666
FXUS61 KRNK 191838
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
238 PM EDT FRI APR 19 2019
SYNOPSIS
A STRONG COLD FRONT WILL BRING SHOWERS AND THUNDERSTORMS THROUGH
TONIGHT. UPSLOPE SHOWERS COULD LINGER WEST OF THE BLUE RIDGE FOR
SATURDAY AND EARLY SUNDAY. HIGH PRESSURE WILL ARRIVE BY EARLY
NEXT WEEK TO PROVIDE DRIER CONDITIONS.
NEAR TERM /THROUGH SATURDAY/
AS OF 230 PM EDT FRIDAY...
A SPECIAL 15Z SOUNDING WAS CONDUCTED TO GAUGE THE SEVERE WEATHER
THREAT, AND THE SHEAR NUMBERS HAVE SIGNIFICANTLY INCREASED SINCE
THE PREVIOUS 12Z SOUNDING. THE 0-1 KM WIND SHEAR IN THIS
SPECIAL RNK SOUNDING REACHES 55 KT, WHILE THE 0-6 KM WIND SHEAR
IS UP TO 74 KT. THIS SHEAR ENVIRONMENT IS EXTREMELY FAVORABLE
FOR SUPERCELLS CAPABLE OF DAMAGING WINDS, HAIL, AND TORNADOES.
THE SOUNDING ALSO REVEALS SURFACE CAPE OF ABOUT 700 J/KG, SO
THERE IS STILL ENOUGH INSTABILITY FOR THESE STORMS TO FIRE
DESPITE THE PREVALENT CLOUD COVER OVERHEAD. REPORTS OF
SIGNIFICANT STRUCTURAL DAMAGE HAVE ALREADY BEEN RELAYED TO US
SOUTH OF ROCKY MOUNT, VIRGINIA. A TORNADO WATCH REMAINS IN
EFFECT FOR MOST OF SOUTHWEST VA AND NORTHWEST NC UNTIL 5 PM EDT.
NEEDLESS TO SAY, EVERYONE SHOULD REMAIN ALERT THROUGH THIS
EVENING AS THESE SHOWERS AND THUNDERSTORMS TRACK NORTHEASTWARD.
IN ADDITION, THESE THUNDERSTORMS WILL PRODUCE HEAVY RAIN THAT
COULD LEAD TO HYDROLOGICAL ISSUES. WHILE THEY ARE MOVING AT
SPEEDS UP TO 50 KT, IT WILL BE REPEATED ROUNDS OF RAIN FROM
PREFRONTAL CONVECTION AND THE EVENTUAL LINE ALONG THE COLD FRONT
ALONG WITH THE POTENTIAL FOR TRAINING THAT MAY LEAD TO
LOCALIZED FLASH FLOODING AND URBAN/SMALL STREAM FLOODING.
PRECIPITABLE WATER VALUES HAVE CLIMBED TO 1.25 INCHES, BUT THERE
IS CONSIDERABLE MOISTURE ADVECTION STILL ONGOING FROM THE GULF
OF MEXICO COURTESY OF DEEP SOUTHERLY FLOW ALOFT. THE HYDRO
THREAT COULD LINGER FURTHER INTO TONIGHT AFTER THE SEVERE
THREATS TAPER BEYOND SUNSET. IT IS TOO EARLY TO TELL WHETHER ANY
RIVER FLOODING THREATS WILL MATERIALIZE, BUT THIS FACET WILL BE
CLOSELY MONITORED.
THE CULPRIT RESPONSIBLE FOR THE PREVIOUSLY MENTIONED MULTITUDE
OF WEATHER HAZARDS IS A STRONG COLD FRONT APPROACHING THE MID
ATLANTIC. A CLOSED UPPER LEVEL LOW IN ASSOCIATION WITH THIS
COLD FRONT IS IN THE PROCESS OF TILTING NEGATIVELY. AFTER THE
FRONTAL PASSAGE PROJECTED TO BE AROUND MIDNIGHT TONIGHT, NOTABLY
COOLER AIR SHOULD ARRIVE. PLENTIFUL LOW CLOUDS SHOULD SHUT DOWN
THE LOW-LEVEL INSTABILITY, BUT LINGERING SHOWERS MAY CONTINUE
THROUGHOUT THE DAY ALONG AND WEST OF THE BLUE RIDGE. HIGH
TEMPERATURES BY SATURDAY AFTERNOON MAY NOT ESCAPE THE 40S IN THE
HIGHER ELEVATIONS.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/
AS OF 230 PM EDT FRIDAY...
BY SATURDAY NIGHT, THE CLOSED UPPER LEVEL LOW WILL SLOWLY TRACK
OVERHEAD. WITH 850 MB TEMPERATURES FALLING BELOW FREEZING
OVERNIGHT, LINGERING RAIN SHOWERS IN THE HIGHEST ELEVATIONS
WEST OF THE BLUE RIDGE COULD CHANGE OVER TO LIGHT SNOW SHOWERS.
ANY PRECIPITATION SHOULD DISSIPATE BY SUNDAY AS THE UPPER LEVEL
LOW HEADS TOWARD THE NORTHEAST. LOW CLOUDS COULD LINGER ALONG
AND WEST OF THE BLUE RIDGE UNTIL LATER IN THE AFTERNOON, BUT
CONFIDENCE IS HIGHER THAT DRIER CONDITIONS SHOULD ENSUE BY
SUNDAY NIGHT. HIGH PRESSURE WILL BUILD OVER THE MID ATLANTIC TO
PROVIDE SUNSHINE FOR MONDAY. THE UPPER LEVEL PATTERN WILL BE
CHANGING AS WELL DUE TO RIDGING ALOFT, SO EXPECT MILDER AIR TO
ARRIVE FOR MONDAY AND MONDAY NIGHT.
LONG TERM /TUESDAY THROUGH FRIDAY/
AS OF 230 PM EDT THURSDAY...
ANOTHER COLD FRONT SHOULD CROSS OVER THE OHIO RIVER VALLEY BY
TUESDAY, WHILE ITS ASSOCIATED UPPER LEVEL TROUGH SWINGS THROUGH
THE NEW ENGLAND STATES. THE RETURN FLOW OF MOISTURE ALONG WITH
DIURNAL HEATING COULD SPARK A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE MOUNTAINS BY THE AFTERNOON. IT IS WORTH
NOTING THAT THE ECMWF MODEL IS A LITTLE SLOWER AND DRIER FOR
TUESDAY, WHILE THE GFS INDICATES THIS SLIGHT CHANCE. WEDNESDAY
APPEARS TO BE MORE FAVORABLE FOR SHOWERS AND THUNDERSTORMS AS
THE COLD FRONT MOVES CLOSER.
THE MODEL SOLUTIONS DIVERGE NOTABLY BY THURSDAY AS THE ECMWF
BECOMES MORE PROGRESSIVE AS IT PUSHES THE COLD FRONT OFFSHORE TO
BRING HIGH PRESSURE BY FRIDAY, BUT THE GFS STALLS THE FRONTAL
BOUNDARY TO THE NORTH OF THE CWA DURING BOTH DAYS. GIVEN THAT
BOTH MODELS PRODUCE MOS HIGH TEMPERATURES IN THE 60S AND 70S FOR
THURSDAY AND FRIDAY AND THE POTENTIAL PROXIMITY OF THIS BOUNDARY,
THERE APPEARS TO BE ENOUGH INSTABILITY TO ADVERTISE A GENERAL
THREAT FOR AFTERNOON SHOWERS AND THUNDERSTORMS THROUGHOUT THIS
TIMEFRAME. LATER MODEL RUNS WILL HOPEFULLY PAINT MORE DETAILS TO
ADD CONFIDENCE FOR THIS PORTION OF THE FORECAST.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
AS OF 230 PM EDT FRIDAY...
THE THREAT FOR NUMEROUS SHOWERS AND THUNDERSTORMS THIS
AFTERNOON INTO EARLY TONIGHT HAS NECESSITATED PUTTING THUNDER IN
ALL TAF SITES. SOME OF THESE STORMS COULD BECOME SEVERE AND
POSE A SIGNIFICANT THREAT TO AVIATION WITH STRONG WINDS ALOFT,
ESPECIALLY ALONG AND EAST OF THE BLUE RIDGE. MVFR/IFR CONDITIONS,
HEAVY RAIN, AND SIGNIFICANT TURBULENCE WILL LIKELY ACCOMPANY
THESE STORMS AS WELL.
THE CONVECTIVE THREAT SHOULD WANE AFTER 04Z AS A STRONG COLD
FRONT PASSES EAST OF KLYH AND KDAN. HOWEVER, LINGERING SHOWERS
AND LOW CLOUDS POINT TO A HIGH CONFIDENCE OF MVFR CEILINGS. IT
IS POSSIBLE THAT SOME CEILINGS MAY DIP LOWER TOWARD IFR, BUT A
DECENT SURFACE SOUTH WIND OVERNIGHT MAY PREVENT IT FROM ACTUALLY
OCCURRING. CONDITIONS SHOULD SLOWLY IMPROVE ON SATURDAY
MORNING, BUT IT WILL BE QUESTIONABLE IF ANY OF THE TAF SITES CAN
LEAVE THE MVFR CATEGORY.
EXTENDED AVIATION DISCUSSION...
A CLOSED UPPER LEVEL LOW SHOULD MOVE OVERHEAD DURING SATURDAY
NIGHT, WHICH WILL KEEP MVFR CEILINGS AND LINGERING SHOWERS ALONG
AND WEST OF THE BLUE RIDGE INTO SUNDAY MORNING. VFR CONDITIONS
APPEAR LIKELY TO RETURN BY SUNDAY EVENING. HIGH PRESSURE SHOULD
BRING GOOD FLYING WEATHER FOR MONDAY AND MOST OF TUESDAY.
HOWEVER, THE CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS WILL
INCREASE BY WEDNESDAY.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...PW
NEAR TERM...PW
SHORT TERM...PW
LONG TERM...PW
AVIATION...PW
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