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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