Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 140835
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
335 AM EST SUN FEB 14 2016

.SYNOPSIS...
COLD ARCTIC HIGH PRESSURE CENTERED NEAR THE GREAT LAKES WILL
RIDGE DOWN INTO THE CAROLINAS INTO MONDAY AS IT EVENTUALLY MOVES OFF
THE NEW ENGLAND COAST.  EXPECT A MOIST STORM SYSTEM TO CROSS FROM
THE WEST LATE TODAY INTO TUESDAY. A FAST MOVING UPPER LEVEL SYSTEM
WILL REACH THE MOUNTAINS LATE TUESDAY...BEFORE DRY AND MILDER HIGH
PRESSURE RETURNS AND REMAINS THROUGH THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM...WIND CHILLS CONTINUE TO BE MARGINAL...AS WINDS ARE
DIMINISHING EARLY THIS MORNING. SO WILL CANCEL THE WIND CHILL
ADVISORY WITH THE MORNING PACKAGE BY 4 AM.

A CHILLY DAY ON TAP FOR THE CWFA...AS THE AXIS OF ARCTIC HIGH
PRESSURE LINES UP JUST EAST OF THE MTNS. TEMPS WILL BE STARTING OUT
QUITE COLD...AND MODELS IN GOOD AGREEMENT THAT PLENTY OF MID AND
HIGH CLOUDS WILL BE STREAMING ACROSS THE AREA THRU THE
DAY...LIMITING INSOLATION. I WENT ON THE COOL SIDE OF GUIDANCE FOR
MAX TEMPS...MAINLY 20-25 DEGREES BELOW NORMAL. MOST OF THE NC ZONES
WILL STAY BELOW FREEZING...WHILE THE SC/GA ZONES TOP OUT IN THE MID
30S TO LOWER 40S.

AS A POTENT MID LEVEL SHORT WAVE CROSSES THE OH VALLEY...ISENTROPIC
LIFT AND LOW LEVEL RH WILL INCREASE ACROSS THE OH/TN VALLEYS WITHIN
WESTERLY FLOW. THE OPERATIONAL MODELS AND THE CAMS AGREE THAT A BAND
OF SNOW WILL LIKELY DEVELOP AND ENTER THE NC MTNS BY EARLY EVENING.
THIS BAND MAY BE ENHANCED BY SOME 700 MB FRONTOGENESIS...AS IT
STREAKS ACROSS THE NC COUNTIES ALONG AND NORTH OF I-40.
HOWEVER...CONFIDENCE IN EXACT INTENSITY AND POSITION WITH THESE
TYPES OF BANDS IS ALWAYS ON THE LOW SIDE. I BLENDED IN THE NAM QPF
AND THINK A QUICK 1-3" OF SNOW ACCUM FROM ABOUT 4 PM TO 4 AM IS
LIKELY. THE REST OF THE AREA WILL SEE MORE SHOWERY PRECIP (CHANCE
POP) BREAKING OUT AS STRONG 850 MB WAA SETS UP WITHIN SWLY FLOW. THE
MODEL CONSENSUS FORECAST SOUNDINGS AND PARTIAL THICKNESS NOMOGRAMS
SUGGEST THAT ONSET OVERNIGHT SHOULD BE PRIMARILY SNOW...BUT QUICKLY
MIXING IN WITH SLEET AND FREEZING RAIN ALONG AND SOUTH OF I-85
BEFORE DAYBREAK MONDAY. QPF LOOKS VERY LIGHT WITH THIS ACTIVITY
OUTSIDE THE NORTHERN NC MTNS AND FOOTHILLS. SO GENERALLY A HALF INCH
OF SNOW OR LESS...A LITTLE SLEET AND A FEW HUNDREDTHS OF AN INCH OF
ICE EXPECTED ACROSS THE PIEDMONT AND SOUTHERN MTNS. WITH ROAD TEMPS
LIKELY IN THE 20S WITH THIS OVERNIGHT PRECIP...EXPECT EVEN LIGHT
SNOW/ICE WILL STICK...MAKING TRAVEL HAZARDOUS EARLY MONDAY. I HAVE
MIN TEMPS RANGING FROM THE TEENS IN THE NORTHERN NC MTNS...TO UPPER
20S IN THE LOWER PIEDMONT.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 315 AM EST SUNDAY...UNCERTAINTY CONTINUES IN THE FORECAST FOR
MONDAY...PRIMARILY OVER PRECIPITATION TYPE ISSUES AS THE COLD
WEDGE LAYER RETREATS...A WARM NOSE INVADES FROM THE SOUTH...AND WARM
AND MOIST AIR ARRIVES FROM THE WEST WITH THE ADVANCING LOW. THERE IS
ENOUGH CONFIDENCE ON IMPACT FROM EXPECTED SNOW...SLEET...AND
FREEZING RAIN TO UPGRADE THE NORTHERN NC MOUNTAINS AND FOOTHILLS TO
A WINTER STORM WARNING AT THIS POINT. WINTRY ACCUMULATIONS ACROSS
THE REST OF THE FORECAST AREA REMAINS MORE UNCERTAIN...WITH SNOW/ICE
FORECASTS GENERALLY BELOW WINTER STORM CRITERIA AT PRESENT...BUT
WITH SOME POTENTIAL FOR SIGNIFICANT IMPACTS GIVEN THE COLD AIR
ALREADY IN PLACE. THE WATCH WILL THUS BE RETAINED IN CURRENTLY
ADVERTISED AREAS SOUTH OF THE WARNING. IN ADDITION...A WINTER
WEATHER ADVISORY COULD BE NEEDED FOR SECTIONS JUST SOUTH OF THE
CURRENT WATCH AREA LATER TODAY.

THE SALIENT FEATURES REMAIN A CENTRAL CONUS TROUGH DEEPENING FROM
THE PLAINS TO THE MS RIVER VALLEY ON MONDAY...WHILE COLD SURFACE
HIGH PRESSURE SLOWLY RETREATS OFFSHORE. HYBRID COLD AIR DAMMING WILL
BE SOLIDLY IN PLACE OVER THE REGION AT THE START OF THE PERIOD
MONDAY MORNING AS LOW LEVEL MOIST UPGLIDE STEADILY IMPROVES AHEAD OF
THE ADVANCING TROUGH. THE INCREASING WARM ADVECTION ABOVE THE WEDGE
LAYER THROUGH THE DAY WILL PERMIT A WARM NOSE TO BLOSSOM AND SURGE
NORTHWARD...BUT PROBABLY SLOWER THAN PROGGED GIVEN THE COLD AND DRY
AIRMASS BEING DISPLACED. WILL THUS ALLOW MORE OF THE INITIAL
PRECIPITATION MONDAY MORNING INTO EARLY AFTERNOON TO BE REALIZED AS
FREEZING/FROZEN TYPES ACROSS A GOOD CHUNK OF OUR AREA. IN
FACT...SURFACE WET BULB TEMPERATURES COULD WELL GET LOCKED IN AT OR
BELOW FREEZING ALONG AND EAST OF THE BLUE RIDGE INTO MONDAY EVENING.
THIS WILL BE PARTICULARLY DANGEROUS FOR THE NORTHERN TIER SINCE
DEEPER MOISTURE AND BETTER UPPER SUPPORT WILL BE ARRIVING WITH THE
APPROACHING TROUGH AXIS MONDAY EVENING.

THE LATEST MODEL RUNS HAVE TRENDED TOWARD KEEPING THE PRIMARY
SURFACE LOW TRACK WEST OF THE MOUNTAINS AND FOCUSING HEAVIER QPF ON
WESTERN MOUNTAIN SECTIONS. FORTUNATELY...THE DEEPEST MOISTURE AND
STRONGEST FORCING OF THE EVENT WILL THROUGH THE AREA MONDAY NIGHT
ONCE TEMPERATURES HAVE WARMED SUFFICIENTLY TO PRODUCE MAINLY RAIN IN
MOST AREAS. ANY BAND OF STRONGER FRONTOGENETICAL FORCING WILL BE
MUCH SHORTER DURATION AS WELL WITHOUT ANY CLOSING OFF OF THE PASSING
LOW. A POCKET OF STEEPER LAPSE RATES WILL LIFT THROUGH OVERNIGHT
MONDAY NIGHT...BUT ANY SURFACE BASED INSTABILITY APPEARS SHUNTED FAR
ENOUGH TO THE SE TO PRECLUDE ANY THUNDER MENTION. WITH THE WESTWARD
SHIFT IN THE BETTER QPF...HYDRO PROBLEMS APPEAR A BIT LESS
LIKELY...BUT STILL CANNOT BE TOTALLY RULED OUT OVER MOUNTAIN AND
NORTHERN FOOTHILL SECTIONS WHERE STORM TOTAL PRECIPITATION COULD
REACH 1.5 INCHES OR MORE.

THE DRY SLOT WRAPPING IN BEHIND THE DEPARTING WAVE WILL ALLOW THE
BULK OF TUESDAY TO BE DRY BETWEEN SYSTEMS. LINGERING NW FLOW
MOISTURE TUESDAY MORNING MAY BRIEFLY TRANSITION BACK OVER TO
FREEZING/FROZEN TYPES IN THE UPSLOPE AREAS BEFORE ENDING. A POTENT
TRAILING SHORTWAVE WILL THEN DIVE QUICKLY SOUTHEAST THROUGH THE
MIDWEST ON TUESDAY AND CROSS THE NORTHERN TIER OF THE FORECAST AREA
TUESDAY EVENING. NW FLOW MOISTURE IN THE COLD AIR BEHIND THE SYSTEM
SHOULD WRING OUT SCATTERED UPSLOPE SNOW SHOWERS INTO WED MORNING.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 330 AM EST SUNDAY...DEEP LAYER NW FLOW IS EXPECTED BETWEEN THE
WESTERN RIDGE AND EASTERN TROUGH ON WED. HEIGHTS WILL RISE FROM THE
WEST THROUGH THURSDAY...WITH COOL AND DRY SURFACE HIGH PRESSURE
SETTLING OVER THE EAST. MODEL TIMING DIFFERENCES EXIST ON A
DEAMPLIFYING WAVE MOVING EAST IN THE RELATIVELY ZONAL FLOW OVER THE
EASTERN CONUS FRIDAY THROUGH SATURDAY. THICKNESSES WILL WARM
SUFFICENTLY AHEAD OF AN APPROACHING FRONT TO PERMIT ABOVE CLIMO
TEMPS FOR THE FIRST TIME IN A QUITE WHILE BY FRIDAY. THE BEST
CONSENSUS FOR NOW IS THAT A DECAYING BAND OF FRONTAL MOISTURE COULD
REACH THE SOUTHERN APPALACHIANS ON SATURDAY.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED THRU THE DAY...WITH
GRADUAL INCREASE IN MID AND HIGH CLOUDS...WITH BASES LOWERING TO LOW
VFR BY LATE AFTN/EARLY EVE. TONIGHT...GUIDANCE GENERALLY AGREES THAT
A WARM FRONTAL ZONE WILL ACTIVATE ATOP THE CWFA...DRAWING MOISTURE
FROM THE SOUTH. LIGHT PRECIP MAY START DEVELOPING BEFORE 06Z ACRS
THE WESTERN CAROLINAS. FCST PROFILES SHOW THAT THE ONSET OF PRECIP
SHOULD BE ALL SNOW. SO WILL GO WITH PROB30 AT ALL SITES...EXCEPT
KAND...WHERE THE POP IS LESS THAN 30 PCT. WINDS WILL FAVOR A NNW
DIRECTION AT KAVL...AND NE ACRS THE PIEDMONT THRU ABOUT
19-20Z...THEN SHIFT ESE TO SE.

OUTLOOK...A STRONG LOW PRESSURE SYSTEM WILL DEVELOP AND CROSS THE
AREA LATE TONIGHT THRU TUESDAY...BRINGING WIDESPREAD CLOUDS/PRECIP.
PRECIP IS EXPECTED TO START OUT AS SNOW OR WINTRY MIX...THEN
GRADUALLY TRANSITION TO ALL RAIN AT THE TAF SITES BY MONDAY EVENING.
DRY AIR WILL RETURN DURING THE DAY ON TUESDAY.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  91%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING
     FOR GAZ010-017-018-026.
NC...WINTER STORM WARNING FROM 6 PM THIS EVENING TO MIDNIGHT EST
     MONDAY NIGHT FOR NCZ033-035-049-050-501>506.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING
     FOR NCZ036-037-056-057-063>065-068>072-507>510.
     WINTER STORM WATCH FROM THIS EVENING THROUGH MONDAY EVENING
     FOR NCZ048-051>053-058-059-062.
SC...WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING
     FOR SCZ001>009.

&&

$$
SYNOPSIS...DEO
NEAR TERM...ARK
SHORT TERM...HG
LONG TERM...HG
AVIATION...ARK


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