Area Forecast Discussion
Issued by NWS Greer, SC

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141
FXUS62 KGSP 061123
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
623 AM EST SAT FEB 6 2016

.SYNOPSIS...
SURFACE HIGH PRESSURE WILL SLOWLY CROSS THE FORECAST AREA THROUGH
THE WEEKEND...AND EVEN AS AN UPPER LEVEL DISTURBANCE SPAWNS STRONG
LOW PRESSURE OFF THE CAROLINA AND GEORGIA COAST...OUR AREA IS
EXPECTED TO REMAIN DRY. A COLD FRONT WILL PUSH THROUGH THE REGION
ON MONDAY...USHERING IN BELOW NORMAL TEMPERATURES AND AN INCREASE
OF MOISTURE INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 620 AM...SFC HIGH PRESSURE OVER THE AREA WEAKENS AS A STRONG
UPPER LOW MOVES EAST ALONG THE GULF COAST. HIGH CLOUDS WILL STREAM
OVER THE AREA THRU THE DAY WITH SOME MID LEVEL CLOUDS MOVING IN BY
THE END OF THE DAY. LINGERING COOL THICKNESSES AND CLOUDS WILL KEEP
HIGHS UP TO 5 DEGREES BELOW NORMAL.

THE UPPER LOW STAYS CLOSE TO THE GULF COAST AS IT MOVES EAST AND
REACHES THE ATLANTIC COAST OVERNIGHT. ALTHOUGH DEEP AND STRONG
FORCING WILL BE ASSOCIATED WITH THE UPPER LOW...IT REMAINS WELL
SOUTH OF THE CWFA. THE ASSOCIATED SFC LOW WILL REMAIN WELL SOUTH OF
THE AREA AS WELL. THIS KEEPS LOW LEVEL MOISTURE AND ISENTROPIC LIFT
SOUTH OF THE AREA AS THE LOW LEVEL FLOW REMAINS NELY. THE 06Z NAM
HAS COME IN MUCH FARTHER NORTH AND WEST WITH PRECIP THAN THE
PREVIOUS RUN...AND MOST OTHER GUIDANCE. HAVE KEPT FCST DRY FOR NOW.
EXPECT SOME LINGERING CLOUDS OVER THE AREA...ESPECIALLY ALONG AND
SOUTH OF I-85. LOWS WILL BE NEAR OR SLIGHTLY BELOW NORMAL.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 315 AM SATURDAY...RAPID CYCLOGENESIS WILL OCCUR OVER THE GULF
STREAM IN RESPONSE TO TIGHT CLOSED UPPER LOW MOVING OFF THE GA/SC
COAST. DETERMINISTIC MODELS STILL KEEP ANY QPF WITH THIS BOMBING
SYSTEM SOUTH AND EAST OF THE CWFA...WITH THE SREF POPS IMPLYING
ONLY A VERY NEAR MISS FOR OUR LOWER PIEDMONT ZONES. I WILL MAINTAIN
SUB-SCHC POP. THE EXCEPTIONALLY STRONG GRADIENT AROUND THE BOMBING
LOW WILL KEEP A BREEZY AND SOMEWHAT GUSTY NORTHERLY FLOW ACRS OUR
AREA DURING THE DAY. TEMPS WILL EDGE A BIT HIGHER /JUST ABOVE CLIMO/
WITH DOWNSLOPE WARMING PROBABLY OFFSET BY RESTRICTED HEATING UNDER
THE WIND.

COMING QUICKLY ON THE HEELS OF THE DEPARTING OFFSHORE LOW WILL
BE A BROAD UPPER CYCLONE PUSHING SOUTH OUT OF CANADA SUN NIGHT
INTO MON. AN WAVE EMBEDDED IN THE CIRCULATION AND ASSOCIATED VORT
LOBE WILL REACH THE SRN APPALACHIANS MON MRNG...WITH THE CORE OF
THE TROUGH REACHING THE OHIO VALLEY EARLY TUESDAY. STRONG Q-VECTOR
CONVERGENCE IS SEEN OVER THE AREA AHEAD OF THIS FEATURE...ALONG WITH
FAIRLY DEEP MOISTURE EVEN EAST OF THE MTNS...PIQUING OUR INTEREST
SINCE WE DON/T GET MOISTURE WITH THESE FAST-MOVING SHORTWAVES EVERY
TIME THEY OCCUR. NAM AND EC ARE A LITTLE MORE EXCITING THAN THE GFS
IN THAT THEY DELAY THE LOBE A FEW HOURS...THUS BRINGING THE BETTER
QG FORCING LATER IN THE DAY...WHEN THE FALLING HEIGHTS ALOFT WILL
HAVE ALLOWED LAPSE RATES TO STEEPEN ENOUGH FOR SOME SFC-BASED
CONVECTION TO BE POSSIBLE. AS USUAL THE NAM SBCAPE VALUES ARE
NOTABLY HIGHER THAN THE GFS...THOUGH THE GFS IN THIS CASE COULD BE
IMPACTED BY THE DIFFERENT TIMING OF THE WAVE. MOST TEMP GUIDANCE
JUST KEEPS AFTN TEMPS TOO WARM TO EXPECT SNOW SHOWERS EAST OF THE
MTNS DURING THE PEAK OF THE CONVECTIVE POTENTIAL. ANY CONVECTIVE
CELLS WOULD HAVE TO BE PRETTY ROBUST TO PRODUCE RATES CAPABLE OF
RAPID WET-BULBING NECESSARY TO OVERCOME THE DRY AIR AND RELATIVELY
WARM TEMPS BELOW THE CLOUD LAYER. CONTINUED PRESENCE OF THE TROUGH
AND POTENTIALLY A SECOND EMBEDDED SHORTWAVE ARRIVING MONDAY NIGHT
DO SUGGEST A SLOW TAPERING OF POPS AT THAT TIME...AND BY EVENING
TEMPS COOL ENOUGH THAT I INCLUDED A RAIN/SNOW MENTION FOR THE
PIEDMONT...WITH NO ACCUMULATION. THE GROUND WOULD PROBABLY STILL
BE TOO WARM ANYWAY.

FOR THE MOUNTAINS...DURING THE DAY MONDAY A PRETTY GOOD SETUP FOR NW
FLOW SNOW WILL DEVELOP...PARTICULARLY WHEN WINDS VEER SLIGHTLY THE
WAKE OF THE FIRST SHORTWAVE. ON ACCOUNT OF THE VERY COLD AIR WORKING
IN...TEMP AND MOISTURE PROFILES LOOK GOOD FOR SNOW CRYSTALLIZATION
AND LIGHT BUT STEADY ACCUMULATION IS EXPECTED. THIS WILL CONTINUE
INTO TUE MRNG WITH LITTLE CHANGE SEEN IN THE PROFILES. ONCE THE
MONDAY PERIOD ENTERS THE RANGE OF THE CONVECTION-ALLOWING GUIDANCE
WE WILL BE ABLE TO REFINE TOTALS A LITTLE MORE CONFIDENTLY...AND
A WINTER STORM WATCH OR WINTER WX ADVISORY COULD BE ISSUED. TEMPS
WILL BOTTOM OUT A CATEGORY OR TWO BELOW CLIMO FOR TUE MRNG. SUB-ZERO
WIND CHILLS ARE EXPECTED IN THE HIGHEST ELEVATIONS...AND THAT MAY
BE WRAPPED INTO ANY WINTER PRODUCTS.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF EARLY SATURDAY MORNING...NO DRAMATIC CHANGES FROM PREVIOUS
PACKAGE IN THE MEDIUM RANGE. FROM TUESDAY INTO AT LEAST EARLY
THURSDAY THE FCST WILL REVOLVE...NO PUN INTENDED...AROUND THE DEEP
EASTERN CONUS UPPER TROUGH AND THE VORT LOBES ENCIRCLING IT.
WESTERLY UPSLOPE FLOW INTO THE APPALACHIANS WILL ALLOW PERIODS OF
SNOW TO CONTINUE NEAR THE TENNESSEE BORDER...WITH MOISTURE BECOMING
INCREASINGLY SHALLOW WED...IMPLYING THEY WILL TAPER OFF BY THAT
TIME. FOR THE AREA EAST/SOUTH OF THE BLUE RIDGE...AS IS TO BE
EXPECTED THERE REMAINS RUN-TO-RUN VARIATION IN TIMING OF THE VORT
LOBES...AND IN THE FINE DETAILS THAT MIGHT ALLOW SNOW SHOWERS.
850-700MB LAPSE RATES UNDER THE TROUGH WILL LIKELY BE SLIGHTLY
WEAKER TUE...BUT STILL MARGINALLY FAVORABLE FOR SFC-BASED
CONVECTION. THE BEST SHOT AT ANY PIEDMONT ACCUMS IN THIS PERIOD DOES
APPEAR TO BE TUE AFTN...THOUGH WITH FAVORED MODEL BLEND...MAX TEMPS
SHOULD STILL BE TOO WARM FOR ACCUMULATING SNOW OUTSIDE THE MTNS.
SAME WET-BULB CONCERNS EXIST TUE AS NOTED FOR MON IN THE SHORT-RANGE
DISCUSSION. THAT IS...ACCUMULATION EAST OF THE MTNS IS UNLIKELY
OVERALL AND WOULD PROBABLY BE SPOTTY.

TUESDAY NIGHT...SFC LOW PRESSURE MOVES FROM THE ERN GREAT LAKES
TO NEW ENGLAND AND A HIGH MOVES FROM THE CANADIAN PRAIRIE INTO
THE MIDWEST. PROGRESSION OF THESE FEATURES BRINGS A REINFORCING
SHOT OF COLD AIR FOR WEDNESDAY...MAKING IT THE COLDEST DAY OF THE
PERIOD...AND ALSO BRINGING THE GREATEST POTENTIAL FOR IMPACTFUL
GUSTS AND WIND CHILLS. HEIGHTS WILL FINALLY INCREASE WED NIGHT
AND THU AS THE TROUGH AXIS MOVES OFFSHORE. THE MODIFYING HIGH
WILL SETTLE OVER THE SOUTHEAST TO END THE WEEK. TEMPS DO MODERATE
AS IT DOES SO. NEXT WAVE IN THE POLAR CIRCULATION DOES DIVE ACRS
THE GREAT LAKES FRI NIGHT...AND AN ATLANTIC COASTAL LOW DEVELOPS
ON BOTH GFS/EC. HOWEVER THEY DIFFER ON WHETHER ANY PRECIP WILL
DEVELOP OVER LAND OR EVENT THIS FAR SOUTH...SO WILL NOT ADVERTISE
ANY PRECIP CHANCES EAST OF THE MTNS AT THIS TIME.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE
PERIOD. HIGH CLOUDS WILL REMAIN ACROSS THE AREA THRU THE DAY WITH
SOME MID CLOUD MOVING IN THIS AFTERNOON AND CONTINUING OVERNIGHT...
ESPECIALLY FOR THE I-85 TAF SITES. THE 06Z NAM HAS COME IN MUCH
FARTHER NORTH AND WEST WITH PRECIP THAN THE PREVIOUS RUN...AND MOST
OTHER GUIDANCE. GIVEN THE BIG CHANGE...DID NOT FOLLOW THAT TREND AND
KEPT PRECIP AND RESTRICTIONS OUT OF KCLT FOR NOW. N TO NE WIND
CONTINUES THRU THE PERIOD...WITH NLY WIND AT KAVL.

OUTLOOK...WEAK HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH
THE WEEKEND. A STRONG UPPER AIR DISTURBANCE COULD BRING ENOUGH
MOISTURE TO WRING OUT A FEW RAIN OR SNOW SHOWERS ON MONDAY.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-06Z
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 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 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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...RWH
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...RWH



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