Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 200645 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 245 AM EDT WED AUG 20 2014 .SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES IN NORTHWEST FLOW ALOFT WILL CROSS THE REGION THIS WEEK. A BACK DOOR COLD FRONT IS FORECAST TO SLIP INTO THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 245 AM WEDNESDAY... W-NW FLOW ALOFT BETWEEN THE UPPER LEVEL RIDGE BUILDING FROM THE WESTERN GULF OF MEXICO INTO THE NRN PLAINS AND THE PERSISTENT MID- LEVEL CYCLONE MOVING SLOWLY EASTWARD THROUGH THE GREAT LAKES WILL PERSIST THROUGH THE PERIOD. VORTICITY LOBE EMBEDDED WITHIN THE BROADER TROUGH OVER THE NORTHERN/NE CONUS WILL TRAVERSE THE MID- ATLANTIC REGION...ONCE AGAIN DURING PEAK HEATING...BETWEEN 18 TO 03Z. WEAK DPVA COUPLED WITH SEASONABLY MOIST AIRMASS AND UNSTABLE AIR WILL SUPPORT ISOLATED TO WIDELY SCATTERED POPS...WITH BEST CHANCE ACROSS THE NORTHERN TIER INVOF THE BETTER UPPER SUPPORT. CONVECTIVE PARAMETERS ARE NEARLY IDENTICAL TO TUESDAY(WEAK SHEAR 20KTS OR LESS AND ML CAPE 1200 TO 1500 J/KG)...RESULTING A LOW/NON- ZERO SEVERE THREAT. HIGHS IN THE 89 TO 94. LOWS IN THE UPPER 60S TO LOWER 70S.
-- End Changed Discussion --
&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
-- Changed Discussion --
AS OF 245 AM WEDNESDAY... LITTLE CHANGE ON THE SYNOPTIC PATTERN ON THURSDAY. CENTRAL NC WILL REMAIN POISED TO SEE VORT DISTURBANCES EMBEDDED IN THE NW FLOW ALOFT AS THE UPPER LOW OVER THE GREAT LAKES WEAKENS THROUGH THE DAY AS IT MOVES EAST INTO THE NE US. AT THIS TIME...CAN NOT FIND A DISCERNIBLE FEATURE THAT WOULD SUPPORT MORE THAN ISOLATED SLIGHT CHANCE POPS THURSDAY/THURSDAY NIGHT...IN FACT...500MB HEIGHTS ACTUALLY INCREASE OVER THE AREA ON THURSDAY...WITH ASSOCIATED SUBSIDENCE/WARMING ALOFT POSSIBLY SUPPRESSING CONVECTION TO A POINT WHERE IT COULD END UP BEING ONE OF THE LEAST CONVECTIVELY ACTIVE DAYS OF THE WEEK. AS FAR AS TEMPERATURES...BOTH THE EC AND GFS INDICATE H8 TEMPERATURES WILL WARM TO 22C...WHICH SHOULD SUPPORT HIGHS THURSDAY SOLIDLY IN THE MID 90S. LOWS THURSDAY NIGHT IN THE LOWER 70S.
-- End Changed Discussion --
&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
AS OF 245 AM WEDNESDAY... THE LONG TERM PERIOD WILL BE CHARACTERIZED BY A BUILDING UPPER RIDGE ACROSS THE MISSISSIPPI RIVER VALLEY WITH AN UPPER TROUGH/CLOSED LOW OFF THE NORTHEAST COAST...LEAVING CENTRAL NC UNDER A NORTHWESTERLY UPPER FLOW REGIME. DIFFERENCES REMAIN AMONG THE MODELS WITH RESPECT TO THE EVOLUTION OF THE UPPER AIR PATTERN...ESPECIALLY BY EARLY NEXT WEEK. REGARDLESS...GIVEN THAT MUCH OF OUR PRECIP CHANCES WILL HINGE ON DISTURBANCES ALOFT WITHIN THE NORTHWEST FLOW AND THAT THE PRECISE TIMING OF ANY SUCH DISTURBANCES THIS FAR OUT IS NEARLY IMPOSSIBLE... CONFIDENCE IN THE EXACT DETAILS OF PRECIP CHANCES ARE RATHER LOW. AS A SHORTWAVE TROUGH TRACKS OFF THE NORTHEASTERN US COAST (AND EVENTUALLY TRANSITIONS INTO A CLOSED LOW/DEEP TROUGH JUST OFF THE EAST COAST THROUGH EARLY NEXT WEEK)...A BACKDOOR COLD FRONT WILL BE PUSHED THROUGH THE AREA FRIDAY. THIS SHOULD LEAD TO SOLID CHANCE POPS. MODELS HAVE BACKED OFF ON DRIER AIR FILTERING IN BEHIND THE FRONT AND THEREFORE PRECIP CHANCES WILL REMAIN IN THE FORECAST THROUGH AT LEAST EARLY NEXT WEEK GIVEN THE PERSISTENT NORTHWEST FLOW REGIME AND SUBSEQUENT "TRAIN" OF DISTURBANCES ALOFT TRACKING ACROSS THE AREA. THERE ARE SOME INDICATIONS THAT THE UPPER RIDGE MAY BUILD FAR ENOUGH EAST BY THE VERY END OF THE LONG TERM PERIOD WHICH WOULD RESULT IN DECREASING PRECIP CHANCES. TEMPS ON FRIDAY ARE EXPECTED TO BE IN THE LOW TO MID 90S...WITH SLIGHTLY "COOLER" TEMPS FOR THE WEEKEND AND EARLY NEXT WEEK AS HEIGHTS FALL WHILE THE DEEP UPPER TROUGH BUILDS DOWN THE WESTERN ATLANTIC...WITH MAINLY 80S EXPECTED. TEMPS MAY BEGIN TO REBOUND SOME BY TUESDAY IF THE UPPER RIDGE DOES INDEED START TO BUILD EAST. OVERNIGHT LOWS WILL GENERALLY IN THE UPPER 60S TO LOWER 70S THROUGHOUT THE PERIOD.
-- End Changed Discussion --
&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 110 AM WEDNESDAY... SKIES HAVE CLEARED OFF THIS EVENING. AREA METARS ARE ALREADY REPORTING 2 TO 3 DEGREE DEWPOINT DEPRESSIONS. COMBINED WITH LIGHT WINDS...THIS ALLOW FOR THE DEVELOPMENT OF MOSTLY MVFR FOG. NORTHERN COASTAL PLAIN/NORTHEAST PIEDMONT(KRWI AND KRDU)COULD ALSO SEE SOME STRATUS ADVECT INTO THE AREA AS N-NELY FLOW DEVELOPS. EXPECT CONDITIONS TO IMPROVE TO VFR BETWEEN 14-15Z. SHORTWAVE DISTURBANCES TRAVERSING THE REGION WILL ONCE AGAIN FUEL ISOLATED TO SCATTERED CONVECTION THIS AFTERNOON/EVENING... WITH THE HIGHEST PROBABILITY ACROSS THE NORTHERN TAF SITES. HOWEVER... CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE ANY MENTION OF CONVECTION IN THE TAFS AT THIS TIME. OUTLOOK... EARLY MORNING STRATUS/FOG...ALONG WITH AFTERNOON SHOWERS AND STORMS WILL BE POSSIBLE EACH DAY THIS WEEK INTO THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLS NEAR TERM...CBL SHORT TERM...CBL LONG TERM...KRD AVIATION...CBL/BLS

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.