Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 301913
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
315 PM EDT THU OCT 30 2014

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO OUR REGION THROUGH
TONIGHT...THEN LINGER THROUGH EARLY FRI. A POTENT UPPER LEVEL LOW
CROSSING THE REGION ON SATURDAY AND ASSOCIATED STRONG CYCLOGENESIS
OFF THE MID ATLANTIC COAST WILL RESULT IN WET BLUSTERY CONDITIONS
ON SATURDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 315 PM THURSDAY...

TONIGHT: SHORTWAVE TROUGH OVER THE CENTRAL PLAINS/MID MS VALLEY WILL
AMPLIFY AS IT EJECTS SEWD INTO THE SOUTHERN APPALACHIANS BY
DAYBREAK...WITHIN THE EVOLVING LONG WAVE TROUGH ACROSS THE EASTERN
US AND IN ADVANCE OF A POWERFUL SHORTWAVE TROUGH DIVING SEWD OUT OF
EASTERN MANITOBA. WEAK CYCLOGENESIS ALONG THE STALLED OFFSHORE
FRONTAL ZONE WILL ENSUE IN RESPONSE TO UPSTREAM AMPLIFICATION. WHILE
PRECIP WILL REMAIN OFFSHORE...GFS TIME HEIGHT SECTIONS INDICATE
CENTRAL NC WILL BECOME ENCOMPASSED BY MULTI-LAYER
CLOUDINESS...BOUNDED BY A BROKEN MID-CLOUD LAYER ON OUR WESTERN
FLANKS...WITH ENCROACHING LOW CLOUD DECK ON THE EASTERN FLANKS.
BELIEVE THE MAJORITY OF THE FORECAST AREA WILL REMAIN MOSTLY CLEAR
WITH MORE IN THE WAY OF PARTLY CLOUDY SKIES ON OUR WESTERN AND
EASTERN FRINGES. LOW TEMPERATURES WITHIN A FEW DEGREES EITHER SIDE
OF 40...WITH THE COOLER READINGS IN RURAL/OUTLYING AREAS WHERE WINDS
ARE MOST LIKELY TO GO CALM AT TIMES.

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 1205 PM THURSDAY...

FOR SUN THROUGH MON NIGHT: THE MID LEVEL TROUGH WILL SHIFT TO OUR
EAST SUN... AND WHILE A FEW HIGH CLOUDS MAY LINGER EARLY AS ONE LAST
SPEED MAX ALOFT CROSSES THE AREA... THE DEEP DRYING AND
WARMING/SINKING MID LEVELS WILL TRANSLATE TO MOSTLY SUNNY SKIES.
GUSTY WINDS WILL PERSIST EARLY SUN ESPECIALLY ACROSS THE NRN AND ERN
CWA AS THE MSLP GRADIENT REMAINS TIGHT... AS THE COASTAL LOW SLOWLY
PULLS NE AWAY FROM NC. THIS BOUNDARY LAYER MIXING SHOULD ENSURE THAT
TEMPS HOLD UP A BIT SUN MORNING... HOWEVER AS THE SURFACE HIGH
PASSES OVERHEAD SUN NIGHT/MON MORNING... TEMPS ARE VERY LIKELY TO
DROP TO NEAR OR JUST UNDER FREEZING... COLDEST IN THE WEST. A DRY
ADIABATIC LAPSE RATE ASSUMPTION WITH A SOMEWHAT SHALLOW MIXED LAYER
ON SUNDAY SUPPORTS HIGHS OF 52-57. LOWS SUN NIGHT 27-34... WITH THE
LOWER NUMBERS IN THE NORMALLY COLDER OUTLYING AREAS. ONE POTENTIAL
CAVEAT: A SLUG OF MOISTURE AROUND 700 MB (ASSOCIATED WITH A DIFFUSE
NORTHEAST-MOVING WARM FRONT ALOFT) AND AN OTHERWISE FAVORABLE
PATTERN (INCLUDING INCREASING NW WINDS FROM THE INVERSION ALOFT UP
TO THE TROPOPAUSE) WILL SET THE STAGE FOR POSSIBLE OROGRAPHIC CIRRUS
LATE SUN NIGHT INTO MON MORNING... AND IF THIS OCCURS... IT MAY HOLD
TEMPS UP A BIT IN THE NW PIEDMONT. STAY TUNED. MID LEVEL RIDGING
THEN BUILDS IN FROM THE WEST MON/MON NIGHT AS THE SURFACE HIGH
DRIFTS OFFSHORE AND THE RESIDENT AIR MASS MODIFIES ACCORDINGLY.
EXPECT HIGHS IN THE UPPER 50S TO AROUND 60 MON. WITH A LIGHT WSW
SURFACE FLOW AND MILD THICKNESSES... HAVE LOWS MON NIGHT OF 33-36.

FOR TUE-THU: THE WARMING TREND WILL BE IN FULL SWING WITH
THICKNESSES TRENDING A BIT ABOVE NORMAL... AS THE MID LEVEL RIDGE
SHIFTS EAST AND EXPANDS OFF THE SOUTHEAST COAST. BY MIDWEEK...
TROUGHING NOW WELL OFF THE PACIFIC COAST WILL HAVE MOVED THROUGH WRN
NOAM... CULMINATING IN MID LEVEL TROUGHING OVER ONTARIO/QUEBEC AND
OVER NRN MEXICO AND TX. THE ASSOCIATED SURFACE FRONT WILL APPROACH
FROM THE NW LATE WED INTO THU... AND WHILE IT MAY NOT ACTUALLY GET
INTO NC BY THU AS THE RIDGE LOOKS PRETTY POTENT... WE`RE LIKELY TO
SEE INCREASING CLOUDS AT THE VERY LEAST... AND PERHAPS A FEW SHOWERS
AS ATLANTIC MOISTURE IS DRAWN IN. NEAR NORMAL HIGHS TUE IN THE MID-
UPPER 60S... CLIMBING TO THE MID 60S TO LOWER 70S FOR WED/THU. -GIH

&&

.CLIMATE...

RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST

        LO-MAX

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

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 140 PM THURSDAY...

VFR CONDITIONS WILL CONTINUE THROUGH FRIDAY AFTERNOON...THOUGH SOME
SHALLOW ISENTROPIC ALONG THE EASTERN SLOPES OF THE MOUNTAINS COULD
LEAD TO SCATTERED 3-4KFT CLOUDINESS AT KINT AND KGSO OVERNIGHT.
SURFACE WINDS WILL GENERALLY BE LIGHT AND FROM THE NORTH...AS HIGH
PRESSURE BUILDS EAST OF THE APPALACHIANS THROUGH TONIGHT.

OUTLOOK: CONDITIONS WILL RAPIDLY DETERIORATE FRIDAY EVENING AND
THROUGH THE OVERNIGHT HOURS 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 FRI NIGHT THROUGH
SATURDAY.

A RETURN TO VFR CONDITIONS ARE EXPECTED LATE SATURDAY NIGHT/EARLY
SUNDAY.


&&

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

&&

$$
SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL/HARTFIELD
LONG TERM...HARTFIELD
CLIMATE...CBL
AVIATION...CBL



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