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000
FXUS62 KRAH 161927
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
320 PM EDT SUN MAR 16 2014

.SYNOPSIS... AN AREA OF LOW PRESSURE WILL DEVELOP OVER THE SOUTHERN
PLAINS TODAY AND THEN TRACK EASTWARD ALONG THE NORTHERN GULF COAST
STATES AND COASTAL CAROLINAS THROUGH TONIGHT.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 320 PM SUNDAY...

AN COLD FRONT SLOWLY MAKING ITS WAY THROUGH VA THIS AFTERNOON MARKS
THE LEADING EDGE OF ARCTIC AIR ASSOCIATED WITH HIGH PRESSURE IVER
THE GREAT LAKES REGION.  MEANWHILE...AN ELONGATED AND
COMPLEX...POSITIVELY TILED UPPER TROUGH IS EVOLVING OVER THE
SOUTHERN PLAINS...WITH A LEAD SHORTWAVE AND ASSOCIATED 1002MB
SURFACE LOW KICKING NORTHEAST ACROSS THE LOWER/MID MS RIVER VALLEY
REGION. WARM ADVECTION AND ISENTROPIC LIFT ARE MOSTLY DRIVING THE
EXPANSIVE PRECIP SHIELD THAT HAS FINALLY SPREAD ACROSS ALL OF
CENTRAL NC...WITH THE HEAVIEST PRECIP FOCUSED ALONG AND 850MB WARM
FRONT PUSHING INTO SOUTHERN NC. A DRY SLOT MOVING INTO WESTERN NC IS
RAPIDLY DEPLETING MOISTURE ALOFT AND PRECIP IS DWINDLING OVER THE
FOOTHILLS.  HRRR RUNS SUGGEST THIS TREND WILL CONTINUE THIS
AFTERNOON...WITH THE BEST CHANCES AT A STEADY RAIN THROUGH 00Z.
AFTER 00Z...ICE NUCLEATION IS LOST AND ISENTROPIC LIFT
WEAKENS...SUGGESTING PRECIP WILL BECOME MORE DRIZZLY WITH TIME.

THE BIG QUESTION CONTINUES TO BE TEMPS TONIGHT AND THE POTENTIAL FOR
ICING.  MODEL GUIDANCE HAS OFFERED LITTLE TO CONFIDENCE TODAY...WITH
THE GFS AND NAM STILL SHOWING A 5C DIFFERENCE IN THE COLD NOSE THAT
DEVELOPS TONIGHT.  THE NAM DEPICTION OF A NEAR -10C COLD DOME SEEMS
EXTREME...SO HAVE ELECTED TO USE THE GFS AND ECMWF AND KEEP PRECIP
AS FREEZING RAIN WHEN TEMPS ARE BELOW FREEZING. DEWPOINTS ACROSS
NORTHERN VIRGINIA ARE IN THE TEENS AND THIS AIR WILL PUSH SOUTH
TONIGHT AS THE AFOREMENTIONED SURFACE HIGH MOVES EAST TOWARD NY AND
A WEAK SURFACE LOW DEVELOPS OFF THE CAROLINA COAST. THE SURFACE
WETBULB FREEZING LINE SHOULD PUSH INTO THE NORTHWEST NORTHERN
PIEDMONT AREAS BY AROUND 09Z.  HOWEVER.. THE SURFACE HIGH IS ONLY
AROUND 1025MB AND NOT IS THE MOST FAVORED POSITION...SO WITH ONLY
LIGHT PRECIP AND MARGINAL TEMPS...THIS STILL LOOKS TO BE AN ADVISORY
EVENT.  THERE IS NOTHING GLARING IN GUIDANCE OR OBS THAT SUGGESTS
MAKING ANY CHANGES TO THE ADVISORY THAT IS IN EFFECT....AND IMPACTS
SHOULD BE LIMITED WITH JUST A GLAZE IN TREES AND ELEVATED SURFACES.

MONDAY...
LACK OF SIGNIFICANT PRECIP AND WEAKENING WINDS SHOULD ALLOW TEMPS TO
NUDGE UP A DEGREE OR TWO DURING THE DAY ON MONDAY...GETTING BACK
ABOVE FREEZING BY MIDDAY. NOT COMPLETELY CONVINCED THAT PRECIP WONT
PICK BACK UP AS THE ACTUAL UPPER TROUGH AXIS APPROACHES DURING THE
DAY...BUT MOISTURE PROFILES REMAIN DRY ALOFT.  WHILE DRIZZLE WILL
LIKELY CONTINUE WITH THE CAD AIRMASS WELL ENTRENCHED OVER THE
AREA...FREEZING DRIZZLE IS EXPECTED TO COME TO AN END...AT LEAST FOR
THE AFTERNOON PORTION OF THE DAY.  THUS THE ADVISORY SHOULD BE ABLE
TO END AT NOON. HIGHS 34-42.

&&

.SHORT TERM /MONDAY NIGHT AND TUESDAY/...
AS OF 320 PM SUNDAY...

THE GUIDANCE HAS DEFINITELY TRENDED DRIER WITH THE RECENT MODEL
RUNS...AS BOTH THE NAM AND THE GFS SHOW MINIMAL QPF IN CENTRAL NORTH
CAROLINA OVERNIGHT MONDAY NIGHT INTO TUESDAY. WHILE THE GFS...FOR
EXAMPLE...HAS A SURFACE LOW MAYBE WITH A TREND SLIGHTLY FARTHER
EAST...AND AN UPPER-LEVEL TROUGH FAIRLY CONSISTENT WITH ITSELF...
OVER THE LAST FOUR OR FIVE MODEL RUNS...THERE HAS BEEN A DEFINITE
TREND TOWARD DRIER MID-LEVEL AIR...NOTICEABLY DRIER AT 500MB AND
700MB OVER MUCH OF CENTRAL NORTH CAROLINA USING A BASIC DPROG/DT
FROM THE RUN OF 15/12Z TO THE RUN OF 16/12Z. THE NAM EXHIBITS THE
SAME TREND...WITH MARKED DRYING ONLY FROM ITS LAST MODEL RUN. WITH
THIS IN MIND...WHILE NOT WITH GREAT CONFIDENCE THAT FUTURE RUNS WILL
NOT RETURN THE MID-LEVEL MOISTURE BACK TO CENTRAL NORTH CAROLINA AND
INCREASE THE THREAT OF BETTER GLAZING MONDAY NIGHT INTO TUESDAY...
CERTAINLY THE CONFIDENCE IS TOO LOW...WITH MOS GUIDANCE POPS IN THE
CHANCE CATEGORY AT BEST...TO EXTEND OR INTRODUCE NEW HEADLINES.

THE MID-LEVEL TROUGH MOVES EAST OF THE CAROLINAS AND OFFSHORE
TUESDAY AFTERNOON. AT THE SAME TIME...THE SURFACE LOW SHOULD
GRADUALLY MOVE AWAY FROM THE CAROLINAS AS WELL. THE NAM IS MUCH
SLOWER THAN THE GFS AND ECMWF...THE LATTER IN BETWEEN...THOUGH THE
LATEST TREND OF THE NAM IS FARTHER OFFSHORE THAN ITS PREVIOUS MODEL
RUN. WILL LEAN TOWARD A SOLUTION SLOWER THAN THE GFS...CLOSER TO THE
ECMWF WHICH SEEMS TO BE A GOOD BLEND BETWEEN THE NAM AND THE GFS.

WITH 850MB LIFT MODEST AT BEST OVERNIGHT MONDAY INTO TUESDAY...AND
GENERAL 850MB THETA-E TROUGHINESS IN PLACE...FOR A LARGE PART OF
THIS PERIOD OVER MOST OF CENTRAL NORTH CAROLINA...WILL ONLY HAVE
CHANCE POPS. THE RIGHT ENTRANCE REGION OF THE 300MB JET IS JUST
SOUTHEAST OF THE AREA AS WELL. WILL BEGIN THE PERIOD MONDAY NIGHT
WITH LIKELY CHANCES IN THE SOUTHEAST WHERE MODEL SOUNDINGS ARE MOST
MOIST AT THAT POINT...BUT EVEN THERE THE MID-LEVELS ARE FORECAST TO
DRY DURING THE EVENING. WILL RETAIN CHANCE POPS ALTHOUGH...FOR MUCH
OF THE LATER EVENING AND OVERNIGHT HOURS...THE PRIMARY PRECIPITATION
TYPE...IF ANY...COULD BE FREEZING DRIZZLE OR DRIZZLE AND LATER
FORECASTS MAY ACTUALLY NEED TO ADJUST POPS DOWNWARD IF MODEL TRENDS
CONTINUE. JUST BEFORE SUNRISE...AS THE UPPER TROUGH GETS
CLOSER...THE UPPER LEVELS MOISTEN ENOUGH WHERE THERE COULD BE A
RETURN TO A BETTER CHANCE OF MEASURABLE PRECIPITATION WITH THE
HIGHER CHANCES FOR NOW EAST OF U.S. 1 CLOSER TO THE SURFACE LOW.
ONCE AGAIN THE MID AND UPPER LEVELS SEEM TO DRY TUESDAY AFTERNOON
WHICH SHOULD RESULT IN A RETURN TO MORE SPOTTY PRECIPITATION UNDER A
CLOUDY SKY. THE MENTION OF NON-LIQUID PRECIPITATION FOR THIS PART OF
THE FORECAST WILL BE MAINLY NORTH OF A LINE FROM ABOUT ALBEMARLE TO
WILSON.

DEPENDING ON HOW THE QPF EVOLVES AND HOW MUCH LINGERING MOISTURE
THERE WILL BE LATE MONDAY...AT THIS POINT THE THOUGHT IS THAT THERE
COULD BE THE NEED FOR ANOTHER WINTER WEATHER ADVISORY OVER PARTS OF
CENTRAL NORTH CAROLINA MONDAY NIGHT INTO EARLY TUESDAY. DURING
TUESDAY...THICKNESSES AND SURFACE WET BULB TEMPERATURES INCREASE
SUCH THAT...BY AFTERNOON...TEMPERATURES SHOULD BE WARM ENOUGH TO
PRECLUDE THE THREAT OF NON-LIQUID PRECIPITATION THROUGHOUT CENTRAL
NORTH CAROLINA. THE GRIDDED ICE ACCUMULATION FORECAST...WITH SOME
VERY LIGHT HOURLY AMOUNTS EVEN IN THE CHANCE CATEGORY OF
POPS...COULD END UP BEING A WORST CASE SCENARIO AND THOSE AMOUNTS
ARE...FOR THE ENTIRE EVENT...CURRENTLY AT ABOUT 0.15 INCH OR LESS.
DEFINITELY LEANED TOWARD THE COOLER MET MOS GUIDANCE FOR TUESDAY
WHICH IS CLOSE TO THE ECMWF MOS ENSEMBLE TEMPERATURES AND SEEMS TO
DO BETTER IN COLD AIR DAMMING SCENARIOS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
AS OF 315 PM SUNDAY...

A RIDGE ALOFT BUILDS IN FOR TUESDAY NIGHT...THEN IN A PROGRESSIVE
PATTERN DIFFLUENCE IS FORECAST OVER CENTRAL NORTH CAROLINA WEDNESDAY
BEHIND THE DEPARTING RIDGE...AND AHEAD OF AN UPPER LOW MOVING
THROUGH THE GREAT LAKES. A TROUGH ALOFT THEN MOVES THROUGH THE AREA
AGAIN THURSDAY EXTENDING FROM THAT GREAT LAKES UPPER LOW. AFTER A
FLAT RIDGE ALOFT FRIDAY...THE ECMWF IS DEEPER WITH A TROUGH ALOFT
MOVING THROUGH THE MID-ATLANTIC ON SATURDAY. THESE HIGH-LEVEL
SYNOPTIC TRENDS ARE SIMILAR TO THE GUIDANCE OF LATE FRIDAY INTO
SATURDAY.

LOW-LEVEL MOISTURE STILL SEEMS TO HAVE A HIGH PROBABILITY OF
LINGERING TUESDAY NIGHT INTO MUCH OF WEDNESDAY...AND WITH DRY MID
LEVELS ON BOTH GFS BUFR AND COARSE ECMWF SOUNDINGS...DRIZZLE AND
PATCHY LIGHT RAIN SHOULD PERSIST UNTIL A SURFACE TROUGH MOVES EAST
DURING THE DAY. WET BULB SURFACE TEMPERATURES AND SOUNDINGS WOULD
ALL SUGGEST A HIGH PROBABILITY OF LIQUID PRECIPITATION...ANOTHER
CONSISTENCY IN THE GUIDANCE OVER THE LAST DAY OR SO. WHILE SUCH A
PARAMETER WILL NOT BE FORECAST YET...IT WILL BE INTERESTING TO SEE
IF...AS SKIES CLEAR AND SURFACE DEW POINTS STAY UP AS CURRENTLY
FORECAST...AREAS OF FOG DEVELOP WEDNESDAY NIGHT ESPECIALLY ALONG AND
EAST OF U.S. 1 WHERE THE AIR SHOULD BE MORE MOIST AHEAD OF ANOTHER
SURFACE BOUNDARY HEADED TOWARD CENTRAL NORTH CAROLINA. HIGHS FOR
WEDNESDAY HAVE PROGRESSIVELY BEEN FORECAST COOLER AND WILL CONTINUE
THIS TREND FOR THIS FORECAST...CLOSER TO THE ECWMF MOS ENSEMBLE
GUIDANCE...BUT STILL A DEGREE OR TWO WARMER THAN THAT IN DEFERENCE
TO THE MEX MOS.

ON THURSDAY...ACCOMPANIED BY THE TROUGH ALOFT...THE ECMWF NOTES
SPOTTY QPF IN CENTRAL NORTH CAROLINA...WHILE THE GFS IS DRY. THE GFS
HAS A STRONGER SURFACE RIDGE THAT SHOULD PRECLUDE MOISTURE RETURN
AND STRONG CONVERGENCE ALONG THE FRONT. EVEN THE ECMWF HAS RIDGING
OVER THE GULF WHICH SHOULD ALSO HELP INHIBIT MOISTURE RETURN. AS
SUCH...WILL KEEP THURSDAY DRY IN THE FORECAST AND CONTINUE DRY
CONDITIONS ON FRIDAY UNDER SURFACE HIGH PRESSURE. AN ALTERNATIVE
COULD BE A SMALL CHANCE OF SHOWERS MAINLY TOWARD THE COASTAL PLAIN
AS THE FRONT INTERACTS WITH RELATIVELY HIGHER LOW-LEVEL MOISTURE...
COMPARED TO THE REST OF CENTRAL NORTH CAROLINA...LATER IN THE DAY.

THE HIGH RETREATS LATE FRIDAY AS A COLD FRONT APPROACHES CENTRAL
NORTH CAROLINA FROM THE NORTHWEST. THE MORE AMPLIFIED ECMWF IS
FASTER WITH THE FRONT AND COULD BRING PRECIPITATION INTO AT LEAST
THE WESTERN PIEDMONT AS EARLY AS SUNRISE SATURDAY. THE GFS...NOT AS
AMPLIFIED...IS SLOWER AND WOULD NOT INTRODUCE PRECIPITATION INTO
CENTRAL NORTH CAROLINA UNTIL MAINLY SATURDAY AFTERNOON AND SATURDAY
NIGHT...WITH A PROGRESSION NORTHWEST TO SOUTHEAST GRADUALLY ALONG
THE FRONT. AS THE HIGH RETREATS...THIS COULD ALSO BE A SITUATION
WHERE...WITH ENOUGH LOW-LEVEL MOISTURE RETURN FROM THE ATLANTIC...
SPOTTY SHOWERS COULD OCCUR LATE FRIDAY NIGHT INTO SATURDAY MORNING
CLOSER TO THE COAST. WILL NOTE JUST A SLIGHT CHANCE OF SHOWERS VERY
LATE FRIDAY NIGHT AND EARLY SATURDAY...WITH A CHANCE OF SHOWERS
SATURDAY AFTERNOON AND EVENING. SUNDAY SHOULD BE DRY AND COOL UNDER
HIGH PRESSURE...AND FOR NOW WILL SHOW A DRY SUNDAY NIGHT LOOKING
AHEAD TO POSSIBLY ANOTHER GULF SYSTEM IMPACTING THE SOUTHEAST AFTER
THIS LONG-TERM PERIOD.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 145 PM SUNDAY...

MEDIUM TO LOW CONFIDENCE IN THE CURRENT TAF PERIOD.   PRECIP AND LOW
CEILINGS HAVE BEEN SLOW TO SPREAD ACROSS CENTRAL NC FROM THE
SOUTHWEST...WITH RAIN JUST RECENTLY REACHING THE TRIAD TERMINALS AND
RDU.  CEILINGS ARE STILL AT VFR LEVELS...BUT ARE EXPECTED TO FALL TO
MVFR BY AROUND 21Z AND THEN TO IFR BY 03-06Z.  VSBYS WILL ALSO DROP
TO MOSTLY AROUND 3SM... POSSIBLY LOWER IN HEAVIER RAIN...WHICH IS
MORE LIKELY AT KRWI AND KFAY.  A COASTAL WILL DEVELOP OVERNIGHT AND
CAUSE NORTHEASTERLY WINDS TO INCREASE INTO THE 12-15KT RANGE. LATER
TONIGHT...COLDER AIR WILL PUSH INTO THE AREA FROM THE NORTH...AND A
PERIOD OF FREEZING RAIN OR DRIZZLE WILL BE POSSIBLE AT KGSO AND
KINT...MOSTLY BETWEEN 09Z AND 15Z.  PRECIP RATES WILL REMAIN LIGHT AND
IMPACTS ARE NOT EXPECTED TO BE SIGNIFICANT.  CEILINGS WILL REMAIN
LOW...LIKELY IN THE IFR TO MVFR RANGE THROUGH THE END OF THE TAF
PERIOD.

OUTLOOK... LOW CEILINGS WILL CONTINUE TO PLAGUE AREA TERMINALS
MONDAY INTO TUESDAY...WITH ANOTHER PERIOD OF FREEZING RAIN POSSIBLE
NORTH AND WEST OF KRDU ON MONDAY NIGHT AND EARLY TUESDAY.
IMPROVEMENT WILL LIKELY NOT COME UNTIL WEDNESDAY.

&&

.HYDROLOGY...
AS OF 1115 AM SUNDAY...

WITH FLASH FLOOD GUIDANCE STILL 2.5 INCHES OR GREATER FOR THREE
HOURS OR GREATER...WILL CONTINUE TO REFRAIN FROM ANY FLOOD WATCHES
GIVEN THE EXPECTED QPF. SHOULD NOTE THAT DEEP CONVECTION OVER THE
FAR SOUTHEAST CONUS MAY IMPACT SOME OF THE EXPECTED HIGHER RAINFALL
TOTALS OVER THE SANDHILLS AND COASTAL PLAIN OF CENTRAL NORTH
CAROLINA. CONSISTENTLY IT APPEARS THE PROBABILITY OF MINOR FLOOD
STAGE BEING REACHED IS HIGHEST AT SMITHFIELD WHERE A RIVER FLOOD
WARNING IS IN EFFECT...LESS SO AT CLAYTON...AND NOTICEABLY LOWER AT
OTHER MAINSTEM RIVER SITES EVEN BASED ON THE HIGHEST QPF AVAILABLE
ON THE ENSEMBLE RIVER LEVEL OUTPUT OF THE MMEFS.

&&

.CLIMATE...
THE RECORD LOW MAXIMUM TEMPERATURES FOR MARCH 17 (MONDAY) ARE...

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

THE RECORD LOW MAXIMUM TEMPERATURES FOR MARCH 18 (TUESDAY) ARE...

KGSO...36 DEGREES FROM 1961.
KRDU...36 DEGREES FROM 1892.
KFAY...41 DEGREES FROM 1998.


&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON EDT
MONDAY FOR NCZ007>009-021>023.

&&

$$
SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...DJF
LONG TERM...DJF
AVIATION...SMITH
HYDROLOGY...DJF
CLIMATE...DJF