Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 290715 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 315 AM EDT WED OCT 29 2014 .SYNOPSIS... A COLD FRONT WILL CROSS OUR REGION THIS AFTERNOON AND EVENING. HIGH PRESSURE WILL FOLLOW FOR THU THROUGH FRI. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 240 PM TUESDAY... MODELS IN GOOD AGREEMENT WITH THE TIMING OF THE COLD FRONT AND ASSOCIATED NARROW BAND OF LOW-TOP CONVECTION THROUGH THE AREA WEDNESDAY AFTERNOON-EVENING...~18Z IN THE TRIAD...-21Z THROUGH THE TRIANGLE...EXITING COASTAL PLAIN/I-95 CORRIDOR ~00Z THU. WHILE FAVORABLE DIURNAL TIMING WILL ALLOW FOR SOME DECENT HEATING FROM THE TRIANGLE EASTWARD...WEAK LOW-LEVEL LAPSE RATES AND RELATIVELY LOW SFC DEWPOINTS IN THE MID TO UPPER 50S WILL LIMIT INSTABILITY AND WILL PRECLUDE ANY SEVERE THREAT...THOUGH A CLAP OR TWO OF THUNDER WILL BE POSSIBLE. COMMENCEMENT OF STRONG CAA ACROSS THE WESTERN PIEDMONT DURING THE LATTER/SECOND HALF OF THE DAY...COINCIDENT WITH TYPICAL PEAK HEATING...WILL MAKE FOR A LARGER THAN NORMAL NW-SE TEMPERATURE GRADIENT ACROSS THE FORECAST AREA. HIGHS RANGING FROM MID/UPPER 60S NW TO UPPER 70S SE. POST-FRONTAL HIGH PRESSURE AND CAA WILL LEAD TO WEST-EAST CLEARING OVERNIGHT. LOWS 45 TO 55.
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
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AS OF 310 AM WEDNESDAY... SHORTWAVE RIDGING AND UNDERLYING 1020 MB SURFACE HIGH PRESSURE... BEHIND THE TROUGH ALOFT FORECAST TO MOVE INTO AND AFFECT THE EASTERN US DURING THE NEAR TERM...WILL BUILD EAST ACROSS THE TN/OH VALLEYS AND MIDDLE ATLANTIC STATES ON THU. THE RESULT WILL BE SUNNY AND COOLER CONDITIONS...WITH HIGH TEMPERATURES GENERALLY IN THE MIDDLE 60S TO NEAR 70 DEGREES. FORECAST GUIDANCE INDICATES ANOTHER SHORTWAVE TROUGH OVER THE PAC NW THIS MORNING WILL AMPLIFY SOUTHEASTWARD AND INTO THE SOUTHERN APPALACHIANS BY FRI MORNING...WHILE A MUCH STRONGER ONE IN A PRONOUNCED EARLY SEASON ARCTIC STREAM AMPLIFIES SOUTH SOUTHEASTWARD FROM CENTRAL CANADA TO THE WESTERN GREAT LAKES DURING THE SAME TIME. DESPITE THE ASSOCIATED STEADILY FALLING HEIGHTS ALOFT IN ASSOCIATION WITH THE PAIR OF AMPLIFYING SHORTWAVE TROUGHS...PRECEDING DRYNESS/LIMITED DEEP MOISTURE SUGGESTS THE MAIN IMPACT THROUGH FRI MORNING SHOULD BE MERELY AN UPTICK IN MID LEVEL CLOUDINESS AS THE FLOW ALOFT BACKS TO SOUTHWESTERLY THU NIGHT...WITH LOW TEMPERATURES WITHIN A FEW DEGREES EITHER SIDE OF 40.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 310 AM WEDNESDAY... WEAK HIGH PRESSURE WILL BE OVER THE AREA EARLY ON FRIDAY... AHEAD OF STRONG SHORTWAVE DIVING IN TO THE BASE OF A TROUGH OVER THE EASTERN US. RECENT MODEL TRENDS HAVE SHOWN THIS SHORTWAVE MOVING MUCH FURTHER SOUTHWARD THAN PREVIOUS RUNS... AND INCREASINGLY AMPLIFIED MIDLEVEL FLOW... WITH A CLOSED UPPER LOW CROSSING THE AREA AND INDUCING COASTAL SURFACE LOW DEVELOPMENT. THE RESULTING STRONG PRESSURE GRADIENT WILL BRING BLUSTERY WINDS SATURDAY. IF THIS SCENARIO PLAYS OUT... WE WILL SEE A COLD AND WET DAY... WITH HIGHS IN THE 40S. HAVE BEGUN TO TREND HIGHS LOWER... AND INCREASED TO CHANCE POPS SATURDAY. AS NOTED BY WPC... THE FORECASTED PATTERN IS QUITE ANOMALOUS... AND THEREFORE CONFIDENCE REMAINS BELOW NORMAL AT THIS TIME. SUBSIDENCE IN THE WAKE OF THE DEPARTING LOW WILL BRING CLEARING CONDITIONS ON SUNDAY... WHICH WILL WORK TO PARTIALLY OFFSET COLD ADVECTION... WITH HIGHS REACHING THE 50S. STRONG AND COLD HIGH PRESSURE BUILDING IN TO THE OHIO VALLEY ON SUNDAY WILL MOVE DIRECTLY OVER THE AREA ON MONDAY... WITH FROST AND POSSIBLY FREEZE POTENTIAL SUNDAY AND MONDAY MORNINGS. THE HIGH MOVES OFF THE EAST COAST ON TUESDAY... BEGINNING A MODERATING TREND IN TEMPERATURES... WITH HIGHS BACK IN THE 60S MONDAY AND TUESDAY. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 220 AM WEDNESDAY... ASIDE FROM A MEDIUM PROBABILITY OF LIFR-IFR STRATUS AT KFAY BETWEEN 10-14Z...VFR CONDITIONS ARE EXPECTED UNTIL A COLD FRONT AND ASSOCIATED BAND OF ALONG AND POST-FRONTAL SHOWERS - AND ASSOCIATED IFR-MVFR CEILINGS AND MVFR VISIBILITY RESTRICTIONS - MOVES EAST ACROSS CENTRAL NC THIS AFTERNOON AND EVENING. THE SHOWERS AND SUB-VFR CONDITIONS ARE EXPECTED TO LAST ONLY AROUND 3 HOURS AT ANY ONE LOCATION. A PERIOD OF VFR CEILINGS BETWEEN 4-8 THOUSAND FT WILL LINGER FOR A FEW HOURS EVEN AFTER THE SHOWERS AND SUB-VFR CONDITIONS MOVE EAST. OTHERWISE...SW SURFACE WINDS BETWEEN 7-13 KTS...STRONGEST AND OCCASIONALLY GUSTY INTO THE UPPER TEENS KTS AT FAY AND RWI...WILL VEER TO WNW OR NW BEHIND THE FRONT. OUTLOOK: THE PASSAGE OF A STRONG POLAR FRONT AND SUBSEQUENT DEVELOPMENT OF A STRONG COASTAL LOW WILL RESULT IN A CHANCE OF RAIN...AND BLUSTERY NW WINDS...FRI NIGHT THROUGH SAT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...CBL SHORT TERM...MWS LONG TERM...SEC AVIATION...MWS

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