-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 272031
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
310 PM EST FRI FEB 27 2015

.SYNOPSIS...COLD HIGH PRESSURE OVER THE CENTRAL PLAINS WILL BUILD
INTO THE MID ATLANTIC THROUGH SATURDAY.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
AS OF 250 PM FRIDAY...

TEMPS HAVE WARMED NICELY TODAY (CURRENTLY 50 AT KPOB) ACROSS THE
PORTIONS OF OUR CWA THAT RECEIVED LITTLE OR NO SNOW...WHILE A SHIELD
OF STRATOCU AROUND 5K FT THIS MORNING OVER OUR SNOW-COVERED COUNTIES
LIMITED THE SUNSHINE THRU MID-DAY...WITH TEMPS ONLY CLIMBING TO
AROUND 40 BY 18Z. SINCE THEN...TEMPS THERE HAVE INCREASED A FEW MORE
DEGREES AFTER THE STRATOCU BROKE UP TO JUST CU.

HIGH PRESSURE CURRENTLY CENTERED OVER THE MIDWEST AND OHIO VALLEY
WILL BUILD EAST TONIGHT AND USHER IN A REINFORCEMENT OF COLDER AIR
INTO OUR AREA OVERNIGHT. AFTER THE BL WINDS SHIFT TO NE AND INCREASE
LATER THIS EVENING...WE`LL SEE FALLING TEMPS AND INCREASING MOISTURE
IN THE LOWEST 4K FT...WHICH WILL RESULT IN A LOW STRATUS DECK
FORMING AND EXPANDING TO THE SOUTH AND WEST DURING THE OVERNIGHT
HOURS. SOME OF THE HIGH-RES MODELS EVEN TRY TO CREATE A FEW PATCHES
OF FLURRIES OVERNIGHT WHEN THE LEADING EDGE OF THE COLDER AIR
ARRIVES. EVEN THOUGH THE LOW LEVEL LAPSE RATES WILL BE IMPRESSIVE,
THE DEPTH OF THIS LAYER SEEMS TOO SHALLOW TO PRODUCE PRECIP. WILL
KEEP AN EYE ON THIS THROUGH THE EVENING...BUT FOR NOW WILL LEAVE OUT
OF THE FORECAST. LOWS TONIGHT IN THE MID 20S.

AS FOR BLACK ICE...DESPITE A DAY OF GOOD MELTING TODAY...THE
POTENTIAL FOR BLACK ICE TONIGHT AND SAT MORNING IS STILL THERE FOR
AREAS THAT RECEIVED THE HEAVIEST SNOW. AFTER COORDINATING WITH
OFFICIALS FROM SEVERAL OF THE HARDEST HIT COUNTIES...WE HAVE DECIDED
TO ISSUE AN ADVISORY FOR BLACK ICE FOR TONIGHT FOR OUR VA BORDER
COUNTIES...AND FOR FORSYTH EAST TO FRANKLIN. WE WILL ALSO ISSUE AN
SPS FOR THE REMAINING COUNTIES THAT GOT LESSER AMOUNTS OF SNOW TO
COVER THE MORE ISOLATED NATURE OF BLACK ICE POTENTIAL.

FOR SATURDAY...COOL HIGH PRESSURE WILL CONTINUE BUILDING SOUTH
DURING THE DAY SATURDAY...RESULTING IN FAIR WEATHER WITH BELOW-
NORMAL TEMPS. HIGHS ONLY IN THE MID 30S. LIKE TODAY...IF THERE IS
LESS CLOUD COVER THAN FORECAST...THE SUN COULD HELP WARM TEMPS
SEVERAL DEGREES HIGHER THAN FORECAST.

SATURDAY NIGHT...FLOW IN THE 925-850 MB LAYER WILL TURN TO THE SW
AND BEGIN ADVECTING MOISTURE UP INTO OUR AREA AS THE 850MB RIDGE
MOVES EAST AHEAD OF THE TROUGH MOVING ACROSS THE UPPER MISS VALLEY.
WITH THE SFC RIDGE AXIS HOLDING FIRMLY IN PLACE ACROSS OUR AREA...
THE SUBSEQUENT OVERRUNNING AND UPGLIDE WILL RESULT IN INCREASING
CLOUDS OVERNIGHT. THERE ARE VARYING SOLUTIONS RIGHT NOW REGARDING
WHEN PRECIP WILL DEVELOP ACROSS OUR AREA...BUT THE PRECIP START TIME
IS IMPORTANT BECAUSE IF IT STARTS EARLY ENOUGH...SAY A FEW HOURS
EITHER SIDE OF SUNRISE...IT MAY BE COLD ENOUGH STILL FOR A VERY
BRIEF PERIOD OF FREEZING RAIN AT THE ONSET OF PRECIP. EVEN IF THE
EARLIER SOLUTIONS WERE TO VERIFY...THE QPF DURING THAT TIME WOULD BE
VERY LIGHT...SO LITTLE IF ANY IMPACTS WOULD BE EXPECTED. IT`S
DEFINITELY WORTH KEEPING AN EYE ON. LOWS IN THE MID TO UPPER 20S.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 240 PM FRIDAY...

SURFACE HIGH PRESSURE RIDGING INTO CENTRAL NC FROM THE NORTHEAST
WILL LINGER OVER THE AREA THROUGH SUNDAY...WITH CONTINUED COLD
ADVECTION AND CLOUDY SKIES. HIGHS EXPECTED TO BE MAINLY IN THE UPPER
30S NW TO MID 40S SE. THE SURFACE HIGH WILL BE SUPPRESSED TO THE
SOUTHEAST SUNDAY EVE/NIGHT AS A SURFACE LOW TRAVERSES THE GREAT
LAKES AND ITS ASSOCIATED COLD FRONT PUSHES SE TOWARD THE REGION.
RAINFALL COULD BEGIN AS EARLY AS MONDAY AFT/EVE AHEAD OF THE FRONT
AS WARM MOIST SOUTHWEST FLOW ABOVE THE SURFACE OVERRUNS THE COLD AIR
AT THE SURFACE...PARTICULARLY IN THE WESTERN PORTIONS OF THE AREA...
ALTHOUGH THE GFS IS A BIT MORE EXCITED ABOUT THAT POSSIBILITY THAN
THE ECMWF. THERE WILL HOPEFULLY BE ENOUGH WARM ADVECTION FROM THE
SOUTHWEST AHEAD OF THE FRONT TO KEEP TEMPERATURES ABOVE FREEZING...AS
A NON-DIURNAL TEMPERATURE CURVE IS ANTICIPATED FROM 18Z SUNDAY
THROUGH 00Z TUESDAY. REGARDLESS...FORECAST SOUNDINGS SHOW ENOUGH OF
A WARM NOSE ABOVE THE SURFACE AND LIMITED MOISTURE IN THE ICE
NUCLEATION REGION THAT PRECIPITATION SHOULD BE ALL LIQUID.
TEMPERATURES SHOULD RISE APPROXIMATELY 5 DEGREES OR SO OVERNIGHT
INTO THE UPPER 30S NW TO MID 40S SE BY MONDAY MORNING. BY SUNRISE
MONDAY THE COLD FRONT IS EXPECTED TO BE ON THE DOORSTEP OF CENTRAL
NC...WITH THE BEST RAINFALL CHANCES ACTUALLY ENDING WELL AHEAD OF
THE FRONT. THE MODELS SHOW THE RAINFALL ALONG THE MAIN AXIS OF THE
FRONT DISSIPATING AS IT CROSSES THE MOUNTAINS AND THE FRONT BECOMING
ORIENTED MORE WEST TO EAST THROUGH CENTRAL NC MONDAY AFT/EVE.
DIFFERENCES/UNCERTAINTY IN THE TIMING AND LOCATION OF THE FRONT AS
IT SETTLES SOUTH WILL RESULT IN A FAIRLY BIG MARGIN FOR ERROR IN THE
MAX AND MIN TEMPS AS COLD HIGH PRESSURE BUILDS IN FROM THE NORTH
BEHIND THE FRONT. FOR NOW EXPECT HIGHS AROUND 50 DEGREES NORTH TO
MID 50S SOUTH AND LOWS IN THE LOW 30S NORTH TO UPPER 30S SOUTH.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 310 PM FRIDAY...

A COLORADO LOW IS EXPECTED TO DEVELOP OVER THE MIDWEST EARLY TUESDAY
AS SURFACE HIGH PRESSURE AND NORTHWEST FLOW ALOFT LINGER OVER
CENTRAL NC. THE HIGH WILL SHIFT OFFSHORE TUESDAY AFTERNOON...WITH
WARM MOIST SOUTHERLY RETURN FLOW ADVECTING INTO THE REGION.
SUBSEQUENTLY...THE COLD FRONT WILL LIFT NORTH THROUGH THE AREA AS A
WARM FRONT...WITH THE CHANCE FOR RAIN TO ONCE AGAIN MOVE INTO THE
SOUTHWEST PORTIONS OF THE AREA TUESDAY AFT/EVE AND INTO THE
OVERNIGHT HOURS. ALTHOUGH CONFIDENCE IN TEMPERATURES IS FAIRLY LOW
AT THIS TIME...HIGHS ARE EXPECTED TO BE IN THE MID 40S TO MID 50S
FROM NW TO SE AND WILL AGAIN LIKELY BOTTOM OUT IN THE LATE EVENING
BEFORE GRADUALLY RISING OVERNIGHT TO POTENTIALLY THE LOW 50S NW TO
AROUND 60 DEGREES SE AT SUNRISE WEDNESDAY. THE MODELS STILL DIFFER
QUITE A BIT WITH REGARD TO THE TIMING OF THE FRONT...AND GIVEN THE
HABIT OF THE GFS TO BE A BIT ON THE FAST SIDE...WILL LEAN TOWARD THE
SLOWER SIDE OF THE FROPA TIMING AND THE ASSOCIATED PRE-FRONTAL
RAINFALL. THE GFS BRINGS PRE-FRONTAL CONVECTION INTO THE NW PIEDMONT
AS EARLY AS WEDNESDAY AFTERNOON...WHILE THE ECMWF HOLDS OFF UNTIL
AFTER MIDNIGHT THURSDAY. HIGHEST CHANCES WILL START AROUND 00Z
THURSDAY IN THE NW AND END AROUND 00Z FRIDAY IN THE SE AND DRYING
OUT EVERYWHERE BY FRIDAY AFTERNOON (AS OF THE LATEST RUNS). TEMPS
CONTINUE TO BE LOW CONFIDENCE AS THEY WILL DEPEND STRONGLY ON THE
TIMING OF THE FRONT...BUT WITH THAT BEING SAID HAVE HIGHS WED IN THE
UPPER 50S NW TO LOW 70S SE. LOWS WED NIGHT  AND HIGHS THURSDAY
PROBABLY A BIT TOO COOL...LOW 40S NW TO AROUND 50 DEGREES SOUTH AND
UPPER AROUND 50 DEGREES NW TO UPPER 50S SE...RESPECTIVELY. EXPECT A
COOL BUT DRY PERIOD THU NIGHT INTO FRIDAY...LOWS IN THE MID 20S TO
AROUND 30 DEGREES AND HIGHS UPPER 40S TO AROUND 50 DEGREES.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AS OF 1230 PM FRIDAY...

THROUGH 00Z SAT...EXPECTED A BAND OF STRATOCU WITH BASES AROUND 5K
FT ACROSS THE TRIAD AND NORTHERN PIEDMONT REGION...AND SCATTERED CU
TO THE SOUTHEAST OF THAT REGION.  LIGHT NORTH WINDS.

00Z-12Z SAT...LOW LEVEL WIND WILL SHIFT TO THE NE AND INCREASE AS
HIGH PRESSURE BUILDS TO OUR NORTH. THIS WILL ADVECT LOW LEVEL
MOISTURE INTO THE AREA BENEATH THE INVERSION.  THAT...IN COMBINATION
WITH SNOW COVER ACROSS THE NORTHERN HALF OF OUR CWA...WILL LEAD TO
INCREASING LOW CLOUDS AND SOME FOG OVERNIGHT. IT WILL DEVELOP FIRST
NEAR KRWI (SHORTLY AFTER 00Z)...THEN EXPAND SOUTH AND WEST
OVERNIGHT. LOOKS FOR MVFR OR IFR CONDITIONS DEVELOPING AT ALL OF OUR
TAF SITES (KINT, KGSO, KRDU, KFAY, AND KRWI) DURING THIS TIME.

12Z-18Z SAT...GUIDANCE SHOWS ONLY SLOW IMPROVEMENT AFT SUNRISE...WITH
MVFR CONDITIONS CONTINUING THROUGH 18Z.

AFT 18Z SAT...FLIGHT CONDITIONS WILL IMPROVE SATURDAY AFTERNOON
THROUGH THE NIGHT...THEN RETURNING TO MVFR OR WORSE FROM EARLY
SUNDAY THROUGH MONDAY AS LOW CLOUDS AND PRECIP DEVELOP AHEAD OF...
THEN ALONG THE NEXT COLD FRONT. SOME BRIEF IMPROVEMENT CAN BE
EXPECTED LATE MONDAY BEFORE THE NEXT SYSTEM AND IT`S SUB-VFR
CONDITIONS ARRIVE BY TUESDAY.

&&

.RAH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FOR
BLACK ICE FROM 9 PM THIS EVENING TO 10 AM EST SATURDAY FOR
NCZ007>011-021>026-041.

&&

$$

SYNOPSIS...RAH
NEAR TERM...RAH
SHORT TERM...KC
LONG TERM...KC
AVIATION...RAH