Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 260752
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
252 AM EST MON JAN 26 2015

.SYNOPSIS... A STRONG UPPER LEVEL DISTURBANCE WILL CROSS THE REGION
TODAY INTO EARLY TONIGHT. CHILLY HIGH PRESSURE WILL BUILD IN FROM
THE NORTHWEST TUESDAY THROUGH WEDNESDAY NIGHT. A CLIPPER LOW
PRESSURE SYSTEM WILL MOVE THROUGH THE AREA THURSDAY INTO EARLY
FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 250 AM MONDAY...

INFRARED SATELLITE SHOWS LOW PRESSURE ASSOCIATED WITH THE CLIPPER
SYSTEM MOVING IN FROM THE NORTHWEST OVER EASTERN KY AT THIS TIME.
THIS SYSTEM WILL COMBINE WITH SOUTHERN STREAM MOISTURE OFF OF THE
SOUTHWEST ATLANTIC TO AND RESULT IN A DEEPENING LOW PRESSURE SYSTEM
THAT IS EXPECTED TO STRENGTHEN CONSIDERABLY AS IT MOVES UP THE
EASTERN SEABOARD MONDAY INTO TUESDAY. CENTRAL NC WILL NOT HAVE TO
DEAL WITH THE EXTENSIVE PLUME OF MOISTURE OVER THE OCEAN SO THE
WAVE...WHICH IS PROGGED TO MOVE ACROSS NORTHERN SECTIONS OF THE THE
CWA LATER TODAY WILL NOT BRING MUCH PRECIPITATION WITH IT. WHAT IT
DOES BRING WILL BE IN THE FORM OF RAIN AS AND MAINLY ACROSS THE
NORTHERN HALF OF THE CWA AS TEMPERATURES RISE INTO THE UPPER 40S TO
LOWER 50S ACROSS TEH SOUTH. TIMING IS TRICKY AS IT LOOKS LIKE THERE
COULD BE DIFFERENT PERIODS OF RAIN AS SMALLER WAVE IMPULSES MOVE
THROUGH THE AREA BRINING POCKETS OF FAVORABLE DYNAMICS.
THERMODYNAMICS WILL ALSO GET BETTER AFTER 18Z AND MODELS HINT AT
SOME INSTABILITY THROUGH 00Z WITH VERY SKINNY...MOSTLY ELEVATED CAPE
AND GOOD LAPSE RATES. THEREFORE CANNOT RULE OUT AN ISOLATED
THUNDERSTORM LATE THIS AFTERNOON.

AFTER 00Z THE LOW REALLY BEGINS TO DEEPEN OFF OF THE COAST AND THE
PRESSURE GRADIENT OVER CENTRAL NC WILL TIGHTEN UP CAUSING BREEZY
NORTHERLY WINDS WITH GUSTS OF 20-25 KTS POSSIBLE INTO THE OVERNIGHT
HOURS MONDAY NIGHT INTO TUESDAY MORNING. WITH BREEZY WINDS AND SOME
CLOUDS LINGERING IN THE EAST...RADIATIONAL COOLING PROSPECTS WILL
NOT BE AS GOOD AS BACK TO THE WEST WHERE BOTH WIND AND CLOUD COVER
SHOULD BE LESS. LOW TEMPERATURES WILL BOTTOM OUT IN THE UPPER 20S
WEST TO LOWER 30S IN THE EAST.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 250 AM MONDAY...

BY TUESDAY MORNING...LOW PRESSURE OFF OF THE NEW ENGLAND COAST WILL
HAVE EVOLVED INTO A MATURE NOR`EASTER AND HAVE GROWN CONSIDERABLY IN
SIZE. CENTRAL NC WILL SET UP JUST ON THE WESTERN SIDE OF THE UPPER
LEVEL TROUGH AXIS WITH NORTHERLY WINDS AT THE SURFACE AND
NORTHWESTERLIES ALOFT. MODELS CURRENTLY SHOW VARYING DEGREES OF WRAP
AROUND MOISTURE STILL AFFECTING EASTERN PORTIONS OF THE CWA INTO
TUESDAY MORNING. WHILE IMPACTS OF THIS WILL BE MINUTE...IF
SATURATION UP THROUGH THE SNOW GROWTH ZONE HOLDS ON LONG
ENOUGH...THERE IS A CHANCE OF SEEING SOME SNOW FLURRIES OR A BRIEF
SNOW OR RAIN SHOWER ON TUESDAY MORNING. BEST CHANCES FOR THIS WILL
BE ACROSS THE NORTHEASTERN COUNTIES OF THE CWA. THIS VERY BRIEF
ACTIVITY COULD CONTINUE ON AND OFF THROUGH TUESDAY MORNING BEFORE
THE STORM EVENTUALLY MOVES FAR ENOUGH TO THE NORTHEAST TO PUT
CENTRAL NC IN THE COLD AND DRY SECTOR. THE EFFECT OF ALL THAT COLD
AIR ADVECTION WILL BE A MUCH COOLER DAY ON TUESDAY WITH HIGHS IN THE
LOW TO MID 40S NORTHEAST TO SOUTHWEST. COUPLE THAT WITH A BREEZY
NORTHERLY WIND IT WILL FEEL MORE LIKE THE UPPER 20S TO LOWER 30S
THAN IT WILL THE 40S. DRYING WILL CONTINUE INTO TUESDAY NIGHT WITH
DEWPOINTS FALLING INTO THE TEENS AND LOW TEMPERATURES IN THE MIDDLE
20S.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 210 AM MONDAY...

WED/WED NIGHT: QUIET WEATHER WITH MID LEVEL SHORTWAVE RIDGING
SHIFTING OVERHEAD AS HIGH PRESSURE RIDGING MOVES OVERHEAD. COLUMN IS
STABLE AND FAIRLY DRY WED... SO EXPECT PLENTY OF SUNSHINE. BELOW-
NORMAL THICKNESSES (BY 25-30 M) AND STATISTICAL GUIDANCE SUPPORT
COOL HIGHS OF 42-47. HIGH CLOUDS WILL INCREASE AND THICKEN WED
NIGHT... WITH A FLATTENING AND ACCELERATING WRLY FLOW ALOFT AND
INITIALLY WEAK MID LEVEL DPVA AHEAD OF A CLIPPER SHORTWAVE TROUGH
DIVING THROUGH THE UPPER MIDWEST. THESE HIGH CLOUDS MAY TAKE THE
EDGE OFF AN OTHERWISE GOOD NIGHT FOR RADIATIONAL COOLING... WITH
GENERALLY LIGHT WINDS AND LOW DEWPOINTS... BUT STILL EXPECT CHILLY
LOWS MOSTLY IN THE MID 20S.

THU/THU NIGHT: THIS WILL BE OUR NEXT CHANCE AT PRECIP... ALTHOUGH
SPECIFIC TIMING AND AMOUNTS ARE IN QUESTION AS GFS/ECMWF SOLUTIONS
DIVERGE. THE GREAT LAKES SHORTWAVE TROUGH WILL TRACK ESE THEN
EASTWARD ACROSS THE NORTHEAST/MIDATLANTIC STATES -- TRACKING THROUGH
THE BASE OF THE POLAR LOW OVER HUDSON BAY -- WHILE ITS CORRESPONDING
SURFACE LOW CROSSES THE OH VALLEY AND MIDATLANTIC COAST. GFS BUFR
SOUNDINGS SHOW CLOUD BASES STEADILY LOWERING THU MORNING AS LOW
LEVEL FLOW STRENGTHENS FROM THE WSW... PUSHING PW VALUES UP...
ALTHOUGH THEY PEAK AT JUST SLIGHTLY ABOVE-NORMAL VALUES... WITH A
LINGERING DRY SUBCLOUD LAYER OVER MUCH OF THE CWA. MOISTURE IS
DEEPEST AND MOST PRONOUNCED IN THE EASTERN PART OF THE FORECAST AREA
IN BOTH THE GFS AND ECMWF... HOWEVER THE ECMWF AND ITS DEEPER WAVE
GENERATES MORE QPF MUCH LATER (THU EVENING/NIGHT) COMPARED TO THE
LIGHTER/EARLIER GFS (BEST PRECIP CHANCES THU MORNING). WILL LEAN
TOWARD THE ECMWF... WHICH HAS DONE BETTER SHOWING DEEPER WAVES IN
RECENT WEEKS... BUT WILL KEEP POPS NO GREATER THAN 20-30% LATE THU
THROUGH THU NIGHT... FOCUSED ON THE EASTERN CWA. OVERALL MOISTURE
INFLUX DOES NOT APPEAR SUFFICIENT ENOUGH TO WARRANT ANYTHING MORE
THAN LIGHT QPF. SURFACE WET BULBS SHOULD BE INCHING ABOVE THE
FREEZING MARK BY THE TIME PRECIP BEGINS... AND THE LATER ARRIVAL
TIME SHOULD ENSURE THAT TEMPS THU NIGHT STAY MOSTLY ABOVE FREEZING.
EVEN SO... WE`RE LIKELY TO SEE DRYING ALOFT THU NIGHT AFTER THE MID
LEVEL TROUGH AXIS SWINGS THROUGH... WHICH WOULD LIMIT THE NON-LIQUID
PRECIP THREAT ANYWAY. TOTAL QPF SHOULD BE LIGHT... UNDER A QUARTER
INCH. HIGHS THU 47-52. LOWS THU NIGHT IN THE MID-UPPER 30S.

FRI-SUN: THE POLAR FRONT DROPS TO OUR SOUTH FRI... AND LOW LEVEL
THICKNESSES SLIP BACK TO AROUND 20 M BELOW NORMAL... YIELDING BELOW-
NORMAL HIGHS IN THE MID 40S TO LOWER 50S DESPITE FAIR SKIES AS COOL
HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. LOWS FRI NIGHT IN THE
MID-UPPER 20S. UNCERTAINTY INCREASES FOR SAT/SUN AS THE GFS/ECMWF
SOLUTIONS CONTINUE TO DIVERGE IN IMPORTANT WAYS. BOTH HAVE A POLAR
LOW OVER HUDSON BAY/JAMES BAY AND ANOTHER LOW OVER NRN BAJA EARLY
SAT. THE GFS REMAINS FOCUSED ON THE POLAR STREAM... TAKING YET
ANOTHER CLIPPER WAVE THROUGH THE DAKOTAS AND MIDWEST THROUGH THE
NORTHEAST AND MIDATLANTIC THROUGH SUN... BRINGING ENHANCED
CLOUDINESS AND PERHAPS LIGHT PRECIP TO CENTRAL NC SAT (LIMITED BY
THE WEAK MOISTURE RETURN). THE ECMWF ON THE OTHER HAND IS MORE
FOCUSED ON THE SOUTHERN STREAM... EASING THE BAJA LOW SLIGHTLY
EASTWARD INTO NW MEXICO WITH SURFACE LOW PRESSURE FORMING IN THE NW
GULF... WHILE SRN STREAM ENERGY BEGINS TO SHEARS ENE TOWARD NC. THE
LATTER SOLUTION IS WARMER AND DRIER BUT STARTS TO BRING IN MOIST
OVERRUNNING FLOW BY LATE SUN. GIVEN THIS DISPARITY... PREFER JUST A
SMALL CHANCE POP ON SUN FOR NOW... WITH TEMPS REMAINING BELOW
NORMAL. -GIH

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 105 AM MONDAY...

24 HOUR TAF PERIOD: VFR CONDITIONS CONTINUING TO PREVAIL THIS
MORNING AS HIGH CLOUDS ARE NOW OVERSPREADING THE AREA FROM THE WEST
IN ASSOCIATION WITH THE APPROACHING CLIPPER SYSTEM. BETWEEN NOW AND
12Z MODELS AGREE ON SOME LOWERING OF CEILINGS BUT UPSTREAM
OBSERVATIONS HAVE YET TO SHOW MUCH OF A HINT OF THIS. THIS IS A LOW
CONFIDENCE FORECAST AT THIS TIME AND WILL COVER IN THE TAFS WITH
SOME MVFR VISIBILITIES AND CEILINGS IN THE NORTHWEST LATER THIS
MORNING BUT WILL HOLD OFF IN THE EAST ON ANY DETERIORATION IN
CONDITIONS AT KRDU AND KRWI UNTIL LATER IN THE AFTERNOON. KFAY MAY
REMAIN VFR THROUGH THE TAF PERIOD AS MOST OF THE LIGHT RAIN
ASSOCIATED WITH THIS SYSTEM IS EXPECTED TO REMAIN ACROSS THE NORTH.
FORECAST SOUNDINGS SHOW SOME ELEVATED INSTABILITY LATER IN THE
AFTERNOON AND AN ISOLATED THUNDERSTORM CANNOT BE RULED OUT BUT THIS
WILL BE THE EXCEPTION TO THE RULE. AS THE WAVE PASSES THROUGH WINDS
WILL SHIFT TO NORTHWESTERLY AND BEGIN GUSTING UP TO 20-25
KTS...PRIMARILY AFTER 00Z TUESDAY. GUSTS WILL CONTINUE THROUGH THE
END OF THE TAF PERIOD.

LONG TERM: ONCE VFR CONDITIONS RETURN ON THE HEELS OF THIS
SYSTEM...THEY SHOULD REMAIN VFR UNTIL THE NEXT SYSTEM APPROACHES
FORM THE NORTHWEST ON THURSDAY NIGHT INTO FRIDAY.

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...HARTFIELD
AVIATION...ELLIS


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