AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 320 AM EDT SAT JUL 26 2014 .SYNOPSIS...A SURFACE TROUGH WILL DEVELOP OVER THE WESTERN PIEDMONT THIS WEEKEND...RESULTING IN A VERY WARM SOUTHWEST FLOW. A STRONG COLD FRONT WILL CROSS THE AREA ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 210 AM SATURDAY... SHEARED S/W TROUGH AXIS WILL TRAVERSE THE AREA THIS MORNING... RESULTING IN SCATTERED TO OCCASIONALLY BROKEN MID AND HIGH CLOUDS. SUBSIDENCE WILL FOLLOW IN ITS WAKE...COINCIDENT WITH PEAK AFTERNOON HEATING...WHICH SHOULD LARGELY SUPPRESS CONVECTIVE RAIN CHANCES TODAY AS FORCING WILL OTHERWISE BE CONFINED TO VERY SHALLOW CONVERGENCE ASSOCIATED WITH THE DEVELOPING PIEDMONT SFC TROUGH. LOW-LEVEL THICKNESSES ARE PROGGED TO REBOUND 20M FROM YESTERDAY AND DESPITE SOME MORNING CLOUDS FROM BOTH S/W MOVING THROUGH THE AREA ALONG WITH SLOW LIFTING/DISSIPATION OF MORNING STRATUS ANTICIPATE WE SHOULD REACH FULL SUN READINGS. HIGHS IN THE UPPER 80S/NEAR 90 NORTH TO LOWER 90S SOUTH. LOWS TONIGHT UNDER CLEAR SKIES IN THE LOWER TO MID 70S. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 320 AM SATURDAY... SUNDAY AND SUNDAY NIGHT: A STRONG UPPER TROUGH OVER THE UPPER MS VALLEY SUNDAY MORNING WILL TRACK SOUTHEASTWARD INTO THE OH VALLEY SUNDAY/SUNDAY NIGHT. ACCOMPANYING SURFACE FRONT WILL APPROACH THE SOUTHERN APPALACHIANS LATE SUNDAY NIGHT/MONDAY MORNING. IN THE MEAN TIME...PIEDMONT TROUGH BISECTING THE AREA WILL BEGIN TO SHARPEN UP. IN ADVANCE OF THE MAIN SHORTWAVE...CONVECTION...POSSIBLY A MCS IS EXPECTED TO BE ONGOING OVER THE CENTRAL AND POSSIBLY SOUTHERN APPALACHIANS EARLY SUNDAY. SOME STORMS COULD PERSIST INTO THE AFTERNOON AS THEY MOVE EASTWARD INTO THE VIRGINIA PIEDMONT AND COASTAL PLAIN. IF THIS CONVECTIN DOES INDEED HOLD TOGETHER...OUTFLOW FROM THESE STORMS COULD SUPPORT A SLIGHT TO SMALL CHANCE OF STORMS MAINLY ACROSS THE NORTH/NORTHEAST SUNDAY AFTERNOON AS HINTED BY THE LATEST EC AND SOME OF THE CONVECTION ALLOWING MODELS. IF STORMS DO DEVELOP...A MODIFIED EML LAYER CHARACTERIZED BY LAPSE RATES OF 7.25-7.50 COULD SUPPORT ISOLATED SEVERE STORM THAT COULD LARGE HAIL. WILL RETAIN SLIGHT TO SMALL CHANCE POPS SUNDAY NIGHT WITH BEST CHANCE IN PROXIMITY TO SURFACE FRONT TO OUR NW. DEEP MIXING AND 850MB TEMPS IN EXCESS OF 21C WILL LEAD TO HIGHS IN THE MID AND UPPER 90S. MIXING WILL DROP DEWPOINTS A BIT...ESPECIALLY WEST OF THE PIEDMONT TROUGH...BUT TO THE EAST DEWPOINTS ARE FORECAST TO REMAIN IN THE UPPER 60S TO AROUND 70. THE RESULTING HEAT INDEX VALUES ARE IN THE 100-103. LOWS SUNDAY NIGHT IN THE LOWER TO MID 70S. MON/MON NIGHT: FOCUS ON MONDAY WILL BE THE LIKELIHOOD FOR SEVERE WEATHER AS A STRONG COLD FRONT APPROACHES AND MOVES THROUGH THE AREA. THIS FRONT WILL BE PROPELLED TOWARDS THE REGION AS A UNSEASONABLE STRONG UPPER LEVEL TROUGH PUSHES EAST...WITH STRONG 40-60M HEIGHT FALLS EXPECTED TO OVERSPREAD CENTRAL NC. THIS WILL COMBINE WITH THE EXPECTED STRONG INSTABILITY (~1500-2000 J/KG MLCAPE) AND 40-50 KNOTS OF BULK SHEAR TO PRODUCE SCATTERED SEVERE STORMS...WITH SUPERCELLS PROBABLE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS. ALTHOUGH CONFIDENCE IS HIGH THAT THERE WILL BE SEVERE WEATHER ON MONDAY... THERE ARE STILL SOME UNCERTAINTIES. DEEP WESTERLY FLOW MAY LIMIT MOISTURE AND ULTIMATE COVERAGE...HOWEVER ANY STORM THAT DOES FORM WILL LIKELY BE INTENSE. IN ADDITION...OUTFLOW BOUNDARIES AND DEBRIS CLOUDINESS FROM CONVECTION SUNDAY NIGHT WILL HAVE AN IMPACT ON CONVECTIVE DEVELOPMENT/LOCATION. REGARDLESS...AT THIS TIME...THE BEST CHANCE FOR FOR PRECIP AND ULTIMATE SEVERE STORMS LOOKS TO BE ACROSS THE EASTERN HALF OF THE FORECAST AREA (ALONG AND EAST OF THE EXPECTED LOCATION OF THE LEE/PREFRONTAL TROUGH) AND POSSIBLY MORESO ALONG AND EAST OF THE I-95 CORRIDOR WHERE ALL THE PARAMETERS WILL LINE UP THE BEST. HIGH TEMPS ARE EXPECTED TO CLIMB INTO THE LOW TO MID 90S AHEAD OF THE FRONT...WITH OVERNIGHT LOWS GENERALLY IN THE MID TO UPPER 60S. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 AM SATURDAY... UPPER LEVEL TROUGHING WILL STAY IN PLACE OVER THE EAST COAST THROUGHOUT THE ENTIRE LONG TERM PERIOD PERIOD...WHILE AT THE SURFACE COOL...CANADIAN HIGH PRESSURE WILL SETTLE OVER THE AREA. ALL OF THIS WILL LEAD TO BELOW NORMAL TEMPS...WITH HIGHS GENERALLY IN THE LOW/MID 80S AND OVERNIGHT LOWS IN THE LOW/MID 60S...POSSIBLY EVEN SOME UPPER 50S IN THE NORMAL COOLER SPOTS. IN ADDITION... MOSTLY DRY CONDITIONS ARE EXPECTED THROUGH THE END OF THE WEEK...ALTHOUGH WILL SHOW A SLIGHT INCREASE IN PRECIP CHANCES BY FRIDAY AS MOISTURE SLOWLY RETURNS. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 130 AM SATURDAY... 24-HR TAF PERIOD: RESIDUAL LOW-LEVEL MOISTURE AND LIGHT SELY WINDS WILL RESULT IN STRATUS OVERNIGHT AND POCKETS OF FOG OVERNIGHT. CEILINGS OF IFR TO MVFR ARE POSSIBLE WITH GUIDANCE SUGGESTING THE BEST FOG POTENTIAL IN THE EAST...NEAR KFAY AND KRWI...WHERE SFC DEWPOINTS HAVE REMAINED IN THE LOWER 70S. PERHAPS SOME LINGERING MVFR STRATOCUMULUS COULD LINGER INTO THE LATE MORNING BEFORE VFR CONDITIONS RETURN BY EARLY AFTERNOON WITH OVERALL DRY CONDITIONS EXPECTED. LOOKING AHEAD: A COLD FRONT WILL APPROACH FROM THE NW SUNDAY/EARLY NEXT WORK WEEK... BRINGING THE POTENTIAL FOR SHOWERS/STORMS AND SUB- VFR CONDITIONS LATE SUNDAY (IN THE NORTHWEST) INTO MONDAY... PARTICULARLY MONDAY (ESPECIALLY EAST). VFR CONDITIONS ARE EXPECTED TO RETURN BEHIND THE FRONT ON TUESDAY AND CONTINUE THROUGH AT LEAST MID WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. &&
Posted on: Sat, 26 Jul 2014 10:53:40 +0000
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