIONS IN THE WARM SECTOR/EASTERN TAF SITES MAY EXPERIENCE MORE TRANSIENT SUB-VFR CONDITIONS...OR REMAIN VFR ALTOGETHER. AREAS OF FOG WILL ALSO ACCOMPANY THE LOW STRATUS; AND SOME OF THIS FOG MAY BECOME DENSE...PARTICULARLY AT INT AND GSO LATE TONIGHT. IN ADDITION...THE COMBINATION OF THE FRONT AND A SURGE OF MOISTURE ADVECTION IN SOUTHERLY FLOW FROM OFF THE SW ATLANTIC OCEAN WILL ALSO CAUSE AN AXIS OF SHOWERS AND EVEN AN ISOLATED THUNDERSTORM OR TWO TO INCREASE IN COVERAGE AND INTENSITY OVER CENTRAL NC TONIGHT -CENTERED NEAR RDU- BEFORE SHIFTING NE INTO EASTERN NC AND SE VA EARLY THU. OTHERWISE... LIGHT SOUTHERLY WINDS TO THE EAST OF THE FRONT (FAY)...NORTH TO ENE ONES TO THE WEST OF IT (INT/GSO)...AND LIGHT AND VARIABLE ONES NEAR IT (RDU/RWI). SOUTHERLY FLOW WILL CAUSE THE LOW CEILINGS AND VISIBILITY RESTRICTIONS TO MIX OUT ON THU...WITH VFR CONDITIONS LIKELY BY AFTERNOON AT ALL TAF SITES...THOUGH WITH A THREAT OF SOME LINGERING SUB-VFR CEILINGS AT INT/GSO WHERE LOW OVERCAST CLIMATOLOGICALLY LINGERS LONGEST. OUTLOOK: THE RETURN TO VFR WILL BE SHORT-LIVED...OWING TO THE PASSAGE OF A COLD FRONT AND ACCOMPANYING NARROW BAND OF SHALLOW CONVECTION WITH GUSTY WNW WINDS THU NIGHT...AND FOLLOWING IFR-MVFR CEILINGS AND TRAILING (ANAFRONTAL) RAIN THAT WILL AFFECT CENTRAL NC THROUGH MUCH OF FRI. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RAH NEAR TERM...RAH SHORT TERM...CBL LONG TERM...22 AVIATION...RAH

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