Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010827 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 326 AM EST SUN MAR 1 2015 .SYNOPSIS... WHILE COLD HIGH PRESSURE WILL EXTEND ACROSS THE AREA TODAY...INCREASING MOISTURE WILL HELP PROVIDE FOR UNSETTLED WEATHER. A COLD FRONT WILL MOVE THROUGH THE AREA MONDAY...FOLLOWED BY HIGH PRESSURE FOR TUESDAY...BEFORE ANOTHER COLD FRONT MOVES INTO THE REGION LATE WEDNESDAY. && .NEAR TERM /THROUGH SUNDAY NIGHT/... AS OF 1030 PM SATURDAY... STRONG 1043MB HIGH CENTERED OVER THE DELMARVA HAS SUPPLIED A VERY DRY AIRMASS FOR CENTRAL NC THIS EVENING WITH DEWPOINTS WELL INTO THE TEENS. MODELS HAVE STRUGGLED WITH THE AIRMASS A BIT...WITH THE GFS AND ECMWF BEING TO COLD THIS EVENING...BUT THE WETBULB FREEZING LINE IS SUPPRESSED WELL SOUTH TO THE NC/SC BORDER. EARLY ON... RADAR RETURNS HAVE BEEN CONFINED TO CENTRAL AND EASTERN SC AND APPEAR TO BE INITIALLY DRIVEN BY WARM ADVECTION UP NEAR 700MB. DRIER AIR BELOW HAS KEPT THE PRECIP SPOTTY BUT THERE ARE SOME REPORTS OF LIGHT RAIN IS SC. WITH TIME...THE WARM ADVECTION AND ISENTROPIC LIFT WILL INCREASE ACROSS SOUTHERN AND WESTERN NC IN RESPONSE TO AN UPPER LEVEL JET CROSSING THE MID-MISSISSIPPI VALLEY REGION. DRY AIR SHOULD ALSO KEEP PRECIP SPOTTY INITIALLY...BUT THE LOW-LEVEL JET IS FORECAST TO INTENSIFY TO 40-50KT FROM THE PIEDMONT NORTH INTO VA AFTER 09Z...SO EXPECT PRECIP TO FILL IN AND QPF TO INCREASE MORE TOWARD THE 12-15Z TIME FRAME. MOISTURE NEVER REALLY REACHES ABOVE -6 TO -8C...SO WHILE BRIEF PERIODS OF SLEET ARE POSSIBLE...FREEZING RAIN WILL BE THE PREDOMINATE PTYPE. MODEL QPF RANGES A TENTH OF AN INCH THROUGH 18Z ON THE ECMWF TO UP TO A QUARTER OF AN INCH ON THE NAM. THE GFS IS OVERDONE UPSTREAM OVER GEORGIA...SO HAVE DISCOUNTED IT FOR NOW. AS YOU GO EAST...CONFIDENCE IN MEASURABLE PRECIP IS MUCH LOWER TONIGHT AS MOISTURE IS SHALLOWER...AND BY THE TIME BETTER PRECIP SPREADS EAST TOMORROW...WARMING SHOULD ALLOW TEAMS AND WETBULB VALUES TO RISE ABOVE 32 BY MID-MORNING. THE MAIN CONCERN AND CHANGE IN THE FORECAST THIS EVENING IS IN THE NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN WHERE INCREASING QPF MAY OVERLAP WITH SUB- FREEZING TEMPS FOR A LONGER PERIOD THAN PREVIOUSLY EXPECTED SUNDAY MORNING. GENERALLY STILL EXPECT A TENTH OF AN INCH OF ICE AT MOST ACROSS THE NORTHWEST PIEDMONT...BUT SOME AREAS OVER THE NORTHERN PIEDMONT COULD SEE A TENTH OF AN INCH AS WELL. GIVEN THE QUESTIONABLE MODEL PERFORMANCE AND CONSISTENCY WITH THIS EVENT SO FAR...CONFIDENCE IN THE WINTER WEATHER ADVISORY IS BEST ONLY IN THE WEST AND MUCH LOWER IN THE EAST. HAVE ELECTED TO EXPAND THE ADVISORY TO COVER ALL OF CENTRAL NC...AND WILL MESH THE NEW AREAS WITH THE PREVIOUS ADVISORY SEGMENTS...ENDING FROM NORTH TO SOUTH THROUGH THE MORNING HOURS. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... AS OF 220 PM SATURDAY... THE APPROACHING UPPER LEVEL TROUGH WEAKENS AS IT MOVES THROUGH CENTRAL NC ON MONDAY. LATEST MODEL RUNS INDICATE MONDAY WILL BE MOSTLY DRY...WITH A SLIGHT CHANCE OF SOME LIGHT PRECIPITATION EARLY IN THE DAY...DRYING INTO THE AFTERNOON AS THE RAINFALL ALONG THE FRONT DISSIPATES OVER THE MOUNTAINS. THE COLD FRONT WILL TILT TO A MORE WEST TO EAST ORIENTATION AND SLIDE THROUGH THE AREA BY MONDAY EVENING. SURFACE HIGH PRESSURE WILL BUILD IN THEREAFTER AND REMAIN THROUGH MONDAY NIGHT. ALTHOUGH TEMPERATURES SHOULD RISE DURING THE DAY GIVEN GRADUALLY CLEARING SKIES AND THUS GOOD SUNSHINE...THE INCREASES WILL BE GREATEST ACROSS THE SOUTH WHERE THE FROPA HAPPENS LATER. HIGHS WILL RANGE FROM UPPER 40S ACROSS THE NORTH TO UPPER 50S IN THE SOUTH...ALTHOUGH THEY ARE HIGHLY DEPENDENT ON THE TIMING OF THE FRONT. OVERNIGHT LOWS SHOULD BE IN TEH UPPER 20S NORTH TO UPPER 30S SOUTH. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... AS OF 320 PM SUNDAY... MONDAY NIGHT AND TUESDAY: SURFACE HIGH PRESSURE LOCATED JUST TO THE NORTH OF CENTRAL NC AND AND MID LEVEL RIDGING EXTENDING INTO THE AREA FROM THE SOUTH WILL BOTH QUICKLY SHIFT EASTWARD ON MONDAY NIGHT INTO TUESDAY. HOWEVER... THE LINGERING COLD DRY SURFACE AIR DEPOSITED BY THE SURFACE HIGH WILL AGAIN SET THE STAGE FOR AN INSITU CAD EVENT ON TUESDAY INTO TUESDAY NIGHT... POSSIBLY LINGERING INTO WEDNESDAY MORNING ACROSS THE FAR NORTHWEST PIEDMONT. WARM MOIST AIR WILL INCREASING IN SOUTHERLY TO SOUTHWESTERLY FLOW ALOFT. GIVEN THIS AND THE LINGERING COLD SURFACE AIRMASS... WE SHOULD SEE SOME ISENTROPICALLY DRIVEN PRECIP DEVELOP TUESDAY MORNING INTO THE AFTERNOON. TUESDAY MORNING LOW TEMPS ARE EXPECTED TO BE AROUND 30 NORTH TO NEAR 40 SOUTH. MODELS CONTINUE TO BRING THE LIGHT PRECIP IN AFTER SURFACE TEMPS AND DEWPOINTS INCREASE ENOUGH TO AVOID AND NUISANCE FREEZING RAIN. HOWEVER... HIGH TEMPS WILL BE WELL BELOW NORMAL AND GREATLY AFFECTED BY THE CAD AIRMASS. MAV STATISTICAL GUIDANCE APPEARS TO BE WAY TOO WARM FOR TUESDAY... WITH THE RAW GFS TEMPS CLOSER TO MET GUIDANCE VALUES. FOR NOW WILL LOWER TEMPS FURTHER... AND THIS MAY NOT EVEN BE FAR ENOUGH. WILL WO WITH HIGH TEMPS RANGING FROM THE UPPER 30S NORTH TO NEAR 50 IN THE FAR SOUTHEAST. TUESDAY NIGHT THROUGH THURSDAY NIGHT: ANOTHER STRONG ARCTIC COLD FRONT WILL APPROACH THE REGION ON TUESDAY NIGHT... BEFORE SLOWLY MOVING ACROSS THE AREA WEDNESDAY INTO THURSDAY MORNING. THE FRONT IS EXPECTED TO BECOME PARALLE WITH THE MID LEVEL FLOW AS THE MID/UPPER LEVEL TROUGH BECOMES MORE OF A FULL LATITUDE TROUGH... WHICH APPEARS TO PHASE SOME THE THE SOUTHERN STREAM ENERGY WITH THE NORTHERN STREAM... RESULTING IN A DEEP FETCH OF SOUTHWESTERLY MID LEVEL FLOW... ALONG WITH SEVERAL SURFACE LOWS TRACKING ALONG THE FRONT FROM TIME TO TIME. MOST OF THE SHOWERS WILL BE ALONG AND BEHIND THE FRONT... MAINLY FROM WEDNESDAY MID-MORNING INTO THE AFTERNOON UNTIL LATE THURSDAY (WITH A GOOD CHANCE OF PRECIP... POSSIBLY SOME HEAVY AMOUNTS OF RAIN). IN ADDITION... MODELS HAVE TRENDED FASTER WITH SURGING THE STRONG/DEEP COLD LOW LEVEL AIRMASS INTO THE REGION. IF THIS WERE TO OCCUR... WE COULD POSSIBLE SEE SOME WINTRY P-TYPES ON THURSDAY. HOWEVER... GIVEN WE ARE STILL TALKING ABOUT DAY 5 IN THE FORECAST AND WE ARE NOW IN THE MONTH OF MARCH... WILL WAIT TO ADD ANY NON-LIQUID P-TYPE TO THE FORECAST. DRY WEATHER IS EXPECTED TO RETURN FOR AT LEAST FRIDAY. HOWEVER... THE SYNOPTIC PATTERN MAY REMAIN CONDUCIVE FOR WAVES OF LOW PRESSURE TO DEVELOP AND TRACK ALONG THE FRONT... WHICH IS EXPECTED TO BE LOCATED OFF THE CAROLINA COAST LATE WEEK INTO THE WEEKEND. THUS... WE COULD CONCEIVABLY SEE SOME PRECIP IF ONE SUCH SYSTEM DEVELOPS NEXT WEEKEND. TEMPS DURING THE MEDIUM RANGE WILL INCLUDE SOME DECENT SWINGS... WITH HIGHS TEMPS WEDNESDAY IN THE 60S AND 70S... THURSDAY 40S AND 50S (MAYBE COLDER)... WITH FRIDAY BACK IN THE 40S (WITH MAYBE SOME 30S EVEN). WE WILL SEE SOME MODERATING BY SATURDAY... GENERALLY BACK INTO THE 50S... GIVEN WE REAMIN DRY. LOWS WILL FOLLOW A SIMILAR PATTERN. AS MENTIONED ABOVE... ALL PRECIP AS OF NOW APPEARS TO BE IN THE FORM OF LIQUID FOR THE MEDIUM RANGE... OUTSIDE OF *MAYBE* A BRIEF PERIOD AS THE PRECIP ENDS ON THURSDAY. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 100 AM SUNDAY... ADVERSE AVIATION CONDITIONS WILL OVERSPREAD CENTRAL NC FROM THE SOUTH THROUGH 12Z WITH MVFR/IFR CEILINGS AND PATCHES OF LIGHT RAIN OR LIGHT FREEZING RAIN. BY 12Z...EXPECT WIDESPREAD LOW END MVFR/IFR CEILINGS ALONG WITH AREAS OF LIGHT FREEZING RAIN OVER THE PIEDMONT AND SANDHILLS...AND EITHER LIGHT RAIN OR FREEZING RAIN IN THE COASTAL PLAIN. BETWEEN 12Z- 15Z...THE LIGHT FREEZING RAIN IN THE SANDHILLS AND EASTERN PIEDMONT SHOULD TRANSITION TO A COLD RAIN. IN ADDITION...A STRENGTHENING LOW LEVEL JET JUST ABOVE THE SURFACE WILL RESULT IN LOW LEVEL WIND SHEAR CONDITIONS...ESPECIALLY IN VICINITY OF KRDU...KFAY AND KRWI. THE FREEZING RAIN IN THE NW PIEDMONT WILL GRADUALLY CHANGE TO A COLD RAIN BY MID AFTERNOON. ELSEWHERE EXPECT AREAS OF LIGHT RAIN OR DRIZZLE WITH IFR/LIFR CEILINGS. WHILE THE BULK OF THE RAIN WILL TAPER OFF BY SUNSET...WIDESPREAD FOG AND DRIZZLE ALONG WITH IFR/LIFR CEILINGS WILL PERSIST INTO TONIGHT. MONDAY...A COLD FRONT WILL CROSS THE REGION. WEST-NW FLOW BEHIND THE BOUNDARY WILL ADVECT A DRIER AIR MASS...LEADING TO A SCOURING OF THE MURKY NEAR SURFACE AIR MASS. EXPECT IMPROVING AVIATION CONDITIONS LATE MONDAY THROUGH MONDAY NIGHT. HIGH PRESSURE OVER THE AREA TUESDAY WILL PROVIDE VFR CONDITIONS. ANOTHER COLD FRONT WILL APPROACH WEDNESDAY AND CROSS THE REGION WEDNESDAY NIGHT AND THURSDAY. THIS WEATHER SYSTEM WILL LIKELY CAUSE ANOTHER PERIOD OF SUB VFR CONDITIONS ACROSS CENTRAL NC. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ042-077- 078-083>086-088-089. WINTER WEATHER ADVISORY FROM 4 AM TO NOON EST THIS MORNING FOR NCZ008>011-024>028-040-041-043-073>076. WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM EST TODAY FOR NCZ007-021>023-038-039. && $$ SYNOPSIS...WSS NEAR TERM...SMITH/HARTFIELD SHORT TERM...KC LONG TERM...BSD AVIATION...WSS

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