Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 300626 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 226 AM EDT THU OCT 30 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD INTO OUR REGION THROUGH TONIGHT...THEN LINGER THROUGH EARLY FRI. AN UNSEASONABLY STRONG POLAR FRONT WILL MOVE INTO THE CAROLINAS LATE FRI AND FRI NIGHT...FOLLOWED BY THE DEVELOPMENT OF A STRONG COASTAL LOW OFF THE NC COAST ON SAT..
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 905 PM WEDNESDAY... SHOWERS CONTINUE TO DEVELOP OVER THE AREA. THE LATEST SURFACE ANALYSIS SHOWS THE PREFRONTAL WIND SHIFT HAVING MOVED INTO THE COASTAL PLAIN... WHILE THE SYNOPTIC COLD FRONT (INDICATED BY A FALL- OFF IN DEWPOINTS AND SURFACE THETA-E IN ITS WAKE) IS A BIT FURTHER NW... STRETCHING ACROSS THE WRN PIEDMONT. MID LEVEL VORTICITY SWEEPING AROUND THE BASE OF THE INCOMING TROUGH... AS WELL AS UPPER DIVERGENCE IN THE RIGHT ENTRANCE REGION OF THE 90+ KT JET TO OUR NNE... APPEAR RESPONSIBLE FOR THE REBIRTH OF SHOWER ACTIVITY OVER THE WRN PIEDMONT... WELL MODELED BY THE LATEST RAP MODEL. THE RAP ALONG WITH THE HI RES WRF ARW/NMM MAINTAIN AT LEAST SCATTERED COVERAGE OVER ALL BUT THE FAR NW CWA FOR THE REST OF THE EVENING INTO THE EARLY OVERNIGHT HOURS... BEFORE SHIFTING RAIN JUST EAST OF THE FORECAST AREA BY 07Z OR 08Z. WILL MAKE MINOR CHANGES WITH TIMING AND TO INCREASE COVERAGE... BUT OTHERWISE THE GENERAL PATH OF THE FORECAST IS ON TRACK. EXTRAPOLATION OF OBSERVED AND UPSTREAM TEMPS ALONG WITH NEAR TERM GUIDANCE FROM THE GLAMP AND HRRR CONTINUE TO SUPPORT LOWS FROM 44 NW TO 56 SE... WITH GRADUALLY CLEARING SKIES FROM NW TO SE AS DOWNSLOPE LOW LEVEL FLOW TAKES OVER. -GIH && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 250 PM WEDNESDAY... LEAD SHORTWAVE ENERGY OVER THE NORTHERN ROCKIES WILL EJECT SEWD ACROSS THE CENTRAL US AND INTO THE SOUTHERN APPALACHIANS BY DAYBREAK FRIDAY...WITHIN THE EVOLVING LONG WAVE TROUGH ACROSS THE EASTERN US IMPELLED BY THE VIGOROUS SHORTWAVE TROUGH DIVING SEWD OUT OF EASTERN MANITOBA. DRY TRANQUIL WEATHER AND MOSTLY SUNNY/CLEAR SKIES WILL PREVAIL THROUGH THE DAY ON THURSDAY...WITH PERHAPS AN INCREASE IN HIGH CLOUDS LATE THURSDAY NIGHT IN RESPONSE TO UPSTREAM HEIGHT FALLS AND VEERING SWLY FLOW ALOFT. MODEST COLD AIR ADVECTION IN THE WAKE OF THE TONIGHTS FROPA WILL YIELD SLIGHTLY BELOW NORMAL TEMPERATURES FOR LATE OCTOBER. HIGHS 63 TO 68. LOWS IN THE LOWER 40S...WITH SOME UPPER 30S POSSIBLE IN THE TYPICALLY COOLER LOCATIONS. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 320 PM WEDNESDAY... ...ANOMALOUS PATTERN ON SATURDAY WILL BRING CHILLY, WINDY AND RAW CONDITIONS TO CENTRAL NC... A MODERATE AMPLITUDE EASTERN U.S. TROUGH AT 12Z FRIDAY DEEPENS SIGNIFICANTLY AS AN INTENSE JET AT 500 HPA DROPS INTO THE OH VALLEY AND STRENGTHENS TO ~105KTS ON 00 UTC SUNDAY AS IT REACHES THE BASE OF THE NOW CLOSED TROUGH OFF THE SC COAST. GUIDANCE FROM THE GFS/EC/NAM ARE ALL RATHER SIMILAR WITH THE UPPER AIR PATTERN PATTERN WITH 500 HPA ANOMALIES OF 4-5 SD FROM NORMAL LATE SATURDAY WITH CIPS ANALOG GUIDANCE SUGGESTING A SIMILAR OUTCOME. AT THE SURFACE WEAK HIGH PRESSURE SLIPS OFF THE COAST EARLY ON FRIDAY AS A COLD FRONT AND WEAK SURFACE LOW ASSOCIATED WITH THE UPPER TROUGH MOVES INTO CENTRAL NC AROUND 00 UTC ON SATURDAY. WHILE THE EXACT TRACK OF THE SURFACE LOW IS UNCLEAR...CONSENSUS SUGGESTS THAT THE SURFACE LOW WILL MOVE INTO THE COASTAL PLAIN TOWARD 12 UTC AND THEN MOVES OFFSHORE AND DEEPENS AGGRESSIVELY. LIGHT RAIN IS EXPECTED TO SPREAD INTO THE WESTERN PIEDMONT LATE FRIDAY EVENING...LIKELY AFTER MOST TRICK OR TREATING ACTIVITIES END...AND THEN SPREAD EAST OVERNIGHT. A CHILLY AND RAW SATURDAY SHOULD FEATURE A FAIRLY WIDESPREAD RAIN THAT TAPERS OFF FROM WEST TO EAST DURING THE AFTERNOON AND EVENING. CONSENSUS PRECIPITATION GUIDANCE PROVIDES AROUND A HALF INCH TO THREE QUARTERS OF AN INCH OF RAIN WITH AN ARC OF HEAVIER RAIN LIKELY TO EXTEND NORTHWEST TO SOUTHEAST JUST NORTH OF THE UPPER LOW TRACK. WHILE THICKNESS VALUES WILL CRASH EARLY SATURDAY...BOUNDARY LAYER TEMPERATURES WILL BE SUFFICIENTLY WARM AND DEEP TO PRECLUDE ANY WINTRY PRECIPITATION... EVEN ACROSS THE WESTERN PIEDMONT WHERE SURFACE TEMPERATURES MAY FALL INTO THE UPPER 30S. A STRENGTHENING GRADIENT WILL RESULT IN A COLD AND GUSTY NORTH TO NORTHWEST WIND SATURDAY AFTERNOON AT 10-20 MPH WITH GUSTS TO 25 MPH OR MORE. HIGHS ON SATURDAY WILL BE COMPLICATED BY PRECIPITATION AND COLD AIR WRAPPING AROUND THE DEEPENING LOW OFF THE COAST WITH DAYTIME HIGHS RANGING IN THE LOWER 40S IN THE TRIAD TO THE LOWER 50S IN THE EAST. THESE VALUES ARE 15 TO 25 DEGREES BELOW NORMAL AND COULD THREATEN RECORD LOW MAX TEMPERATURES IN THE PIEDMONT ON SATURDAY(SEE CLIMATE SECTION BELOW FOR RECORD VALUES). PRECIPITATION SHOULD WRAP UP EVERYWHERE BY SATURDAY EVENING WITH CLEARING SKIES AND A BRISK NORTHWEST WIND OVERNIGHT. A CHILLY AIRMASS WILL PERSIST OVERNIGHT WITH LOW LEVEL THICKNESS VALUES BY SUNDAY MORNING RANGING IN THE 1305-1315M RANGE. DESPITE THE CLEARING SKIES AND CHILLY THICKNESS VALUES...MIXING SHOULD KEEP TEMPERATURES FROM BOTTOMING OUT COMPLETELY. LOWS SHOULD RANGE IN THE LOWER TO MID 30S. MOSTLY SUNNY SKIES ARE EXPECTED ON SUNDAY WITH SOME HIGH CLOUDS AND DIMINISHING WINDS. HIGHS WILL RANGE ABOUT 15 DEGREES BELOW NORMAL...RANGING BETWEEN 50-55 DEGREES. HIGH PRESSURE BUILDS OVERHEAD SUNDAY NIGHT WHICH SHOULD RESULT IN THE COLDEST NIGHT OF THE PERIOD WITH LOWS TUESDAY MORNING IN THE LOWER 30S AND PERHAPS SOME UPPER 20S IN SPOTS. FAIR WEATHER WITH MODERATING TEMPERATURES ARE EXPECTED ON MONDAY AND TUESDAY AS HEIGHTS RISE AND AN UPPER LEVEL RIDGE BUILDS TOWARD THE EASTERN SEABOARD. SOME MORNING LOW CLOUDS OR FOG IS POSSIBLE ON MONDAY AND ESPECIALLY TUESDAY AS A RETURN FLOW OFF THE ATLANTIC DEVELOPS. A SHEARING UPPER TROUGH APPROACHES FROM THE WEST ON WEDNESDAY. THIS SYSTEM MAY BE ABLE TO PRODUCE SOME SHOWERS BUT GIVEN THE LATE ARRIVAL ON DAY 7...HAVE OPTED TO KEEP THE FORECAST DRY AND JUST INCREASE CLOUD COVER. HIGHS IN THE UPPER 50S TO NEAR 60 ON MONDAY WILL MODERATE TO THE MID 60S TO AROUND 70 BY WEDNESDAY. -BLAES && .CLIMATE...
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RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST LO-MAX RDU 50/1925 GSO 45/1925 FAY 48/1988
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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AS OF 215 AM THURSDAY... VFR CEILINGS MAINLY BETWEEN 4-9 THOUSAND FT WILL ONLY SLOWLY CLEAR OUT FROM THE WEST...AS THE APPROACH OF A TROUGH ALOFT DRAWS MOIST AIR UP AND OVER A SURFACE FRONT OVER EASTERN NC. IN ADDITION...A SHORT PERIOD OF MVFR CEILINGS WILL BE PROBABLE OVER EAST-CENTRAL NC - INCLUDING AT KRWI - IN CLOSER PROXIMITY TO THE SURFACE FRONT AND LOWER CLOUD BASES...THROUGH ABOUT 10Z. SURFACE WINDS WILL GENERALLY BE IN THE 4-8 KT RANGE FROM THE NORTH...AS HIGH PRESSURE BUILDS EAST OF THE APPALACHIANS THROUGH TONIGHT. OUTLOOK: THE PASSAGE OF A STRONG POLAR FRONT AND SUBSEQUENT DEVELOPMENT OF A STRONG COASTAL LOW WILL RESULT IN RAIN; SUB-VFR CONDITIONS; AND BLUSTERY NW WINDS...FRI NIGHT THROUGH SAT.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...HARTFIELD SHORT TERM...CBL LONG TERM...BLAES CLIMATE...CBL AVIATION...MWS

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