-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 062018
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
318 PM EST THU MAR 6 2014

.SYNOPSIS...COLD HIGH PRESSURE WILL EXTEND INTO THE REGION FROM THE
NORTH THROUGH TONIGHT. A LOW PRESSURE SYSTEM DEVELOPING OVER THE
NORTHEAST GULF OF MEXICO THIS AFTERNOON WILL INTENSIFY AS IT TRACKS
NORTHEAST ALONG THE CAROLINA COAST ON FRIDAY.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
AS OF 215 PM THURSDAY...

...CONFIDENCE INCREASING IN WINTER STORM CONDITIONS FOR A GOOD
PORTION OF THE NORTHWEST PIEDMONT... AND PERSON COUNTY (MAINLY ALONG
AND NORTH OF I-85) TONIGHT INTO MID-DAY FRIDAY...

PRELIMINARY WARNINGS INCLUDE...FORSYTH...DAVIDSON...GUILFORD...
ALAMANCE...AND PERSON.

PRELIMINARY ADVISORIES INCLUDE...RANDOLPH...CHATHAM...ORANGE...
DURHAM...GRANVILLE...AND VANCE.

THE PARENT HIGH PRESSURE (1038+ MB) WAS CENTERED OVER UPPER NY
STATE. THIS AFFECTS OF THIS HIGH EXTEND SOUTHWARD THROUGH THE
CAROLINAS INTO GEORGIA. IT IS OF SUFFICIENT STRENGTH AND OF ADEQUATE
LOCATION TO DELIVER CAA/DAA... AND IS MORE THAN COLD ENOUGH TO
DELIVER CAA/DAA INTO OUR PIEDMONT DAMMING REGION FOR A WINTER
WEATHER EVENT. THIS IS OCCURRING AS THE MID/UPPER CLOSED LOW OVER
THE DEEP SOUTH APPROACH FROM THE SW... WHICH WILL INDUCE A MILLER-A
TYPE LOW PRESSURE THAT IS FORECAST TO TRACK FROM THE NORTHERN GULF
OF MEXICO THIS EVENING... NE ALONG THE SE US COAST TONIGHT AND
FRIDAY. TYPICALLY... MILLER-A STORMS CARRY A NARROW TRANSITION
ZONE... FROM SIGNIFICANT IMPACT TO LITTLE IMPACT CONCERNING WINTER
WEATHER. THIS MAY END UP THE CASE AGAIN WITH THIS STORM.

WHAT IS VERY INTERESTING ABOUT THIS STORM IS THAT THE STORM TYPE...
TRACK... AND CLASSICAL DAMMING PATTERN (AT LEAST AT THE ONSET OF THE
STORM) STRONGLY SUGGEST MORE SNOW THAN THE MODELS HAVE DEPICTED IN
THE DAMMING REGION. TYPICALLY... THERE WOULD BE MORE SNOW EXPECTED
OVER THE NW PIEDMONT WITH A NARROW TRANSITION ZONE OF MIXED SNOW AND
RAIN... TO ALL RAIN IN THE EAST AND SOUTH. LED BY THE NAM... THERE
HAS BEEN A PROMINENT WARM NOSE ALOFT DEPICTED ALL ALONG WITH THE
STORM WHICH HAS PRECLUDED SNOW FROM ITS FORECAST.

NOW THAT THE SYSTEM IS BEARING DOWN ON US... MODELS SEEM TO BE
COMING AROUND TO DEPICT MORE SNOW/SLEET THAN BEFORE BETWEEN 00Z/06Z
OR SO IN THE NW TONIGHT... THEN ICING BETWEEN 06Z-12Z. THIS SEEMS
VERY REASONABLE AND IT MAY YET BE UNDERDONE WITH THE SNOW/SLEET
(FROZEN SIDE) OF THE STORM.

THIS CONTINUES TO BE A FORECAST BATTLE OF THE PLACEMENT OF THE WARM
AND COLD NOSES. THE LATEST NAM CONTINUES STEADFAST IN THE
DEVELOPMENT OF THE STRONGEST WARM NOSE ALOFT (+6 DEGREES/C) DRIVEN
BY 50-70KT FLOW OFF THE ATLANTIC INTO EASTERN SC/NC IN THE LAYER
BETWEEN H85 AND H75. THE LATEST OPERATIONAL EC AND GFS CONTINUE TO
FORECAST THE MOST PROMINENT COLD NOSE CENTERED AT H9 FROM
CHARLOTTESVILLE TO DANVILLE THROUGH THE TRIAD...BOTTOMING OUT AT -5
DEGREES/C OVERNIGHT. THIS OCCURS AS A GOOD PART OF THE MAIN
PRECIPITATION FALLS. IT APPEARS THESE RATHER LARGE DIFFERENCES ARE
RELATED TO THE SPEED/TRACK OF THE INDIVIDUAL MODELS WITH THE
APPROACHING MID/UPPER LEVEL LOW. THE 12Z NAM CONTINUES TO BE THE
SLOWEST WITH THE SYSTEM...WHILE THE 12Z GFS REMAINS THE QUICKEST.
THIS IS LIKELY DUE TO CONVECTIVE FEEDBACK OR THE DEEP CONVECTION
THAT WAS MOVING INTO FLORIDA FROM THE EASTERN GULF. GIVEN THAT THE
NAM AT 12Z CAME IN A BIT QUICKER WITH THE STORMS MOVEMENT... THE GFS
AND THE QUICKER SOLUTIONS MAY BE THE WAY TO GO. THE WARMER NAM MAY
BE RELATED TO THE SLOWER MOVEMENT OF THE MID/UPPER CUT OFF LOW WHICH
GIVES MORE TIME TO TAP WESTERN ATLANTIC AIR INTO THE SYSTEM AND
DRIVE THE WARM NOSE MUCH FARTHER INLAND. THUS THE NAM EXTREME WARM
NOSE WAS NOT ACCEPTED FULLY. HOWEVER... A PROMINENT WARM NOSE ALOFT
IS ANTICIPATED AS IS DEPICTED BY THE MAJORITY OF THE MODELS.

...FOR THE WARNING COUNTIES INCLUDING THE PIEDMONT TRIAD AND
ROXBORO...

PARTIALS IN THE 1000/850 AND 850/700 LAYERS ARE FORECAST BY THE
EC/GFS TO BE IN THE 1295-1300M/1545-1550M RANGE BETWEEN 00Z/09Z OVER
NW AND N PIEDMONT. THE UNIVERSAL NOMOGRAM DEPICTS THE PRECIPITATION
BEGINNING AS SNOW/SLEET IN THE TRIAD EARLY TO MID EVENING... THEN
SLOWLY CHANGING TO MIXED SLEET AND FREEZING RAIN OVERNIGHT. THE
SURFACE WET BULB FORECASTS DROP THE TEMPERATURES TO 29-30
OVERNIGHT... KEEPING THEM THERE THROUGH 12Z... THEN SLOWLY WARM TO
33 OR SO BETWEEN 13Z-15Z. QPF ON THE ORDER OF 0.50 TO 0.75 DURING
THIS CRITICAL TIME SHOULD TRANSLATE TO 1-2 INCHES OF SNOW/SLEET THEN
POTENTIALLY UP TO 0.25 OF FREEZING RAIN. THE MORE SNOW/SLEET AT THE
ONSET... OBVIOUSLY THE MORE HAZARDOUS ROADS WILL BECOME. THE MORE
FREEZING RAIN AFTER MIDNIGHT... THE MORE THAT WOULD WEIGH ON
TREES/POWER LINES. REGARDLESS... TOGETHER THE P-TYPES OF WINTRY
MIXTURE SHOULD EQUAL WINTER STORM CRITERIA WHEN COMBINED WITH TEMPS
IN THE UPPER 20S OVERNIGHT IN THE WARNED COUNTIES. THE FREEZING RAIN
SHOULD BECOME A SELF LIMITING PROCESS AFTER SUNRISE FRIDAY AS THE
COMBINATION OF GOOD RAINFALL RATES... TEMPS RISING INTO THE LOWER TO
MID 30S... AND INSOLATION THROUGH THE CLOUDS LIMIT FREEZING. A
COUPLE OF CONCERNS...LESS OF A WARM NOSE...WOULD MEAN MORE SNOW AND
SLEET THAN CURRENTLY  FORECAST. SENSIBLE WEATHER... SNOW AND SLEET
DEVELOPING THIS EVENING... CHANGING TO SLEET AND FREEZING RAIN AFTER
MIDNIGHT. TOTAL SNOW AND SLEET ACCUMULATION 1-3 INCHES. TOTAL ICE
ACCRUAL UP TO 0.25 OF AN INCH. TOTAL QPF 1.00. LOWS 28-30. FREEZING
RAIN TO RAIN FRIDAY MORNING... ENDING IN THE AFTERNOON. HIGHS IN THE
MID 30S.

...IN THE ADVISORY AREA INCLUDING ASHEBORO TO DURHAM TO OXFORD...

A WINTRY MIXTURE ARRIVING DURING THE EVENING... BECOMING FREEZING
RAIN MIXED SLEET OVERNIGHT. THIS IS SUPPORTED BY PARTIALS IN THE
1300 TO 1305/1550-1560 RANGE...AND SURFACE WET BULBS 31-32. THE
FREEZING RAIN SHOULD BECOME ALL RAIN BEFORE DAYBREAK. TOTAL
SNOW/SLEET ACCUMULATION LESS THAN 0.5. TOTAL ICE ACCRUAL  UP TO 0.1.
LOWS 30-32... WHICH SHOULD MEAN MINIMAL  IMPACTS ON AREA ROADS
UNLESS MORE SNOW/SLEET FALL AT THE ONSET DURING THE OVERNIGHT.

FRIDAY...RAIN...HEAVY AT TIMES. TEMPS RISING INTO THE UPPER 30S.

...AREAS TO THE SOUTH AND EAST OF THE WARNINGS AND ADVISORIES...

RAIN DEVELOPING THIS EVENING...POSSIBLY BEGINNING AS SLEET. LOWS 33-
35...SLOWLY RISING OVERNIGHT TO NEAR 40 OR 45 SE. RAIN FRIDAY...
HEAVY AT TIMES. HIGHS IN THE 40S/LOWER 50S SE.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 300 PM THURSDAY...

SAT/SAT NIGHT: RISING HEIGHTS WILL PREVAIL SAT/SAT NIGHT AS
UNIDIRECTIONAL FLOW ALOFT BECOMES ESTABLISHED IN THE WAKE OF THE
STORM SYSTEM MOVING OFFSHORE THE CAROLINA AND MID-ATLANTIC COAST AND
WEAK HIGH PRESSURE MOVES INTO THE REGION FROM THE WEST. EXPECT
MOSTLY SUNNY SKIES WITH HIGHS IN THE MID 60S. LOWS SAT NIGHT 39-44F.

SUN/SUN NIGHT: A SHEAR AXIS WILL APPROACH THE REGION FROM THE WEST
ON SUNDAY...WITH AN ATTENDANT SFC TROUGH AND WEAK COLD FRONT
APPROACHING FROM THE NORTHWEST. AT THIS TIME IT DOES NOT APPEAR THAT
MOISTURE/FORCING WILL BE SUFFICIENT TO WARRANT ANY CHANCE FOR RAIN
SUN AFT/EVE...AND WILL MAINTAIN A DRY FCST. DESPITE SOME INCREASE IN
CLOUD COVER DURING THE DAY...EXPECT HIGHS SIMILAR TO SAT IN THE MID
60S. LOWS SUN NIGHT MID/UPPER 30S TO LOWER 40S. -VINCENT

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
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AS OF 315 PM THURSDAY...

EXPECT A BENIGN WEATHER PATTERN AND ABOVE NORMAL TEMPERATURES TO
PERSIST EARLY NEXT WEEK GIVEN UNIDIRECTIONAL FLOW ALOFT AND A LIGHT
SOUTHWEST FLOW IN THE LOWER LEVELS. CHANCES FOR RAIN WILL INCREASE
BY MID NEXT WEEK (WED/THU) IN ASSOCIATION WITH AN INCREASINGLY
AMPLIFIED UPPER LEVEL PATTERN OVER THE EAST CONUS. -VINCENT
-- End Changed Discussion --

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 215 PM THURSDAY...

24-HR TAF PERIOD: EXPECT DETERIORATING CONDITIONS FROM SOUTH TO NORTH
THIS EVENING INTO TONIGHT AS PRECIP OVERSPREADS THE REGION FROM THE
NORTH IN ADVANCE OF A LOW PRESSURE SYSTEM TRACKING NORTHEAST FROM
THE GULF OF MEXICO TO THE CAROLINA COAST. PRECIP WILL FALL PRIMARILY
AS RAIN AT THE FAY/RWI TERMINALS...A WINTRY MIX BETWEEN 00-06Z AT
THE RDU TERMINAL...AND A LONGER PERIOD OF WINTRY WEATHER AT THE
INT/GSO TERMINALS WHERE A WINTER STORM WARNING IS NOW IN EFFECT.
NORTHEAST/NNE WINDS AT 10-15 KT WITH GUSTS UP TO 20-25 KT CAN BE
EXPECTED THROUGH TONIGHT AND FRIDAY MORNING. ADVERSE AVIATION
CONDITIONS (IFR/LIFR) WILL PERSIST THROUGH THE REMAINDER OF THE TAF
PERIOD (18Z FRI).

LOOKING AHEAD: CONDITIONS WILL IMPROVE TO VFR FRIDAY EVENING INTO
FRIDAY NIGHT AS THE LOW PRESSURE SYSTEM TRACKS FURTHER OFFSHORE. VFR
CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE WEEKEND AND EARLY
NEXT WEEK. -VINCENT

&&

.RAH WATCHES/WARNINGS/ADVISORIES...

WINTER STORM WARNING FROM 9 PM THIS EVENING TO NOON EST FRIDAY FOR
NCZ007-021>023-038.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING
TO NOON EST FRIDAY FOR NCZ008-009-024-025-039-040-073-074.

&&

$$

SYNOPSIS...BADGETT
NEAR TERM...BADGETT
SHORT TERM...VINCENT
LONG TERM...VINCENT
AVIATION...VINCENT