000
FXUS62 KRAH 082106
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
406 PM EST MON FEB 8 2016

.SYNOPSIS... AN UPPER LEVEL DISTURBANCE AND COLD FRONT WILL CROSS
THE REGION THIS EVENING AND OVERNIGHT...FOLLOWED BY AND EXTENDED
PERIOD OF COLD TEMPERATURES THROUGH THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 315 PM MONDAY...

A DEEP TROUGH DIGGING THROUGH THE MIDWEST WILL SPREAD 100-150M
HEIGHT FALLS ACROSS THE REGION THIS EVENING...WITH AN ASSOCIATED PAIR
OF COLD FRONTS TO IMPACT THE REGION OVER THE NEXT 48 HOURS.

THE BIGGEST FORECAST INTEREST THIS AFTERNOON AND EVENING IS THE BAND
OF SHOWERS FORMING ALONG THE LEAD FRONT AND PREFRONTAL
TROUGH OVER THE WESTERN PIEDMONT AND FOOTHILLS. THE BAND
STRETCHING FROM THE TRIAD THROUGH CHARLOTTE IS FORECAST BY CONVECTION
ALLOWING MODELS TO PROGRESS  EAST ACROSS CENTRAL NC BETWEEN 21Z AND
03Z. WITH DEWPOINTS ONLY IN THE UPPER 20S AND LOWER
30S...THERE IS VERY LITTLE CAPE...IF ANY AT ALL. HOWEVER...AN AXIS OF
STEEP 7-7.5 C/KM MID-LEVEL LAPSE RATES ASSOCIATED WITH THE DRAMATIC
COOLING UNDERWAY ALOFT HAS ADVECTED OVER CENTRAL NC...PER SPC
MESOANALYSIS. THIS COUPLED WITH THE (RELATIVE) WARM SOUTHERLY FLOW
MAY ALLOW FOR SOME WEAK INSTABILITY TO DEVELOP...ESPECIALLY JUST IN
ADVANCE OF THE FRONT. THE HRRR SHOWS THE BAND OF SHOWERS
STRENGTHENING A BIT WITH TIME AND EASTWARD EXTENT LATE THIS
AFTERNOON...AND GIVEN A FAIRLY DRY SUB-CLOUD LAYER AND STEEPENING
LOW-LEVEL LAPSE RATES...WIND GUSTS OF 30-40MPH WITH THE SHOWERS
SEEMS ENTIRELY POSSIBLE.  A FEW LIGHTNING STRIKES ARE ALSO PLAUSIBLE
WITHIN THE LINE GIVEN THE THE STEEP MID-LEVEL LAPSE RATES...BUT
WITHOUT BETTER FORECASTS CAPE...PREFER TO MONITOR THE EVOLUTION OF
THE CONVECTIVE ELEMENTS BEFORE ADDING THUNDER TO THE FORECAST.

A WEAK SURFACE LOW IS FORECAST TO DEVELOP OVER SOUTHEAST VA BY
MIDNIGHT AND THEN QUICKLY MOVE OFF THE COAST TUESDAY MORNING. MODELS
HAVE TRENDED DRIER WITH PRECIP WRAPPING AROUND THE LOW LATE
TONIGHT...ALTHOUGH THE NAM CONTINUES TO SHOW SOME OMEGA AND MOISTURE
IN THE -12C TO -18C LAYER FROM DANVILLE TO EMPORIA...SO IT SEEMS
LESS LIKELY THAT WE`LL SEE ANY PRECIP THAT CHANGES OVER TO SNOW
AFTER MIDNIGHT BUT A FEW FLURRIES CANNOT BE RULED OUT.  LOWS 28-33.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 315 PM MONDAY...

THE DEEP UPPER TROUGH TO OUR WEST WILL MAKE ITS WAY OVERHEAD ON
TUESDAY...WITH A DISTURBANCE WITHIN THE TROUGH FORECAST TO SWING
ACROSS VA AND NORTHERN NC DURING THE AFTERNOON.  STEEP LAPSE RATES
ALOFT...ALONG WITH THE STRONG DCVA AND MOISTENING BETWEEN 5-10K
FEET(COINCIDENT WITH THE ICE NUCLEATION ZONE)...MAY LEAD SOME
ISOLATED SHOWERS NEAR THE NC/VA BORDER....ESPECIALLY LATER IN THE
DAY FROM ROXBORO TO ROANOKE RAPIDS. HOWEVER...MODELS CONTINUE TO
INDICATE MUCH BETTER COVERAGE NORTH OF THE BORDER AND THE ECMWF IS
THE ONLY MODEL TO INDICATE ANY QPF IN THE NORTHERN COASTAL PLAIN.
HIGHS WILL REACH THE UPPER 30S WEST TO MID 40S EAST...BUT DEWPOINTS
IN THE LOWER 20S WOULD PUSH WETBULB PROFILES COLD ENOUGH TO SUPPORT
SNOW SHOWERS OR FLURRIES.  COLD ADVECTION WILL CONTINUE TUESDAY
NIGHT BEHIND THE ARCTIC FRONT...WITH TEMPS FALLING INTO THE LOW/MID
20S.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
AS OF 400 PM MONDAY...

COLD MID-LATE WEEK...AND EVEN COLDER --PERHAPS RECORD SO-- THIS
WEEKEND...WITH A COUPLE OF OPPORTUNITIES FOR PRECIPITATION (LATE FRI-
FRI NIGHT AND LATE MON-TUE).

A HIGHLY AMPLIFIED PATTERN CHARACTERIZED BY A STRONG WESTERN NOAM
RIDGE AND EASTERN NOAM TROUGH WILL UNDERGO A BRIEF RELAXATION LATE
IN THE WEEK...IN ADVANCE OF A POLAR VORTEX THAT WILL SETTLE ACROSS
SOUTHEAST CANADA AND NEW ENGLAND...AND EFFECTIVELY RE-AMPLIFY THE
FLOW...THIS WEEKEND. A PROGRESSIVE PACIFIC TROUGH WILL THEN FLATTEN
THE WESTERN NOAM RIDGE SUN-MON.

WITHIN THE NW FLOW ALOFT...SHEAR VORTICITY AND ASSOCIATED LOW
AMPLITUDE TROUGHS WILL AMPLIFY INTO THE BASE OF THE TROUGH OVER THE
EASTERN STATES MID-LATE WEEK...WITH EACH SUPPORTING AN AREA OF LIGHT
PRECIPITATION STREAKING SOUTHEASTWARD FROM THE NORTHERN PLAINS TO
THE CENTRAL-SOUTHERN APPALACHIANS. THE MODELS SUGGEST THE LEAD
DISTURBANCE WILL HAVE A MORE LIMITED MOISTURE SUPPLY AND LITTLE LOW
LEVEL SUPPORT FOR THE MAINTENANCE OF PRECIPITATION EAST OF THE
APPALACHIANS ON THU...WHILE THE SECOND WILL BE ACCOMPANIED BY A LOW-
MID LEVEL WAA REGIME AND CONSEQUENTLY HAVE A BETTER CHANCE OF
SUPPORTING A BRIEF PERIOD OF LIGHT PRECIPITATION...MOST LIKELY IN
THE FORM OF SNOW...OR A RAIN/SNOW MIX ACROSS THE SOUTHERN
COUNTIES...CENTERED AROUND FRI EVENING.

A POTENTIALLY MORE SIGNIFICANT SYSTEM WILL ACCOMPANY THE
AFOREMENTIONED PACIFIC TROUGH...AS THE AFOREMENTIONED POLAR VORTEX
SUPPRESSES THE NORTHERN STREAM/PROMOTES CONFLUENT FLOW ALOFT...WHICH
WOULD SUPPORT THE SOUTHEASTWARD MAINTENANCE OF A 1040-1045 MB HIGH
FROM THE ARCTIC. WHILE THIS WOULD YIELD INITIALLY JUST NEAR RECORD
COLD CONDITIONS FOR THE WEEKEND...THE EASTWARD MIGRATION OF THE
PACIFIC TROUGH AND AN INCREASINGLY ACTIVE SOUTHERN STREAM WOULD
RAISE THE PROBABILITY OF STREAM INTERACTION...AND STORMINESS AND
APPALACHIAN COLD AIR DAMMING...MON-TUE.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 100 PM MONDAY...

SOUTHERLY WINDS WILL SLOWLY INCREASE THIS AFTERNOON AHEAD OF A COLD
FRONT AND BAND OF SHOWERS EXPECTED TO CROSS CENTRAL NC BETWEEN 20Z
AND 02Z...THEN TURN TO WESTERLY BEHIND THE FRONT.  A BRIEF PERIOD OF
MVFR CONDITIONS AND A WIND GUST TO 30-35MPH IS POSSIBLE WITH THE
SHOWERS...THOUGH THE STRONGER GUSTS WOULD BE VERY ISOLATED AND ARE
NOT INCLUDED IN THE TAF. AS THE SHOWERS EXIT THE COASTAL PLAIN LATE
THIS EVENING...A SURFACE LOW IS FORECAST TO FORM ALONG THE FRONT
OVER SOUTHERN VA..WHICH MAY DRAW SOME ADDITIONAL MOISTURE SOUTH
ACROSS THE NORTHERN COASTAL PLAIN AND CAUSE A FEW EXTRA SHOWERS OR
SNOW SHOWERS...MAINLY NORTH OF KRDU AND KRWI AFTER 09Z.

WESTERLY WINDS WILL INCREASE TO 9-12KT AND GUST TO AROUND 20KT ON
TUESDAY

OUTLOOK...WEDNESDAY AND THURSDAY WILL FEATURE VFR CONDITIONS WITH
GUSTY NORTHWEST WINDS OF 20-25.  THE NEXT CHANCE OF SUB-VFR
CONDITIONS WILL COME FRIDAY AS A WEAK LOW PRESSURE SYSTEM CROSSES
THE AREA.

&&

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


&&

$$

SYNOPSIS...BADGETT
NEAR TERM...SMITH
SHORT TERM...SMITH
LONG TERM...2
AVIATION...SMITH

NWS RAH Office Area Forecast Discussion