FXUS62 KRAH 160745
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
245 AM EST WED DEC 16 2009
.SYNOPSIS...
COLD HIGH PRESSURE CENTERED OVER THE MIDWEST THIS MORNING WILL BUILD
SOUTHEAST INTO OUR REGION THROUGH FRIDAY. A LOW PRESSURE SYSTEM IS
EXPECTED TO TRACK FROM THE GULF OF MEXICO NORTHEAST...TO A
POSITION OFF THE SOUTH CAROLINA COAST ON SATURDAY. THE CHANCE AND
TYPE OF PRECIPITATION FRIDAY NIGHT INTO THE WEEKEND WILL GREATLY
DEPEND ON THE TRACK AND STRENGTH OF THE LOW PRESSURE SYSTEM.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 AM WEDNESDAY...
SFC ANALYSIS THIS MORNING SHOWED 1037 MB ARCTIC HIGH PRESSURE
CENTERED OVER THE MIDWEST...WITH A RIDGE AXIS EXTENDING EASTWARD
INTO THE CAROLINAS AND MID-ATLANTIC. ALOFT...LATEST WV IMAGERY AND
RUC DATA SHOWED A SOUTHERN STREAM UPPER LOW OVER NORTHERN MEXICO...
AND A NORTHERN STREAM TROUGH OVER QUEBEC/NEW ENGLAND...EXTENDING
SOUTHWARD INTO THE NORTHERN MID-ATLANTIC. A POSITIVELY TILTED SHEAR
AXIS STRETCHED NORTHEAST FROM THE SOUTHERN STREAM LOW INTO THE LOWER
MIDWEST AND SOUTHERN OH VALLEY.
TODAY:
THE NORTHERN STREAM TROUGH WILL MOVE OFFSHORE THE MID-ATLANTIC AND
NEW ENGLAND TODAY...AND WE WILL SEE H5 HEIGHT RISES ACROSS THE
REGION IN ITS WAKE. AT THE SAME TIME...WITH ARCTIC HIGH PRESSURE
BUILDING IN FROM THE WEST/NW...WE WILL SEE COLD ADVECTION IN THE
LOWER LEVELS. ALTHOUGH MOST OF THE COLUMN WILL BE DRY...UPPER LEVEL
MOISTURE CONTINUES TO STREAM INTO THE CAROLINAS THIS MORNING
(DOWNSTREAM OF THE SOUTHERN STREAM UPPER LOW)...AND WILL LIKELY
CONTINUE TO DO SO THROUGH THE DAY. HOWEVER...FCST SOUNDINGS SHOW
THAT NVA/SUBSIDENCE IN THE WAKE OF THE NORTHERN STREAM TROUGH SHOULD
HELP TO DRY OUT THE UPPER LEVELS AND AT *LEAST* THIN CLOUD
COVER...IF NOT SUBLIMATE MOST OF IT. WILL SHOW MOSTLY CLOUDY SKIES
THROUGH SUNRISE...WITH PARTLY CLOUDY TO MOSTLY CLEAR SKIES THIS
AFTERNOON...WITH ANY CLOUD COVER AOA 25 KFT. A BLEND OF GFS/NAM
1000-850MB THICKNESSES SHOWS VALUES RANGING FROM 1295-1310M
TODAY...WHICH WOULD ARGUE FOR HIGHS IN THE MID/UPPER 40S TO LOWER
50S. MOS GUIDANCE IS GENERALLY IN AGREEMENT WITH THAT RANGE.
NORTHERLY WINDS SHOULD INITIALLY BE GUSTY AT THE ONSET OF MIXING
AFTER SUNRISE THIS MORNING...AND GUSTS TO 20KT WILL BE POSSIBLE
BEFORE THE GRADIENT SLACKENS THIS AFTERNOON.
TONIGHT:
THE SURFACE HIGH CURRENTLY OVER THE MIDWEST IS EXPECTED TO BUILD
INTO THE OH VALLEY BY 12Z THU. A LIGHT NORTHERLY WIND MAY CONTINUE
DURING THE OVERNIGHT HOURS...ALTHOUGH THE NOCTURNAL INVERSION MAY
ALLOW WINDS TO GO LIGHT/VARIABLE OR CALM IN SHELTERED LOCATIONS.
SKIES SHOULD BE CLEAR ACROSS CENTRAL NC...WITH ANY UPPER LEVEL CLOUD
COVER ASSOC/W THE SFC LOW IN THE NORTHWEST GOMEX GENERALLY REMAINING
SOUTH OF THE CAROLINAS. LOW TEMPS EXPECTED TO DROP INTO THE MID TO
UPPER 20S...OR 25-29F. -VINCENT
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
AS OF 245 AM WEDNESDAY...
THURSDAY AND THURSDAY NIGHT:
THE SOUTHERN STREAM UPPER LOW IS PROGGED TO EJECT EASTWARD FROM
NORTHERN MEXICO INTO THE NORTHERN GOMEX DURING THIS PERIOD...WITH
THE ASSOC SFC LOW DEEPENING AND MOVING ENE FROM THE NORTHWEST GOMEX
TO JUST SOUTH OF THE LA/MS/AL GULF COAST BY 12Z FRI. AS A RESULT...
EXPECT AN INCREASE IN UPPER LEVEL (~25 KFT) CLOUD COVER DOWNSTREAM
OF THE GOMEX LOW PRESSURE SYSTEM BY LATE THU EVENING OR THU
NIGHT...WITH AN INCREASE IN MID-LEVEL (~15 KFT) CLOUD COVER BY 12Z
FRI. WITH MOSTLY SUNNY SKIES ON THU...WILL BASE HIGH TEMPS ON A
GFS/NAM BLEND OF THICKNESSES...WHICH YIELD HIGHS A FEW DEGREES
COLDER THAN TODAY...RANGING FROM 44-51F FROM NORTH-SOUTH. LOW TEMPS
THU NIGHT WILL ENTIRELY DEPEND ON HOW QUICKLY WE SEE MID/UPPER LEVEL
CLOUD COVER THICKENING OVER THE AREA. AT THIS TIME WILL SHOW LOW
TEMPS A FEW DEGREES WARMER THAN THU MORNING DUE TO INCREASING
MID/UPPER LEVEL CLOUD COVER...RANGING FROM THE UPPER 20S TO LOWER
30S...OR 27-32F. -VINCENT
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 145 AM WEDNESDAY...
THE +PNA/-NAO PATTERN COMBINED WITH WITH A STRONGLY NEGATIVE ARCTIC
OSCILLATION (AO) IS ONE THAT TYPICALLY SPELL COLD TEMPERATURES WITH
WINTERY PRECIPITATION FOR OUR REGION. IT MAY ACTUALLY LEAD TO A
SIGNIFICANT STORM NEAR THE SE COAST THIS WEEKEND. HOW STRONG THE
STORM BECOMES...AND HOW CLOSE THE STORM TRACKS TO THE SE COAST
WILL BE THE MAJOR CONCERN FOR US...ESPECIALLY WITH THE COLD AIR
BECOMING ENTRENCHED THROUGHOUT THE EASTERN UNITED STATES.
GENERALLY MOST OF THE 00Z/16 DECEMBER MODEL SOLUTIONS KEEP THE LOW
TRACK JUST FAR ENOUGH OFFSHORE SATURDAY INTO SATURDAY NIGHT...THAT
MOSTLY LIGHT OR MODERATE PRECIPITATION WOULD BE EXPECTED INLAND
FROM THE COAST. THIS WOULD MEAN THAT THE NW EDGE OF THE
PRECIPITATION SHIELD WOULD AFFECT AT LEAST A PORTION OF OUR
REGION. HOWEVER...SOME MODEL SOLUTIONS INCLUDING THE 12Z ECMWF
AND THE 00Z GEM/NAM HAVE THE LOW TRACK TUCKED UP AGAINST THE SC
COAST...PROVIDING A FAVORED WINTER STORM TRACK FOR PORTIONS OF
CENTRAL NC.
THE KEY TO THE STORM TRACK AND INTENSITY APPEARS TO LIE IN WHAT
OCCURS UPSTREAM IN THE MID AND UPPER LEVELS. THIS IS WHERE THE
MODELS CONTINUE TO SHOW GREAT SPREAD IN SOLUTIONS IN THE FORECAST
DEEPENING OF A MID LEVEL TROUGH NEAR THE OHIO RIVER VALLEY. THE
00Z/NAM AND THE PREVIOUS 12Z/ECMWF WERE SLOWER AND DEEPER WITH THE
TROUGH DEVELOPMENT...WHILE OTHER MODELS WERE GENERALLY FASTER AND
WEAKER. THE TREND IN THE MODELS WAS GENERALLY FOR A FASTER AND
WEAKER TROUGH...WHICH WOULD FAVOR THE MORE OFFSHORE SOLUTION.
EVEN SO...THE LATEST GUIDANCE STILL BRINGS SOME PRECIPITATION
INLAND OVER OUR REGION FRIDAY NIGHT INTO SATURDAY NIGHT. SINCE A
COMPROMISE SOLUTION IS IN ORDER THIS MORNING...WE WILL MAINTAIN
OUR CURRENT FORECAST WITH ONLY A COUPLE OF ADDITIONS. SINCE THIS
FORECAST IS A LOW CONFIDENCE FORECAST...AND WILL NOT BE RESOLVED
UNTIL POSSIBLY FRIDAY...IT IS RECOMMENDED THAT EVERYONE SHOULD
KEEP UP WITH THE LATEST INFORMATION ON A POTENTIAL WINTER STORM
FOR PORTIONS OF OUR REGION THIS WEEKEND.
AS FOR P-TYPE...WE WILL ADD A SLIGHT CHANCE OF SNOW INTO THE
CLIMATOLOGICAL PREFERRED AREAS BASED ON THE MILLER A TYPE LOW...
FAVORED STORM TRACK...LOW LEVEL THICKNESS FORECASTS...AND COLD
HIGH OF SUFFICIENT STRENGTH (1025+ MB) AND LOCATION (NY TO NC)...
FOR A CONTINUED DELIVERY OF CAA AS THE STORM APPROACHES FRI NIGHT
INTO SATURDAY.
EXPECT INCREASING CLOUDS AND CHILLY CONDITIONS FRIDAY WITH HIGHS IN
THE 40S. CLOUDY FRIDAY NIGHT WITH A CHANCE OF RAIN SE...AND
SLIGHT CHANCE OF RAIN/SNOW NW. LOWS 30-35. CLOUDY SATURDAY AND
SATURDAY NIGHT WITH A CHANCE OF RAIN SE... AND SLIGHT CHANCE OF
SNOW/RAIN NW. HIGHS 35-45 NW TO SE. LOWS 30-35. VARIABLY CLOUDY
SUNDAY. BREEZY AND CHILLY WITH HIGHS IN THE UPPER 30S NW RANGING
INTO THE 40S SE. EXPECT THE POP NUMBERS TO CHANGE SIGNIFICANTLY
WHEN A PREFERRED STORM TRACK AND STRENGTH IS FINALLY AGREED UPON.
WE WILL PLAY IT CONSERVATIVE UNTIL THAT OCCURS.
FOR SUNDAY NIGHT THROUGH TUESDAY...PARTLY CLOUDY AND COLD. LOWS
20-27. HIGHS 38-45. -BADGETT
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
AS OF 1245 AM WEDNESDAY...
24-HR TAF PERIOD:
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD AS ARCTIC HIGH
PRESSURE BUILDS TOWARD THE CAROLINAS FROM THE WEST. WITH COLD
ADVECTION ONGOING THROUGH 12Z THIS MORNING...EXPECT SUSTAINED
NORTHWEST WINDS OF ~10 KT...WITH SPORADIC GUSTS TO 20 KT. NORTHWEST
WINDS SHOULD DECREASE TO 5-10 KT BY 18Z. LIGHT/VARIABLE WINDS ARE
EXPECTED AFTER SUNSET THIS EVENING.
TONIGHT THROUGH FRIDAY:
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE DAY FRIDAY IN
ASSOC/W ARCTIC HIGH PRESSURE OVER THE AREA. MID-LEVEL CEILINGS ARE
EXPECTED TO INCREASE FROM THE SOUTH THROUGHOUT THE DAY FRIDAY AS A
LOW PRESSURE SYSTEM TRACKS NORTHEAST ACROSS THE FLORIDA PENINSULA.
FRIDAY NIGHT THROUGH SUNDAY:
THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS (IFR/LIFR
CEILINGS/VISBYS) WILL ARRIVE AS EARLY AS FRIDAY EVENING...AND
PERSIST THROUGH THE DAY SATURDAY AS A LOW PRESSURE SYSTEM
INTENSIFIES OFF THE SOUTHEAST COAST. VFR CONDITIONS WOULD BE
EXPECTED TO RETURN DURING THE DAY SUNDAY. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...BADGETT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...BADGETT
AVIATION...VINCENT
