FXUS62 KRAH 020722 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 321 AM EDT WED APR 2 2014 .SYNOPSIS...A WEAK FRONT WILL STALL NEAR THE VIRGINIA BORDER ON WEDNESDAY...THEN WILL LIFT NORTH AS A WARM FRONT ON THURSDAY. THE NEXT COLD FRONT WILL MOVE ACROSS THE CAROLINAS FRIDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 240 AM WEDNESDAY... A LOW-AMPLITUDE RIDGE WILL HOLD OVER THE SOUTHEAST TODAY...DOWNSTREAM OF THE PACIFIC SHORTWAVE TROUGH FORECAST TO EJECT EAST-NORTHEASTWARD ACROSS THE FOUR CORNERS STATES AND CENTRAL/SOUTHERN ROCKIES REGION TODAY AND TONIGHT. AT THE SURFACE...A WEST-EAST ORIENTED FRONTAL ZONE EXTENDING FROM THE CENTRAL ROCKIES EASTWARD TO THE MID-ATLANTIC REGION WILL SAG SOUTH THROUGHOUT THE DAY...BEFORE STALLING NEAR THE NC-VA BORDER THIS EVENING AND TONIGHT. TODAY: WITH THE FRONT EXPECTED TO REMAIN NORTH OF THE AREA...FORECAST THICKNESSES ARE PROGGED TO BE NEARLY IDENTICAL TO YESTERDAY WITH THE CONTINUED WEAK SOUTHERLY RETURN FLOW AROUND THE SURFACE HIGH OVER THE WESTERN ATLANTIC. HIGHS IN THE LOWER TO MID 80S...12 TO 15 DEGREES ABOVE NORMAL. TONIGHT: AS THE FRONT SETTLES ALONG THE NC-VA BORDER...MID-LEVEL CLOUDS WILL INCREASE...HOWEVER IT SHOULD REMAIN MOSTLY DRY. THE EXCEPTION MAY BE BE ACROSS THE NW PIEDMONT...WHERE NON-MEASURABLE SPRINKLES COULD OCCUR AS THE 00Z/02 NAM SHOWS DEEPER SATURATION OWING TO WEAK S/W ENERGY CRESTING ATOP THE RIGE ALOFT. LOWS IN THE LOWER 50S TO MID 50S. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 250 AM WEDNESDAY... THU: A COLD FRONT OVER THE LOWER OH AND TN VALLEYS THIS MORNING WILL DRIFT SOUTH IN BACKDOOR FASHION EAST OF THE APPALACHIANS THROUGH TONIGHT...TO A POSITION NEAR OR JUST SOUTH OF THE VA BORDER BY THU MORNING - 50 TO 100 MILES FARTHER SOUTH THAN FORECAST 24 HOURS AGO. WHILE THE POST-FRONTAL AIR MASS IS A COLD ONE OF ARCTIC ORIGIN - WITH TEMPERATURES IN THE SINGLE DIGITS BENEATH THE CENTER OF THE 1024 HIGH OVER THE NORTHERN PLAINS THIS MORNING - AN EQUALLY STRONG HIGH HAS BECOME ESTABLISHED OVER THE SOUTHWEST ATLANTIC. EQUILIBRIUM BETWEEN THE TWO HIGHS SUGGESTS THAT THE FRONT WILL MEET RESISTANCE AS IT TRIES TO DRIFT INTO CENTRAL NC...AND AS SUCH...THE FARTHER SOUTH FRONTAL POSITIONING OF THE NAM...SOUTH OF US HWY 64...IS CONSIDERED AN OUTLIER AT THIS TIME. THE QPF SOLUTION OF LIGHT PRECIPITATION NEAR THE VA BORDER. A MORE LIKELY SCENARIO IS ONE INDICATED BY THE EC AND GFS...SUCH THAT THE FRONT WILL LIKELY STALL CLOSER TO THE VA BORDER...ROUGHLY ALONG AN ARC FROM KDAN-KETC- KHAT...AND WHOSE POSITION WILL LIKELY BE INFLUENCED LESS BY THE AFOREMENTIONED LARGER SCALE PROCESSES/EQUILIBRIUM AND MORE BY MESOSCALE ONES DRIVEN BY NORTHEASTERLY FLOW ACROSS COOL (MID 30S-MID 40S FAHRENHEIT) MID-ATLANTIC SHELF WATERS PER AVHRR-OBSERVED SST DATA. THE RESULTANT HIGH TEMPERATURES HAVE BEEN INCREASED BY UP TO A FEW DEGREES (INTO THE LOWER 80S) SOUTH THE OF THE EXPECTED FRONTAL POSITION...BASED UPON THE ANTECEDENT WARMTH THAT RESULTED IN HIGHS MOSTLY IN THE LOWER 80S ALREADY ON TUE...WITH TEMPS CLOSE TO THOSE PREVIOUSLY FORECAST NEAR THE VA BORDER (IN THE MID-UPPER 70S). BOTH THE 00Z/2ND NAM AND EC ALSO GENERATE LIGHT PRECIPITATION OVER SOUTHERN VA AND NORTHERN NC...IN ASSOCIATION WITH A LOW AMPLITUDE DISTURBANCE FORECAST TO DEAMPLIFY AROUND THE TOP OF A 318-319 DM RIDGE OVER THE FL PENINSULA. MOISTURE IN BOTH MODELS IS MOSTLY OF THE MID LEVEL VARIETY...SO THE PROSPECTS OF RAINFALL - OTHER THAN PERHAPS A SPRINKLE - IS LOW...PARTICULARLY SINCE THE PARENT ALREADY LOW AMPLITUDE SHOULD ONLY FURTHER WEAKEN AS IT APPROACHES THE RIDGE OVER THE SE. THU NIGHT: THE FRONT WILL RETREAT NORTHWARD THROUGH VA THU NIGHT...IN ADVANCE OF A CYCLONE FORECAST TO DEEPEN AND MIGRATE ACROSS THE MID MS VALLEY AND UPPER MIDWEST. MILD LOW MOSTLY IN THE UPPER 50S ARE EXPECTED. FRI AND FRI NIGHT: OVERALL MINIMAL SENSIBLE WEATHER CHANGES...THOUGH NWP GUIDANCE HAS TRENDED SLIGHTLY QUICKER WITH THE COLD FRONT TRAILING THE AFOREMENTIONED SURFACE LOW TRACKING TOWARD THE GREAT LAKES. CONTINUED WARM FRI...WITH TEMPERATURES AGAIN IN THE UPPER 70S NW PIEDMONT WHERE MULTI-LAYERED CLOUDS WILL THICKEN ESPECIALLY AFTER NOON...RANGING TO PERSISTENCE LOWER 80S IN THE COASTAL PLAIN. DESPITE AROUND 500 J/KG OF INSTABILITY FRI...AND SIGNIFICANT INLAND PENETRATION OF THE SEA BREEZE OWING TO AN ONSHORE COMPONENT TO THE SURFACE FLOW...BUFR FORECAST SOUNDINGS CONTINUE TO DEPICT A MID LEVEL CAP AND ASSOCIATED CINH BETWEEN 100-150 J/KG. AS SUCH...IT WILL BE DIFFICULT FOR ANY CUMULUS TO BREAK THE CAP UNTIL BETTER DYNAMICS IN THE FORM OF WEAK HEIGHT FALLS ALOFT...BUT STRONG LOW LEVEL MOISTURE TRANSPORT ALONG THE AXIS OF A 40-50 KT LLJ...ARRIVE FROM THE WEST LATE IN THE DAY AND DURING THE EVENING HOURS. IN FACT...IT IS LIKELY THAT A PRE-FRONTAL LINE OR TWO OF SHOWERS AND STORMS WILL EVOLVE FROM THE LOWER OH VALLEY TO THE GULF COAST STATES...IN CONFLUENT LOW LEVEL FLOW AHEAD OF THE DEEPENING CYCLONE AND PARENT S/W TROUGH/UPPER LOW...AND THE REMNANTS OF THIS ACTIVITY WILL SPREAD EASTWARD ACROSS CENTRAL NC MOSTLY DURING THE EVENING HOURS...OR PERHAPS LATE IN THE AFTERNOON OVER THE WESTERN PIEDMONT. THESE SHOWERS AND STORMS WILL LIKELY WEAKEN WITH BOTH TIME AND WITH EASTWARD EXTENT...OWING TO BOTH NOCTURNAL STABILIZATION AND THE WELL TO OUR NW PASSAGE OF THE PRIMARY HEIGHT FALLS ALOFT THROUGH THE GREAT LAKES. NONETHELESS...STRONG VERTICAL WIND SHEAR WILL BE SUPPORTIVE OF STRONG TO MARGINALLY DAMAGING WIND GUSTS...MORE LIKELY WEST OF THE TRIANGLE WHERE THE TIMING OF THE CONVECTION WILL BETTER COINCIDE WITH PEAK DIURNAL HEATING. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 315 AM TUESDAY... SAT THROUGH SUN: THE FRONT MAY LINGER IN THE COASTAL PLAIN TO SUPPORT AN ISOLATED SHOWER OR STORM THERE THROUGH EARLY AFTERNOON SAT...BUT LOWER HUMIDITY VALUES IN WNW POST-FRONTAL FLOW WILL OTHERWISE PREVAIL. STILL WARM...WITH TEMPERATURES MOSTLY IN THE LOWER TO MIDDLE 70S. COOLER WITH LOWS IN THE MID-UPPER 40S SAT NIGHT. COOLER SUN - IN THE 60S - IN NE FLOW AROUND 1025 MB HIGH PRESSURE OVER THE MIDDLE ATLANTIC STATES. CLOUDS WILL INCREASE FROM THE SOUTH DURING THE AFTERNOON...IN ADVANCE OF A SOUTHERN STREAM WAVE WHOSE TIMING IS FASTER BY ABOUT 12 HOURS VERSUS WHAT IT APPEARED YESTERDAY. NWP GUIDANCE INDICATES THE SOUTHERN STREAM WILL INDEED BECOME MORE ACTIVE AND BUCKLE NORTHWARD INTO THE MIDDLE ATLANTIC STATES LATE SUN- MON. THE ASSOCIATED CONFLUENCE ALOFT INDUCED BY THE BUCKLING OF THE SOUTHERN STREAM WILL LIKELY SUPPORT SOME DEGREE OF A DAMMING HIGH EAST OF THE APPALACHIANS...IN ADVANCE OF A DEVELOPING STORM SYSTEM APPROACHING FROM THE WESTERN GOM. CLOUDS WILL CONTINUE TO GRADUALLY THICKEN AND LOWER IN A STRENGTHENING REGIME OF ISENTROPIC LIFT ATOP THE SURFACE HIGH...SUN NIGHT-MON. CAD AND RAIN WILL LIKELY ENSUE FOR SUN NIGHT-MON. BRIEFLY DRY IN WEAK HIGH PRESSURE TUE...BUT THE DEVELOPMENT OF A L/W TROUGH IN THE EASTERN STATES MAY SUPPORT ANOTHER PERIOD OF UNSETTLED WEATHER BY MID-WEEK. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 130 AM WEDNESDAY... 24 HOUR TAF PERIOD: THERE IS HIGH CONFIDENCE THAT CONDITIONS WILL REMAIN VFR THROUGH THE 24 HOUR TAF PERIOD. MID AND HIGH LEVEL CLOUD COVER INCREASE LATE IN THIS AFTERNOON AND EVENING...ESPECIALLY ACROSS THE NORTHERN TERMINALS AS AN WEST-EAST ORIENTED FRONTAL ZONE OVER THE MID-ATLANTIC STATES SAGS SOUTH THROUGHOUT THE DAY...STALLING ALONG THE NC/VA BORDER OVERNIGHT BEFORE LIFTING BACK NORTH DURING THE DAY ON THURSDAY. WITH THE FRONT EXPECTED TO STALL NORTH OF THE AREA...WINDS WILL REMAIN FROM THE SOUTHWEST AT 10KTS OR LESS. OUTLOOK: OUTSIDE OF SOME EARLY MORNING FOG/STRATUS...EXPECT PREDOMINATELY VFR CONDITIONS THROUGH FRIDAY AFTERNOON. A COLD FRONTAL PASSAGE THROUGH THE AREA FRIDAY NIGHT...MIGHT BRING A BRIEF PERIOD OF SHOWERS WITH ASSOCIATED SUB-VFR RESTRICTIONS. OTHERWISE... VFR CONDITIONS WILL RETURN SATURDAY AND SATURDAY NIGHT. A SOUTHERN STREAM STORM SYSTEM WILL BRING ADVERSE AVIATION CONDITIONS AS OVERRUNNING PRECIP SPREADS INTO THE AREA FROM THE SOUTH ON SUNDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE && $$ SYNOPSIS...NP NEAR TERM...CBL SHORT TERM...MWS LONG TERM...MWS AVIATION...CBL