652
FXUS61 KRNK 180233
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
933 PM EST SUN FEB 17 2019
SYNOPSIS
AN AREA OF LOW PRESSURE WILL PROGRESS INTO AND ACROSS THE AREA
TONIGHT WITH ITS ASSOCIATED FRONTAL BOUNDARY CROSSING THE CAROLINAS.
AFTER A BRIEF BREAK IN TEH WET WEATHER MONDAY NIGHT INTO EARLY
TUESDAY, THE FORECAST TURNS VERY SOGGY FOR THE REMAINDER OF THE WEEK.
TUESDAY NIGHT INTO WEDNESDAY, ENOUGH COLDER AIR WILL BE OVER THE
REGION FOR THE STRONG POTENTIAL FOR A SIGNIFICANT WINTER EVENT.
NEAR TERM /THROUGH MONDAY/
AS OF 930 PM EST SUNDAY...
LOW PRESSURE WAS HEADING EASTWARD THROUGH CENTRAL KENTUCKY,
ASSOCIATED WITH A LARGE SWATH OF RAIN ACROSS THE MID-ATLANTIC.
RAIN IS EXPECT FOR MUCH OF THE OVERNIGHT UNTIL THE LOW CLEARS
THE AREA EARLY MONDAY MORNING. IN ADVANCE OF THE LOW, A WEDGE OF
HIGH PRESSURE ON THE EAST SIDE OF THE APPALACHIANS WAS
MAINTAINING A COLD AIRMASS NEAR THE SURFACE. THIS WAS PRIMARILY
RESULTING IN A COLD RAIN WITH SOME ICING NEAR THE BLUE RIDGE
PARKWAY AND ACROSS THE HIGHLANDS OF VA/WV. AT 9PM, TEMPERATURES
WERE STILL FLIRTING WITH 32 DEGREES IN SOME OF THESE LOCATIONS
WHICH IS ALLOWING THE ICE ACCRETION ON THE TREES TO PERSIST.
TEMPERATURES ARE EXPECTED TO WARM A FEW DEGREES OVERNIGHT, SO
LITTLE OR NO ADDITIONAL ICING IS EXPECTED. THE EVENING RNK
SOUNDING WAS +8 DEG C JUST ABOVE 850 MB... WHICH EQUATES TO 46
DEGREES F. THE HIGHER MOUNTAIN RIDGES MAY ACTUALLY WARM INTO THE
LOWER 40S OVERNIGHT AS THIS WARM AIR LOWERS IN ALTITUDE JUST
AHEAD OF THE APPROACHING LOW PRESSURE. THE ACTUAL TEMPERATURE OF
THE RAIN ALSO GETS MODIFIED A FEW DEGREES BEFORE REACHING THE
SURFACE, SO THE MORE IT RAINS, THE WARMER IT SHOULD GET
OVERNIGHT.
OVERALL PRECIPITATION AMOUNTS RANGED FROM A QUARTER TO THREE
QUARTERS OF AN INCH SUNDAY. THERE WERE EVEN REPORTS OF THUNDER
DURING THE AFTERNOON, SOME OF WHICH RESULTED IN ISOLATED RAIN
AMOUNTS OF UP TO 1 INCH. ADDITIONAL RAIN OVERNIGHT IS EXPECTED
TO REMAIN UNDER A HALF INCH. THAT SAID, NOT OUT OF THE QUESTION
FOR A FEW LOCATIONS TO SEE 24 HOUR AMOUNTS (ENDING 7AM MONDAY)
TO RANGE FROM 1.0 TO 1.5. GIVE THE LOCALIZED NATURE OF THE
HEAVIEST RAIN, FLOODING IS NOT EXPECTED. NEVER THE LESS, PONDING
OF WATER IS A HIGH LIKELIHOOD WITH SOME POOR DRAINAGE ISSUES.
OVERALL, THE CURRENT RAINFALL INCREASES THE SENSITIVITY OF THE
STREAMS AND CREEKS TO FUTURE RUNOFF FROM RAIN LATER IN THE WEEK,
BUT NOTHING OF THE LIFE THREATENING VARIETY AT THE MOMENT.
ON MONDAY, WE WILL BE ON THE BACK SIDE OF THE DEPARTING SYSTEM, AND
WINDS WILL SHIFT NORTHWEST AND BECOME GUSTY. GUSTS OF 30 TO 40 MPH
WILL BE COMMON ACROSS THE HIGHEST TERRAIN ALONG AND WEST OF THE
CREST OF THE BLUE RIDGE. GUSTS OF 15 TO 25 MPH WILL BE COMMON ACROSS
THE PIEDMONT REGION. THESE SAME NORTHWEST WINDS WILL ALLOW FOR DRIER
AIR TO ERODE CLOUD COVER ACROSS THE PIEDMONT. HOWEVER, CLOUDS WILL
BE SLOWER TO ERODE ACROSS THE MOUNTAINS THANKS TO AN UPSLOPE
COMPONENT. LIGHT PRECIPITATION IN THE FORM OF LIGHT RAIN/DRIZZLE OR
LIGHT FREEZING RAIN/DRIZZLE WILL BE POSSIBLE ACROSS WESTERN
GREENBRIER COUNTY HEADING INTO THE AFTERNOON. A FEW FLAKES OF SNOW
ARE POSSIBLE AS THE TOP OF THE SHALLOW MOISTURE LAYER COOLS TO ABOUT
-10C LATE IN THE DAY. HIGH TEMPERATURES TOMORROW WILL RANGE FROM THE
LOW TO MID 40S ACROSS THE MOUNTAINS WITH LOW TO MID 50S ACROSS THE
PIEDMONT.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/
AS OF 400 PM EST SUNDAY...
VERY ACTIVE AND UNSETTLED PATTERN TO CONTINUE THROUGH THE
PERIOD WITH SIGNIFICANT POTENTIAL FOR A WINTER STORM, WITH BOTH
SIGNIFICANT ICE AND SNOW ACCUMULATIONS POSSIBLE, FOLLOWED BY AN
EXTENDED PERIOD OF MODERATE TO HEAVY RAIN EVENTS. AREAL FLOODING
AND RIVER FLOODING SEEM ALMOST CERTAIN AS WE MOVE INTO THE MID
PART OF THE WEEK AND THE WEEKEND. THE CULPRIT WILL BE A VERY
ACTIVE SOUTHWEST FLOW AS DEEP TROUGHING REMAINS ANCHORED ACROSS
THE SOUTHWEST U.S. WITH AN ENDLESS SERIES OF VIGOROUS EMBEDDED
SHORT WAVES TRACKING FROM THE SOUTHWEST U.S. INTO THE SOUTH
CENTRAL U.S. THEN MOVING EAST-NORTHEAST TO NORTHEAST TOWARD THE
MID-ATLANTIC. IN ESSENCE THE MAIN STORM TRACK WILL BE RIGHT
ACROSS OUR AREA THROUGH THE ENTIRE TIME FRAME. THIS WILL SUPPLY
PERSISTENT CLOUD COVER AND NUMEROUS ROUNDS OF PRECIPITATION.
FLOODING FROM EXCESSIVE RAINFALL AND SATURATED GROUND WILL
CLEARLY BE THE MAIN CONCERN, ESPECIALLY AS THE WEEK PROGRESSES
CONTINUING INTO THE LONG TERM PERIODS.
UNFORTUNATELY, WITH A CANADIAN AIR MASS LINGERING JUST TO OUR
NORTH AND MEANDERING/OSCILLATING BACK/FORTH ACROSS OUR LATITUDE,
THERE WILL BE A DEFINITE CONCERN FOR WINTER WEATHER. THAT
CONCERN HAS SOLIDIFIED CONSIDERABLY FROM YESTERDAY AS THE DEPTH
OF COLD AIR APPEARS MORE CERTAIN AND FURTHER SOUTH THAN
INDICATED YESTERDAY, WHICH IS CONSISTENT WITH A DEEPER WEDGE
DEVELOPING IN RESPONSE TO THE SLOW DEEPENING TROUGH IN THE SOUTH
CENTRAL U.S. AS THE WARM NOSE FROM A STRONG SOUTHWESTERLY JET
WORKS ITS WAY OVER THE SHALLOW COLD AIR MASS LATER IN THE
NIGHT/WEDNESDAY MORNING, THE PRECIPITATION WILL TRANSITION TO
SLEET AND THEN FREEZING RAIN. MODEL SIGNALS ARE STRONG FOR
SIGNIFICANT SNOW, SLEET, AND ICE ACCUMULATIONS, AND THIS COULD
WELL BE THE MOST SIGNIFICANT WINTER STORM IN TERMS OF TOTAL
ACCUMULATION SINCE THE MID-DECEMBER EVENT. WITH GOOD
COLLABORATION VIA WPC AND NEIGHBORING OFFICES THIS AFTERNOON, WE
CONCURRED ON THE POTENTIAL FOR WINTER WEATHER WITH THIS EVENT
AND HAVE FOLLOWED THEIR SNOW AND ICE ACCUMULATIONS CLOSELY,
NAMELY WINTER STORM WARNING CRITERIA ICE OF .25 TO .50 INCH AND
SNOW ACCUMULATIONS OF 4-8 INCHES ACROSS THE NORTH WITH 1-3
INCHES IN THE SOUTH. GIVEN THAT THIS IS 72+ HOURS OUT, NO
HEADLINES HAVE BEEN ISSUED YET, BUT WILL STRONGLY HIGHLIGHT THE
POTENTIAL IN THE HWO/EHWO.
CURRENT INDICATIONS ARE THAT THE WINTER WEATHER EVENT WILL
TRANSITION INTO A FLOODING EVENT THROUGH THE DAY WEDNESDAY AND
WEDNESDAY NIGHT. CURRENT QPF PROJECTIONS ARE IN THE 2-4 INCH
RANGE FOR THE TUE-THU TIME FRAME, WHICH IS IN ADDITION TO ALL
THE RAIN WE HAVE RECEIVED OVER THE WEEKEND AND EARLY THIS WEEK.
WPC HAS NOTED THAT THERE ARE NUMEROUS MODELS WITH STRONG SIGNALS
FOR FLOODING ACROSS A LARGE PORTION OF THE SOUTHEASTERN U.S., TN
VALLEY, AND INTO THE SOUTHERN APPALACHIANS. AGAIN, BEING THAT
THIS IS OVER 72 HOURS OUT, NO HEADLINES HAVE BEEN ISSUED AT THIS
TIME, BUT AREAL FLOODING AND RIVER FLOODING APPEARS LIKELY.
PLEASE PLAN ACCORDINGLY.
TEMPERATURES WILL AVERAGE NEAR NORMAL DURING THIS PERIOD AS WE
OSCILLATE BETWEEN THE COLDER CANADIAN AIR MASS PRESENT JUST TO
OUR NORTH AND THE MUCH MILDER AIR TO OUR SOUTH. THUS, THERE WILL
BE SOME FLUCTUATIONS ABOVE AND BELOW NORMAL THROUGH THE TIME
PERIOD. WEDNESDAY WILL REMAIN BELOW NORMAL, BUT MUCH ABOVE
NORMAL TEMPERATURES ARE EXPECTED AS THE WEEK PROGRESSES.
/CONFIDENCE IN FORECAST PARAMETERS/
TEMPERATURES - MODERATE TO HIGH,
PRECIPITATION PROBABILITIES - HIGH,
WINTER WEATHER POTENTIAL - MODERATE,
FLOODING POTENTIAL - MODERATE TO HIGH,
WINDS - MODERATE TO HIGH.
LONG TERM /THURSDAY THROUGH SUNDAY/
AS OF 430 PM EST SUNDAY...
VERY WET AND UNSETTLED WEATHER CONTINUES WITH A POSITIVELY
TILTED MEAN TROUGH IN THE WESTERN U.S. AND A BROAD SUBTROPICAL
RIDGE REMAINING ANCHORED OFF THE SOUTHEAST U.S. COAST. THIS WILL
KEEP A CONVEYOR BELT OF DEEP MOISTURE ANCHORED OVER THE AREA
ALONG WITH AN ACTIVE BAROCLINIC ZONE. TEMPERATURES WILL START
OUT BELOW NORMAL ON WEDNESDAY, THEN CREEP TO ABOVE NORMAL LEVELS
BY THE END OF THE WEEK AS THE BAROCLINIC ZONE IS NUDGED A TAD
FURTHER NORTH THANKS TO THE PERISTENT SUBTROPICAL RIDGE OFF THE
SOUTHEAST U.S. COAST. INDICATIONS ARE THAT THE BAROCLINIC ZONE
WILL SLIP SOUTH OF THE AREA BRIEFLY AS HIGH PRESSURE BUILDS TO
OUR NORTH ON THURSDAY, TO PROVIDE A SMALL OPPORTUNITY FOR THE
HEAVIER RAIN TO SHIFT SOUTH OF OUR AREA. HOWEVER, ANOTHER
SIGNIFICANT WAVE EMANATING FROM THE SOUTHWEST U.S. TROUGH IS
PROGGED TO PUSH THE BAROCLINIC ZONE BACK NORTH INTO OUR AREA
SATURDAY WITH MORE HEAVY RAIN AND FLOODING POSSIBLE AT THAT
TIME.
AT ANY RATE, TEMPERATURES WILL FINALLY WARM ENOUGH WITH
SOUTHWEST FLOW TO ERODE THE RETURNING WEDGE, THAT THE MAIN
FOCUS THROUGH THIS PERIOD WILL BE FLOODING, NOT WINTER WEATHER.
WPC DAYS 1-7 PRECIP OUTLOOK CURRENTLY HIGHLIGHTS AREAS EXCEEDING
4" MAINLY IN WESTERN NC, EASTERN TN, AND SOUTHWEST VA. AREAWIDE,
EXPECT AT LEAST 2-3", WITH LOCAL AMOUNTS OF 4-5 INCHES LIKELY.
PLEASE REMAIN ABREAST OF THE THREAT OF FLOODING AND RIVER
FLOODING WITH LATER FORECASTS AS THEIR IS AN INCREASING THREAT
FOR AREAL FLOODING AND RIVER FLOODING, ESPECIALLY DURING THE
LATER HALF OF THE WEEK.
AS NOTED ABOVE, WITH THE REGION INCREASINGLY IN THE WARM SECTOR
DURING THIS PERIOD, TEMPERATURES WILL AVERAGE ABOVE NORMAL AND
REMAIN MOSTLY ABOVE FREEZING.
AVIATION /01Z MONDAY THROUGH FRIDAY/
AS OF 930 PM EST SUNDAY...
IFR/LIFR A HIGH LIKELIHOOD OVERNIGHT. RAIN IS EXPECTED FOR MOST
OF THE OVERNIGHT WITH LOW STRATUS AND FOG. THE AREA OF LOW
PRESSURE RESPONSIBLE FOR THE POOR FLIGHT CONDITIONS IS FORECAST
TO MOVE EAST OF THE AREA EARLY MONDAY. THIS WILL BEGIN A PERIOD
OF CLEARING WITH IMPROVEMENT BACK INTO THE VFR RANGE FROM MONDAY
AFTERNOON INTO EARLY TUESDAY. THE ONLY EXCEPTION WITH BE THE
WESTERN SIDE OF THE APPALACHIANS FROM THE EASTERN OH VALLEY INTO
PA/WV WHERE LOW LEVEL STRATO-CU WILL PERSIST PROMOTING MVFR.
IN THE WAKE OF THIS STORM SYSTEM, WINDS WILL SHIFT NORTHWEST
AND TREND GUSTY. WINDS GUSTS OF 15 TO 25 KTS WILL BE COMMON
MONDAY AND EARLY MONDAY NIGHT.
FORECAST CONFIDENCE IN THE ABOVE SCENARIO IS MODERATE.
EXTENDED AVIATION DISCUSSION...
LINGERING MOUNTAIN CLOUDINESS IS EXPECTED TO MAINTAIN MVFR CIGS
ACROSS THE MOUNTAINS THROUGH MONDAY NIGHT.
BRIEF BREAK IN THE WET WEATHER IS EXPECTED TUESDAY, CONDITIONS
PRIMARILY VFR. TUESDAY NIGHT AND WEDNESDAY ANOTHER LOW PRESSURE
SYSTEM WILL BRING SUB-VFR CONDITIONS AS WELL AS PROVIDING
ANOTHER OPPORTUNITY FOR WINTER PRECIPITATION.
A FRONTAL BOUNDARY WILL REMAIN CLOSE TO THE REGION THURSDAY
INTO FRIDAY KEEPING PRECIPITATION AND THE POTENTIAL FOR SUB-VFR
CONDITIONS IN THE FORECAST.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...DS
NEAR TERM...DS/PM
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...DS/PM
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