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000
FXUS62 KRAH 160056 RRA
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
855 PM EDT SAT MAR 15 2014

.SYNOPSIS...
A WEAK COLD FRONT WILL SETTLE SOUTH THROUGH THE CAROLINAS
TONIGHT. MEANWHILE...AN AREA OF LOW PRESSURE WILL DEVELOP OVER
THE SOUTHERN PLAINS AND THEN TRACK EASTWARD ALONG THE NORTHERN
GULF COAST STATES AND COASTAL CAROLINAS SUNDAY AND SUNDAY NIGHT.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
AS OF 855 PM SATURDAY...

LATEST SURFACE ANALYSIS SHOWS A WEAK BOUNDARY...MAINLY DENOTED BY A
WIND SHIFT TO NW AND ABOUT A 5-10 DEG DEWPOINT DROP...ALONG A KFVX-
KDAN-KHKY LINE. THIS BOUNDARY IS PROGGED BY THE LATEST HRRR TO
CONTINUE DRIFTING SOUTH OVERNIGHT...BUT HAVING LITTLE OR NO IMPACT
ON OUR SENSIBLE WEATHER DURING THAT TIME. OTHERWISE...MID AND HIGH
CLOUDS WILL CONTINUE TO THICKEN AND LOWER OVERNIGHT AHEAD OF THE
STORM SYSTEM TO OUR WEST. THIS WILL IMPACT OUR TEMP TREND
OVERNIGHT...WITH LIMITED IF ANY RADIATIONAL COOLING THE REST OF THE
NIGHT. BOTH MAV AND MET GUIDANCE WAS ABOUT 2-4 DEG TOO COLD FOR ITS
00Z PROG. THUS MAKING APPROPRIATE ADJUSTMENTS SUGGESTS LOWS TONIGHT
BOTTOMING OUT IN MID-UPR 40S...COLDEST NORTH.  WILL MAKE A FEW
SUBTLE TWEAKS TO THE TEMP GRIDS FOR OVERNIGHT...OTHERWISE...REST OF
THE 1ST PERIOD FORECAST LOOKS GOOD FOR THE EVENING UPDATE.

SUNDAY AND SUNDAY NIGHT...
THE UPPER TROUGH TO OUR WEST WILL UNDERGO A SLOW EVOLUTION OVER THE
NEXT COUPLE OF DAYS...BECOMING ELONGATED AND POSITIVELY TILTED WEST
OF THE APPALACHIANS.  A SURFACE LOW IS FORECAST TO MOVE TOWARD THE
TN VALLEY ON SUNDAY...WITH A SECONDARY LOW DEVELOPING OFF THE
CAROLINA COAST SUNDAY NIGHT.  PRECIPITATION...MOSTLY FOCUSED ALONG
AN 850MB FRONT TO OUR SOUTH SUNDAY MORNING...WILL OVERSPREAD THE
AREA FROM SOUTHWEST TO NORTHEAST DURING THE DAY AS THE FRONT PUSHES
NORTH AND ISENTROPIC LIFT INCREASES ATOP A WEAK IN-SITU CAD AIRMASS.
PRECIPITABLE WATER PEAKS AROUND 1.3 INCHES AND A ROUGH MODEL
CONSENSUS GIVE 1 TO 1.25 INCHES OF QPF THROUGH 06Z...GREATEST
ACROSS THE SOUTH AND WEST. MID-LEVEL LAPSE RATES ARE FAIRLY WEAK
THROUGH THE PERIOD..SO ELEVATED CONVECTION DOES APPEAR TO BE AN
ISSUE...WITH ALL LOW-LEVEL BASED INSTABILITY OFFSHORE. HAVE
HIGHLIGHTED THE POTENTIAL FOR MINOR RIVER FLOODING...MAINLY ALONG
THE NEUSE...IN THE HYDROLOGY SECTION BELOW.

TEMPS ARE TRICKY AND WILL FOLLOW A NON-DIURNAL CURVE WITH BEST HEAT
ACROSS THE NORTH PRIOR TO THE ARRIVAL OF LOWER CLOUD BASES AND
PRECIP.  EXPECT TEMPS TO REACH THE LOW TO MID 50S ACROSS THE NORTH
EARLY ON...WITH MID 40S NORTHWEST AND UPPER 40S POSSIBLE IN THE
NORTH.

THE FORECAST BECOMES EXTRA TRICKY SUNDAY NIGHT AS A SECONDARY
FRONT AND LEADING EDGE OF A CANADIAN AIRMASS PUSHES INTO NC FROM
THE NORTH. THE PARENT SURFACE HIGH...WHILE NOT VERY STRONG
(1025MB)...WILL SETTLE TOWARD UPSTATE NY...AND ALL MODELS HAVE
TRENDED COLDER WITH BOUNDARY LAYER TEMP PROFILES BETWEEN 06 AND
12Z MONDAY MORNING. THE SURFACE WETBULB FREEZING LINE IS FORECAST
TO PUSH INTO THE NORTHWEST AND NORTHERN PIEDMONT AREAS BETWEEN 06Z
AND 09Z...REACHING ROUGHLY A LING FROM DAVIDSON TO ORANGE TO VANCE
COUNTIES BY 12Z. THE BIGGEST UNCERTAINTY DURING THIS TIME FRAME
WILL BE QPF AS A DRY SLOT PUNCHES NORTHEAST ACROSS THE AREA...ICE
NUCLEATION IS LOST...AND PRECIP RATES FALL OFF TREMENDOUSLY. A TOP
DOWN APPROACH WOULD FAVOR RAIN CHANGING TO FREEZING RAIN AND
DRIZZLE BY 12Z....WITHOUT A SIGNIFICANTLY COLD ENOUGH COLD NOSE
FOR MORE THAN A BRIEF PERIOD OF SLEET DURING THE TRANSITION...WHEN
MOISTURE IS STILL SUFFICIENTLY DEEP ENOUGH FOR ICE ALOFT. WITH
MODELS SHOWING ONLY A FEW HUNDREDTHS OF QPF...ITS DIFFICULT TO
HAVE MUCH CONFIDENCE IN SIGNIFICANT ICE ACCRUAL...BUT AN ADVISORY
MAY BE NEEDED. POPS WILL REMAIN IN THE LIKELY CATEGORY BECAUSE
MOST AREAS WILL CONTINUE TO SEE SOME FORM OF LIGHT PRECIP...BUT
ACCUMULATION WILL BE VERY LIGHT. LOWS 31-32 IN THE AREAS MENTIONED
FOR FREEZING RAIN AND 33- 40 TO THE SOUTH AND EAST.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
AS OF 300 PM SATURDAY...

BY MONDAY MORNING...BOTH THE GFS AND THE NAM FORECAST DRYING IN THE
MID-LEVELS MOVING INTO CENTRAL NORTH CAROLINA. HUMIDITIES ARE
LIMITED ABOVE THE MOIST BOUNDARY LAYER TO NEAR -10C...WHICH MAY MAKE
ICE NUCLEATION DIFFICULT FOR SUBSTANTIAL PRECIPITATION FOR MUCH OF
THE DAY. IF THIS OCCURS...WHILE THE SURFACE WET BULB TEMPERATURE IS
BELOW 0C FOR MUCH OF THE DAY IN THE NORTHWEST PIEDMONT IN
PARTICULAR...THE PRECIPITATION RATES MAY BE LIGHT. THE LATEST WRF
GUIDANCE SUGGESTS THIS...AND QPF FROM THE GFS AND THE NAM IS LIGHT
FOR THE DAY ON MONDAY. ASSUMING THE QPF IS ACCURATE...THIS IS
FORTUNATE AS IF THE PRECIPITATION RATES WERE HIGHER...WITH A GOOD
COLD NOSE IN PLACE...JUST A LITTLE MORE SATURATION COULD RESULT IN
TEMPERATURES COOLING TO THE WET BULB AND STAYING THERE...AND THE
PRECIPITATION TYPE THROUGHOUT THE DAY WOULD ALMOST CERTAINLY BE NON-
LIQUID. HOWEVER...DESPITE A CLOUDY DAY AND A NORTHEAST FLOW...IF
PRECIPITATION RATES WANE AS EXPECTED...TEMPERATURES MAY BE ABLE TO
RISE EVEN A LITTLE BIT...AND LOWER PRECIPITATION RATES WOULD MEAN
MORE OF A LIGHT RAIN OR LIGHT DRIZZLE WITH SOME PATCHY SLEET OUTSIDE
OF LIGHT FREEZING RAIN IN THE MORNING WHERE TEMPERATURES ARE BELOW
FREEZING. FOR THE SENSIBLE WEATHER MONDAY WILL ONLY SHOW LIQUID
MAINLY SOUTH OF A LINE FROM ABOUT ALBEMARLE TO WILSON...WITH A
CHANCE OF A WINTRY MIX NORTH OF THIS LINE THROUGHOUT THE DAY. WILL
GO WITH LIKELY POPS FOR THE DAY AS A WHOLE...THOUGH EXPECT THERE
WILL BE PERIODS OF DRY CONDITIONS OR...AGAIN...JUST LIGHT
PRECIPITATION. DAYTIME HIGHS CERTAINLY WELL BELOW NORMAL...ONLY MID
TO UPPER 30S NORTH OF U.S. 64...AND NEAR 40 TO 45 FROM THERE SOUTH.

THE FORECAST MONDAY NIGHT IS ALSO QPF DEPENDENT...AND WHILE THE NAM
IS DRIER...THE GFS AND THE NEW ECMWF ARE NOTICEABLY WETTER...WITH AS
MUCH AS A QUARTER-INCH OF QPF OVERNIGHT MONDAY AS THE UPPER TROUGH
APPROACHES CENTRAL NORTH CAROLINA FROM THE WEST. IF THIS TREND
CONTINUES...GIVEN THE TEMPERATURE PROFILE ALOFT THIS COULD BE THE
PERIOD WHERE PRECIPITATION TYPE PROBLEMS COULD BE MOST ACUTE...
ESPECIALLY FROM THE TRIANGLE WEST AND NORTH. THIS WOULD ALSO BE A
SLIGHTLY MORE FAVORABLE TIME FOR CONCERN DUE TO THE TIME OF DAY...OR
NIGHT. LOW TEMPERATURES IN THAT AREA ARE FORECAST A COUPLE OF
DEGREES BELOW FREEZING OR SO... AND THE BUFR SOUNDINGS ARE STILL
COLD...YIELDING A LIKELIHOOD OF NON-LIQUID PRECIPITATION AS SURFACE
WET BULB TEMPERATURES THERE CONTINUE TO BE BELOW 0C. WHILE AN
ADVISORY-TYPE SCENARIO OVERALL IS PREFERRED AT PRESENT AS THE EVENT
DRAWS NEAR...IF THERE WAS ONE PERIOD IN THIS PART OF THE FORECAST
WHERE WINTER WEATHER HEADLINES MAY NEED TO BE RAISED A
CATEGORY...THIS COULD BE THE ONE. PRUDENT TO SEE HOW GUIDANCE TRENDS
REGARDING THIS FIFTH PERIOD FORECAST FOR NOW.

ON TUESDAY...WET BULB TEMPERATURES AND 1000-850MB THICKNESSES SHOULD
GRADUALLY RISE AS SURFACE LOW PRESSURE STARTS TO MOVE NORTH ALONG
THE CAROLINA COAST...AND COLD SURFACE HIGH PRESSURE STARTS TO
RETREAT. FOR THIS FORECAST CONFINED ANY PRECIPITATION-TYPE ISSUES TO
EARLY IN THE DAY...NOTING BY LATE MORNING ONLY LIQUID PRECIPITATION
IN CENTRAL NORTH CAROLINA. MORE CONFIDENT IN LIKELY CHANCES TO START
THE DAY...THEN DEPENDING ON THE TRACK AND SPEED OF LOW PRESSURE OFF
OF THE COAST...DIMINISHED POPS TO CHANCE BY LATE IN THE DAY...THOUGH
AT A MINIMUM IT SHOULD STILL BE CLOUDY AND DAMP. HIGHS AROUND 40 IN
THE NORTHWEST PIEDMONT...TO AROUND 50 IN THE FAR SOUTHEAST...LEANING
TOWARD THE ECMWF MOS MEAN TEMPERATURE GUIDANCE THEN.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 300 PM SATURDAY...

FOR MUCH OF THIS PERIOD...IN GENERAL...THE GFS IS THE MORE
PROGRESSIVE MODEL WITH SURFACE AND UPPER-LEVEL FEATURES...WHILE THE
ECMWF IS MORE AMPLIFIED AND SLOWER. BOTH MODELS...HOWEVER...SUGGEST
SURFACE HIGH PRESSURE BEGINNING TO RETREAT LATE TUESDAY INTO
WEDNESDAY...SUCH THAT AS SURFACE LOW PRESSURE REMAINS NEAR THE
CAROLINA COAST...AND LOW-LEVEL MOISTURE LINGERS...1000-850MB
THICKNESSES RISE OVERNIGHT AND MODEL SOUNDINGS SUGGEST WARMING AS
WELL. WET BULB SURFACE TEMPERATURES AFTER 00Z WEDNESDAY ON BOTH
MODELS REMAIN 35F OR ABOVE...ALSO SUGGESTIVE THAT LINGERING
PRECIPITATION TUESDAY NIGHT INTO WEDNESDAY SHOULD BE LIQUID. MOST
PRECIPITATION THAT OCCURS SHOULD BE LIGHT...AS THE MID LEVELS ARE
CURRENTLY FORECAST TO BE RATHER DRY...AND WHAT MAY BE THE SENSIBLE
WEATHER RESULT OVER MOST OF CENTRAL NORTH CAROLINA IS PATCHES OF
LIGHT RAIN AND AREAS OF DRIZZLE. HOW MUCH CLEARING TAKES PLACE
WEDNESDAY IS SOMEWHAT UNCERTAIN GIVEN THE SLOWER EASTWARD PROGRESS
OF THE ECMWF AND DRIER AIR...BUT FOR THIS FORECAST WILL MENTION
SMALL CHANCES OF RAIN WEDNESDAY MORNING FOLLOWED BY DRY CONDITIONS
BY WEDNESDAY AFTERNOON USING A BLEND OF THE GFS AND ECMWF. HAVE
TRENDED TEMPERATURES COLDER WEDNESDAY FOR THIS FORECAST ANTICIPATING
MORE CLOUDS AT LEAST THROUGH THE FIRST HALF OF THE DAY...IN A
RELATIVE SENSE WARMEST SOUTHWEST INTO THE MID 60S WHERE ANY CLEARING
SHOULD TAKE PLACE EARLIEST.

FRONTAL TIMING REMAINS DIFFERENT ON THE GFS AND ECMWF WITH THE GFS
BRINGING A FRONT THROUGH DRY WEDNESDAY EVENING...AND THE ECMWF
BRINGING A FRONT THROUGH MOSTLY DRY DURING THURSDAY. THESE SOLUTIONS
ARE FAIRLY CONSISTENT WITH THE PREVIOUS RUNS OF THE INDIVIDUAL
MODELS...ALBEIT DRIER. SURFACE RIDGING OVER THE GULF SHOULD LIMIT
MOISTURE RETURN...ALTHOUGH THE ECMWF DOES HAVE QPF FROM THE COASTAL
PLAIN TOWARD THE COAST THURSDAY AFTERNOON LIKELY AS THE FRONT WITH
ITS ECMWF TIMING INTERACTS WITH A LITTLE MORE AVAILABLE MOISTURE AND
INSTABILITY TOWARD THE COAST. FOR THIS FORECAST...WILL SHOW DRY
CONDITIONS ESPECIALLY GIVEN THE GENERAL STABILITY OF THE COARSE
ECMWF MODEL SOUNDINGS...AND THE DRY AND STABLE GFS SOUNDINGS...
THOUGH AN ALTERNATIVE COULD BE A SMALL CHANCE OF SHOWERS MAINLY EAST
OF U.S. 1 WITH THE FRONTAL PASSAGE THURSDAY IF THE ECMWF VERIFIES
EXACTLY. THURSDAY COULD END UP BEING MODESTLY BREEZY...BUT THE
SURFACE DEW POINTS AS CURRENTLY FORECAST SHOULD KEEP ANY INCREASED
FIRE DANGER CONCERNS NEGLIGIBLE.

AT THE END OF THE PERIOD...THE ECMWF IS ACTUALLY A LITTLE MORE
PROGRESSIVE WITH THE APPROACH OF A SURFACE FRONT TRAILING A STRONG
SURFACE LOW MOVING THROUGH THE GREAT LAKES. SURFACE RIDGING ALONG
THE GULF DIMINISHES MORE ON THE GFS THAN THE ECMWF...SUCH THAT WHILE
THE ECMWF IS FAIRLY DRY WITH THE FRONTAL PASSAGE THE GFS ADVECTS
MORE MOISTURE NORTHWARD AND DEVELOPS A BETTER CHANCE FOR SHOWERS
DURING THE DAY SATURDAY...AND INTO SATURDAY NIGHT. WILL FORECAST
BROAD SLIGHT CHANCES FOR SHOWERS THROUGHOUT CENTRAL NORTH CAROLINA
SATURDAY DUE TO THE UNCERTAINTY OUT TO THE SEVENTH DAY...BUT A
PLAUSIBLE SCENARIO IS THAT MUCH OF THE DAY IS DRY...BREEZY AND WARM
AHEAD OF THE SURFACE FRONT...WITH SCATTERED SHOWERS POSSIBLE FROM
NORTHWEST TO SOUTHEAST IMMEDIATELY IN VICINITY OF THE FRONT AS IT
MOVES SOUTHEAST.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 810 PM SATURDAY...

VFR CONDITIONS WILL CONTINUE THROUGH THE OVERNIGHT HOURS... AS THE
PASSAGE OF DRY COLD FRONT FROM THE NORTHWEST IS MARKED ONLY BY A
WIND SHIFT FROM WSW TO NW AND THEN NE BY 06Z. RAIN WILL MOVE IN FROM
THE SW TOMORROW IN ASSOCIATION WITH A LOW PRESSURE SYSTEM... AND
WILL OVERSPREAD THE AREA BETWEEN 15-18Z... WITH MVFR CIGS.
CONDITIONS WILL LIKELY DETERIORATE TO IFR BETWEEN 18Z-21Z.

OUTLOOK... RAIN...POSSIBLY CHANGING TO FREEZING RAIN IN THE TRIAD
WILL COME TO AN END MONDAY MORNING. THERE IS HIGH CONFIDENCE THAT
POOR AVIATION CONDITIONS WITH LOW CLOUDS AND DRIZZLE WILL THEN
CONTINUE THROUGH MONDAY AND AT LEAST INTO TUESDAY. CONDITIONS MAY
NOT IMPROVE UNTIL WEDNESDAY.

&&

.HYDROLOGY...
AS OF 300 PM SATURDAY...

BASED ON THE LATEST QPF...AND CURRENT AND FORECAST RIVER LEVELS...
THE GREATEST POTENTIAL FOR MINOR FLOODING SHOULD BE ON THE NEUSE
RIVER AT SMITHFIELD. FLASH FLOOD GUIDANCE IS MOSTLY IN THE THREE-
INCH RANGE OR BETTER OVER SIX HOURS IN CENTRAL NORTH CAROLINA...SO
FOR THIS FORECAST PLAN TO REFRAIN FROM ANY FLOOD WATCHES. WILL
CONTINUE TO MENTION MAINSTEM RIVER RISES IN THE HWO...WITH A
POSSIBILITY OF MINOR FLOOD STAGES IN GENERAL...BUT IT APPEARS THE
PROBABILITY OF MINOR FLOOD STAGE BEING REACHED IS HIGHEST AT
SMITHFIELD.

&&

.CLIMATE...

FOR INFORMATIONAL PURPOSES...THE RECORD LOW MAXIMUM TEMPERATURES FOR
MARCH 17 ARE...

KGSO...38 DEGREES FROM 2005.
KRDU...32 DEGREES FROM 1892.
KFAY...39 DEGREES FROM 2005.

&&

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

&&

$$

SYNOPSIS...SMITH
NEAR TERM...NP/SMITH
SHORT TERM...DJF
LONG TERM...DJF
AVIATION...SEC/SMITH
HYDROLOGY...DJF
CLIMATE...DJF