537  
FXUS61 KRLX 210030  
AFDRLX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHARLESTON WV  
830 PM EDT SAT APR 20 2019  
   
SYNOPSIS
 
 
UPPER LEVEL LOW SLOWLY MOVES OFF TO THE EAST TONIGHT THROUGH  
SUNDAY NIGHT. HIGH PRESSURE MONDAY. COLD FRONT APPROACHES FROM  
THE NORTH TUESDAY, THEN REMAINS NEAR THE AREA THROUGH FRIDAY.  
 

 
   
NEAR TERM /THROUGH SUNDAY/
 
 
AS OF 815 PM SATURDAY...  
 
MUCH OF THE ORGANIZED SHOWERS ARE PIVOTING THRU CENTRAL AND  
EASTERN PORTIONS OF THE CWA CURRENTLY. I HAVE UPDATED THE POP  
GRIDS TO REFLECT THIS A BIT BETTER. THE THUNDERSTORM ACTIVITY  
FROM EARLIER THIS AFTERNOON ACROSS THE NORTHERN  
LOWLANDS/MOUNTAINS HAS SHIFTED WELL NORTH OF THE AREA, SO NOT  
EXPECTING ANY THUNDER FOR THE REMAINDER OF THE NIGHT. THE UPPER  
LOW LOOKS TO HAVE CROSSED INTO SOUTHERN WV AS OF THIS WRITING  
AND WILL SLOWLY PIVOT NORTHEAST OVERNIGHT.  
 
OF CONCERN IS HOW POOR THE MODELS ARE HANDLING THE AMOUNT OF  
COOLING IN THE LOWER LEVELS FROM THESE SHOWERS IN COMBINATION  
WITH THE ADVANCING LOW LEVEL COLD POOL. WEBCAMS REVEAL SNOW IS  
FALLING AT SNOWSHOE AT THE SUMMIT (ABOUT 4800 FEET), WITH A  
SKIFF ON THE GROUND AND 32 DEGREES. THIS IS OCCURRING SEVERAL  
HOURS FASTER THAN EVEN LATEST NEAR TERM MODELS ARE SUGGESTING.  
RAIN REMAINS THE DOMINATE PRECIP TYPE JUST BENEATH THE SUMMIT,  
HOWEVER. I HAVE LOWERED HOURLY TEMPERATURES ON THE HIGHEST  
RIDGES THROUGH THE NIGHT A FEW DEGREES AND ALLOWED FOR SOME SNOW  
IN THE WX GRIDS. CURRENT THINKING IS THE SNOW LEVELS WILL LOWER  
TO AROUND 3500 OR 4000 FT OVERNIGHT. GIVEN THE SKIFF ALREADY  
SEEN ON THE WEBCAMS, I ALLOWED FOR UP TO AN INCH ABOVE 4500 FEET  
TONIGHT.  
 
AS OF 230 PM SATURDAY...  
 
UPPER LEVEL LOW SLOWLY LUMBERS AWAY FROM THE AREA TO THE EAST  
THIS PERIOD. AFTER MAKING SHOWERS NUMEROUS THIS AFTERNOON FROM  
ITS POSITION OVER THE HTS TRI-STATE AREA, IT DRIFTS EASTWARD  
ACROSS THE AREA TONIGHT, AND THEN SLOWLY EAST OF THE AREA ON  
SUNDAY.  
 
SHOWERS WERE MOST NUMEROUS BENEATH THE UPPER LEVEL LOW, AND IN  
AN AREA BENEATH UPPER LEVEL DIFFLUENT FLOW AHEAD OF A  
NEGATIVELY TILTED TROUGH AXIS EXTENDING SOUTHEASTWARD FROM THE  
UPPER LEVEL LOW THIS AFTERNOON. SHOWER COVERAGE WILL WAVE FROM  
WEST TO EAST AS THE SUN SETS THIS EVENING, AND THEN SCATTERED  
SHOWERS WILL GRADUALLY WAVE OVERNIGHT THROUGH SUNDAY, AS THE  
UPPER LEVEL LOW BEGINS TO NUDGE ITS WAY EAST OF THE FORECAST  
AREA.  
 
THE COLD CORE ALOFT, ALONG AND JUST SOUTH OF THE UPPER LEVEL  
LOW, DRIFTS EASTWARD THROUGH THIS EVENING, AND THEN ACROSS THE  
MOUNTAINS OVERNIGHT INTO SUNDAY. THIS MAKES SNOW SHOWERS A  
POSSIBILITY OVER THE HIGHER MOUNTAINOUS TERRAIN, BUT WITH  
ACCUMULATION UNLIKELY AS SNOWSHOE JUST ABOUT GETS DOWN TO  
FREEZING EARLY SUNDAY MORNING.  
 
THE THERMAL TROUGH CONTINUES TO ENVELOP MUCH OF THE AREA ON  
SUNDAY, SO CLOUDS WILL REMAIN PLENTIFUL. HOWEVER, LACK OF  
FORCING, AND LIGHT FLOW LIMITING UPSLOPE EFFECTS, WILL ALLOW  
THE PROBABILITY OF PRECIPITATION TO CONTINUE TO WANE.  
 
BLENDED ON NEAR TERM, CONSENSUS AND MOS GUIDANCE FOR  
TEMPERATURES, WITH CLOUDS LIMITING THE DIURNAL RANGE.  
 

 
   
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 255 PM SATURDAY...  
 
A PERSISTENT UPPER LEVEL LOW MOVES OUT TO SEA SUNDAY NIGHT,  
ALLOWING UPPER/MID-LEVEL RIDGING TO MOVE IN BY MONDAY. THIS  
OFFERS A FANTASTIC WEATHER DAY ON MONDAY, WITH HIGH PRESSURE  
KEEPING THINGS DRY AND A SOUTHWEST WIND WARMING THE REGION INTO  
THE 60'S AND 70'S. THIS RUNS ABOUT 5 DEGREES ABOVE NORMAL FOR  
THIS TIME OF YEAR. WILL NEED TO SEE HOW LOW-LEVEL MOISTURE  
DISSIPATES WITH THE SYNOPTIC PATTERN CHANGE (TROUGHING TO  
RIDGING). EARLY INDICATIONS ARE THAT LL STRATUS COULD IMPACT  
PORTIONS OF CENTRAL APPALACHIA MONDAY MORNING AND PERHAPS LINGER  
INTO THE MIDDAY, WHICH WOULD LIKELY RESULT IN A STUNTED DIURNAL  
TEMPERATURES TREND.  
 
WEAK RIDGING TO ZONAL FLOW ALOFT KEEPS THE MAJORITY OF THE AREA  
QUIET THROUGH THE REMAINDER OF THE SHORT-TERM PERIOD. BUT, A  
WEAKLY-FORCED NORTHERN STREAM WAVE AND ASSOCIATED SURFACE  
FEATURES ENTERING THE GREAT LAKES REGION COMPLICATE MATTERS.  
WARM FRONTAL FORCING POSSIBLY PRODUCES SHOWERS AND SOME STORMS  
TUESDAY ACROSS THE NORTH, BUT REGARDLESS ALLOWS FOR GUSTY WINDS  
AND MOISTURE TO ONCE AGAIN CONVERGE IN THE OHIO VALLEY.  
 
TEMPERATURES CONTINUE TO TREND UPWARD TUESDAY UNDER WARM  
ADVECTION, WITH AFTERNOON HIGHS REACHING TO +/- 3 DEGREES OR SO  
OF 80 WHILE THE HIGHEST RIDGES STILL MAKE IT WELL INTO THE 60'S.  
DEW POINTS IN THE EASTERN MOUNTAINS WILL NEED TO BE MONITORED,  
AS TUESDAY COULD DEVELOP FIRE DANGER.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
 
 
AS OF 300 PM SATURDAY...  
 
MODELS REMAIN OUT OF AGREEMENT IN THE LONG-TERM PORTION OF THE  
FORECAST, ALTHOUGH GENERALLY UNSETTLED WEATHER REMAINS A  
CONSENSUS THROUGH LATE NEXT WEEK. TUESDAY NIGHT, MOISTURE  
CONVERGES ALONG A COLD FRONT DRIVEN BY A NORTHERN STREAM  
SHORTWAVE TROUGH SLIDING ACROSS THE GREAT LAKES. THE MORE  
AGGRESSIVE GFS AND CMC CLOSE THE TROUGH OFF RESULTING IN A MORE  
AGGRESSIVE COLD FRONT MOVING SOUTH THROUGH THE AREA ON  
WEDNESDAY, STALLING SOUTH OF THE AREA. MEANWHILE THE ECMWF KEEPS  
A WEAKLY-FORCED OPEN WAVE SLOWLY STALLING THE FRONT OVERHEAD  
THROUGH THURSDAY.  
 
IN EITHER CASE, RAIN AND CLOUDS WILL LIKELY BE IN THE AREA  
WEDNESDAY AND THURSDAY WITH THE REMNANT FRONT AROUND. THUNDER  
WILL PREFER SOUTHERN AREAS AS INSTABILITY IS MOST LIKELY TO  
DEVELOP ON THE WARM SIDE OF THE BOUNDARY. MODELS DO AGREE ON A  
CLOSED SOUTHERN STREAM TROUGH FORMING OVER THE SOUTHERN PLAINS  
PHASED WITH AN OPEN NORTHERN STREAM TROUGH BY THURSDAY. THIS  
SPURS CYCLOGENESIS ACROSS THE SOUTH BY FRIDAY AND ENHANCES  
FRONTOGENETIC FORCING ALONG THE REMNANT BOUNDARY. THESE COMBINED  
RETURN WIDESPREAD PRECIPITATION CHANCES BY FRIDAY, AND PUSH  
THROUGH A BREATH OF FRESHER, DRIER AIR BY SATURDAY.  
 

 
   
AVIATION /00Z SUNDAY THROUGH THURSDAY/
 
 
AS OF 820 PM SATURDAY...  
 
LIGHT TO MODERATE SHRA CONTINUE TO AFFECT MOST TERMINALS THIS  
EVENING, ASIDE FROM HTS. VFR REMAINS THE PREDOMINATE CATEGORY  
INITIALLY BUT EXPECT BASES TO GRADUALLY LOWER FROM WEST TO EAST  
THIS EVENING AND OVERNIGHT. MVFR CIGS WILL LOWER INTO IFR AT  
SOME TERMINALS OVERNIGHT, MAINLY HTS/CRW/BKW. AS THE LOW LEVEL  
FLOW WEAKENS, SOME PATCHY DENSE FOG IS EXPECTED TO FROM,  
ESPECIALLY IN THE VALLEYS. I DO HAVE VSBY RESTRICTIONS CODED UP  
AT CRW AND BKW OVERNIGHT, WHERE LOCAL AFFECTS MAY ALLOW THE FOG  
TO REACH UP TO THE TERMINALS.  
 
THE UPPER LOW WILL PIVOT NORTHEAST OF THE AREA SUNDAY WITH  
GRADUALLY IMPROVING FLIGHT CONDITIONS AS THE DAY PROGRESSES. IT  
WILL TAKE LONGEST FOR THIS TO OCCUR AT CRW, WHERE MODELS KEEP  
NEAR IFR CIGS THRU LATE MORNING. ALL TERMINALS WILL SEE BASES  
LIFT INTO VFR BY LATE AFTERNOON, HOWEVER.  
 
SURFACE FLOW WILL BECOME LIGHT SOUTHWEST TO CALM TONIGHT, AND  
THEN LIGHT WEST ON SUNDAY, ALL BENEATH LIGHT SOUTHWEST ALOFT.  
 
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z MONDAY...  
 
ALTERNATE SCENARIOS: CEILINGS MAY VARY TONIGHT INTO SUNDAY.  
 
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY  
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:  
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.  
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.  
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.  
 
DATE SUN 04/21/19  
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11  
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07  
CRW CONSISTENCY H H H H H H M H H L L L  
HTS CONSISTENCY H H H H H H H H H H H H  
BKW CONSISTENCY H H H H H H H H L M L M  
EKN CONSISTENCY H H H H H H H H H H H H  
PKB CONSISTENCY H H H H H H H H H H H H  
CKB CONSISTENCY H M M H M H H H H H H M  
 
AFTER 00Z MONDAY...  
IFR POSSIBLE IN FOG AND / OR STRATUS OVERNIGHT SUNDAY NIGHT  
INTO MONDAY MORNING. BRIEF IFR AT TIMES IN THUNDERSTORMS  
MIDWEEK, BEGINNING UP NORTH AS EARLY AS LATE TUESDAY NIGHT.  
 

 
   
RLX WATCHES/WARNINGS/ADVISORIES
 
 
WV...NONE.  
OH...NONE.  
KY...NONE.  
VA...NONE.  
 

 
 

 
SYNOPSIS...RPY/TRM/MZ  
NEAR TERM...TRM/30  
SHORT TERM...MC  
LONG TERM...MC  
AVIATION...30  
 
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