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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 270227
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
926 PM EST THU FEB 26 2015

.SYNOPSIS... LOW PRESSURE WILL MOVE AWAY FROM THE NORTH CAROLINA
COAST THIS EVENING. HIGH PRESSURE OVER THE CENTRAL PLAINS WILL BUILD
INTO THE MID ATLANTIC ON FRIDAY INTO SATURDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 320 PM THURSDAY...

...WINTER WEATHER ADVISORY FOR BLACK ICE IN EFFECT FROM 9PM TONIGHT
THROUGH 10 AM FRIDAY...

ANOTHER COMPLICATED FORECAST FOR TONIGHT AND INTO FRIDAY WITH LOTS
OF CONSIDERATIONS INCLUDING LOW TEMPERATURES FCST ISSUES...BLACK
ICE...FOG OR FREEZING FOG AND PERHAPS SOME SPOTTY LIGHT FREEZING
RAIN OR SNOW ACROSS THE NORTHWEST PIEDMONT.

WIDESPREAD LOW OVERCAST CONTINUES ACROSS CENTRAL NC THIS AFTERNOON
WITH JUST A FEW BREAKS ACROSS THE WESTERN PIEDMONT. WHILE SOME
ADDITIONAL BREAKS MAY DEVELOP THIS EVENING...AN APPROACHING SHEARED
SHORT WAVE TROUGH ALOFT AND SHALLOW LOW LEVEL ASCENT SHOULD WORK TO
MAINTAIN A FAIR DEGREE OF CLOUDINESS OVERNIGHT. MODEL BUFR
SOUNDINGS...ESPECIALLY THE NAM/HRRR AND RAP AGGRESSIVELY COOL THE
SURFACE AND GENERATE A NOTABLE AREA OF SHALLOW STRATUS AND/OR DENSE
FOG. NOT VERY CONFIDENT ON THE HOW THIS WILL EVOLVE AND THE DEGREE
OF FOG DEVELOPMENT GIVEN MIXED SIGNALS IN THE PATTERN. CONDITIONS AT
THE GROUND LEVEL ARE VERY MOIST WITH EITHER A FRESH SNOW COVER OF
WET SNOW OR MELT WATER OR JUST DAMP CONDITIONS FROM HEAVY RAIN LAST
NIGHT. SKIES ARE NOT EXPECTED TO CLEAR MUCH OVERNIGHT SO RADIATIONAL
CONDITIONS ARE NOT IDEAL. IN ADDITION WEAK WEAK COOL ADVECTION OVER
A SNOW PACK GENERALLY ISN`T FAVORABLE FOR FOG DEVELOPMENT. STILL SOME
FOG IS EXPECTED AND WILL BE ADDED TO THE FORECAST.

TO FURTHER COMPLICATE THINGS...THE NAM AND GFS SUGGEST SOME SPOTTY
LIGHT PRECIPITATION WILL DEVELOP OVERNIGHT IN THE TRIAD AS A WEAK
SURFACE TROUGH DROPS SOUTHEAST AND A SHEARING SHORT WAVE CROSSES THE
REGION. HIGH RES CONVECTION ALLOWING MODELS ALSO GENERATE SOME
PRECIPITATION. WHILE CONFIDENCE IS LOW...FEEL IT IS PRUDENT TO ADD A
SLIGHT CHANCE OF SOME SPOTTY FREEZING DRIZZLE. THE SATURATION IS
SHALLOW BUT MAY BE SUFFICIENTLY DEEP TO APPROACH THE ICE NUCLEATION
REGION AND WARRANT THE INCLUSION OF SOME SPOTTY LIGHT SNOW. SO WEVE
ADDED A SLIGHT CHANCE OF SOME FREEZING RAIN AND LIGHT SNOW IN THE
TRIAD TONIGHT.

LOW TEMPERATURES TONIGHT ARE ALSO PROBLEMATIC GIVEN THE NEW SNOW
COVER WHICH WOULD GENERALLY PROMOTE COOLING AND LOWER TEMPERATURES.
HIGHER RESOLUTION GUIDANCE INCLUDING THE RAP AND HRRR JUMP ALL OVER
THE LOCALIZED COOLING AND SUGGEST LOWS IN THE 10-15 RANGE ACROSS
MUCH OF THE FRESH SNOW COVER AREA. GIVEN THE AMOUNT OF CLOUD COVER
AND NON IDEAL RADIATIONAL CONDITIONS...THIS SEEMS OVERDONE. ALSO THE
RIPENESS OF THE SNOW WOULD SUGGEST A LOWER CHILLING EFFECT OF THE
SNOW COMPARED TO A NEW VIRGIN SNOW COVER. HAVE GONE WITH A FORECAST
OF LOWS RANGING FROM THE 21 TO 27 DEGREES FROM NORTHEAST TO
SOUTHWEST.

WITH THESE TEMPERATURES IN MIND...EXPECT ANY LINGERING MOISTURE ON
AREA ROADS TO REFREEZE OVERNIGHT. TEMPERATURES GENERALLY WONT FALL
BELOW FREEZING UNTIL AFTER 9PM AND EXPECT REFREEZING TO BE MOST
PROBLEMATIC AFTER MIDNIGHT.

FRIDAY SHOULD FEATURE A GOOD DEAL OF CLOUDINESS TO START.
TEMPERATURES WILL SLOWLY CLIMB TO AROUND FREEZING BY 10AM ALTHOUGH
THIS COULD BE DELAYED IF CLOUD COVER HOLDS LONGER OR LOWS TONIGHT
BOTTOM OUT EVEN FURTHER THAN FORECAST. EXPECT SOME BREAKS IN THE
CLOUDS ON FRIDAY AFTERNOON WITH HIGHS CLIMBING INTO THE UPPER 30S TO
LOWER 40S. -BLAES

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
AS OF 320 PM THURSDAY...

1044 HPA HIGH BUILDING ACROSS THE GREAT LAKES BEGINS RIDGING SOUTH
INTO THE AREA. IN ADDITION...A WEAK SHORT WAVE WILL BE RACING ACROSS
THE NORTHERN TIER OF THE STATE IN FAST WEST SOUTHWEST FLOW. THE
LATEST GFS AND NMM SHOW SPOTTY SHOWERS IN THE FOOTHILLS AND A FLURRY
INTO THE FAR NORTHWEST LOOKS POSSIBLE...BUT MOISTURE WILL VERY
LIMITED (PW ~0.25 IN) AND WILL MAINTAIN A DRY...BUT MOSTLY CLOUDY
FORECAST OVERNIGHT. COOL AIRMASS IN PLACE AND REINFORCED CAA
OVERNIGHT WILL PRODUCE MINS IN THE UPPER TEENS IN THE NORTHEAST...
WITH MOSTLY LOWER 20S ACROSS THE SOUTH.

CONSIDERABLE CLOUDINESS ALONG WITH DAMMING SETTLED IN PLACE SATURDAY
WILL PRODUCE ANOTHER WELL-BELOW NORMAL DAY. HIGHS IN THE 30S...FROM
LOW 30S NORTHEAST UNDER THE RIDGE AXIS...TO NEAR 40 IN THE FAR
SOUTHWEST. MINS SATURDAY NIGHT WILL BE SIMILAR TO FRIDAY
NIGHT...PERHAPS A DEGREE OR TWO LOWER IF SKIES ARE CLEAR ENOUGH TO
PROMOTE BETTER RADIATION...WITH TEENS IN THE NORTHEAST TO MOSTLY
LOWER 20S ELSEWHERE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 320 PM THURSDAY...

THERE IS A LOT OF UNCERTAINTY AS TO PRECIPITATION TIMING AS SPLIT
FLOW PATTERN CONTINUES INTO NEXT WEEK. INITIAL COLD AIR DAMMING
SUNDAY WILL BE NUDGED OFFSHORE BY A NORTHERN STREAM SHORT WAVE AND
ASSOCIATED COLD FRONT WHICH WILL BE MOVING ACROSS THE AREA SUNDAY
NIGHT...WITH PRECIP AHEAD OF THE FRONT EARLY SUNDAY NIGHT SPREADING
INTO THE EAST AFTER MIDNIGHT. HIGHS SUNDAY WILL BE MOSTLY IN THE LOW
TO MID 40S. MINS WILL BE MODERATING A BIT SUNDAY NIGHT WITH HEAVIER
CLOUDINESS AND SCOURING OF THE ARCTIC AIRMASS KEEPING MINS IN THE
30S.

THE AIRMASS SETTLING IN BEHIND THE FRONT WILL BE CONSIDERABLY
MILDER...BUT THE OVERALL PATTERN CONTINUES TO FAVOR YET ANOTHER
TRANSITION TO A DAMMING SCENARIO BY TUESDAY. A BACKDOOR FRONT SAGS
SOUTH ON MONDAY...WITH GOOD CHANCES OF RAIN WHICH WOULD DAMPEN/DELAY
THE POTENTIAL WARMUP INTO MID WEEK. WILL MAINTAIN A WARMUP INTO THE
50S PRE-FROPA ON MONDAY...ALONG WITH RAIN WHICH WOULD PRODUCE AN IN-
SITU COOLOFF ON TUESDAY...WITH HIGHS IN THE MID 40S WEST TO MID 50S
EAST. PROBABILITY OF RAIN WILL REMAIN AT LEAST IN THE CHANCE
CATEGORY ON WEDNESDAY INTO THURSDAY AHEAD OF A STRONG FRONTAL SYSTEM
APPROACHING FROM THE WEST. THIS SLOW MOVING SYSTEMS TIMING IS NOT
VERY CERTAIN AT THIS TIME...BUT IT LOOKS LIKE IT WOULD BE ON
WEDNESDAY NIGHT...WITH WARM AIR ADVECTION AHEAD OF THE SYSTEM
WARMING US INTO THE 60S ON WEDNESDAY AND EVEN THURSDAY AS COLD AIR
ADVECTION IS DELAYED TIL LATE DAY.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 900 PM THURSDAY...

24-HR TAF PERIOD: BELOW NORMAL CONFIDENCE THROUGH 12Z FRI. AREAS OF
FOG/FREEZING FOG AND LOW STRATUS ARE EXPECTED TO DEVELOP OVERNIGHT.
LIFR/VLIFR CONDITIONS ARE POSSIBLE. CONDITIONS WILL GRADUALLY
IMPROVE AFTER SUNRISE WITH LINGERING FOG AND STRATUS GIVING WAY TO
SCT/BKN CEILINGS WITH BASES 3-4 KFT BY FRIDAY AFTERNOON.

LOOKING AHEAD: GENERALLY FAIR WEATHER CONDITIONS ARE EXPECTED FRIDAY
NIGHT INTO SATURDAY NIGHT. AVIATION CONDITIONS ARE LIKELY TO
DETERIORATE ON SUNDAY WITH ADVERSE AVIATION CONDITIONS LIKELY
PERSISTING INTO MID WEEK. -VINCENT/BLAES

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST
FRIDAY FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089.

&&

$$

SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...MLM
LONG TERM...MLM
AVIATION...VINCENT/BLAES