000
FXUS62 KRAH 152358
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
655 PM EST SUN FEB 15 2009

.SYNOPSIS...

AN UPPER LEVEL DISTURBANCE WILL MOVE SOUTHEAST ACROSS OUR REGION
OVERNIGHT. COLD DRY HIGH PRESSURE WILL BUILD INTO THE STATE FROM
THE MIDWEST MONDAY INTO TUESDAY. A WARM FRONT WILL APPROACH FROM THE
SOUTH ON WEDNESDAY AS A STORM SYSTEM MOVES FROM THE MISSISSIPPI
VALLEY INTO THE OHIO VALLEY. THE COLD FRONT WILL PUSH EAST ACROSS NC
WEDNESDAY NIGHT OR THURSDAY MORNING.
&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 245 PM SUNDAY...

AN INTERESTING FORECAST IS SHAPING UP TONIGHT AS SHORTWAVE ENERGY
OVER THE LOWER MS VALLEY IS EXPECTED TO TRACK ALONG THE NC/SC BORDER
OVERNIGHT. ALL OF THE GUIDANCE SHOWS LIFT INCREASING THIS EVENING
ACROSS THE NC MOUNTAINS AND FOOTHILLS AS THE SHORTWAVE APPROACHES.
THE LIFT APPEARS TO BE GENERATED BY A COUPLE OF FACTORS. FIRST...THE
SHORTWAVE WILL BE ACCOMPANIED BY A 160-170 KT 250 MB JET...WHICH
PASSES TO OUR SOUTH AND PLACES OUR AREA IN THE DIVERGENT LEFT EXIT
REGION. SECOND...925-850 MB CONVERGENCE INCREASES ACROSS THE
FOOTHILLS TONIGHT AS THE SHORTWAVE MOVES IN FROM THE WEST. AN
UPSLOPE COMPONENT AT THE 925 MB LEVEL ALSO DEVELOPS...AIDING AT
LEAST A LITTLE BIT TO THE OVERALL LIFT. THEREFORE...PRECIPITATION
SHOULD BEGIN TO INCREASE IN COVERAGE AND INTENSITY THIS EVENING
ACROSS THE MOUNTAINS AND FOOTHILLS...MOVING TOWARD THE NW PIEDMONT
LATE TONIGHT. THIS LOW LEVEL CONVERGENCE QUICKLY DIMINISHES IN THE
EARLY MORNING HOURS AS THE PRECIP LEAVES THE HIGHER TERRAIN AND THE
SHORTWAVE QUICKLY EXITS OFF THE COAST BY 12Z MONDAY. GIVEN THE
OVERALL CONSENSUS IN THE FORCING MECHANISMS...HAVE RAISED THE NW
PIEDMONT TO LOW LIKELY POPS...WITH LESSER POPS (LOW END CHANCE)
FURTHER EAST ACROSS THE COASTAL PLAIN.

GIVEN THAT PRECIPITATION IS LOOKING MORE LIKELY ACROSS THE WESTERN
PIEDMONT...P-TYPE ISSUES BECOME MORE OF A CONCERN AND AS IS
TYPICALLY THE CASE...THE SITUATION IS NOT CLEAR CUT.
FORTUNATELY...THE GFS AND NAM ARE IN RATHER GOOD AGREEMENT ON LOW
LEVEL THICKNESSES COOLING SUFFICIENTLY TO SUPPORT ALL SNOW ACROSS
THE NW PIEDMONT BY 06Z...AND A FEW HOURS LATER FURTHER EAST TOWARD
THE TRIANGLE. FORECAST SOUNDINGS ALSO SUPPORT THIS...EXCEPT FOR IN
THE LOWEST 1000 FT OR SO WHERE BOUNDARY LAYER ISSUES COULD POSE A
PROBLEM. IT MAY VERY WELL TAKE A FEW HOURS OF PRECIPITATION TO
EFFECTIVELY WET BULB TEMPS DOWN INTO THE LOWER TO MIDDLE 30S TO
SUPPORT SNOW REACHING THE GROUND...AND CONSIDERING THERE WILL ONLY
BE A SHORT WINDOW OF PRECIP ACTUALLY FALLING...THERE IS LITTLE ROOM
FOR ERROR. TEMPS STAYING A DEGREE OR TWO WARMER IN THE BOUNDARY THAN
CURRENTLY SUGGESTED WOULD RESULT IN MOSTLY A RAIN EVENT. AS IT
STANDS...THINK THE HIGHER TERRAIN AND CLIMATOLOGICALLY FAVORED AREAS
OF THE NW PIEDMONT STAND THE BEST CHANCE OF A CHANGE OVER TO SNOW
SHOWERS NEAR OR SHORTLY AFTER MIDNIGHT...WITH SNOW POSSIBLY MIXING
IN WITH THE RAIN FURTHER EAST A FEW HOURS LATER. IF PRECIP LINGERS
THROUGH SUNRISE...THEN TEMPS SHOULD SUPPORT MAINLY SNOW SHOWERS OVER
MOST OF THE AREA.

REGARDING ANY POTENTIAL ACCUMULATION... THE RECENT WARM SPELL HAS
RESULTED IN SOIL TEMPERATURES CLIMBING INTO THE MID TO UPPER 40S
ACROSS THE REGION. THUS...EVEN IF SNOW BEGINS TO FALL...IT WILL NOT
IMMEDIATELY BEGIN TO STICK AS IT WILL TAKE AWHILE TO COOL THE SFC
SUFFICIENTLY TO AID IN ACCUMULATION POTENTIAL. IN ADDITION...SFC
TEMPS ARE LIKELY TO STAY JUST ABOVE FREEZING DURING THE EVENT. THERE
IS ALSO THE QUESTION AS TO HOW MUCH PRECIP WILL EVEN FALL. THE NAM
BY FAR IS THE WETTEST SOLUTION SHOWING 0.3-0.4 INCHES OF LIQUID IN
THE NW PIEDMONT WHILE THE GFS/ECMWF ONLY HAVE ABOUT 0.1-0.15 NW TO
ONLY A FEW HUNDREDTHS IN THE EAST. WILL LEAN TOWARD THE CONSENSUS OF
THE GFS/ECMWF FOR NOW AS THERE IS NO DEEP MOISTURE FEED INTO THIS
SYSTEM (NO GULF/ATLANTIC MOISTURE TRANSPORT). EVEN WITH JUST OVER A
TENTH OF AN INCH...NOT ALL OF THAT LIQUID EQUIVALENT WILL GO INTO
SNOW ACCUMULATION. SO WE ARE THEN LEFT WITH ONLY A SMALL AMOUNT OF
PRECIP. THIS FORECAST WILL CALL FOR THE POTENTIAL OF A DUSTING OVER
THE NW PIEDMONT (A FEW TENTHS OF AN INCH ON GRASSY AND ELEVATED
AREAS) AND NO ACCUMULATION FURTHER EAST AS BOUNDARY LAYER TEMPS AND
DIMINISHING DYNAMICS DO NOT FAVOR ANY ACCUMULATION. LOWS 31 FAR NW
TO 36 SE.

THE SHORTWAVE PASSES BY TO THE EAST ON MONDAY MORNING WITH NORTHWEST
FLOW DEVELOPING. AS WE BEGIN TO DEEPLY MIX BY LATE MORNING...THE
DOWNSLOPING WIND SHOULD HELP TO SCOUR OUT RESIDUAL LOW LEVEL
MOISTURE AND LEAVE US WITH A PARTLY TO MOSTLY SUNNY AFTERNOON.
FAIRLY STRONG COLD AIR ADVECTION DEVELOPS DURING THE DAY...WITH LOW
LEVEL THICKNESSES STAYING IN THE UPPER 1280S. THESE VALUES ALONG
WITH DRY ADIABATIC PROFILES TO 850 MB SUPPORT TEMPS WELL BELOW
GUIDANCE. TAKING INTO ACCOUNT THE DOWNSLOPE MAY ADD A FEW
DEGREES...WILL ADJUST HIGHS TO 43 NW TO 50 SE...SLIGHTLY BELOW MOS
GUIDANCE. WINDS BECOMES STEADY OUT OF THE NW AROUND 10-13 KT...BUT
GUSTS SHOULD NOT BE MUCH OF AN ISSUE WITH ONLY UPWARDS OF 20 KT
PRESENT IN THE MIXED LAYER.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 145 PM SUNDAY...

MODELS ARE IN GOOD AGREEMENT THROUGH TUESDAY NIGHT IN BRINGING A
COLD DRY SURFACE HIGH OVER NC MONDAY NIGHT AND TUESDAY. THE N-NW
WINDS WILL DECREASE RAPIDLY MONDAY EVENING. CLEAR SKIES AND LIGHT
WINDS OVERNIGHT WILL LEAD TO A HARD FREEZE. LOWS WILL DIP INTO THE
MID 20S EXCEPT SOME LOWER 20S IN THE NORTH CENTRAL PIEDMONT... AND
UPPER 20S SOUTHEAST. MOSTLY SUNNY SKIES ARE EXPECTED TUESDAY...
WITH LIGHT AND VARIABLE WINDS. HIGHS CLOSER TO THE MET GUIDANCE IN
THE 47-51 RANGE EXPECTED.

MODELS ARE GENERALLY IN AGREEMENT IN THE FORECAST OF A SIGNIFICANT
RAIN EVENT WEDNESDAY INTO WEDNESDAY NIGHT OVER OUR REGION. A MAIN
STORM TRACK FROM THE MISSISSIPPI VALLEY NE THROUGH THE SOUTHERN
GREAT LAKES STATES AND INTO NEW ENGLAND IS FORECAST. IT STILL
APPEARS THAT STRONG ISENTROPIC LIFT WILL OCCUR ALONG AND AHEAD OF
A DEVELOPING H85 TO SURFACE WARM FRONT... THAT IS FORECAST TO LIFT
NNE THROUGH CENTRAL NC WEDNESDAY... SUPPORTED BY THE ECMWF/GFS.
THIS WOULD BE FOLLOWED BY THE COLD FRONT DURING WEDNESDAY NIGHT
(WHICH HAS BEEN SPEEDING UP IN THE PAST FEW MODEL RUNS). THE FRONT
IS NOW EXPECTED TO BE ALONG AND EAST OF I-95 BY 12Z THURSDAY...
CUTTING OFF THE RAIN CHANCES. GIVEN THE INCREASING CONFIDENCE...
WE WILL RAISE THE POP TO LIKELY WEDNESDAY... AND CONTINUE THE
LIKELY POP FROM THE PREVIOUS FORECAST FOR WEDNESDAY NIGHT. QPF ON
THE ORDER OF 0.5 TO POSSIBLY 1 INCH WILL BE POSSIBLE (THE NAM
SUGGESTS LESSER AMOUNTS). THIS COULD BE THE FIRST GOOD SOAKING IN
SEVERAL WEEKS.

THE TEMPERATURES FOR TUESDAY NIGHT MAY RISE TOWARD DAYBREAK... AS
THE CLOUDS THICKEN AND LOWER... AND THE LOW LEVEL ESE FLOW
INCREASES WITH THE WARM FRONTAL APPROACH. LOWS ABOVE MOS WILL BE
FORECAST (MID TO UPPER 30S)... WITH RISING TEMPS POSSIBLE LATE. NO
POP TUESDAY NIGHT. RAIN IS LIKELY WEDNESDAY INTO WEDNESDAY NIGHT.
HIGHS SHOULD BE SHORT OF GUIDANCE ESPECIALLY OVER THE PIEDMONT
WHERE THE WARM FRONT MAY LINGER LONGER THAN MODELS DEPICT WITH
HYBRID DAMMING POTENTIAL INTO WED EVENING. HIGHS 48 NW RANGING
INTO THE LOWER 60S SE.

THE RAIN SHOULD TAPER TO SHOWERS WEDNESDAY NIGHT AS THE H85 FLOW
QUICKLY BECOMES WESTERLY... AND A PRE-FRONTAL TROUGH MOVES THROUGH
PRIOR TO THE COLD FRONT. LOWS SHOULD STAY IN THE 40S... EXCEPT
SOME 50S SE.
&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 145 PM SUNDAY...

FOR THURSDAY... IT APPEARS THE COLD FRONT WILL PUSH THROUGH VERY
EARLY IN THE DAY... AND EVEN IF IT LINGERS BACK TO THE WEST FOR A
FEW HOURS... THE RAIN SHOULD BE WELL EAST (ALONG THE PRE-FRONTAL
TROUGH). THEREFORE... NO POP THURSDAY AFTER 12Z... WITH CLEARING
AND WINDY CONDITIONS EXPECTED DURING THE AFTERNOON. HIGHS SHOULD
STILL REACH" onClick="return popup(this, 'notes')">REACH THE 50S TO LOWER 60S NW TO SE.

THURSDAY NIGHT AND FRIDAY... MUCH COLDER AND DRIER AIR CAN BE
EXPECTED. IT WILL BE WINDY THURSDAY EVENING... WITH DIMINISHING
WIND OVERNIGHT. LOWS 25-30. FRIDAY WILL BE SUNNY AND CHILLY WITH
HIGHS 50-55.

SATURDAY AND SUNDAY LOOK TO BE MOSTLY DRY AND CHILLY. DISTURBANCES
ROTATING AROUND THE UPPER LOW CENTERED OVER NEW ENGLAND AND SE
CANADA WILL MAY BECOME A NUISANCE FOR CENTRAL NC. AT THIS TIME...IT
APPEARS THAT ONE SUCH DISTURBANCE WILL MOVE OVER THE STATE LATE
SATURDAY... FOLLOWED BY A SURFACE COLD FRONT SATURDAY NIGHT. THE
EXPECTED IMPACT OF THIS SYSTEM AS FAR AS PRECIPITATION IN CENTRAL
NORTH CAROLINA IS NIL AT THIS TIME... BUT WILL NEED TO BE MONITORED.
THE SYSTEM WILL HAVE LITTLE TO NO MOISTURE TRANSPORT AHEAD OF IT AND
LOOKS DRY EAST OF THE MOUNTAINS. EXPECT INCREASING CLOUDS
SATURDAY... LOWS 25-32. HIGHS 50-55.

DRY COLD AIR SHOULD FOLLOW THE FRONT SUNDAY. LOWS AGAIN WILL BE IN
THE 20S... WITH HIGHS IN THE 40S TO LOWER 50S SE.
&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 640 PM SUNDAY...

VFR CONDITIONS TO PERSIST THROUGH THE EVENING ACROSS CENTRAL NORTH
CAROLINA WITH SFC RIDGING FROM THE NORTH AND A WEAK TROUGH OF LOW
PRESSURE TO THE SOUTHWEST PROVIDING A LIGHT AND VARIABLE WIND.

AN UPPER LEVEL SHORTWAVE CURRENTLY TRAVERSING ACROSS TN/MS/AL/GA WILL
TRACK ACROSS CENTRAL NORTH CAROLINA LATE THIS EVENING INTO THE
OVERNIGHT HOURS. SUFFICIENT LIFT APPEARS TO BE PRESENT IN THE
FOOTHILLS AND WESTERN PIEDMONT TO PRODUCE A BRIEF WINDOW OF RAIN AND
SNOW SHOWERS. THIS PRECIPITATION WILL SPREAD EAST OVERNIGHT... BUT
LIKELY DIMINISH IN COVERAGE AND INTENSITY AS THE UPPER LEVEL
DYNAMICS WEAKEN SOMEWHAT. DUE TO THE INITIALLY VERY DRY NEAR SFC
LAYER AND QUESTIONS ON JUST HOW HEAVY THE PRECIP WILL BE...HAVE GONE
NO LOWER THAN MVFR CONDITIONS OVERNIGHT. DID NOT CARRY ANY MENTION
OF PRECIP AS FAR EAST A FAY/RWI DUE TO LACK OF CONFIDENCE THE PRECIP
WILL SURVIVE THAT FAR EAST. LINGERING LOW LEVEL MOISTURE IN THE WAKE
OF THE DEPARTING DISTURBANCE WILL KEEP PERIODS OF LOW END VFR/MVFR
CONDITIONS ACROSS THE TERMINALS THROUGH MONDAY MORNING.

AS THE UPPER LEVEL DISTURBANCE MOVES EAST OF THE AREA ON MONDAY...
CIGS WILL LIFT TO AROUND 5 KFT... EVENTUALLY BECOMING SCATTERED AS
SUBSIDENCE BY BEHIND THE SHORTWAVE CAUSES CLOUDS TO DISSIPATE.
EXPECT SUSTAINED SURFACE WINDS OF 10 TO 13 KTS OUT OF THE NNW. VFR
CONDITIONS SHOULD THEN PERSIST THROUGH TUESDAY NIGHT.

A STRONG UPPER LEVEL DISTURBANCE AND ITS ATTENDANT COLD FRONT WILL
LIKELY RESULT IN RAIN AND MVFR/IFR CONDITIONS WEDNESDAY INTO
WEDNESDAY NIGHT.

&&

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

&&

$$
SYNOPSIS...BADGETT
NEAR TERM...JFB
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...JFB/BSD