Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 260530
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1230 AM EST MON JAN 26 2015

.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS THE CENTRAL APPALACHIANS
TONIGHT...THEN INTENSIFY INTO A STRONG EAST COAST LOW MONDAY THROUGH
TUESDAY. DRY HIGH PRESSURE BUILDS IN FROM THE WEST ON
WEDNESDAY...THEN A COLD FRONT WILL CROSS THE REGION LATE THURSDAY.

&&

.NEAR TERM /THROUGH TODAY/...
0515 UTC UPDATE...WINDS WERE UPDATED WITH A TWO TO ONE BLEND OF THE
NAM AND ADJMAV...FAVORING THE FORMER FOR BETTER GUSTS POTENTIAL AT
HIGH ELEVATIONS.

915 PM UPDATE...BAND OF LIGHT DRIZZLE OR SPRINKLES MADE ITS WAY ACRS
THE MTNS AND WILL CONTINUE TO PROGRESS EWD THRU THE CWFA OVER THE
NEXT COUPLE HRS. STILL WATCHING WEAKLY CONVECTIVE SHOWER ACTIVITY
OVER EAST TN AND NW GA BENEATH CORE OF THE APPROACHING
SHORTWAVE. SOME OF THIS ACTIVITY WILL MOVE INTO OUR WRNMOST MTNS
BEFORE MIDNIGHT. LATEST MODEL RUNS SUGGEST THAT THE FIRST CHANCE AT
MEASURABLE POPS IN THE MTNS WILL COME WITH THESE SHOWERS...WHICH
MAY FIZZLE OR MOVE OUT BEFORE THE NW FLOW RAMPS UP. VAD PROFILES
FROM KMRX RADAR INDICATE MOSTLY SW FLOW ALOFT...WHICH NAM THINKS
WILL NOT LINE UP FOR GOOD UPSLOPING UNTIL NEAR DAYBREAK. IN LIGHT OF
THIS...REVISED POP AND QPF TRENDS IN THE MTNS TO FOCUS MORE ON THE
MRNG ACTIVITY AND LIMITED THE NUMBERS OVERNIGHT. ALSO...REVISED TEMP
TRENDS BASED ON THOSE FROM OUR SHORT TERM CONSENSUS PRODUCT WHICH
HAS VERIFIED WELL LATELY. THE WARMER NUMBERS AND LOWER QPF LEAD TO
LESS SNOW. I WILL UPDATE THE WSW TEXT FOR THE LATEST THINKING BUT
NOT EXPAND IT TO ANY ADDITIONAL ZONES.

AS OF 240 PM...ANOTHER TRICKY FORECAST AS A STRONG UPPER LOW WITH A
STRONG LEAD SHORT WAVE ROTATING AROUND THE LOW MOVE INTO THE AREA
TONIGHT THEN EAST OF THE AREA MONDAY AS CHANNELED VORTICITY MOVES IN
MON AFTERNOON IN THE NWLY FLOW BEHIND THE DEPARTING LOW. THE
ASSOCIATED SFC LOW MOVES NORTH OF THE AREA TONIGHT DRAGGING A COLD
FRONT ACROSS THE CWFA. THE LOW THEN REFORMS NEAR THE NC/VA COAST
LATE IN THE DAY. THERE WILL BE WAA FLOW...ISENTROPIC LIFT AHEAD OF
THE SYSTEM WITH DEVELOPING DEEP MOISTURE...BUT LITTLE IN THE WAY OF
UPPER DIVERGENCE TONIGHT. THE BEST DEEP LAYER FORCING WILL BE
TONIGHT WITH THE LEAD SHORT WAVE. BOTH THE FORCING AND MOISTURE WILL
BE A QUICK SHOT...SO WHILE THERE IS A CHC OF RAIN OUTSIDE OF THE
MTNS...QPF WILL BE VERY LIGHT. THE MOISTURE AND FORCING WILL BE
BETTER ACROSS THE MTNS...SO HAVE RETAINED CAT POP ALONG THE TN
BORDER. TEMPS FALL ENUF THE PRECIP WILL QUICKLY CHANGE TO SNOW
ACROSS THE HIGHER ELEVATIONS...BUT MAY ONLY MIX WITH SNOW ACROSS THE
VALLEYS. TEMPS MAY DROP ENUF FOR SOME SNOW TO FALL ACROSS THE NC
FOOTHILLS AND THE MTNS OF THE UPSTATE AND NE GA. HOWEVER...THE
BOUNDARY LAYER REMAINS QUITE WARM...LIMITING THE AMOUNT OF SNOW THAT
CAN SURVIVE TO THE SFC.

THE UPPER LEVEL COLD POOL ASSOCIATED WITH THE UPPER LOW SLIDES
ACROSS THE AREA MONDAY...KEEPING A CHC OF PRECIP ACROSS THE NC
FOOTHILLS AND PIEDMONT...AND THE ERN UPSTATE. AGAIN...ANY PRECIP
WOULD BE VERY LIGHT. ALTHOUGH THERE IS SOME LOW LEVEL INSTABILITY...
THE BOUNDARY LAYER REMAINS RELATIVELY WARM. THIS AGAIN WILL LIMIT
ANY SNOW OR GRAUPEL THAT COULD FORM IN THIS REGION...LEADING TO
MAINLY RAIN.

ACROSS THE MTNS...COPIOUS LOW LEVEL MOISTURE...DEVELOPING NWLY FLOW
AND LOW LEVEL INSTABILITY WILL KEEP ELEVATION DEPENDENT RAIN/SNOW
GOING THRU THE MORNING. THE PRECIP WILL TAPER OFF IN THE AFTERNOON.
LITTLE TO NO SNOW WILL MIX WITH THE RAIN ACROSS THE NE GA/UPSTATE
MTNS. HOWEVER...SNOW WILL CONTINUE ACROSS THE HIGH ELEVATIONS OF THE
NC MTNS WITH SOME SNOW MIX ACROSS THE VALLEYS. GIVEN THE FORECAST
QPF...TEMPS AND PRECIP DURATION...LOOKS LIKE THE HIGH ELEVATIONS
ALONG THE TN BORDER FROM HAYWOOD SOUTH COULD SEE ADVISORY LEVEL
ACCUMS. THE HIGH ELEVATIONS FROM MADISON NORTH COULD APPROACH ADV
LEVEL...BUT THE BULK OF THE AREA SHUD REMAIN BELOW. THEREFORE...WILL
ISSUE A WINTER WX ADV FOR THE SRN PORTION ABOVE 3500 FEET.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS OF 230 PM SUNDAY...FOR MONDAY NIGHT THRU TUESDAY...THE CWFA WILL
BE WITHIN THE NWLY BACKSIDE OF THE DEEP NOREASTER THAT WILL BE
TRACKING NE UP ALONG THE COAST. THE 12Z NAM AND GFS HAVE TRENDED A
LITTLE LESS BULLISH ON MOISTURE AND SNOW POTENTIAL ALONG THE TN
BORDER. HOWEVER...STILL LOOKS LIKE AT LEAST PERIODS OF SCATTERED TO
NUMEROUS SNOW SHWRS WILL EXIST DURING THESE TWO PERIODS. AN
ADDITIONAL 1 TO 2" OF SNOW CAN BE EXPECTED IN THE USUAL FAVORED
SPOTS...WHICH MAY APPROACH LOW-END ADVISORY CRITERIA. WILL CONTINUE
TO MENTION IN THE HWO. OTHERWISE...GRADUAL CLEARING IS EXPECTED EAST
OF THE MTNS...WITH MORE CLOUDS LINGERING EAST OF I-77 CLOSER TO THE
COASTAL LOW. TEMPS WILL BE NEAR NORMAL OVERNIGHT...THEN STAY A
CATEGORY OR TWO BELOW NORMAL ON TUESDAY.

TUESDAY NIGHT AND WEDNESDAY...AS THE NOREASTER PULLS AWAY...DRY HIGH
PRES WILL BUILD FROM THE WEST...WITH THE SFC RIDGE AXIS CROSSING THE
AREA WEDNESDAY AFTN. FCST SNDGS SHOW VERY DRY AIR ATOP THE BL...SO
EXPECT TEMPS TO DIP BELOW NORMAL TUESDAY NIGHT. ON WEDNESDAY...TEMPS
REBOUND A CATEGORY OR TWO...ESP IN THE HIGH TERRAIN. MAY SEE NEAR
CRITICAL RH FOR FIRE WX CONCERNS...BUT WINDS WILL BE LIGHT. POPS
SHUD TAPER OFF ALONG THE TN BORDER BY AROUND MIDNIGHT...WITH DRY
WX/SUNNY SKIES FOR WEDNESDAY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 145 PM EST SUNDAY...SOME MEASURE OF SPREAD IN THE HANDLING OF
THE 500 MB PATTERN SHOWS UP ON THURSDAY. THE GFS AND GEFS MEAN
DEPICT A SERIES OF FAIRLY WEAK CLIPPERS CROSSING THE CENTRAL
APPALACHIANS THU INTO FRI. THE 00Z RUN OF THE ECMWF HAS A MORE
AMPLIFIED SYSTEM DIGGING THROUGH THE OH VALLEY LATE IN THE
WEEK...WHICH SHOWED DECENT CONSISTENCY OVER THE PAST FEW RUNS. BOTH
MODELS FEATURE A RELATIVELY NARROW BAND OF MOISTURE AHEAD OF THE
WAVES ALONG A COLD FRONT FOR THU...BUT WITH BETTER MOISTURE
ACCOMPANYING THE MORE AMPLIFIED WAVE IN THE COLD ADVECTION FLOW ON
THE ECMWF THU NIGHT INTO FRI. THE AMPLIFIED...BUT SLIGHTLY MORE
MUTED...12Z ECMWF SOLUTION LOOKS TO BE A REASONABLE COMPROMISE. THIS
WILL KEEP CONTINUED MTN PRECIP CHANCES THU NIGHT INTO FRI...MAINLY
AS LIGHT SNOW DURING THE BEST COLD ADVECTION.

ONCE THE LATE WEEK WAVES MOVE EAST...THE SOLUTIONS SURPRISINGLY
APPEAR MORE CONSISTENT FOR THE WEEKEND...WITH AN ACTIVE NRN STREAM
BRINGING A WEAK CLIPPER TYPE WAVE THROUGH THE APPALACHIANS SAT
NIGHT...WHILE A STRONG SW SYSTEM NEAR THE BAJA PENINSULA STALLS
THROUGH THE WEEKEND. SOME MOISTURE SHOULD WORK BACK INTO THE
FORECAST AREA FROM THE WEST ON THE SHEARED FLOW BETWEEN THESE
SYSTEMS ON SATURDAY...BUT DEEP MOISTURE AND FORCING LOOK UNLIKELY AT
PRESENT. THIS WILL YIELD MAINLY CHC RAIN/SNOW POPS PRIMARILY ACROSS
THE WRN MOUNTAINS THROUGH THE LATTER HALF OF THE WEEKEND. ALSO
EXPECT A TIGHT PRESSURE GRADIENT TO SET UP IN THE NW FLOW ACROSS THE
SRN APPALACHIANS ON SUNDAY...WITH WINDY MOUNTAIN CONDITIONS AND
DOWNSLOPE DRYING EAST OF THE MTNS THROUGH LATE WEEKEND. EXPECT NEAR
CLIMO MINS BUT BELOW CLIMO MAXES THROUGH THE MEDIUM RANGE PERIOD.

&&

.AVIATION /05Z MONDAY THROUGH FRIDAY/...
AT KCLT...THE CIG WILL LOWER TO MVFR BEFORE DAWN AS LOW LEVEL
MOISTURE ASSOCIATED WITH AN APPROACHING COLD FRONT INCREASES.
ALTHOUGH PRECIPITATION CHANCES ARE LIMITED OVERNIGHT AND EARLY IN
THE MORNING...THEY ARE HIGH ENOUGH FOR A MENTION IN THE TAF...AND
GUIDANCE SUPPORTS SOME MVFR VSBY AROUND DAYBREAK. THE CIG IS
EXPECTED TO IMPROVE TO LOW VFR BY MIDDAY AS BEHIND THE DEPARTING
COLD FRONT AND A WEAKENING SURFACE LOW....AND ERODE BY EVENING.
WINDS WILL VEER FROM S TO SW BY DAWN...THEN TO WNW BY MIDDAY BEHIND
THE FRONT. MODEST GUSTS ARE EXPECTED THIS AFTERNOON AND TONIGHT.

ELSEWHERE...GUIDANCE SUPPORTS MVFR VSBY SETTING UP OVERNIGHT AS LOW
LEVEL MOISTEN WITH THE APPROACH OF A COLD FRONT. THERE IS SOME
LIMITED SUPPORT FOR IFR AT KAVL...BUT CONFIDENCE IS TOO LOW TO
ACCEPT THIS. ALTHOUGH PRECIPITATION IS POSSIBLE AT ALL SITES
OVERNIGHT AND EARLY IN THE MORNING...CHANCES ARE BEST IN NC...WHERE
UPPER LEVEL SUPPORT IS BEST. SNOW COULD MIX IN AT KAVL AROUND DAWN.
PRECIPITATION IS EXPECTED TO LINGER AT KAVL UNTIL MIDDAY. NC SITES
ARE ALSO WHERE GUIDANCE SUPPORTS MVFR VSBY AROUND DAYBREAK. FOOTHILL
SITES SEE CIGS IMPROVE TO LOW VFR BY MIDDAY...ERODING IN SC DURING
THE AFTERNOON...AND AT KHKY IN THE EARLY EVENING. THE KAVL CIG
REMAINS MVFR UNTIL ERODING IN THE EARLY EVENING. WINDS WILL VEER
FORM S TO SE OVERNIGHT...EXCEPT NW AT KAVL. WINDS VEER NW AT
FOOTHILLS SITES BY MIDDAY BEHIND THE FRONT. ALL SITES WILL SEE GUSTS
INCREASE TODAY AND STAY UP TONIGHT.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z
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 100%
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%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ051-052-
     058-059.
SC...NONE.

&&

$$
SYNOPSIS...ARK
NEAR TERM...RWH/WIMBERLEY
SHORT TERM...ARK
LONG TERM...HG
AVIATION...JAT



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