AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
316 AM EDT FRI OCT 31 2014

.SYNOPSIS...AN ARCTIC AIRMASS WILL SPILL SOUTHWARD FROM CANADA INTO 
THE CENTRAL UNITED STATES TONIGHT AS A POTENT UPPER LEVEL 
DISTURBANCE DIGS SOUTHEAST THROUGH THE UPPER GREAT LAKES. MULTIPLE 
WAVES OF LOW PRESSURE WILL DEVELOP ALONG THE CAROLINA COAST IN 
ADVANCE OF THE UPPER LEVEL DISTURBANCE FRIDAY INTO FRIDAY NIGHT. AN 
EARLY SEASON NOR EASTER WILL DEVELOP ON SATURDAY AS THE UPPER LEVEL 
DISTURBANCE TRACKS INTO THE CAROLINAS.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 930 PM THURSDAY... 

OVERNIGHT: SHORTWAVE ENERGY DIGGING SOUTHEAST THROUGH THE CENTRAL MS 
RIVER VALLEY ALONG THE EASTERN PERIPHERY OF AN AMPLIFYING UPPER 
LEVEL RIDGE OVER THE ROCKIES WILL RESULT IN AMPLIFICATION OF THE 
MEAN LONGWAVE TROUGH IN PLACE EAST OF THE MISSISSIPPI TONIGHT AS IT 
TRACKS INTO AL/GA. THOUGH BROAD/MODEST HEIGHT FALLS (60 METER/12-HR 
AT 500 MB) WILL OVERSPREAD THE CAROLINAS/MID-ATLANTIC AND RESULT IN 
GRADUAL MID-LEVEL COOLING/MOISTENING OVER THE REGION TONIGHT...AN 
INITIALLY DRY AIRMASS (0.35" PWAT PER 00Z GSO SOUNDING) AND LACK OF 
STRONG/FOCUSED DPVA WILL ENSURE BENIGN WEATHER WITH CLEAR SKIES 
BECOMING PARTLY CLOUDY BY MORNING. EXPECT LOWS IN THE UPPER 30S/ 
LOWER 40S WHERE WINDS REMAIN CALM IN THE TYPICAL RURAL/LOW-LYING 
AREAS TO MID 40S WHERE A LIGHT NORTHERLY BREEZE PERSISTS. -VINCENT

FRIDAY: DPVA FROM PASSAGE OF LEAD SHORTWAVE TROUGH WILL RESULT IN 
WEAK LIFT WITH INCREASING MID AND UPPER CLOUD COVER THROUGHOUT THE 
DAY...WITH EVEN A FEW SPRINKLES/ISOLATED SHOWERS POSSIBLE ACROSS THE 
FAR WESTERN ZONES LATE FRIDAY FRIDAY/EARLY FRIDAY EVENING IN 
PROXIMITY TO THE DEEPER MOISTURE AXIS PUSHING EAST OF THE MOUNTAINS. 
INCREASE IN CLOUD COVER SHOULD RESULT IN HIGHS A GOOD CATEGORY 
COOLER...POSSIBLY 2 CATEGORIES COOLER IN THE TRIAD. HIGHS IN THE 
LOWER 60S NW PIEDMONT TO MID 60S SOUTH/SOUTHEAST. 


&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 315 PM THURSDAY...

FRIDAY NIGHT: POTENT SHORTWAVE DIVING SOUTHEAST OVER THE SOUTHERN 
OHIO/TN VALLEY FRIDAY EVENING WILL CLOSE OFF AND WILL MOVE ACROSS 
THE SOUTHERN APPALACHIANS AND INVOF THE UPSTATE SC/SOUTHWEST NC BY 
DAYBREAK SATURDAY. INTENSE SFC CYCLOGENESIS NEAR THE NC/SC COAST 
WILL ENSUE BETWEEN 00 TO 12Z SATURDAY...ON THE LEADING EDGE OF A 
STRONG POLAR FRONT ADVANCING EASTWARD ACROSS THE AREA.  CONDITIONS 
WILL DETERIORATE RAPIDLY FRIDAY EVENING-FRIDAY NIGHT...WITH DEEP F-
GEN RESPONSE IN A DEVELOPING DEFORMATION BAND PROGGED TO SET UP 
ACROSS THE WESTERN PIEDMONT...THOUGH THIS WILL ULTIMATELY DEPEND ON 
THE EXACT LOW PRESSURE TRACK AND LOCATION.

WIDESPREAD RAIN LOOKS LIKE IT WILL HOLD OFF LONG ENOUGH TO KEEP MOST 
OF THE LITTLE TRICK TREATERS DRY...ALTHOUGH RESIDENTS IN THE TRIAD 
MAY HAVE TO CONTEND WITH A LITTLE LIGHT RAIN IF THEY STAY OUT MUCH 
AFTER 9PM. BY DAYBREAK...EXPECT CATEGORICAL POPS ACROSS MUCH OF THE 
PIEDMONT...SPREADING EASTWARD INTO THE COASTAL PLAIN BY LATE 
MORNING. COLD MID-LEVEL TEMPERATURES ATOP STRONG LOW-LEVEL CAA WILL 
SUPPORT A MIXTURE OF RAIN AND SNOW ACROSS THE FAR WESTERN ZONES 
AROUND DAYBREAK SATURDAY...ALTHOUGH ANY CONVECTIVE ELEMENTS 
UNDERNEATH THE STEEP MID-LEVEL RATES WITHIN THE DEFORMATION BAND 
COULD SUPPORT A DUSTING ON ELEVATED SURFACES. TRAVEL PROBLEMS ARE 
HIGHLY UNLIKELY GIVEN THE WARM GROUND TEMPS. LOWS IN THE MID/UPPER 
30S NW TO MID 40S SE.  -CBL

FOR SAT/SAT NIGHT: SEVERAL ISSUES TO CONCERN OURSELVES WITH... 
INCLUDING THE POTENTIAL FOR LIGHT FROZEN PRECIP IN THE WRN 
PIEDMONT... BRISK WINDS... AND A POSSIBLE KILLING FREEZE THIS 
WEEKEND. 

OVERVIEW: HIGHLY ANOMALOUS (HEIGHTS DROPPING TO AROUND 4 STANDARD 
DEVIATIONS BELOW NORMAL) MID LEVEL LOW PRESSURE OVER INDIANA LATE 
FRI IS STILL EXPECTED TO INTENSIFY AS IT DROPS SOUTHEAST... TO NEAR 
AVL BY SAT MORNING... CROSSING SC SAT BEFORE SWINGING NE OFF THE NC 
COAST SAT NIGHT. THE GREATEST HEIGHT FALLS WILL BE OVER SC (NEARLY 
180 M IN 12 HRS) BUT STILL IMPRESSIVE AT 100-150 M OVER CENTRAL/SRN 
NC. AT THE SURFACE... WEAKER PRIMARY LOW PRESSURE JUST OFF THE NC 
COAST FRI NIGHT WILL MOVE NE AS SECONDARY LOW PRESSURE FORMS OVER 
SOUTH CENTRAL NC... TRACKING EAST WHILE DEEPENING OVER THE SRN NC 
COAST THROUGH SAT MORNING... THEN STRENGTHENING JUST OFF THE OUTER 
BANKS THROUGH LATE SAT. 

POPS: GIVEN THE INTENSE DEEP LAYER FORCING FOR ASCENT... PEAK IN MID 
LEVEL DEFORMATION... AND STRENGTHENING LOW LEVEL MOISTURE 
TRANSPORT... AN UPTICK IN POPS TO CATEGORICAL EXTENDING THROUGH MUCH 
OF SAT APPEARS WARRANTED. THE HIGHER POPS SHOULD BE FOCUSED OVER THE 
CENTRAL/SRN PIEDMONT AND SANDHILLS... OR THE WRN AND SRN CWA... 
WHERE DPVA WILL BE MAXIMIZED AND WHERE UPPER DIVERGENCE IN THE LEFT 
EXIT REGION OF THE DIVING JET TO OUR WEST WILL BE STRENGTHENING... 
ALL YIELDING DEEP AND VIGOROUS DYNAMIC LIFT. WILL BE SLOWER TO TAPER 
DOWN POPS IN THE SOUTHEAST AND ERN CWA GIVEN THE STEEPER LAPSE RATES 
AND GREATER DEFORMATION HERE... PLUS ADDITIONAL WEAKER SHEARED 
VORTICITY WILL BE DIVING DOWN THE WEST SIDE OF THE LOW. 

PTYPE AND THUNDER: WHILE THE MODELS HAVE BEEN TRENDING WARMER (MORE 
REASONABLY SO) WITH THE SKIN AND BOUNDARY LAYER TEMPS... LATEST 
FORECAST SOUNDINGS DEPICT THE FREEZING LEVEL IN THE TRIAD FALLING 
BELOW 1000 FT SAT MORNING... AS THE STRENGTHENING COASTAL LOW 
INTENSIFIES LOW LEVEL COLD AIR ADVECTION INTO OUR FAR NRN AND WRN 
CWA. AN EXPECTED SATURATED NEAR-FREEZING ISOTHERMAL LAYER UP TO 
AROUND 850 MB IS TOPPED BY STEEP LAPSE RATES OF 6.5-7.0 C/KM AND 
PLENTY OF MOISTURE UP THROUGH -25C... WHICH IN CONJUNCTION WITH 
PARTIAL THICKNESSES SUPPORTS SOME SNOW MIXING IN WITH RAIN OVER THE 
WRN PIEDMONT LATE FRI NIGHT THROUGH SAT MORNING. TRAVEL PROBLEMS ARE 
HIGHLY UNLIKELY GIVEN THE WARM GROUND TEMPS... HOWEVER A LIGHT 
DUSTING ON ELEVATED SURFACES IS CERTAINLY POSSIBLE. CONSIDERING HOW 
INTENSE THIS SYSTEM IS EXPECTED TO BECOME WITH WHAT SHOULD BE AN 
INCREDIBLE AGEOSTROPHIC RESPONSE TO THE HEIGHT FALLS ALOFT AND 
DEEPENING SURFACE LOW... OTHERWISE ATYPICAL LATE-OCTOBER WEATHER 
INCLUDING A POTENTIAL LIGHT DUSTING OF SNOW ON ELEVATED SURFACE 
CANNOT BE RULED OUT. REGARDING THUNDER CHANCES... PREDICTED MUCAPE 
WILL REMAIN LOW AND CONFINED LARGELY TO THE COASTAL AREAS... HOWEVER 
THE NAM DOES INDICATE 100-200 J/KG OVER THE SW/SRN CWA FRI NIGHT... 
AND WITH EXPECTED STEEP LAPSE RATES ALOFT AND STRONG ASCENT THROUGH 
SAT MORNING COUPLED WITH 40-50 KT DEEP LAYER SHEAR... A FEW 
LIGHTNING STRIKES MAY OCCUR... BUT SHOULD BE TOO ISOLATED TO INCLUDE 
IN THE FORECAST AT THIS TIME. IT'S WORTH NOTING THAT ANY CONVECTIVE 
ELEMENTS THAT MAY DEVELOP AND ANY RESULTING HEAVIER PRECIP RATES 
COULD RAISE THE RISK OF A DUSTING OF SNOW ON ELEVATED SURFACES.

WINDS: IT SHOULD TAKE AWHILE FOR THE SURFACE WINDS TO PICK UP SAT... 
GIVEN THE INITIAL SLACK GRADIENT AS THE SECONDARY LOW FORMS OVER 
SOUTH CENTRAL NC. AS THIS LOW SHIFTS EAST AND OFFSHORE AND DEEPENS 
DURING THE DAY AND SAT NIGHT... THE RAPIDLY TIGHTENING GRADIENT 
SHOULD RESULT IN SUSTAINED WINDS PEAKING AT 15-20 KTS (POTENTIALLY 
HIGHER IN SPOTS) IN THE LATE AFTERNOON THROUGH EVENING. STILL EXPECT 
GUSTS OF 25-35 KTS. THIS IS JUST UNDER WIND ADVISORY CRITERIA... BUT 
IMPACT-WISE WE SHOULD STILL SEE LIGHT OBJECTS GETTING TOSSED AROUND 
AND A FEW BRANCHES COMING DOWN... ESPECIALLY CONSIDERING THAT MOST 
LEAVES ARE STILL ON THE TREES. WIND CHILLS MAY HOLD IN THE 30S OVER 
THE WRN HALF OF THE CWA SATURDAY. 

TEMPS: PATTERN OF EARLIER FORECASTS TO UNDERCUT STATISTICAL GUIDANCE 
SUBSTANTIALLY STILL APPEARS PRUDENT... WITH A CHILLY CANADIAN-SOURCE 
AIR MASS MOVING IN... STRENGTHENING COLD AIR ADVECTION... STEADY 
PRECIP FOR A GOOD CHUNK OF THE DAY... AND ABUNDANT CLOUD COVER. 
EXPECT HIGHS FROM 44 TO 53... ORIENTED ROUGHLY WEST TO EAST... 
ALTHOUGH HIGHS IN THE ERN CWA WILL BE AROUND MIDDAY WITH TEMPS 
STEADY OR SLOWLY FALLING IN THE AFTERNOON. LOWS 32-37 WEST-TO-
EAST... AS THE OVERNIGHT MIXING SHOULD HOLD TEMPS UP A BIT... 
LEAVING THE BETTER CHANCE OF A KILLING FROST/FREEZE EVENT FOR SUN 
NIGHT. -GIH

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/... 
AS OF 314 AM FRIDAY...

STRONG COASTAL STORM WILL BE MOVING NORTHEASTWARD OFF THE COAST... 
WITH A STRONG 1032 MB HIGH BUILDING IN TO THE OHIO VALLEY. GUSTY 
WINDS WILL STILL BE POSSIBLE UNTIL THE PRESSURE GRADIENT RELAXES 
LATE IN THE DAY SUNDAY AS THE HIGH BEGINS TO MOVE INTO THE AREA. 
SKIES WILL BE CLEAR ON SUNDAY... WITH DRY NORTHWESTERLY FLOW. THE 
HIGH WILL MOVE OVER THE AREA SUNDAY NIGHT... SETTING THE STAGE FOR 
EXCELLENT RADIATIONAL COOLING... AND LIKELY FROST/FREEZE CONDITIONS 
MONDAY MORNING. MOSTLY SUNNY CONDITIONS WILL CONTINUE THROUGH 
MONDAY... WITH HIGHS NEAR 60. HIGH PRESSURE WILL MOVE OFF THE EAST 
COAST ON TUESDAY... AND TEMPERATURES WILL CONTINUE TO MODERATE INTO 
THE 60S AS FLOW BECOMES SOUTHWESTERLY.

NORTHERN STREAM SHORTWAVE ENERGY WILL MOVE ALONG THE CANADIAN 
BORDER... AND THE ASSOCIATED WEAK COLD FRONT WILL ENTER THE AREA 
LATE THURSDAY/EARLY FRIDAY. THE STRONGEST FORCING WILL REMAIN NORTH 
AND MOISTURE LOOKS TO BE LIMITED... AND MODEL QPF IS CONSEQUENTLY 
NEAR 0 ACROSS THE AREA. WILL KEEP POPS TO SLIGHT CHANCE AT THIS 
TIME... BUT IF THE CURRENT TREND FOR A DRY FRONTAL PASSAGE 
CONTINUES... EVEN THIS MAY BE OVERDONE.

&&

.CLIMATE...

RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST
 
        LO-MAX   

RDU     50/1925
GSO     45/1925 
FAY     48/1988     

&&

.AVIATION /06Z THURSDAY THROUGH TUESDAY/... 
AS OF 145 AM FRIDAY...

VFR CONDITIONS ARE GENERALLY EXPECTED TO CONTINUE THROUGH AROUND 00Z 
SATURDAY... AS SURFACE HIGH PRESSURE LOCATED TO THE NORTH OF THE 
REGION THIS MORNING WILL EXTEND INTO OUR AREA WHILE SHIFTING 
EASTWARD TODAY. THE ONE EXCEPTION COULD BE A BRIEF PERIOD OF 
IFR/MVFR VISBYS AT FOG PRONE KRWI. OTHERWISE... WINDS ARE GENERALLY 
EXPECTED TO BE LIGHT AND VARIABLE THIS MORNING THROUGH TODAY. 
MEANWHILE... A POTENT MID/UPPER LEVEL DISTURBANCE WILL APPROACH THE 
AREA TODAY... ALLOWING FOR VFR CLOUD COVER TO INCREASE GENERALLY IN 
A WEST TO EAST FASHION TODAY WITH PRECIP AND SUB-VFR CONDITIONS 
SPREADING INTO THE WESTERN PIEDMONT BY AROUND 03Z FOR SO. MVFR 
CONDITIONS LATE THIS EVENING WILL LIKELY FALL QUICKLY TO IFR/LIFR BY 
AROUND 06Z SATURDAY.
 
OUTLOOK: CONDITIONS WILL CONTINUE TO RAPIDLY DETERIORATE ACROSS THE 
ENTIRE AREA TONIGHT INTO SATURDAY MORNING AS AN ANOMALOUSLY STRONG 
UPPER LOW SWINGS THROUGH THE REGION. SUB-VFR CONDITIONS IN PERIODS 
OF RAIN AND BLUSTERY NW WINDS WILL IMPACT THE AREA TONIGHT THROUGH 
SATURDAY. 

A RETURN TO VFR CONDITIONS ARE EXPECTED BY SUNDAY AS THE POTENT 
SYSTEM LIFTS OFF TO THE NORTHEAST. VFR CONDITIONS ARE THEN EXPECTED 
TO CONTINUE ACROSS THE REGION AS SURFACE HIGH PRESSURE BUILDS ACROSS 
THE AREA.
 
 
 
&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT/CBL
SHORT TERM...CBL/HARTFIELD
LONG TERM...SEC 
CLIMATE...CBL 
AVIATION...BSD/CBL



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