Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 120704 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 300 AM EDT SAT APR 12 2014 .SYNOPSIS...A DRY SURFACE RIDGE ASSOCIATED WITH ATLANTIC HIGH PRESSURE WILL PERSIST ACROSS THE CAROLINAS THROUGH SUNDAY. MEANWHILE...A STALLED FRONT OVER THE OHIO VALLEY AND MID ATLANTIC WILL GRADUALLY LIFT NORTH INTO NEW ENGLAND AS LOW PRESSURE STRENGTHENS UPSTREAM ACROSS THE CENTRAL PLAINS AND CENTRAL MISSISSIPPI RIVER VALLEY. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 245 AM SATURDAY... BROAD CYCLONIC FLOW OVER THE REGION WILL GIVE WAY TO RISING HEIGHTS/ RIDGING ALOFT ACROSS THE EASTERN SEABOARD TODAY/TONIGHT AS AN UPPER LEVEL TROUGH DEEPENS OVER THE WESTERN CONUS IN ASSOCIATION WITH A SOUTHERN STREAM LOW (IN SOUTHERN CA THIS MORNING) TRACKING INTO THE DESERT SOUTHWEST AND NORTHERN STREAM SHORTWAVE ENERGY DIGGING THROUGH THE PACIFIC NORTHWEST INTO THE INTERMOUNTAIN WEST. A WEAK PRE-FRONTAL TROUGH IN ADVANCE OF A STALLED FRONTAL ZONE TO THE NORTH WILL LIKELY LINGER ACROSS PORTIONS OF THE WESTERN/NORTHERN PIEDMONT UNTIL RISING HEIGHTS ALOFT REINFORCE THE SFC RIDGE AXIS EXTENDING INTO THE REGION FROM THE ATLANTIC LATE THIS AFT/EVE. AN MCV (AND/OR SHORTWAVE TROUGH) MOVING INTO NORTHERN GA AT 06Z THIS MORNING IS EXPECTED TO TRACK THROUGH SOUTH CAROLINA AND PROGRESS OFFSHORE BY NOON. AS SUCH...THIS FEATURE IS UNLIKELY TO PROVIDE FORCING FOR ASCENT IN THE RIGHT AREA (TOO FAR SOUTH) OR RIGHT TIME (TOO EARLY). ALTHOUGH MODEL GUIDANCE INDICATES ~250 J/KG (MLCAPE) BY 21Z IN ASSOCIATION WITH DIURNAL DESTABILIZATION...FORCING FOR ASCENT THROUGHOUT THE COLUMN WILL BE INSUFFICIENT FOR CONVECTION TO DEVELOP DURING PEAK HEATING GIVEN SUCH WEAK THERMODYNAMICS...A PROHIBITIVELY DRY AIRMASS ALOFT AND A THOROUGH LACK OF DEEP LAYER FORCING. AS SUCH...WILL CONTINUE TO INDICATE A DRY FORECAST. EXPECT HIGHS SIMILAR TO YESTERDAY (UPPER 70S TO NEAR 80F). LOWS TONIGHT IN THE MID 50S. -VINCENT && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 300 AM SATURDAY... TO BE POSTED SHORTLY. && .LONG TERM /MONDAY THROUGH FRIDAY/...
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AS OF 300 AM SATURDAY... ...A SIGNIFICANT SYSTEM WILL AFFECT THE REGION LATE MONDAY NIGHT THROUGH TUESDAY NIGHT... POSSIBLY INTO WEDNESDAY... ...TURNING SHARPLY COLDER MID-WEEK. MODELS WERE STILL ADVERTISING A VERY WET AND POTENTIALLY STORMY SYSTEM FROM THE MISSISSIPPI VALLEY TRACKING EASTWARD THROUGH OUR REGION DURING THE EARLY TO MID WEEK PERIOD. AN ENSEMBLE MEAN APPROACH USING MAINLY THE EUROPEAN AS GUIDANCE CONTINUES TO BE FAVORED. THIS WAS DUE IN PART TO THE LARGE SPREAD NOTED WITHIN THE MODEL SOLUTIONS CONCERNING TIMING AND STRENGTH OF THE SYSTEM AS IT PRESSES EASTWARD THROUGH THE MISSISSIPPI VALLEY TOWARD THE APPALACHIANS AND THE EASTERN SEABOARD. THIS ENSEMBLE MEAN APPROACH WILL CONTINUE TO BE FAVORED WHICH SUPPORTS THE MAIN WEATHER HAZARDS OF HEAVY RAIN AND POSSIBLE SEVERE THUNDERSTORM THREATS... CENTERED ON TUESDAY AND TUESDAY NIGHT. CURRENT PROJECTIONS INDICATE 1-2 INCHES OF RAIN WITH LOCALLY 3 INCHES POSSIBLE WITH TRAINING OF HEAVY RAIN POTENTIAL. IN ADDITION... ALTHOUGH INSTABILITY IS EXPECTED TO BE A MAIN LACKING INGREDIENT FOR A SEVERE WEATHER OUTBREAK... ISOLATED SEVERE THUNDERSTORMS MAY STILL BE POSSIBLE WITH THE SHARP COLD FRONTAL PASSAGE. HOWEVER... VERY DEEP MOISTURE INFLUX INTO THE COLD FRONT AND FRONTAL WAVE FAVOR THE HEAVY RAIN THREAT MORE THAN ISOLATED SEVERE STORMS. THIS IS YET TO BE DETERMINED. AFTER THE FRONT PASSES OUR REGION... MUCH COLDER TEMPERATURES WILL ADVECT INTO THE REGION DRIVEN BY GUSTY NE WINDS. THE HAZARDOUS WEATHER FOCUS WILL THEN TURN TO A POTENTIAL SECONDARY WAVE ALONG THE SHARP FRONT AS IT PUSHES OFFSHORE LATER TUESDAY INTO WEDNESDAY. IT WOULD NOT BE OUT OF THE REALM OF POSSIBILITIES FOR SOME WET SNOW FLAKES TO MIX WITH THE RAIN INTO SOME OF THE MORE ELEVATED PIEDMONT COUNTIES AROUND THE NW PIEDMONT TRIAD REGION. HOWEVER... IT WOULD OBVIOUSLY BE DIFFICULT TO GET ANY SNOW ACCUMULATION THIS TIME OF YEAR EAST OF THE MOUNTAINS. THEREFORE... EVEN IF THIS HAPPENS... IT IS NOT ANTICIPATED TO BE A WEATHER HAZARD IN CENTRAL NC. SENSIBLE WEATHER BY WEDNESDAY INTO THURSDAY WILL BE SHARPLY COLDER TEMPERATURES AND THE CHANCE OF A VERY CHILLY NE WIND DRIVEN RAIN (ESPECIALLY WEDNESDAY). HIGHS WEDNESDAY MAY FALL FROM THE 50S/40S DURING THE DAY. GRADUAL CLEARING IS THEN ANTICIPATED THU... WITH TEMPERATURES LIKELY DIPPING NEAR FROST/LIGHT FREEZE READINGS (30-35) FOR MANY AREAS BY THURSDAY AND/OR FRIDAY.
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&& && .AVIATION /06Z SATURDAY THROUGH THURSDAY/... AS OF 210 AM SATURDAY... VFR CONDITIONS WILL RULE THROUGH THE TAF PERIOD. A WEAK PRE-FRONTAL SFC TROUGH...ASSOCIATED WITH A STALLED FRONT WASHING OUT TO THE NORTH...WILL EVENTUALLY DISSIPATE ACROSS THE NC PIEDMONT THIS AFTERNOON AS A SFC RIDGE AXIS (ASSOC/W ATLANTIC HIGH PRESSURE) CONTINUES TO EXTEND SOUTHWEST INTO CENTRAL/EASTERN PORTIONS OF THE STATE. ANY CEILINGS WILL BE CONFINED TO SCATTERED FLAT DIURNAL CU WITH BASES BETWEEN 4500-6000 FT AGL. EXPECT LIGHT/VARIABLE WINDS THROUGHOUT THE TAF PERIOD...THOUGH IT IS POSSIBLE THAT A PREDOMINANT SOUTHERLY FLOW AT 5-8 KT WILL DEVELOP IN SOME (IF NOT ALL) AREAS BY MID TO LATE AFTERNOON. LOOKING AHEAD: VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH SUNDAY IN ASSOCIATION WITH A DRY/CAPPED AIRMASS ACROSS THE REGION. MVFR CEILINGS MAY DEVELOP IN ASSOC/W AN INCREASINGLY MOIST SOUTHERLY RETURN FLOW SUNDAY NIGHT. WIDESPREAD ADVERSE AVIATION CONDITIONS ARE EXPECTED MID-MONDAY INTO TUESDAY...IN ASSOC/W A SLOW MOVING COLD FRONT APPROACHING FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...WSS AVIATION...VINCENT

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