Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 151420 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1010 AM EDT TUE APR 15 2014 .SYNOPSIS...
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WARM AND MOIST SOUTHERLY FLOW WILL PERSIST TODAY... AHEAD OF A COLD FRONT THAT WILL CROSS THE REGION THIS AFTERNOON THROUGH EARLY EVENING. UNUSUALLY CHILLY HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH TONIGHT THROUGH THURSDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1010 AM TUESDAY... HAVE JUST UPDATED THE FORECAST TO ACCOUNT FOR THE CONVECTIVE LINE NOW EXITING THE ERN CWA. LATEST SURFACE ANALYSIS SHOWS THE FRONT NOW ALONG THE NC MOUNTAINS AND EXPECT A STEADY EASTWARD PROGRESS THIS AFTERNOON... PROPELLED BY THE DENSITY OF THE ANOMALOUSLY COLD INCOMING AIR MASS AS WELL AS THE MID LEVEL TROUGH MOVING EAST OF THE MS RIVER VALLEY. A FEW ROTATING ELEMENTS AND SHORT SEGMENTS WITH ENHANCED WIND GUSTS WERE OBSERVED WITH THIS PRIMARY LINE OF CONVECTION... AND AS THIS DEPARTS ALONG WITH THE BETTER INSTABILITY... WE SHOULD SEE A BRIEF LULL WITHIN THE REARWARD SUBSIDENCE ZONE. BUT ADDITIONAL CONVECTION NOW OVER S/E GA AND SC SHOULD SPREAD UP INTO THE S/E CWA IN THE NEXT SEVERAL HOURS... AND THIS EXTRAPOLATION IS SUPPORTED BY RAP/HRRR GUIDANCE. INSTABILITY IS NOT PROJECTED TO BE PARTICULARLY STRONG WITH THIS (AROUND 250 J/KG POTENTIALL APPROACHING 500 J/KG) BUT WILL LIKELY BE ACCOMPANIED BY AN UPTICK IN LOW LEVEL SHEAR NEAR/EAST OF WHAT THE SHORT RANGE MODELS INDICATE WILL BE A PREFRONTAL WEAK SURFACE LOW... AND IN FACT THE RAP FORECAST SOUNDINGS SHOW A PERIOD OF CURVED HODOGRAPHS EARLY THIS AFTERNOON. THIS MAY POSE OUR BEST CHANCE FOR AN ADDITIONAL SEVERE WEATHER THREAT... IN THE FORM OF DAMAGING WINDS WITHIN BOWING SEGMENTS AND AN ISOLATED WEAK TORNADO... LARGELY EAST OF I-95 AS THIS IS WHERE THE SREF SHOWS THE BEST COMBINATION OF (MODEST) INSTABILITY AND DEEP LAYER SHEAR AHEAD OF THE FRONT. THE THREAT OF ANY STRONG STORMS SHOULD BE OVER (TO OUR EAST) BY 00Z. IN ANY CASE... MOST PLACES SHOULD SEE AN ADDITIONAL PERIOD OF SHOWERS (IF NOT STORMS) FROM LATE MORNING THROUGH MID/LATE AFTERNOON EITHER WITH THE ACTIVITY TO OUR SOUTH OR ALONG AND JUST BEHIND THE COLD FRONT. PW VALUES WILL REMAIN WELL ABOVE NORMAL... WITH ABUNDANT MOISTURE WITH DEW POINTS HOLD IN THE 60S TO LOWER 70S. LIFT WILL BE AUGMENTED BY UPPER DIVERGENCE IN THE RIGHT REAR QUAD OF THE SRLY JET STREAK TO OUR NNW. SO... AFTER A SHORT LULL WILL TREND POPS BACK UP FOR THIS AFTERNOON. ADJUSTED HOURLY TEMPS TOWARD THE GLAMP AND HRRR RAPID- UPDATE GUIDANCE... TO INDICATE FALLING TEMPS IN THE WEST THIS AFTERNOON. THIS YIELDS HIGHS FROM THE MID 60S WEST TO UPPER 70S EAST. -GIH MINIMAL ADJUSTMENT NEEDED FOR LOWS IN STRONG CAA TONIGHT...INTO THE 30 TO 37 DEGREE RANGE...COOLEST WEST. THE FREEZE WATCH HAS BEEN CONSEQUENTLY BE UPGRADED TO A WARNING. -MWS
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 235 AM TUESDAY... WED AND WED NIGHT: RISING HEIGHTS ALOFT/DNVA AND ASSOCIATED STRONG SUBSIDENCE WILL RESULT IN FURTHER DEEP LAYER DRYING (SUNSHINE) WED...FOLLOWED BY GENERALLY NEUTRAL VERTICAL MOTION...BUT WITH A STILL STRONGLY CAPPED AND RESIDUALLY DRY REGIME OVER OUR REGION THROUGH WED NIGHT. BENEATH THE STRONG SUBSIDENCE ALOFT...SURFACE HIGH PRESSURE WILL CONSEQUENTLY BECOME UNSEASONABLY STRONG INTO THE 1040-1045 MB RANGE AS IT BUILDS FROM THE OH VALLEY TO NEW ENGLAND. COOL NORTHEASTERLY FLOW AND DRY ADIABATIC MIXING THROUGH 900 MB...WITH A COUPLE OF DEGREES ADDED TO ACCOUNT FOR A USUAL SLIGHT COOL BIAS WITH THIS TECHNIQUE LIKELY IN PART OWING TO A SUPER- ADIABATIC NEAR SURFACE LAYER...SUPPORTS HIGHS IN THE LOWER TO MIDDLE 50S. PROJECTED LOW LEVEL THICKNESS VALUES IN THE 1300-1310 METER RANGE AT 12Z THU...WITH OPTIMAL RADIATIONAL COOLING...WOULD SUPPORT MIDDLE 20S. HOWEVER...A PROJECTED 4-6 MB RISE IN MSL PRESSURE WITH THE STRENGTHENING HIGH WED NIGHT WILL LIKELY MAINTAIN A NORTHEASTERLY STIRRING FOR MOST AREAS OVERNIGHT...THOUGH WITH TYPICALLY COOLER/SHELTERED AREA LIKELY TO EXPERIENCE PERIODS OF CALM. IN ADDITION...MOISTURE ADVECTION IN NORTHEASTERLY FLOW BENEATH THE CAPPING INVERSION MAY RESULT IN SCT TO BKN LOW CLOUDS MAINLY IN THE COASTAL PLAIN LATE. AS SUCH...TEMPERATURES ARE APT TO DISPLAY A RELATIVELY LARGE RANGE...FROM 28-30 DEGREES IN RURAL WESTERN PIEDMONT LOCATIONS (IN CLOSEST PROXIMITY TO THE RIDGE AXIS) TO AROUND FREEZING IN URBAN AREAS FROM RDU WESTWARD TO THE TRIAD...TO 33-37 DEGREES IN THE COASTAL PLAIN AND EASTERN SANDHILLS. -MWS THURSDAY THROUGH THURSDAY NIGHT: THIS PERIOD SHOULD REMAIN DRY WITH HIGH PRESSURE RIDGING IN FROM THE NORTHEAST...ALTHOUGH EXPECT CLOUDS TO INCREASE DURING THE EVE/OVERNIGHT...ESPECIALLY ACROSS THE SOUTH AND EAST...AS A LOW DEVELOPS OFF THE COAST. WITH THE CONTINUED NE FLOW AND CAA...STILL EXPECT TEMPS TO BE BELOW NORMAL. HOWEVER... GIVEN LOW-LEVEL THICKNESSES INCREASING FROM THE PREVIOUS NIGHT BY A GOOD 30-40 METERS...EXPECT TEMPS TO INCREASE BY 5-10 DEGREES...HIGHS IN THE LOW TO MID 60S AND LOWS IN THE UPPER 30S TO LOW 40S. -KCP && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 AM TUESDAY... THERE IS STILL A SLIGHT CHANCE OF RAIN ACROSS THE SOUTHEAST FRIDAY NIGHT/SATURDAY MORNING AS THE ELONGATED LOW OFF THE COAST MOVES AWAY FROM THE AREA...OTHERWISE THE LATEST GFS AND ECMWF RUNS KEEP THE FORECAST DRY THROUGH MONDAY. AN UPPER LEVEL LOW SKIRTS NORTH OF CENTRAL NC SATURDAY NIGHT/SUNDAY. THE GFS IS A BIT MORE AMPLIFIED WITH THE LOW...BRINGING IT CLOSER TO THE AREA. DESPITE THE STRONG UPPER LEVEL FORCING AND MOISTURE IN THE UPPER LEVELS...THE DRY AIR EXPECTED IN THE MID LEVELS MAY BE ENOUGH TO KEEP THINGS DRY. HIGHS FRIDAY IN THE MID TO UPPER 60S WITH LOWS IN THE MID 40S TO AROUND 50 DEGREES. HIGH PRESSURE TO THE NORTH WILL RIDGE INTO THE AREA SUNDAY AND MONDAY. ASIDE FROM SOME HIGH CLOUDS...EXPECT EASTER SUNDAY TO BE DRY AND MOSTLY SUNNY. HIGHS MAINLY IN THE LOW TO MID 70S WITH LOWS IN THE MID TO UPPER 40S THROUGH THE END OF THE PERIOD. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 740 AM TUESDAY... 24 HOUR TAF PERIOD: A LINE OF HEAVY SHOWERS AND THUNDERSTORMS CONTINUES TO MOVE THROUGH THE AREA...APPROACHING KRWI...AND MOVING OVER THE TERMINAL DURING THE NEXT HOUR OR TWO. WITH THE BREAK IN THE PRECIP THIS MORNING AT THE OTHER TERMINALS...CONDITIONS HAVE/SHOULD TEMPORARILY IMPROVE(D) BACK TO VFR/MVFR. ADDITIONAL SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND WILL LIKELY RESULT IN PERIODS OF REDUCED CIGS AND VISBYS. IN THE WAKE OF THESE AFT/EVE SHOWERS AND STORMS...THE COLD FRONT WILL TRAVERSE FROM WEST TO EAST THROUGH CENTRAL NC. ALTHOUGH WINDS WILL REMAIN STRONG THROUGH 12Z... EXPECT THEM TO VEER TO THE WEST THEN NORTHWEST BEHIND THE FRONT. THE GUSTS MAY BRIEFLY DIE OUT BETWEEN 06Z AND 12Z WEDNESDAY MORNING. CIGS WILL LIFT AND VISBYS WILL IMPROVE BEHIND THE FRONT...WITH VFR CONDITIONS EXPECTED FOR THE LAST 6-12 HOURS OF THE TAF PERIOD. -KC LOOKING AHEAD: MOSTLY VFR CONDITIONS WILL PERSIST THROUGH THE END OF THE WORK WEEK. THERE COULD BE SOME MORNING STRATUS BOTH FRIDAY AND SATURDAY MORNING AS MOISTURE ONCE AGAIN INCREASES AHEAD OF OUR NEXT SYSTEM APPROACHING FROM THE SOUTH THIS WEEKEND. -KRD && .CLIMATE... THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR WED AND THU MORNING... AND THE RECORD LOW MAXIMUM TEMPERATURES FOR WED: WED 04/16 THU 04/17 LOW/YEAR LOW MAX/YEAR LOW/YEAR FAY: 28/1943 56/1950 31/1953 GSO: 25/1943 48/1929 29/1953 RDU: 28/1950 46/1890 29/1962 && .RAH WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR NCZ007>010- 021>026-038>041-073>077-083-084. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD/MWS SHORT TERM...MWS/KCP LONG TERM...KCP AVIATION...KCP CLIMATE...MWS

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