Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180658 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 255 AM EDT MON AUG 18 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES IN NORTHWEST FLOW ALOFT WILL CROSS THE REGION THIS WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 255 AM MONDAY... SCATTERED TO WIDESPREAD SHOWERS AND STORMS ARE EXPECTED TO ACCOMPANY THE PASSAGE OF THE WELL-DEFINED MID-LEVEL TROUGH CURRENTLY OVER EASTERN TN/KY AND ATTENDANT SECONDARY LOW PRESSURE DEVELOPMENT INVOF OF CENTRAL NC TODAY. CONVECTIVE EVOLUTION...PARTICULARLY LATER THIS AFTERNOON IS A BIT UNCERTAIN WITH AN AREA OF SHOWERS CROSSING THE AREA FROM WEST TO EAST THIS MORNING AND INTO THE AFTERNOON APT TO LIMIT DESTABILIZATION. HOWEVER IF SUFFICIENT DESTABILIZATION DOES OCCUR....20 TO 30 KT WSWLY FLOW COULD SUPPORT A SEVERE MULTI-CELL CLUSTER OR TWO...WITH ASSOCIATED RISK FOR THUNDERSTORM WIND DAMAGE. ADDITIONALLY...HIGH +2.0 PWATS ACCOMPANYING THE MID-LEVEL WAVE COUPLED WITH ENHANCED LOW-LEVEL CONVERGENCE AS THE SURFACE LOW TRACKS EAST THROUGH THE AREA WILL BRING THE THREAT OF LOCALLY HEAVY RAINFALL AND FLASH FLOODING...ESPECIALLY IN URBAN AREAS AND LOCATIONS THAT HAVE RECEIVED RECENT HEAVY RAINFALL. CONVECTIVE CHANCES SHOULD DIMINISH FROM WEST TO EAST BETWEEN 00 TO 06Z IN ASSOC/W A PERIOD OF SUBSIDENCE IN THE WAKE OF THE SHORTWAVE TRACKING OFFSHORE. HIGH TEMPERATURES TODAY WILL BE QUITE CHALLENGING DUE TO THE EARLY ONSET OF PRECIP THIS MORNING AND CONVECTIVE UNCERTAINTY THIS AFTERNOON. WILL UNDERCUT GUIDANCE...ESPECIALLY IN THE NW PIEDMONT. HIGHS IN THE LOWER LOWER 80S NW TO NEAR 90F SE. LOWS TONIGHT IN THE 70S.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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AS OF 300 AM MONDAY... MID/UPPER LEVEL SHORTWAVE VORT DISTURBANCE INVOF OF ARKLATEX THIS MORNING IS FORECAST TO PROGRESS EAST ACROSS THE LOWER MS VALLEY TODAY AND ACROSS THE SOUTHEAST DURING PRIME HEATING TUESDAY AFTERNOON. CONVECTIVE COVERAGE SHOULD BE MORE SCATTERED IN NATURE WITH HIGHEST POPS IN THE EAST WITHIN THE CONTINUED HIGH +2.0 PWAT AS DRIER AIR BEGINS TO SPREAD IN FROM THE WEST. 0-6KM SHEAR DROPS OFF TO 10-15KTS BUT STRONGER HEATING AND RESULTANT MODERATE DESTABILIZATION COULD SUPPORT AN ISOLATED STRONG TO SEVERE STORM TUESDAY AFTERNOON. MUCH LIKE MONDAY NIGHT...PERIOD OF SYNOPTIC SCALE SUBSIDENCE TUESDAY EVENING/NIGHT IN THE WAKE OF THE UPPER WAVE MOVING OFF THE SE COAST SHOULD RESULT IN DRY CONDITIONS TUESDAY NIGHT. WARMER ON TUESDAY WITH HIGHS RANGING FROM UPPER 80S NW TO LOWER 90S SE. LOWS TUESDAY NIGHT IN THE UPPER 60S NW TO LOWER 70S SE.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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AS OF 300 AM MONDAY... THE LONG TERM PERIOD WILL BE CHARACTERIZED BY A BUILDING UPPER RIDGE ACROSS THE MISSISSIPPI RIVER VALLEY WITH A CLOSED UPPER LOW OFF THE NORTHEAST COAST...LEAVING CENTRAL NC UNDER A NORTHWESTERLY UPPER FLOW REGIME. THERE ARE DIFFERENCES AMONG THE MODELS WITH RESPECT TO THE AMPLITUDE OF THE UPPER AIR PATTERN...ESPECIALLY BY THE WEEKEND. TO BEGIN ON WEDNESDAY...THE UPPER FLOW WILL BE MORE ZONAL IN NATURE AS THE UPPER RIDGE WILL JUST BE TAKING SHAPE OVER THE NORTHERN GULF WHILE A SHORTWAVE TROUGH WILL BE TRACKING ACROSS THE GREAT LAKES. MODELS DO INDICATE A SHEAR AXIS APPROACHING THE AREA LATE WEDNESDAY AFTERNOON AND THIS COULD RESULT IN SOME CONVECTION. HOWEVER...PER FORECAST SOUNDINGS...DEEP MOISTURE WILL BE LACKING (PWAT VALUES 1.5- 1.75 INCHES...HIGHEST ACROSS THE EAST) AND THEREFORE CONVECTIVE COVERAGE IS NOT ANTICIPATED TO BE THAT GREAT. SIMILAR SET UP ON THURSDAY ALTHOUGH THE NORTHWESTERLY FLOW ALOFT WILL BEGIN TO SET UP OVER THE REGION AND THE REGION WILL BE UNDER THE INFLUENCE OF ANY POSSIBLE DISTURBANCES WITHIN THE UPPER FLOW. HOWEVER...WITH RELATIVELY LIMITED DEEP MOISTURE...WILL KEEP POPS CAPPED AT CHANCE. STILL UNDER THE INFLUENCE OF DISTURBANCES ALOFT WITHIN THE NORTHWESTERLY FLOW...WILL SHOW A GRADUAL INCREASE IN POPS BY FRIDAY AND INTO THE WEEKEND AS MOISTURE SURGES BACK INTO THE REGION (PWAT VALUES PROGGED TO EXCEED 2 INCHES). AS STATED ABOVE...MODEL DIFFERENCES BECOME MORE APPARENT OVER THE WEEKEND...WITH THE GFS PERSISTING WITH A VERY AMPLIFIED UPPER PATTERN AND THE ECMWF BEGINNING THE BREAK DOWN THE RIDGE OVER THE MISSISSIPPI VALLEY. REGARDLESS...WITH A VERY MOIST AND UNSTABLE AIR MASS...WILL KEEP PRECIP CHANCES IN THE FORECAST (MAINLY DIURNAL IN NATURE). TEMPS ON WEDNESDAY AND THURSDAY ARE EXPECTED TO BE IN THE LOW TO MID 90S...WITH SLIGHTLY "COOLER" TEMPS FOR THE REMAINDER OF THE PERIOD GIVEN THE INCREASED CLOUDS AND PRECIP CHANCES...WITH MAINLY 80S EXPECTED BY THE WEEKEND. OVERNIGHT LOWS WILL GENERALLY IN THE UPPER 60S TO LOWER 70S THROUGHOUT THE PERIOD.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...CBL SHORT TERM...CBL LONG TERM...KRD AVIATION...CBL/VINCENT

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