Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210442 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1240 AM EDT TUE APR 21 2015 .SYNOPSIS...HIGH PRESSURE WILL BUILD OVER NC FROM THE SOUTHWEST TODAY AND TONIGHT... THEN SHIFT EAST OFF THE COAST TUESDAY NIGHT INTO WEDNESDAY. A DRY COLD FRONT WILL APPROACH FROM THE NORTH WEDNESDAY NIGHT AND PUSH SOUTH OF THE REGION THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1055 PM MONDAY... ALTHOUGH SEVERE THUNDERSTORM WATCH #89 HAS BEEN ALLOWED TO EXPIRE... THERE REMAINS A CONDITIONAL RISK OF ISOLATED SEVERE THUNDERSTORMS THROUGH AROUND 2 AM. STRONG Q-VECTOR CONVERGENCE ASSOCIATED WITH A NEGATIVELY-TILTED TROUGH ALOFT -ONE WHICH WV IMAGERY INDICATES INCLUDES AN IMPULSE OVER NE GA AND A MORE SUBSTANTIAL SHORTWAVE TROUGH OVER THE TN VALLEY...WITH MARKED DRYING IMMEDIATELY BEHIND THE LATTER- WILL CONTINUE TO PIVOT NE ACROSS CENTRAL NC THROUGH 04Z IN THE SOUTHERN AND WESTERN PIEDMONT TO 08Z OVER THE NE PIEDMONT AND COASTAL PLAIN. IN ADDITION...OBJECTIVE ANALYSIS DATA INDICATE A PLUME OF STEEP MID LEVEL LAPSE RATES BETWEEN 7 AND 7.5 C/KM SAMPLED BY THE BMX 00Z RAOB HAS FINALLY ADVECTED INTO CENTRAL NC...SUPPORTIVE OF AN UPTICK IN MLCAPE TO BETWEEN 500-1000 J/KG...DESPITE BOTH NOCTURNAL AND DIABATIC OUTFLOW COOLING. LASTLY...THE SURFACE COLD FRONT WAS ANALYZED AT 02Z OVER THE FOOTHILLS OF THE CAROLINAS...WITH A PRE- FRONTAL TROUGH IMMEDIATELY AHEAD OF THE FRONT; AND THESE FEATURES ARE FORECAST TO MOVE EAST ACROSS CENTRAL NC WITH SIMILAR TIMING AS THE AFOREMENTIONED UPPER FORCING. THE MAIN LIMITING FACTOR WITH ANY APPRECIABLE CONVECTIVE REDEVELOPMENT WILL BE DEEP MOISTURE...WITH OBSERVED PRECIPITABLE WATER VALUES OF ONLY AROUND THREE QUARTERS OF AN INCH AT GSO AND MHX. FURTHERMORE...SURFACE DEWPOINTS REMAIN RELATIVELY MODEST EVEN AHEAD OF THE FRONT OVER THE WESTERN PIEDMONT AND FOOTHILLS...WHERE SURFACE DEWPOINTS AT 02Z WERE ONLY IN THE MID-UPPER 50S. RELATIVELY RICHER LOW LEVEL MOISTURE...CHARACTERIZED BY SURFACE DEWPOINTS IN THE LOWER TO MIDDLE 60S...WAS OBSERVED OVER THE REMAINDER OF CENTRAL NC. DESPITE THE LIMITED MOISTURE...THERE HAS ALREADY BEEN REDEVELOPMENT OF A RELATIVELY STRONG LINE OF STORMS FROM NEAR TDF TO BUY; AND THIS ACTIVITY...AS WELL AS NEW ISOLATED TO WIDELY SCATTERED DEVELOPMENT ALTOGETHER...WILL REMAIN POSSIBLE UNTIL THE AFOREMENTIONED FRONT AND UPPER FORCING CLEAR CENTRAL NC. BOTH LOW AND DEEP LAYER SHEAR...THE LATTER OF WHICH IS CHARACTERIZED STILL BY LONG AND STRAIGHT HODOGRAPHS FROM OBSERVED PROXIMITY RAOB DATA...ARE MORE THAN SUPPORTIVE OF ORGANIZED STORM MODES...INCLUDING SUPERCELLS AND/OR BOWS WITHIN MULTI-CELL LINE SEGMENTS. POST-FRONTAL LOW TEMPS...ACCOMPANIED BY MUCH LOWER RELATIVE HUMIDITY VALUES BY DAYBREAK...SHOULD RANGE FROM AROUND 50 DEGREES NW TO AROUND 60 SE. && .SHORT TERM /TODAY THROUGH WEDNESDAY/...
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AS OF 1240 AM TUESDAY... THE COLD FRONT WILL MOVE OFFSHORE EARLY THIS MORNING. HIGH PRESSURE WILL FOLLOW THE FRONT TODAY AS IT BUILDS INTO THE REGION FROM THE GULF COAST STATES. THE PRESSURE GRADIENT WILL BE FAIRLY TIGHT THROUGH THIS AFTERNOON WITH DECENT DAA/CAA. HIGHS GENERALLY EXPECTED TO BE IN THE 70-75 RANGE. MUCH DRIER AIR ADVECTING IN WITH ALSO ALLOW FOR SKIES TO BE SUNNY. CLEAR AND COOL CONDITIONS EXPECTED TONIGHT. LOWS IN THE MID 40S WITH LIGHT WINDS. WEDNESDAY... THE MAIN ISSUE WILL BE THE EXPECTED GUSTY RETURN FLOW DEVELOPING LATE MORNING THROUGH THE AFTERNOON FROM THE SW. WINDS SHOULD INCREASE TO 15-20 MPH WITH GUSTS TO 30 MPH OUT AHEAD OF THE APPROACHING DRY COLD FRONT. HIGHS WILL WARM INTO THE MID TO UPPER 70S WITH PARTLY SUNNY SKIES.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... AS OF 1212 AM TUESDAY... A MOISTURE STARVED COLD FRONT IS EXPECTED TO PUSH SOUTH THROUGH CENTRAL NORTH CAROLINA WEDNESDAY NIGHT... THEN STALL WELL SOUTH OVER SOUTH CAROLINA THURSDAY INTO FRIDAY. THE MAIN MOISTURE SOURCES ARE FORECAST TO BE CUT OFF AS THIS FRONT MOVES THROUGH WEDNESDAY NIGHT. WEAK HIGH PRESSURE WILL BUILD SOUTHEAST FROM THE OHIO VALLEY INTO NORTH CAROLINA LATER THURSDAY INTO FRIDAY. SENSIBLE WEATHER WEDNESDAY NIGHT WILL FEATURE ONLY A CHANCE OF A SPRINKLE OR TWO OR A VERY LIGHT SHOWER WITH THE FRONT. LOWS GENERALLY FROM 50 NORTH INTO THE UPPER 50S SOUTH. MOSTLY SUNNY SKIES THURSDAY WILL GIVE WAY TO SOME INCREASE IN MID AND HIGH CLOUDS IN THE WEST AND SOUTH FRIDAY. HIGHS BOTH DAYS SHOULD BE AROUND 70 INTO THE LOWER 70S SOUTH. LOWS THURSDAY NIGHT GENERALLY IN THE 40S. SATURDAY THROUGH MONDAY... THE BEST CHANCE OF RAIN IS EXPECTED TO BE SATURDAY INTO SUNDAY AS THE ACTIVE SOUTHERN BRANCH JET SYSTEM TRACKS ACROSS THE LOWER MISSISSIPPI VALLEY TOWARD THE SOUTHEASTERN STATES. UNCERTAINTY WITHIN THE MODELS CONTINUE WITH THE TIMING/STRENGTH/ AND TRACK WITH THE SYSTEM. MODELS CONTINUE TO SHOW A DEEP TROUGH OVER SE CANADA AND THE EASTERN STATES AS WELL WHICH WILL ESSENTIALLY GUARANTEE BELOW NORMAL LATE APRIL TEMPERATURES THIS WEEKEND INTO NEXT WEEK. THE BIG QUESTION WILL BE HOW MUCH RAIN WILL FALL OVER THE WEEKEND WITH THE SOUTHERN BRANCH SYSTEM. WE WILL MAINTAIN CHANCE POP WITH INCREASING CONFIDENCE FOR THE WEEKEND. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 735 PM MONDAY... SCATTERED STORMS WILL CONTINUE TO AFFECT PORTIONS OF CENTRAL NC WITH BRIEF PERIODS OF SUB-VFR CONDITIONS. ONE BAND OF SCATTERED STORMS WILL AFFECT RDU THROUGH 03Z... AND WILL POTENTIALLY REACH RWI AFFECTING THAT SITE 02Z-05Z. AT THIS TIME... IT APPEARS THAT THE STORMS WILL HOLD LARGELY TO THE NORTHEAST OF FAY. A SECOND BAND OF STORMS OVER THE NRN FOOTHILLS AND NRN MOUNTAINS OF NC MAY SKIRT NEAR INT BUT IS ALSO EXPECTED TO STAY MAINLY NW OF THE TRIAD. BRIEF MVFR TO IFR CONDITIONS ARE POSSIBLE IN AND NEAR STORMS... AS WELL AS PEA TO QUARTER SIZE HAIL. OTHERWISE... VFR CONDITIONS WILL DOMINATE THROUGH TONIGHT. WINDS FROM THE SW AT 10-15 KTS GUSTING TO 20-25 KTS WILL PERSIST... VEERING AROUND TO WESTERLY WITH DIMINISHING GUSTS AFTER PASSAGE OF A COLD FRONT AFTER 04Z. A SHORT PERIOD OF MVFR CIGS ARE POSSIBLE WITH FRONTAL PASSAGE... BUT GENERALLY WE EXPECT VFR CONDITIONS LATE TONIGHT THROUGH THE END OF THE TAF VALID PERIOD WITH MOSTLY CLEAR SKIES. LOOKING BEYOND 00Z WED... VFR CONDITIONS SHOULD HOLD THROUGH WED AS HIGH PRESSURE BUILDS OVER THE REGION. A FEW HOURS OF SUB-VFR CIGS/VSBYS WITH A FEW SHOWERS ARE POSSIBLE WED EVENING/NIGHT INTO EARLY THU AS A DISTURBANCE MOVES QUICKLY ACROSS THE DEEP SOUTH AND SOUTHEAST STATES. VFR CONDITIONS AND COOLER WEATHER WILL FOLLOW FOR LATE THU INTO SAT. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...RAH SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...HARTFIELD

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