Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 181744 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1240 PM EST THU DEC 18 2014 .SYNOPSIS...HIGH PRESSURE OVER THE MISSISSIPPI RIVER VALLEY WILL EXTEND EASTWARD INTO THE MID ATLANTIC AND CAROLINAS ON THROUGH FRIDAY. A LOW PRESSURE SYSTEM WILL DEVELOP ALONG THE TEXAS COAST ON FRIDAY AND TRACK EAST ALONG THE GULF COAST ON SATURDAY...THEN MOVE OFFSHORE THE SOUTHEAST COAST SATURDAY NIGHT INTO SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 920 AM THURSDAY... AN ALREADY LOW AMPLITUDE TROUGH ALOFT OVER THE MID-MISSISSIPPI RIVER VALLEY THIS MORNING WILL CONTINUE TO DEAMPLIFY AS IT SKIRTS ACROSS THE TENNESSEE VALLEY AND VIRGINIA THROUGH TONIGHT. AN AREA OF LIGHT RAIN MOVING ACROSS EASTERN TENNESSEE...FOCUSED NEAR THE H925-H85 FRONTAL ZONE WHERE ISENTROPIC LIFT IS GREATEST...CONTINUES TO GRADUALLY WEAKEN WITH EASTWARD EXTENT. EXPECT THIS TREND TO THE CONTINUE AS THE UPPER DISTURBANCE MOVES OFF TO THE EAST-NORTHEAST AND THE FORCING DECOUPLES. SO NO PRECIP IS EXPECTED OVER CENTRAL NC. EAST OF THE MOUNTAINS...THE AIRMASS REMAINS VERY DRY WITH ALL MOISTURE ABOVE 12K FT. WHILE THERE IS A FAIR AMOUNT OF HIGH LEVEL MOISTURE UPSTREAM...GUIDANCE SUGGESTS THERE WILL PERIODS OF SUN MIXED IN WITH THE HIGH CLOUDS (POTENTIALLY OROGRAPHICALLY ENHANCED AT TIMES THIS MORNING. TEMPS SHOULD GET TO WITHIN A COUPLE DEGREES OF THE CURRENT FORECAST HIGHS OF 49-55. IF ANYTHING...THEY WILL END UP ON THE COOLER SIDE. SKIES WILL BEGIN TO CLEAR OFF BY EARLY FRIDAY MORNING WITH THE PASSAGE OF THE AFOREMENTIONED MID LEVEL TROUGH. GIVEN A RATHER WEAK MSLP GRADIENT ACROSS THE AREA WITH SURFACE HIGH PRESSURE EXTENDING INTO THE AREA FROM THE WEST... WE SHOULD SEE LIGHT AND VARIABLE TO CALM WINDS OVERNIGHT. THIS COMBINED WITH CLEAR SKIES WILL ALLOW US TO COOL QUITE NICELY TONIGHT. EXPECT LOW TEMPS WILL RANGE FROM THE UPPER 20S TO AROUND 30 (WITH MAYBE EVEN A FEW MID 20S) IN THE USUAL RURAL COLD LOCATIONS TO THE LOWER 30S ELSEWHERE. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 310 AM THURSDAY... FRIDAY AND FRIDAY NIGHT: ANOTHER SOUTHERN STREAM DISTURBANCE IS EXPECTED TO APPROACH THE AREA ON FRIDAY. S/W ENERGY IS EXPECTED TO LIFT NORTHEASTWARD OUT OF THE SOUTHERN PLAINS ON FRIDAY. MEANWHILE CENTRAL NC WILL EXPERIENCE BRIEF S/W RIDGING AGAIN ON FRIDAY IN BETWEEN THE AFOREMENTIONED SYSTEM TONIGHT AND THE APPROACHING SYSTEM ON FRIDAY. THIS WILL YIELD MOSTLY SUNNY SKIES... POSSIBLY BECOMING PARTLY SUNNY BY LATE IN THE DAY AS HIGH LEVEL CLOUD COVER BEGINS TO STREAM NORTH AND EASTWARD IN ADVANCE OF THE NEXT SYSTEM. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO BE A BIT LOWER ON FRIDAY... AROUND 5 METERS OR SO. HOWEVER... WITH MORE SUN EXPECTED ON FRIDAY THINK WE WILL SEE SIMILAR HIGH TEMPS COMPARED TO TODAY. THUS... EXPECT HIGH TO RANGE FROM 50 TO 55. AS THE MID LEVEL DISTURBANCE SHIFTS NORTHEASTWARD TOWARDS OUR REGION FROM THE LOWER MS RIVER VALLEY ON FRIDAY EVENING/EARLY SATURDAY MORNING SURFACE LOW PRESSURE WILL DEVELOP ACROSS THE NORTHERN GULF OF MEXICO AND BEGIN TRACKING EASTWARD. AS THE SYSTEM APPROACHES MOISTURE WILL STREAM NORTHWARD ACROSS CENTRAL NC... WITH SHALLOW ISENTROPIC LIFT BEGINNING TO INCREASE ACROSS THE WESTERN AND SOUTHWESTERN PORTION OF THE CWA DURING THE EARLY MORNING HOURS OF SATURDAY. AT THE ONSET OF LIGHT PRECIP SPREADING INTO NORTHWEST PIEDMONT WE COULD SEE A BRIEF PERIOD OF SOME SLEET MIXED IN WITH THE LIGHT RAIN. HOWEVER... TEMPS ARE EXPECTED TO REMAIN ABOVE FREEZING ACROSS THE WESTERN/NORTHWESTERN PIEDMONT ON SATURDAY MORNING NO IMPACTS ARE EXPECTED. IN FACT WILL KEEP ANY MENTION OF SLEET OUT OF THE FORECAST FOR NOW.... AS ANY OCCURRENCE WOULD BE BRIEF AND OF NO IMPACT. LOW TEMPS SATURDAY MORNING WILL RANGE FROM THE UPPER 30S SOUTH/SOUTHWEST TO THE LOWER 30S NORTHEAST. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 347 AM WEDNESDAY... SATURDAY...WHILE A SFC DRY AIR RIDGE AND PARENT HIGH ARE STILL IN A FAVORABLE LOCATION TO SUPPORT A COLD AIR DAMMING EVENT SATURDAY...THE LATEST MODEL GUIDANCE HAS TAKEN THE MID LEVEL S/W ON A MORE SLY TRAJECTORY THAN PREVIOUS MODEL RUNS AND PARENT HIGH A FEW MILLIBARS WEAKER THAN PREVIOUS MODEL RUNS. THIS STILL YIELDS A HYBRID DAMMING EVENT THOUGH PRECIP AMOUNTS APPEAR TO BE LIGHTER THAN EARLIER FORECASTS. S/W HAS RECENTLY ENTERED THE UPPER AIR RAWINSONDE NETWORK SO THE 12Z MODEL RUN SHOULD GIVE AN INDICATION OF EVENTUAL STRENGTH/TRACK OF THIS SYSTEM REGARDLESS...OVERCAST SKIES AND AREAS/WIDESPREAD LIGHT RAIN WILL RESULT IN A COLD DAMP DAY. MOS GUIDANCE APPEARS TOO WARM AND AM RELUCTANT TO RAISE MAX TEMPS SATURDAY FROM CURRENT FORECAST (NEAR 40 NW TO UPPER 40S FAR SE). IF RAIN COVERAGE ENDS UP BEING SPOTTY VERSUS WIDESPREAD...THEN COULD SEE AN ADJUSTMENT IN MAX TEMPS TO VALUES COMPARABLE TO THE NAM MOS (MID-UPPER 40S, NEAR 50 SE). SATURDAY NIGHT...SUBSIDENCE BEHIND THE EXITING S/W SHOULD AID TO DIMINISH LIGHT PRECIP WITH GREATEST THREAT FOR SPOTTY LIGHT PRECIP OVER THE SANDHILLS/SOUTHERN COASTAL PLAIN (AGAIN DUE TO THE MORE SLY TRACK OF THE S/W). OTHERWISE CONTINUED CONSIDERABLE CLOUDINESS WITH PATCHY DRIZZLE AND/OR LIGHT FOG. MIN TEMPS MID-UPPER 30S. SUNDAY THROUGH WEDNESDAY...A MAJOR STORM MAY AFFECT THE SE U.S. LATE TUESDAY INTO WEDNESDAY (INCLUDING CENTRAL NC) WITH POTENTIAL IMPACT ON TRAVEL DUE TO HEAVY RAIN AND STRONG GUSTY WINDS. MODEL GUIDANCE FLIP-FLOPPED A BIT FOR SUNDAY INTO MONDAY WITH GUIDANCE NOW INDICATING A NARROW DRY AIR SFC RIDGE ACROSS THE REGION SUNDAY WITH ANOTHER S/W IN THE SOUTHERN STREAM INITIATING ANOTHER AREA OF RAIN LATE SUNDAY INTO MONDAY. THIS SCENARIO HAS ALSO BEEN PICKED-UP BY THE LATEST ECMWF. PARTIAL THICKNESSES SUPPORT ALL LIQUID ACROSS THE PIEDMONT AT THIS TIME. DUE TO THE SHIFT...PLAN TO CONFINE POPS TO JUST CHANCE AT THIS TIME LATE SUNDAY INTO MONDAY. IF LATER MODEL RUNS MAINTAIN SOME CONSISTENCY...LIKELY POPS WARRANTED FOR OVERNIGHT SUNDAY INTO MONDAY MORNING. WILL CONTINUE BELOW NORMAL HIGH TEMPS SUNDAY INTO MONDAY...WITH MAX TEMPS MONDAY AS MUCH AS 7-8 DEGREES BELOW NORMAL IF RAIN MATERIALIZES. TUESDAY INTO WEDNESDAY...AMPLIFYING L/W TROUGH IN THE NORTHERN STREAM WILL TAP GULF MOISTURE AND STREAM IT NORTHWARD INTO THE CAROLINAS TUESDAY INTO TUESDAY NIGHT. MODEL GUIDANCE INDICATE A STRONG JET ROUNDING BASE OF TROUGH LATE TUESDAY NIGHT INTO WEDNESDAY MORNING CAUSING THE TROUGH TO BECOME NEGATIVELY TILTED ACROSS THE SE U.S. IF THIS HOLDS TOGETHER...COULD SEE A BAND OF HEAVY SHOWERS WITH A FEW STORMS CROSS CENTRAL NC OVERNIGHT TUESDAY NIGHT INTO EARLY WEDNESDAY. THE PARENT LOW DEEPENS SIGNIFICANTLY WEDNESDAY AND WEDNESDAY NIGHT WITH THE POTENTIAL FOR STRONG GUSTY WINDS ACROSS CENTRAL NC. A BRIEF BUMP UP IN TEMPS TUESDAY AHEAD OF THE STORM SYSTEM TUESDAY FOLLOWED BY ANOTHER ROUND OF BELOW NORMAL MAX TEMPS THOUGH TRULY FRIGID AIR NOT SEEN IN OUR REGION THROUGH CHRISTMAS. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... AS OF 1240 PM THURSDAY... VFR CONDITIONS WILL CONTINUE THIS AFTERNOON THROUGH THE END OF THE TAF PERIOD. A WEEK DISTURBANCE WILL CROSS VIRGINIA THIS EVENING...BUT THE ONLY IMPACT OVER NC WILL BE INCREASING MID/HIGH CLOUDS....MAINLY ACROSS THE NORTHERN HALF OF THE AREA. WINDS WILL BE LIGHT OUR OF THE NORTH-NORTHWEST...INCREASING TO 4-6KT DURING THE DAY FRIDAY. OUTLOOK...A LOW PRESSURE SYSTEM MOVING FROM THE GULF COAST TO THE CAROLINA COAST FRIDAY NIGHT AND SATURDAY WILL BRING A ROUND OF SUB- VFR CONDITIONS TO CENTRAL NC ON SATURDAY AND SATURDAY NIGHT. HOWEVER....THIS SYSTEM MAY NOT BE AS SIGNIFICANT AS ONCE EXPECTED. VFR CONDITIONS ARE EXPECTED TO BRIEFLY RETURN FOR SUNDAY... BEFORE ANOTHER DISTURBANCE LIFTS NORTHEASTWARD OUT OF THE GULF... SPREADING RAIN INTO CENTRAL NC SUNDAY NIGHT INTO MONDAY... WITH SUB-VFR CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BSD/VINCENT NEAR TERM...BSD/BLS SHORT TERM...BSD LONG TERM...WSS AVIATION...BLS

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