FXUS62 KRAH 151922
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
222 PM EST TUE JAN 15 2008

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE WEST TONIGHT
AND WEDNESDAY. A LOW PRESSURE SYSTEM WILL DEVELOP IN THE GULF OF
MEXICO ON WEDNESDAY AND THEN TRACK NORTHEAST ALONG THE CAROLINA
COAST LATE WEDNESDAY AND THURSDAY.
&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 215 PM TUESDAY...
LATEST SFC ANALYSIS AT 18Z SHOWS SFC MOVING INTO THE COASTAL 
PLAIN. WINDS HAVE BECOME NW AT KHNZ, KRDU, AND KMEB. DEWPOINTS
ARE DROPPING INTO THE 5 TO 10 DEG RANGE ACROSS TE WESTERN PIEDMONT
BASED ON DRIER AIR ADVANCING INTO THE REGION AND SOME DOWNSLOPING.
BAND OF MOISTURE AROUND THE 850 TO 750 MB LAYER CONTINUES TO
PRODUCE SOME STRATO-CU WITH SCT/BKN CIGS. SKIES SHOULD CLEAR IN
THE NEXT FEW HOURS WITH TE LOSS OF DIURNAL HEATING...A DRYING AIR
MASS AND AN EASTWARD ADVANCEMENT OF THE 850 MB TROF AXIS. GUSTY
WINDS SHOULD DIMINISH AS HEATING SUBSIDES AND SFC WIND FIELD WILL
SLACKEN THIS EVE AS SFC GRADIENT DIMINISHES WITH A BUILDING SFC
RIDGE.

TROFINESS AT 500 MB ACROSS THE MID ATLANTIC AND NORTHEAST TONIGHT 
GIVES WAY TO RIDGING ON WED. THE 500 MB RIDGE AXIS IS LOCATED
ACROSS THE APPALACHIANS WED AFTN AND THEN SHIFTS OFF THE COAST
DURING THE EVE. LOW LEVEL COLD ADVECTION THIS EVE DIMINISHES
OVERNIGHT AND IS NEUTRAL ON WED WITH 850 RIDGE OVERHEAD.

THE RESULTING WEATHER WILL FEATURE CLEAR SKIES TONIGHT WITH 
INCREASING HIGH CLOUDS ON WED AFTERNOON. DIMINISHING WINDS
TONIGHT AND A COLD AIR MASS WILL PRODUCE COLD TEMPS TONIGHT.
CONSENSUS MOS GUIDANCE GIVES LOWS IN THE LOWER 20S. MOS GUIDANCE
CONSISTENT ON WED WITH TEMPS ABOUT 5 DEG BELOW NORMAL IN THE MID
40S. -BLAES

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 145 PM TUESDAY...
JET STREAM WINDS STRENGTHEN IN SW FLOW AHEAD OF A LARGE AMPLITUDE
TROUGH OVER THE SOUTHERN PLAINS. THIS HELPS INDUCE LOW PRESSURE
DEVELOPMENT OVER THE NE GULF OF MEXICO WED NIGHT. MODELS ARE IN
GOOD AGREEMENT WITH A SURFACE LOW TRACKING NE TO NEAR CHARLESTON
SC MIDDAY THU TO NEAR THE NE NC COAST AROUND MIDNIGHT THU NIGHT.
AHEAD OF THE LOW...EASTERLY LOW LEVEL FLOW VEERS WITH HEIGHT
SHOWING STRONG ISENTROPIC UPGLIDE...35-55 KNOTS CROSS CONTOUR
FLOW...WITHIN SATURATED AIR ATOP A VERY COLD SURFACE BASED LAYER.
ALTHOUGH THE SURFACE HIGH IS SOMEWHAT PROGRESSIVE...IT STARTS WITH
A 1030 CENTER OVER SRN VA WED NIGHT WHICH IS PLENTY STRONG TO
MAINTAIN CAD AT THE THROUGH THE ONSET OF OVERRUNNING PCPN AND
POSSIBLY MOST OF THE DAY IN THE TRIAD AREA. WITH SURFACE DEW
POINTS STARTING IN THE TEENS TO LOWER 20S LATE WED
NIGHT...TEMPERATURES IN THE 30S WED NIGHT WILL DROP INTO THE 28-32
RANGE OVER THE NW TWO-THIRDS ONCE PCPN BEGINS TOWARD DAYBREAK THU.

A WINTER STORM WATCH IS BEING ISSUED FOR THE NW PIEDMONT...ROUGHLY 
NW OF A LINE FROM ROXBORO TO BURLINGTON TO ASHEBORO...FOR 4AM-4PM 
THU. HERE...THERE MAY BE A BRIEF SPURT OF SNOW...THEN SLEET AROUND 
DAYBREAK THU...THEN FREEZING RAIN WITH TEMPERATURES HOLDING NEARLY 
STEADY SLIGHTLY BELOW FREEZING IN MID TO LATE DAY HOURS.  A CORRIDOR 
JUST SE TO NEAR A LINE FROM ROANOKE RAPIDS TO RALEIGH TO SOUTHERN 
PINES TO ROCKINGHAM MAY ALSO HAVE A PERIOD OF SLEET OR FREEZING RAIN 
AROUND DAYBREAK THU...BUT TURNING MORE QUICKLY TO RAIN THAN IN THE 
WATCH AREA. A WINTER WEATHER ADVISORY MAY BE NEEDED FOR THIS 
CORRIDOR.  HIGHS IN THIS AREA AND SOUTHEAST WILL STRUGGLE INTO THE 
MID TO UPPER 30S THU AFTERNOON.

MODEL CONSENSUS CALLS FOR TAPERING PCPN AROUND NIGHTFALL WITH NW LOW 
LEVEL FLOW AND PARTIALLY CLEARING SKIES SAVE CIRRUS CLOUDINESS BY 
DAYBREAK FRI.  THERE MAY BE A POTENTIAL FOR BLACK ICE FORMATION WITH 
TEMPERATURES SLIGHTLY BELOW FREEZING NW HALF FRI MORNING.  

FRIDAY...HIGH CLOUDINESS SPREADS INTO THE AREA WITH FAST SW FLOW 
ALOFT WELL AHEAD OF ANOTHER DISTURBANCE BREWING IN THE GULF.  THIS 
SHOULD LIMIT TEMPERATURE RISE WITH THE SOUTHERN STREAM MODIFIED 
PACIFIC AIRMASS. THICKNESS IMPLIES 50-ISH READINGS...BUT WITH COLD 
GROUND AND FILTERED SUNSHINE...MID 40S IS MORE LIKELY.  -RFG

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...
MEDIUM RANGE MODELS MAINTAIN A LARGE PLANETARY WAVE OVER THE CONUS 
DURING THE PERIOD WITH THE POTENTIAL FOR SOUTHERN STREAM SHORTWAVES 
TO GENERATE LOW PRESSURE DISTURBANCES IN THE GULF AND UP THE EAST 
COAST.  TIMING AND LOCATION OF THE SHORTWAVES AND THEIR IMPACT ON 
CENTRAL NC WEATHER ARE VERY UNCERTAIN AT THIS TIME GIVEN THEIR 
ORIGIN OF THE COMPLEX BUT ENERGETIC PATTERN OVER THE NORTH PACIFIC.

CONSENSUS OF THE LATEST GUIDANCE APPEARS TO FAVOR ONE DISTURBANCE 
BRUSHING BY TO OUR SOUTH FRI NIGHT OR SAT AND THEN ANOTHER AROUND 
TUE OF NEXT WEEK.  BOTH WILL BE HANDLED AT THIS TIME AS CHANCE COLD 
RAIN EVENTS.  ONCE MODEL RESOLUTION AND CONSISTENCY IMPROVES... WE 
MAY FIND P-TYPE ISSUES...MAINLY FOR THE ONSET OF EACH EVENT AND IN 
THE CLIMATOLOGICALLY FAVORED IMPACT AREA NW HALF OF THE CWA. -RFG
&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AS OF 100 PM TUESDAY...
VFR CONDITIONS ARE EXPECTED THROUGHOUT THE TAF PERIOD. SFC TROUGH 
WAS MOVING THROUGH CENTRAL NC EARLY THIS AFTN. A BAND OF SHALLOW 
STARTO-CU WAS NOTED ON VIS SAT AND SFC OBS ACROSS THE NE PIEDMONT 
AND N COASTAL PLAIN. SOME ENHANCEMENT CAN BE SEEN ON SAT/RADAR BUT 
DRY LOW LEVELS SHOULD KEEP ANY LIGHT PRECIP ALOFT AND AWAY FROM SFC. 
STRATO-CU SHOULD DIMINISH QUICKLY THIS EVE WITH THE LOSS OF HEATING 
AND AS DRIER AIR MASS MOVES IN. CLEAR SKIES ARE EXPECTED OVERNIGHT. 
W TO NW WINDS WILL DIMINISH AS WELL THIS EVE. SHOULD BE ENOUGH OF A 
GRADIENT TO KEEP WINDS GOING THROUGH MIDNIGHT AND THEN THEY SHOULD 
BECOME VERY LIGHT AFTER MIDNIGHT. SKC CONDITIONS AND LIGHT WINDS ARE 
EXPECTED ON WED WITH SFC HIGH BUILDING INTO THE MID ATLANTIC. HIGH 
LEVEL MOISTURE SHOULD INCREASE DURING THE AFTERNOON AS MID LEVEL 
RIDGE AXIS MOVES OVERHEAD RESULTING IN SCT-BKN CIRRUS CLOUDS. 

A LOW PRESSURE SYSTEM WILL DEVELOP OVER THE NORTHERN GULF OF MEXICO 
ON WEDNESDAY AND TRACK NORTHEAST NEAR THE SOUTHEAST COAST WEDNESDAY 
NIGHT AND THURSDAY. CLOUDINESS WILL INCREASE WED AFT AND WED NIGHT. 
PRECIPITATION IS EXPECTED TO OVERSPREAD CENTRAL NC NEAR DAYBREAK ON 
THURS AND TAPER OFF THURS EVENING. WIDESPREAD MVFR CONDITIONS WITH 
POTENTIAL IFR CONDITIONS IN PRECIPITATION CAN BE EXPECTED DURING THE 
DAY THURSDAY. VFR CONDITIONS ARE EXPECTED TO RETURN ON FRIDAY BEFORE 
ANOTHER SFC LOW PRESSURE SYSTEM MOVES NORTHEAST ALONG THE COAST 
BRINGING ANOTHER CHANGE OF PRECIPITATION LATE FRIDAY AND SATURDAY. 
AN ARCTIC AIRMASS WILL BUILD INTO THE REGION ON SUN AND VFR 
CONDITIONS SHOULD RETURN. -BLAES

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY 
AFTERNOON FOR NCZ007-021>023-038-039.

&&

$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...RFG
LONG TERM...RFG
AVIATION...BLAES