Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 291143
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
643 AM EST THU JAN 29 2015

.SYNOPSIS...HIGH PRESSURE WILL MOVE OFFSHORE TODAY AND GIVE WAY
TO A COLD FRONT THAT WILL CROSS THE AREA TONIGHT INTO FRIDAY
MORNING. HIGH PRESSURE WILL BUILD IN FROM THE WEST ON FRIDAY...WHICH
WILL HELP TO KEEP CONDITIONS DRY THROUGH MUCH OF THE WEEKEND.


&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
AS OF 230 AM THURSDAY...

OPTIMAL RADIATIONAL COOLING FOR THE NEXT COUPLE OF HOURS WHILE HIGH
PRESSURE OVERHEAD CALMS WINDS AND SKIES REMAIN CLEAR. THIS WONT LAST
FOR TOO LONG HOWEVER AS HIGH CLOUDS ARE BEGINNING TO MOVE IN FROM
THE WEST ASSOCIATED WITH A FRONTAL SYSTEM WITH PARENT MOVING INTO
THE CHICAGO AREA AT THIS TIME. THE ATTENDANT COLD FRONT...WHICH IS
WEAK IS PROGGED TO CROSS CENTRAL NC LATER TONIGHT AND INTO FRIDAY
MORNING. UNTIL THEN...SOUTHERLY RETURN FLOW WILL PICK UP ON THE BACK
SIDE OF THE SURFACE HIGH AFTER SUNRISE WITH SOME GUSTING AROUND 15
KTS POSSIBLE...ESPECIALLY IN THE WEST WHICH IS FURTHER AWAY FROM THE
CENTER OF THE HIGH. USING DRY ADIABATIC METHODS OR LOW LEVEL
THICKNESSES SUGGEST TEMPERATURES IN THE MID TO UPPER 50S BUT WITH
THE INCREASING CLOUD COVER...ESPECIALLY DURING PEAK HEATING THESE
NUMBERS WILL BE CUT BACK TO THE UPPER 40S TO MID 50S. CANT RULE OUT
SOME HIGHER TEMPS IN THE SOUTHEAST...WHERE THE EFFECTS OF THE
APPROACHING SYSTEM WILL BE MOST DELAYED.

AS FAR AS PRECIPITATION CHANCES ARE CONCERNED WITH THE ACTUAL
FRONT...CONDITIONS ARE DRY BUT THE LATEST VERSION OF THE MODELS IS
NOT QUITE AS DRY AS YESTERDAY WITH PW VALUES INCREASING TO NEAR 0.7
INCHES AS OPPOSED TO 0.5 YESTERDAY. A FIRST LOOK AT HIGH RESOLUTION
CONVECTIVE MODELS ALSO SHOWS SOME VERY LIGHT PRECIPITATION IN THE
NORTHWEST PIEDMONT JUST AFTER 21Z AND FADING OUT AS IT HEADS
EASTWARD BEFORE PICKING UP AGAIN OFF THE COAST. FORECAST SOUNDINGS
SHOW A SIMILAR STORY WITH THE BEST SATURATION IN THE TRIAD WITH LESS
LIKELY CHANCES FOR RAIN SOUTH AND EAST. DESPITE BETTER CHANCES IN
THE TRIAD...SATURATION IN THE MODEL SOUNDINGS IS BRIEF AND CONFINED
TO THE 850-700 MB RANGE WITH A LOT OF DRY AIR
UNDERNEATH...SUGGESTIVE OF SPRINKLES OR VIRGA PERHAPS IF MOISTURE
CANT REACH THE SURFACE. THE RESULT IS STILL VERY INCONSEQUENTIAL AS
QPF AMOUNTS WOULD BE A COUPLE OF HUNDREDTHS OF AN INCH AT THE VERY
BEST BUT MORE LIKELY TRACE AMOUNTS OR NOTHING. BETTER UPPER LEVEL
DYNAMICS COME IN AFTER 00Z FRIDAY BUT THE SYSTEM JUST LOOKS TO DRY
TO SUSTAIN ANYTHING AT THAT TIME.

AFTER FRONTAL PASSAGE AROUND 6Z FRIDAY...WINDS WILL SHIFT BACK TO
NORTHWESTERLY AND COLD AIR ADVECTION WILL ONCE AGAIN ENSUE.
LINGERING CLOUD COVER BEHIND THE FRONT WILL KEEP LOWS WARMER...IN
THE LOW TO UPPER 30S NW TO SE. AS DRY AIR WORKS IN BEHIND THE
FRONT...CLOUDS MAY CLEAR OUT FOR THE LATE MORNING PERIOD...BUT THEN
WRAP AROUND MOISTURE ON THE BACK SIDE OF THE EXITING SYSTEM WILL
MOVE IN FROM THE NORTH AND CUT DOWN ON INSOLATION DURING PEAK
HEATING. THIS MAY CAUSE A TEMPERATURE GRADIENT FROM THE NORTH TO
SOUTH RESULTING IN HIGHS IN THE MID 40S TO LOW 50S. DRY CONDITIONS
ARE EXPECTED AND INCREASING WINDS OF 15-20 KTS SUSTAINED WITH GUSTS
OF UP TO 25 KTS COULD CAUSE SOME FIRE WEATHER CONCERNS ON FRIDAY
AFTERNOON. AT THIS TIME MIN RH VALUES WILL HOVER AROUND 30%. WINDS
WILL DIE OFF AFTER SUNSET AND COUPLED WITH CLEAR SKIES WILL CAUSE
OPTIMAL RADIATIONAL COOLING RESULTING IN LOW TEMPERATURES NEAR 20
DEGREES FRIDAY NIGHT INTO SATURDAY MORNING.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 300 AM THURSDAY...

SURFACE HIGH PRESSURE OVER THE TN VALLEY WILL BUILD SOUTHWARD ACROSS
THE AREA ON SATURDAY...SHIFTING SOUTH AND OFF THE SOUTHEAST COAST
SATURDAY NIGHT. ALOFT...WEAK SOUTHERN STREAM IMPULSES EMBEDDED IN
INCREASING ZONAL FLOW ALOFT LATE SATURDAY/SATURDAY NIGHT WILL YIELD
THICKENING CIRRUS LAYER THROUGH THE DAY WITH MOSTLY CLOUDY SKIES BY
SATURDAY NIGHT. HIGHS WILL REMAIN BELOW NORMAL...RANGING FROM LOWER
40S NORTH TO MID/UPPER 40S SOUTH. LOWS SATURDAY NIGHT IN THE LOWER
TO MID 30S.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 300 AM THURSDAY...

SUNDAY THROUGH MONDAY: MINOR MID-LEVEL IMPULSES EMANATING FROM THE
UPPER TROUGH/CLOSED LOW OVER THE SOUTHWEST US...WILL
INTERACT....POTENTIALLY PHASE WITH NORTHERN STREAM ENERGY DIVING
SEWD WITHIN THE BROADENING CONUS TROUGH. ASSOCIATED CYCLOGENESIS
WILL TRACK EASTWARD ACROSS THE LOWER MS VALLEY/MID-SOUTH ON
SUNDAY...CROSSING THE SOUTHERN APPALACHIANS SUNDAY EVENING AND THEN
OFF THE CAROLINA COAST BY MIDDAY MONDAY.  DESPIT MODEL DIFFERENCES
IN THE AMPLITUDE OF THE NORTHERN STREAM TROUGH...TIMING OF THE
BETTER RAIN CHANCES INTO THE AREA ARE SIMILAR...WITH RAIN CHANCES
QUICKLY RAMPING UP LATE SUNDAY AFTERNOON/EARLY EVENING...WITH
CATEGORICAL POPS SUNDAY NIGHT...CUTTING OFF FROM WEST TO EAST
MORNING MONDAY AS THE MID-LEVEL DRY SLOT SPREAD EAST.  CURRENT
MODELS PROJECT A SOLID 0.50-1.0" ACROSS THE AREA...WITH SOME HIGHER
AMOUNTS POSSIBLE IF THE MORE AMPLIFIED--WETTER GFS VERIFIES. NO P-
TYPE CONCERNS. HIGHS BOTH DAYS IN THE 40S NORTH TO AROUND 50 SOUTH.
LOWS SUNDAY NIGHT IN THE MID TO UPPER 30S NORTH TO LOWER-MID 40S
SOUTH.

MONDAY NIGHT THROUGH WEDNESDAY: CONTINENTAL POLAR HIGH PRESSURE WILL
BUILD INTO THE AREA MONDAY NIGHT AND INTO TUESDAY IN THE WAKE OF THE
UPPER LEVEL TROUGH LIFTING OUT OF THE AREA. IF PROJECTED LOW-LEVEL
THICKNESSES VERIFY...STRONG CAA MONDAY NIGHT WILL SUPPORT LOWS
TUESDAY MORNING IN THE TEENS ACROSS MUCH OF THE AREA...WITH HIGHS
TUESDAY AFTERNOON STRUGGLING TO WARM INTO THE 40S.

MODEL SPREAD REMAINS HIGH WITH THE EASTWARD EJECTION OF THE
AFOREMENTIONED UPPER TROUGH/LOW OVER THE SOUTHWEST US. WHILE THE EC
SUGGEST THIS SYSTEM COULD BRING PRECIP CHANCES BACK INTO THE AREA
LATE TUESDAY NIGHT AND INTO WEDNESDAY...THE GFS AND CANADIAN
SUPPRESS THE SYSTEM WELL TO OUR SOUTH...MAINTAINING DRY CONDITIONS
THROUGH LATE WEEK. GIVEN THE UNCERTAINTY HAVE LIMITED POP TO
SLIGHT/SMALL CHANCE.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 645 AM THURSDAY...

24 HOUR TAF PERIOD: MEDIUM HIGH CONFIDENCE OF VFR CONDITIONS THROUGH
THE TAF PERIOD AS A DRY FRONTAL SYSTEM CROSSES THE AREA NEAR THE END
OF THE PERIOD. BANDS OF HIGH CLOUDS HAVE STARTED TO CROSS THE AREA
FROM THE WEST. LATER TODAY CLOUD COVER WILL INCREASE AS BROKEN
CEILINGS SET IN BY 18Z OR SO BUT THESE SHOULD BE IN THE 8-9 KFT
RANGE. THERE IS A SLIGHT CHANCE THAT CEILING COULD APPROACH MVFR
LEVELS AROUND 3Z BUT CONFIDENCE IN THIS IS LOW. AS FAR AS WINDS ARE
CONCERNED...EXPECT SOUTHERLY WINDS AT 5-10 KTS AFTER
DAYBREAK...GUSTING 15-20 KTS BEFORE RELAXING AGAIN AFTER SUNSET.
MAYBE A SPRINKLE OR LIGHT SHOWER IN THE TRIAD AHEAD OF THE FRONT
DURING THE 21-00Z TIMEFRAME.

LONG TERM: SUB-VFR CONDITIONS WILL BE POSSIBLE WITH A LOW PRESSURE
SYSTEM THAT WILL CROSS THE AREA LATE SUNDAY INTO MONDAY. VFR
CONDITIONS WILL PREVAIL FOR MUCH OF THE WEEK AFTER THAT.

&&

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

&&

$$

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


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