Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 140012 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 811 PM EDT SUN APR 13 2014 .SYNOPSIS...WARM AND DRY HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC WILL EXTEND WESTWARD OVER OUR REGION THROUGH TONIGHT. A COLD FRONT WILL SLOWLY APPROACH THE REGION FROM THE WEST ON MONDAY... THEN MOVE EAST ACROSS NORTH CAROLINA AND VIRGINIA LATE MONDAY NIGHT THROUGH TUESDAY. COOL HIGH PRESSURE WILL EXTEND INTO THE AREA FROM THE NORTH WEDNESDAY THROUGH THURSDAY. && .NEAR TERM /THROUGH MONDAY/... AS OF 230 PM SUNDAY... MOISTURE TRANSPORT WILL CONTINUE THROUGH THE PERIOD AS A TROUGH DIGS INTO CENTRAL CONUS...WHICH WILL PROPEL A COLD FRONT TOWARDS THE REGION. HIGH CLOUDS SEEN ON SATELLITE UPSTREAM WILL OVERSPREAD THE AREA THROUGH THE OVERNIGHT HOURS AND WILL CONTINUALLY THICKEN AND LOWER DURING THE DAY ON MONDAY. IN ADDITION...LOW STRATUS CLOUDS WILL LIKELY FORM OVERNIGHT. ALL OF THIS WILL RESULT IN EVEN MILDER OVERNIGHT LOWS...WITH TEMPS ONLY EXPECTED TO FALL INTO THE UPPER 50S TO LOWER 60S. THERE WILL LIKELY BE SOME PREFRONTAL WARM ADVECTION SHOWERS DURING THE DAY ON MONDAY (ESPECIALLY ACROSS THE WESTERN HALF OF THE FORECAST AREA)...LIKELY AIDED BY ANY WEAK PERTURBATIONS IN THE SOUTHWESTERLY FLOW ALOFT. IN ADDITION...SOME WEAK INSTABILITY (UP TO 500 J/KG) MAY BE ENOUGH TO TRIGGER AN ISOLATED THUNDERSTORM OR TWO MONDAY AFTERNOON. GIVEN THE CLOUD COVER AND POSSIBLE PRECIP...TEMPS ON MONDAY SHOULD BE SLIGHTLY LOWER THAN PREVIOUS DAYS. THEREFORE... AM EXPECTING HIGHS TO RISE INTO THE MID/UPPER 70S ACROSS THE WEST TO AROUND 80 DEGREES FURTHER EAST. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 150 PM SUNDAY... A POWERFUL STORM SYSTEM IS ON TRACK TO AFFECT CENTRAL NC TUE WITH THREATS OF HEAVY RAIN AND STRONG STORMS. AFTER THE INITIAL BOUT OF PREFRONTAL SHOWERS EARLY MON NIGHT... THE BULK OF THE RAINFALL WITH THIS SYSTEM IS EXPECTED TO OCCUR LATE MON NIGHT THROUGH EARLY EVENING TUE... WITH CLEARING LATE TUE NIGHT. OVERVIEW FOR MON NIGHT: THE MID LEVEL RIDGE OVER THE SOUTHEAST COAST WILL STRENGTHEN BUT SHIFT OFFSHORE THROUGH MON. THIS MORNING`S UPPER AIR ANALYSES REVEAL TWO TROUGHS OF NOTE -- ONE ENTERING KS/OK/NRN TX AND A STRONGER/DEEPER TROUGH FROM S-CENTRAL CANADA THROUGH MT/ID/WY/UT. THIS REARWARD TROUGH WILL DIG AS IT SHIFTS EASTWARD... KICKING THE SLOWLY DEAMPLIFYING LEAD TROUGH EASTWARD. PASSAGE OF THIS WEAKENING LEAD TROUGH THROUGH THE MIDATLANTIC REGION IN ADDITION TO STEADILY INCREASING MOISTURE ADVECTION SHOULD FACILITATE FORMATION OF SCATTERED TO NUMEROUS SHOWERS HEADING INTO MON NIGHT... WITH THE BEST COVERAGE IN THE WRN CWA WHERE LOW LEVEL FLOW WILL BE ORTHOGONAL TO THE HIGHER TERRAIN THUS INTRODUCING ENHANCED FORCED UPGLIDE THERE... AND IT`S FARTHEST FROM THE INFLUENCES OF THE OFFSHORE-CENTERED RIDGE WITH BETTER LOW LEVEL CONFLUENCE. EXPECT POPS TO RANGE FROM GOOD CHANCE NE TO LIKELY WEST MON NIGHT... WITH STRENGTHENING SURFACE WINDS FROM THE SE AND SOUTH OVERNIGHT. OVERVIEW FOR TUE/TUE NIGHT: THE DEEP TROUGH FROM HUDSON BAY DOWN THROUGH THE GULF COAST WILL SHIFT EASTWARD OVER ERN NOAM THROUGH TUE NIGHT... TRANSITIONING FROM A SLIGHT POSITIVE TILT TO A NEUTRAL OR SLIGHT NEGATIVE TILT BUT DAMPENING IN THE PROCESS DUE TO TROUGHING DEVELOPING OVER CANADA AND THE WRN US. MODELS GENERALLY AGREE ON THE CORRESPONDING SURFACE FRONT REACHING THE FAR NW CWA (TRIAD AREA) BY 17Z-18Z... THEN CROSSING THE CWA BEFORE EXITING THE COASTAL PLAIN JUST PRIOR TO 00Z. A SOUTHERLY 850 MB JET OF 40-50 KTS SHIFTS EAST ACROSS NC TUE MORNING THROUGH AFTERNOON... LEADING TO INCREASING MASS CONVERGENCE OVER CENTRAL/ERN NC. FARTHER ALOFT... THE STRENGTHENING UPPER JET ON THE EAST SIDE OF THE TROUGH RESULTS IN INCREASING UPPER DIVERGENCE OVER NC LATE MON NIGHT THROUGHOUT TUE. GIVEN THIS DEEP LAYER FORCING FOR ASCENT... CATEGORICAL POPS ARE JUSTIFIED AREAWIDE FOR TUE. REGARDING THE HEAVY RAIN CHANCES... POCKETS OF HEAVIER RAIN ARE CERTAINLY POSSIBLE MON NIGHT GIVEN EXPECTATIONS OF INCREASING PW VALUES TO NEAR 200% OF NORMAL... BUT THE GREATEST PW SHOULD ARRIVE TUE WITH MODEL-PROJECTED VALUES WELL OVER 1.5"... WHICH WOULD BE AROUND 250% OF NORMAL. LOW LEVEL MOISTURE TRANSPORT INCREASES OVER THE EAST TUE... MOST MARKEDLY OVER GA/COASTAL SC AND FROM RICHMOND VA UP THROUGH NYC... BUT IS STILL PRONOUNCED OVER CENTRAL AND ESPECIALLY ERN NC IN THE AFTERNOON/EARLY EVENING WITH AN OPEN LONG FETCH FROM THE GULF AND BAHAMAS. WARM RAIN PROCESSES MAY ALSO COME INTO PLAY WITH A SOMEWHAT FAVORABLE WARM LAYER DEPTH OVER 3 KM... AND ANTICIPATED CELL MOVEMENT TOWARD THE NORTH OR NNE MAY LEAD TO TRAINING ECHOES MOVING REPEATEDLY OVER THE SAME AREA. ALL OF THIS SUPPORTS A HEAVY RAIN THREAT... AND WILL CONTINUE TO HIGHLIGHT THIS IN THE HAZARDOUS WEATHER OUTLOOK... WITH A FOCUS ON THE FAR NW AND EASTERN SECTIONS. EXPECT STORM TOTAL AMOUNTS OF JUST OVER AN INCH TO AS MUCH AS TWO INCHES IN ISOLATED SPOTS. AS OF NOW... IT LOOKS LIKE THE ONLY FACTOR THAT MIGHT CURB THIS THREAT WOULD BE IF SUBSTANTIAL CONVECTION TO OUR SOUTH INTERRUPTS MOISTURE TRANSPORT INTO CENTRAL NC. REGARDING THE STRONG/SEVERE STORM THREAT... MODELS INDICATE A COUPLE HUNDRED J/KG OF SBCAPE MON NIGHT... INCREASING TO 500-1000 J/KG FOR TUE... ALTHOUGH FORECAST SOUNDINGS INDICATE THE TUE CAPE IS TALL AND SKINNY WITH MLLR OF 5.5-6.0 C/KM... NOT GREAT FOR INDUCING VERY RAPID UPDRAFTS. 0-6 KM BULK SHEAR STARTS OUT DECENT MON NIGHT AT CLOSE TO 40 KTS AND GETS EVEN BETTER -- 80-90KTS -- TUE AFTERNOON/EARLY EVENING. LATEST SREF PROBABILITIES OF A COMBINATION OF CAPE AOA 500 J/KG AND DEEP LAYER SHEAR AOA 30 KTS WITH PRECIP REMAIN LOW MON NIGHT BUT INCREASE TO NEAR 40% BY EARLY AFTERNOON. THIS ALL SUPPORTS A GOOD CHANCE OF FAST-MOVING BOWING SEGMENTS WITH LOCALLY ENHANCED WIND GUSTS... ESPECIALLY ALONG/EAST OF HIGHWAY 1 TUE FROM VERY LATE MORNING THROUGH THE AFTERNOON HOURS. THIS RISK TOO WILL BE RETAINED IN THE HWO. REGARDING TEMPS: CLOUDS AND STRONG PREFRONTAL WARM AIR ADVECTION WILL LEAD TO VERY MILD LOWS MON NIGHT... AND HAVE WARMED THEM JUST A BIT TO 60-66. TEMPS TUE ARE LIKELY TO FOLLOW AN ATYPICAL TREND... WITH THE FRONTAL PASSAGE CAUSING HIGHS TO OCCUR IN THE EARLY AFTERNOON IN THE WRN CWA WITH A RAPID DROP THEREAFTER... WHILE THE COASTAL PLAIN SHOULD SEE A MORE TYPICAL MAX TEMP TIME IN THE MID- LATE AFTERNOON. EXPECT HIGHS TUE FROM THE MID 60S NW TO THE MID- UPPER 70S IN THE EAST. HAVE KEPT TUE NIGHT LOWS A BIT ON THE WARM SIDE OF GUIDANCE... BUT MODELS HAVE BEEN TRENDING COOLER ESPECIALLY IN THE WRN CWA. IF THIS TREND PERSISTS THROUGH LATER FORECASTS... COULD SEE SOME OUTLYING AREAS OF THE WRN PIEDMONT APPROACHING THE FREEZING MARK TUE NIGHT DESPITE CONTINUED MIXING. LOWS 34-41. -GIH && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 245 PM SUNDAY... FOR WED THROUGH THU NIGHT: THE DAMPENING TROUGH WILL TRACK QUICKLY TO OUR NORTHEAST IN THE PREDAWN HOURS OF WED... AND WILL BE FOLLOWED BY GENERALLY FLAT SW FLOW OVER THE SOUTHEAST/MIDSOUTH/CAROLINAS THROUGH WED. FORECAST SOUNDINGS ARE VERY DRY AND STABLE AS COOL SURFACE HIGH PRESSURE MOVES FROM THE OHIO VALLEY NORTHEASTWARD OVER THE ST LAWRENCE VALLEY WHILE NOSING DOWN THROUGH NC. EXPECT BREEZY AND COOL WINDS FROM THE NE WED... DIMINISHING LATE WED INTO THU AS THE MSLP GRADIENT RELAXES. LOW LEVEL THICKNESSES ARE EXPECTED TO PLUNGE WELL BELOW NORMAL (50-60 M) WED MORNING WITH MODEST RECOVERY DURING THE DAY... TRANSLATING TO HIGHS IN THE LOW-MID 50S. CONTINUED MOSTLY CLEAR THROUGH THU NIGHT WITH DEEP DRY AND STABLE AIR AND SLOWLY RETREATING/MODIFYING SURFACE RIDGING NOSING DOWN FROM THE NORTH. LIGHT WINDS FOSTERING GOOD RADIATIONAL COOLING MAY BRING A RISK OF LIGHT FROST IN SOME SPOTS WED NIGHT IN THE RURAL AREAS OF THE PIEDMONT. NOT QUITE AS COOL THU WITH HIGHS EXPECTED TO BE 60-65. FOR FRI THROUGH SUN: CONFIDENCE IS LOWER THAN USUAL WITH NEXT WEEKEND`S FORECAST. IT DOES LOOK MOST LIKELY THAT WE`LL SEE UNSETTLED WEATHER WITH INCREASING CLOUDS AND A CHANCE OF RAIN DURING THIS TIME FRAME... WITH TEMPS EDGING UPWARD BUT STAYING AT OR BELOW NORMAL... HOWEVER THE UNCERTAINTY LIES IN THE AMOUNTS AND TIMING. MODELS DEPICT THE NEXT TROUGH SHIFTING EASTWARD INTO EASTERN NOAM... BUT THE GFS FOCUSES ON A CLOSED VORTEX CROSSING THE UPPER MIDWEST AND GREAT LAKES/ST LAWRENCE VALLEY FRI-SUN... WITH JUST GENTLY CYCLONIC FLOW OVER THE MIDSOUTH/CAROLINAS... WHILE THE ECMWF DEPICTS AN OPEN BUT MORE AMPLIFIED TROUGH DOWN TO THE GULF. IN EITHER CASE... THE APPROACH OF THE TROUGH ALOFT WITH POTENTIAL PREDECESSOR ENERGY TRACKING NNE OUT OF THE GULF (TO HELP MOISTEN THE COLUMN) AND INCREASING LOW LEVEL FLOW FROM THE SE AND SOUTH (INCREASING ATLANTIC FETCH) SHOULD YIELD AT LEAST A BETTER-THAN-CLIMATOLOGY CHANCE OF RAIN HEADING INTO THE WEEKEND. THE ECMWF EVENTUALLY CLOSES OFF A MID LEVEL LOW OVER OUR AREA WITH A PROMINENT SOUTHEAST COASTAL LOW LATE FRI NIGHT THROUGH SAT WITH HEAVY RAIN POSSIBLE IN CENTRAL/ERN NC... SOMEWHAT SIMILAR TO ITS PREVIOUS RUN BUT NOW STRONGER AND WETTER. WILL MENTION THE INCREASE IN CLOUDS AND CHANCE OF RAIN BUT WILL HOLD OFF ON ANY EXTREMES FOR NOW UNTIL THE MODELS BEGIN TO CONVERGE ON A COMMON SOLUTION. -GIH && .AVIATION /00Z MONDAY THROUGH SATURDAY/...
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AS OF 750 PM SUNDAY... VFR CONDITIONS WILL CONTINUE THIS EVENING INTO PORTIONS OF THE EARLY MORNING HOURS. HOWEVER... LOW LEVEL SOUTHERLY RETURN FLOW ACROSS THE AREA WILL CONTINUE TO MOISTEN THE LOW LEVEL AIRMASS EARLY MONDAY MORNING. WE MAY SEE SOME IFR AND/OR LIFR CIGS DEVELOP AROUND DAYBREAK MONDAY... WITH THE GREATLY PROBABILITY OF OCCURRENCE ACROSS THE WESTERN NORTHWESTERN PIEDMONT (KGSO/KINT). EXPECT ANY LOW STATUS THAT FORMS WILL LIFT BY MID MORNING WITH PERHAPS A BRIEF PERIOD OF SUB-VFR STRATOCUMULUS. VFR CONDITIONS ARE EXPECTED BY LATE MORNING/EARLY AFTERNOON. HOWEVER... A STRONG COLD FRONT WILL APPROACH THE AREA FROM THE WEST ON MONDAY... YIELDING INCREASING CLOUD COVER AND THE THREAT OF SOME AFTERNOON SHOWERS AND ISOLATED STORMS. THE GREATEST THREAT WILL BE ACROSS THE WESTERN PIEDMONT. THUS... HAVE ELECTED TO ADD A PROB 30 GROUP FOR SHOWERS THERE. ANY SHOWERS OR STORMS THAT DEVELOP LATE IN THE DAY WILL HAVE THE POTENTIAL TO PRODUCE SUB-VFR CONDITIONS. IN ADDITION... EXPECT SUSTAINED WINDS WILL INCREASE MONDAY MORNING INTO THE AFTERNOON INTO THE 10 TO 15 MPH RANGE... WITH SOME GUSTS OF UP TO 20 TO 25 MPH POSSIBLE. OUTLOOK...A PROLONGED PERIOD OF WIDESPREAD ADVERSE AVIATION CONDITIONS IS EXPECTED LATE MONDAY THROUGH TUESDAY AS A STRONG COLD FRONT APPROACHES AND CROSSES THE REGION. SHOWERS AND ISOLATED THUNDERSTORMS WILL INCREASE IN COVERAGE MONDAY NIGHT INTO TUESDAY MORNING...WITH THE HIGHEST PRECIP CHANCES (AND ESPECIALLY ISOLATED THUNDERSTORMS) OCCURRING TUESDAY/TUESDAY AFTERNOON. CONDITIONS WILL THEN IMPROVE AGAIN BY MIDWEEK. THEN ANOTHER SYSTEM WILL IMPACT THE AREA LATE FRIDAY INTO SATURDAY.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...KRD SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...BSD/KRD

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