Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 271102 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 700 AM EDT MON JUL 27 2015 .SYNOPSIS...SURFACE HIGH PRESSURE WILL RETREAT OFFSHORE TODAY. A COUPLE OF WEAK DISTURBANCES IN NORTHWEST FLOW ALOFT WILL THEN CROSS THE REGION THROUGH THE MIDDLE OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM MONDAY... WEAK HIGH PRESSURE RIDGE OVER THE AREA THIS MORNING WILL SHIFT OFFSHORE TODAY...WHILE A SERIES OF WEAK DISTURBANCES APPROACH IN NORTHWESTERLY FLOW ALOFT. DEEP MIXING TO JUST ABOVE 850MB AND RELATIVELY DRY BOUNDARY LAYER AIR WILL LIMIT THE POTENTIAL DEWPOINT RECOVERY TODAY...WHILE MID-LEVEL LAPSE RATES REMAIN WEAK AND THE STEEPER LAPSE RATES OVER THE OHIO VALLEY (6-6.5 C/KM OBSERVED AT KILN) STAY TO OUR NORTH. THUS...FORECAST INSTABILITY OVER CENTRAL NC IS WEAK TODAY...300-600 J/KG AT BEST PER NAM/GFS BUFR SOUNDINGS. A STRONG SPEED MAX CROSSING THE MOUNTAINS AND DIFFERENTIAL HEATING SHOULD TRIGGER SCATTERED CONVECTION IN THE MOUNTAINS..WHICH WILL HAVE THE PROPENSITY TO DRIFT SOUTHEAST INTO PIEDMONT THIS EVENING. WITH A LESS FAVORABLE ENVIRONMENT DOWNSTREAM...CONVECTION IS NOT EXPECTED TO MAKE IT FURTHER THAN THE TRIANGLE...IF IT MAKES IT THAT FAR...SO WILL KEEP A CHANCE POP FOR THE TRIAD AREA AND NORTHER PIEDMONT THROUGH LATE EVENING. HIGH CLOUDS POURING IN FROM THE NORTHWEST COULD PROVE TRICKY FOR HIGHS TODAY..BUT AT THE MOMENT THEY DO NOT APPEAR WIDESPREAD TO LIMIT FULL HEATING...WHICH SHOULD YIELD HIGHS IN THE 89-93 RANGE. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 400 AM MONDAY... NORTHWEST FLOW ALOFT CONTINUES ON TUESDAY...THOUGH HEIGHTS ALOFT ALSO START TO RISE SLIGHTLY IN RESPONSE TO AN EASTWARD SHIFT OF THE CENTRAL US RIDGE AXIS. CONTINUED MOISTENING IN THE LOW-LEVELS WILL SUPPORT BETTER INSTABILITY THAN TODAY DESPITE WEAK LAPSE RATES. THE MAIN TRIGGERS FOR CONVECTION WILL AGAIN BE TERRAIN INDUCED CIRCULATION AND THE FLOW OF WEAK DISTURBANCES ALOFT. WITH BETTER INSTABILITY FORECAST..HOWEVER...WIDELY SCATTERED CONVECTION SEEMS POSSIBLE ACROSS MOST OF CENTRAL NC WITH HIGHER CONFIDENCE IN THE WESTERN PIEDMONT. HIGHS MAY BE A DEGREE OR TWO COOLER ON TUESDAY GIVEN INCREASED CLOUD COVER...BUT STILL INT HE UPPER 80S AND LOWER 90S. THE COVERAGE OF STORMS WILL LESSEN TUESDAY EVENING WITH LOSS OF HEATING...BUT GUIDANCE SUGGESTS A FEW STORMS COULD CONTINUE TO PERCOLATE WELL INTO THE NIGHT...ESPECIALLY OVER THE SOUTHERN AND WESTERN PIEDMONT AREAS. LOWS MORE SOLIDLY IN THE LOWER 70S. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 400 AM MONDAY... A SUB-TROPICAL RIDGE CENTERED OVER THE SOUTHERN PLAINS AND MID-MS VALLEY WILL RETROGRESS INTO THE FOUR CORNERS REGION AND CONSEQUENTLY ALLOW A PROGRESSION OF SHORTWAVE TROUGHS TO CARVE A MEAN TROUGH OVER THE EASTERN US. AFTER THE DOMINANCE OF AN APPALACHIAN LEE TROUGH... BUT RELATIVELY MINIMAL CONVECTIVE DEVELOPMENT OWING TO WEAK LAPSE RATES ALOFT DURING THE MIDDLE OF THE WEEK...THE MODELS ARE IN GOOD AGREEMENT THAT A COLD FRONT RELATED TO THE PROGRESSION OF A LEAD SHORTWAVE TROUGH ACROSS THE GREAT LAKES WILL SETTLE EAST OF THE APPALACHIANS LATE THU-FRI...AT WHICH TIME SCATTERED SHOWERS AND STORMS ARE EXPECTED THROUGHOUT CENTRAL NC. THEREAFTER...THERE ARE MIXED SIGNALS REGARDING THE PROBABILITY OF PRECIPITATION THROUGH THE WEEKEND. THE OVERALL CONFIGURATION OF A TROUGH ALOFT IN THE EASTERN US SHOULD SUPPORT ABOVE AVERAGE CHANCES OF PRECIPITATION...BUT THE MODELS INDICATE THE LOW LEVEL FRONTAL ZONE MAY SETTLE JUST SOUTHEAST OF CENTRAL NC...WHICH WOULD TEND TO SUPPRESS THE BRUNT OF THE SHOWERS AND STORMS OVER THE SOUTHEASTERN PART OF THE STATE. GIVEN THE SOMEWHAT CONFLICTING SIGNALS...THIS FORECAST WILL BE WEIGHTED TOWARD CONTINUITY FROM THE PREVIOUS FORECASTS - SLIGHT TO CHANCE POP...HIGHEST SOUTHEAST AND MAXIMIZED DURING THE AFTERNOON AND EVENING. TEMPERATURES WILL PEAK MAINLY IN THE LOWER 90S DURING MID- WEEK...THEN TREND TO AOB AVERAGE FOR THE WEEKEND. LOWS AROUND 70. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
AS OF 655 AM MONDAY... JUST A COUPLE AREAS REPORTING IFR VSBYS THIS MORNING...INCLUDING KFAY AND KRWI. THESE VSBYS WILL IMPROVE TO VFR SHORTLY AFTER 12Z...WHILE MID AND HIGH CLOUDS CONTINUE TO POUR IN FROM THE NORTHWEST. VFR CONDITIONS WILL CONTINUE THROUGH THE AFTERNOON...WITH JUST A CHANCE OF A STORM AROUND KGSO AND/OR KINT LATER THIS AFTERNOON AND EVENING. THE CHANCE OF ANY STORMS MOVING EAST TOWARD KRDU IS LOW AND NO MENTION OF TSRA WILL BE INCLUDED IN THE CURRENT TAF. TONIGHT..WINDS WILL AGAIN BE LIGHT/VARIABLE...WHICH WILL PAVE THE WAY FOR SOME POSSIBLE FOG/STRATUS...MAINLY ACROSS THE COASTAL PLAN BASED ON MOST GUIDANCE. IMPACTS ARE NOT EXPECTED TO BE WIDESPREAD...AND CONFIDENCE IS AVERAGE AT THIS POINT. OUTLOOK...INCREASING MOISTURE WILL LEAD TO BETTER CHANCE OF EARLY MORNING (09-13Z) STRATUS/FOG FROM TUESDAY ONWARD. MEANWHILE... AFTERNOON STORMS WILL ALSO BE POSSIBLE...ESPECIALLY AS A COUPLE DISTURBANCES CROSS THE AREA IN NORTHWESTERLY FLOW ALOFT. A COLD FRONT WILL APPROACH THE AREA LATE IN THE WEEK AND MAY BRING A BETTER CHANCE OF CONVECTION AND ADVERSE AVIATION CONDITIONS.
-- End Changed Discussion --
&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...22 NEAR TERM...22 SHORT TERM...22 LONG TERM...26 AVIATION...22

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.