Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 071740 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 135 PM EDT TUE JUL 7 2015 .SYNOPSIS...
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A WEAK UPPER-LEVEL TROUGH ACROSS THE MID ATLANTIC WILL LIFT AWAY FROM THE REGION TODAY. A RIDGE OF HIGH PRESSURE WILL DEVELOP OVER THE SOUTHEAST AND STRENGTHEN THROUGH THE REMAINDER OF THE WORK WEEK. A COLD FRONT WILL APPROACH THE REGION AND THEN STALL ACROSS THE MID ATLANTIC AND OHIO VALLEY THROUGH THE WEEK INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1110 AM TUESDAY... MORNING ANALYSIS SHOWS THE LOWER AND MID LEVEL TROUGH AXIS SHIFTING EAST ACROSS CENTRAL NC. THE AIR MASS ACROSS CENTRAL NC HAS DRIED CONSIDERABLY IN THE PAST 24 HOURS WITH PW VALUES NEAR 1.1 INCHES IN THE WESTERN PIEDMONT AND 1.6 INCHES IN THE EAST. STRATUS THIS MORNING WAS RATHER LIMITED AND MOST OF THE AREA WAS RECEIVING FULL SUN AS OF MID MORNING. FOCUS FOR CONVECTION TODAY IS GENERALLY CONFINED TO THE EASTERN PIEDMONT AND SANDHILLS...EAST OF THE SURFACE TROUGH AND EASTWARD OF THE SHIFTING LOWER AND MID LEVEL SHEAR AXIS. NWP GUIDANCE SUGGESTS ONLY WEAK INSTABILITY WITH THE INSTABILITY GREATEST ACROSS THE COASTAL PLAIN AND SANDHILLS. MID LEVEL LAPSE RATES ARE PRETTY ANEMIC...RANGING AROUND 5.5 DEG C/KM. GIVEN THIS...CONVECTIVE COVERAGE WILL BE LIMITED AS NOTED BY LATEST CONVECTION ALLOWING MODELS. WILL KEEP POPS CONFINED TO THE SLIGHT CHANCE RANGE AND LOCATED IN THE EAST. HIGHS TODAY WILL BE A FEW DEGREES WARMER THAN MONDAY WITH THICKNESS VALUES VALUES AT GSO 18M WARMER THAN YESTERDAY. HIGHS IN THE 89 TO 94 RANGE LOOK ON TARGET. ANY CONVECTION SHOULD DIMINISH JUST AFTER SUNSET. LOWS WILL RANGE IN THE UPPER 60S AND LOWER 70S. -BLAES && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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AS OF 340 AM TUESDAY... THE SUBTROPICAL RIDGE AND BERMUDA HIGH WILL CONTINUE TO BUILD ACROSS THE SOUTHEAST ON WEDNESDAY...WITH A SHORTWAVE CROSSING THE GREAT LAKES REGION 2EARLY WEDNESDAY AND THE ATTENDANT COLD FRONT BECOMING LAID OUT WEST TO EAST FROM THE MIDWEST TO THE MID-ATLANTIC STATES. THE LEE TROUGH WILL AGAIN SET UP OVER THE NC PIEDMONT...WITH WEAK INSTABILITY AGAIN FOCUSED ACROSS THE EASTERN HALF OF THE CWA. ANY CONVECTION SHOULD PRIMARILY BE CONFINED TO THE SEABREEZE AND/OR HIGHER TERRAIN CIRCULATIONS. THE BIG UNCERTAINTY REGARDING CONVECTION IS WHETHER OR NOT AN UPPER DISTURBANCE...ONE OF A SERIES OF DISTURBANCES TO TRACK NEAR THE FRONTAL ZONE TO OUR NORTH...WILL ENHANCE CONVECTION ALONG BLUE RIDGE...WHICH COULD CONCEIVABLY GROW UPSCALE INTO A LINE OF STORMS THAT MOVES INTO THE PIEDMONT DURING THE LATE AFTERNOON AND EVENING GIVEN THE DEEP MIXING AND STEEP LOW- LEVEL LAPSE RATES (WHICH COULD PROMOTE THE MERGING OF STRONG OUTFLOWS). RIGHT NOW THIS SEEMS MORE LIKELY TO OUR NORTH...BUT GIVEN THE POSSIBILITY...WILL KEEP A SLIGHT CHANCE POP ACROSS THE NORTH INTO THE EVENING HOURS. HIGHS WILL AGAIN BE IN THE LOW TO MID 90S...MAYBE A DEGREE WARMER BASED ON THICKNESSES. LOWS WEDNESDAY NIGHT IN THE LOWER 70S.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 325 AM TUESDAY... THU: THE WEAK PIEDMONT SURFACE TROUGH WILL HOLD OVER CENTRAL NC... WHILE THE SYNOPTIC FRONTAL ZONE SETTLES SOUTHWARD INTO VA. EXPANSIVE MID LEVEL RIDGING FROM THE LOWER MISS VALLEY ACROSS THE SOUTHEAST STATES CONTINUES TO SLOWLY RETROGRADE WHILE SUPPRESSING THE WESTERLIES TO OUR NORTH. ABUNDANT HEATING IS ASSURED.... WHICH WILL PUSH THICKNESSES UP TO 5-10 M ABOVE NORMAL... INDICATING HIGHS IN THE LOWER-MID 90S. FALLING DEWPOINTS WITH MIXING BY AFTERNOON SHOULD KEEP HEAT INDICES BELOW CRITICAL VALUES OVER MUCH OF THE CWA (ALTHOUGH THEY MAY EXCEED 100F BRIEFLY IN THE SE CWA). GIVEN THE DEEP LAYER SUBSIDENCE AND NEAR-NORMAL PW... ANY SUBSTANTIAL RAIN CHANCES WILL BE VERY LOW AND CONFINED TO THE EXTREME NORTH... POTENTIALLY ALONG OUTFLOW EMANATING FROM CONVECTION ALONG THE FRONT (PERHAPS ENHANCED BY A LOW CROSSING MD/DE)... AND ALONG AN INLAND- MOVING SEA BREEZE LATE IN THE DAY. FRI: THE SYNOPTIC FRONT TO THE NORTH APPEARS LIKELY TO DIP NEAR OR JUST INTO NE NC... WITH A RESIDUAL OUTFLOW POTENTIALLY DROPPING FURTHER SOUTH WELL INTO NORTH CENTRAL NC... WHILE ALOFT... THE MID LEVEL ANTICYCLONE CENTER CONTINUES TO DRIFT WESTWARD OVER THE LOWER MISS VALLEY. WITH THE SUBSEQUENT TILT/DIP IN THE WESTERLIES DOWN THE MIDATLANTIC COAST... MODELS DO TREND TOWARD A BIT MORE WEAK SHORTWAVE ENERGY TRACKING SOUTHEASTWARD BRUSHING NE NC FRI NIGHT... ALTHOUGH THE PROJECTED INSTABILITY SHOULD BE LOW (MUCAPE UNDER 750 J/KG ON THE GFS)... AND PW WILL ONLY BE SLIGHTLY ELEVATED OVER THE ERN CWA. WILL PLACE LOW CHANCE POPS ACROSS THE NORTH/NE CWA AND IN THE COASTAL PLAIN... ALONG THE WEAK SURFACE TROUGH. THICKNESSES WILL AGAIN BE 5-10 M ABOVE NORMAL... SO EXPECT HIGHS ONCE AGAIN IN THE LOW-MID 80S. LOWS 70-74 WITH LINGERING ISOLATED POPS OVER THE FAR NORTH AND NORTHEAST OVERNIGHT. SAT-MON: THE COMBINATION OF THE BUILDING RIDGE OVER THE SRN PLAINS AND UP THE FRONT RANGE OF THE ROCKIES AND RESULTING STRENGTHENING NW FLOW FROM THE UPPER MIDWEST THROUGH THE LOWER GREAT LAKES TO THE MIDATLANTIC COAST WILL PLACE NC IN A MORE ACTIVE AND VOLATILE WEATHER PATTERN... HIGHLIGHTED BY POCKETS OF MID LEVEL SHORTWAVE ENERGY CROSSING OUR REGION IN NW STEERING FLOW... TRACKING ALONG THE OLD DIFFUSE SURFACE FRONTAL ZONE. NORTHERN AND EASTERN PORTIONS OF THE FORECAST AREA SHOULD SEE THE BEST CHANCES FOR CONVECTION... ORIGINATING IN A HIGHLY UNSTABLE ENVIRONMENT OVER THE MIDWEST AND THE OH VALLEY MOVING SOUTHEASTWARD OVER VA/NC. WHILE WE CAN`T ACCURATELY TRACK SPECIFIC FEATURES AT THIS RANGE... THE IMPROVING SHEAR AND INSTABILITY ALONG WITH GREATER DYNAMIC FORCING FOR ASCENT SUPPORT BOOSTING POPS TO SLIGHTLY ABOVE CLIMATOLOGY DURING THIS PERIOD... AND NOT NECESSARILY PEAKING IN THE TYPICAL LATE-DAY TIME FRAME EITHER... AS HIGH LAPSE RATES WITHIN AN UPSTREAM EML MAY SUSTAIN NOCTURNAL CONVECTION AS IT MOVES SOUTHEAST. STILL EXPECT ABOVE NORMAL THICKNESSES TO EQUATE TO WARM TEMPS TOPPING OUT DAILY IN THE LOWER TO MID 90S... AND THE THREAT OF 100+F HEAT INDEX VALUES PARTICULARLY FROM THE TRIANGLE TO THE SOUTH AND EAST WILL LINGER INTO EARLY NEXT WEEK. -GIH && .AVIATION /18Z TUESDAY THROUGH FRIDAY/...
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AS OF 135 PM TUESDAY... VFR CONDITIONS ARE GENERALLY EXPECTED THROUGH THE 24 HOUR TAF PERIOD. A FAIRLY WIDESPREAD CUMULUS FIELD HAS DEVELOPED WITH BASES AROUND 4500 FEET. ISOLATED SHOWERS AND PERHAPS A THUNDERSTORM WILL DEVELOP ACROSS THE EASTERN PIEDMONT...SANDHILLS AND COASTAL PLAIN THIS AFTERNOON POSSIBLY AFFECTING THE KRWI AND KFAY TERMINALS. WILL EXCLUDE MENTION OF A THUNDERSTORM BUT KEEP A TEMPO FOR A SHOWER. CHANCES OF PRECIPITATION ARE LESS AT KRDU AND MINIMAL IN THE TRIAD AT KINT AND KGSO. ANY SHOWER ACTIVITY AND THE CUMULUS WILL DIMINISH JUST AFTER SUNSET. FAIR WEATHER IS EXPECTED OVERNIGHT WITH JUST A LIMITED THREAT OF SOME MVFR STRATUS TOWARD DAYBREAK AT KFAY AND KRWI. WITH LIMITED PRECIPITATION EXPECTED AND A LOT OF NWP SPREAD...HAVE OPTED TO EXCLUDE STRATUS FROM THE TAFS FOR NOW GIVEN THE LOW CONFIDENCE OF OCCURRENCE. LOW LEVEL FLOW AT THE TOP OF THE LOW LEVEL INVERSION INCREASES OVERNIGHT WITH A SOUTHWESTERLY WIND AT 25-30KTS AT 1500 FT JUST OUTSIDE OF LLWS CRITERIA SO WILL OMIT THAT FROM THE TAF AS WELL. THE FIRST HALF OF WEDNESDAY WILL FEATURE VFR CONDITIONS WITH THE REDEVELOPMENT OF SCT CUMULUS AT AROUND 4-5KT AND SOME MID-HIGH LEVEL BKN DEBRIS CLOUDINESS FROM UPSTREAM CONVECTION. OUTLOOK...A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE SOUTHEAST THROUGH THE PERIOD SETTING UP A TYPICAL SUMMERTIME PATTERN. VFR CONDITIONS ARE EXPECTED TO DOMINATE OUTSIDE OF MAINLY ISOLATED AFTERNOON OR EVENING THUNDERSTORMS AND PATCHY FOG AROUND DAYBREAK. -BLAES
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&& ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM...22 LONG TERM...HARTFIELD AVIATION...BLAES

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