Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 191359
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
959 AM EDT SUN APR 19 2015

.SYNOPSIS...
HIGH PRESSURE WAS OVER SOUTHEAST CANADA AND LOW PRESSURE WAS IN
ARKANSAS WITH A WARM FROM EXTENDING INTO SOUTH CAROLINA. THE LOW
AND WARM FRONT WILL MOVE NORTH TODAY AND TONIGHT. A COLD FRONT
CROSSES THE REGION ON MONDAY THEN HIGH PRESSURE BUILDS IN FOR
TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 958 AM EDT SUNDAY...

FLOOD WATCHES REMAIN IN EFFECT FROM THIS AFTERNOON INTO TONIGHT.

A WARM FRONT WILL LIFT NORTH TODAY AND CROSS THE FORECAST AREA
TONIGHT. DEEPER MOISTURE AND HIGHER PWATS WILL INCREASE IN THE
WARM ADVECTION WITH THE NORTHWARD ADVANCE OF THE FRONT. THE RNK
WRF-ARW...HIRESW-ARW AND HRRR SHOWED WIDESPREAD RAIN LIFTING
NORTHWARD ACROSS OUR AREA. LOW LEVEL JET INCREASING TO 50-60 KNOTS
FROM THE SOUTHEAST WILL RESULT IN STRONG UPSLOPE AND ISENTROPIC
LIFT. THE STRONG WINDS THROUGH A DEEP LAYER WILL PROVIDE LARGE
HELICITY VALUES LATE THIS AFTERNOON INTO THIS EVENING. THE DAY
ONE CONVECTIVE OUTLOOK (SWODY1) PLACED A MARGINAL (5 PERCENT
CHANCE OF WIND) ACROSS SOUTHWEST PORTION OF CWA. MODIFIED
TEMPERATURES...DEW POINT AND POPS FR THIS MORNING INTO THIS
AFTERNOON. MORE ADJUSTMENTS AS THE DAY PROGRESSES...


AS OF 430 AM EDT SUNDAY...

WARM FRONT ASSOCIATED WITH A LOW IN ARKANSAS WILL MOVE NORTH TODAY
AND WILL CROSS THROUGH THE FORECAST AREA TONIGHT. STRONG SYNOPTIC
SCALE LIFT WILL PRODUCE WIDESPREAD RAIN ACROSS THE FORECAST AREA.
LOW LEVEL JET INCREASING TO 50-60 KNOTS FROM THE SOUTHEAST WILL
RESULT IN STRONG UPSLOPE AND ISENTROPIC LIFT. RAIN WILL SPREAD
INTO THE AREA FROM SOUTHWEST TO NORTHEAST BEFORE 18Z/2PM. MOST
LOCATIONS WILL HAVE ABOUT A 12 HOUR PERIOD OF LIGHT TO MODERATE
RAIN. HAVE PRECIPITATION ENDING FROM SOUTHWEST TO NORTHEAST AFTER
06Z/2AM.

TEMPERATURES STARTING THE DAY QUITE MILD. GRIDDED LAMP GUIDANCE
INDICATED STEADY AND POSSIBLY SLIGHTLY FALLING TEMPERATURES TODAY.
LITTLE CHANGE IN AIR MASS IS EXPECTED TONIGHT WITH TEMPERATURES
AND DEW POINTS REMAINING MAINLY IN THE 50S.

THE STRONG WINDS THROUGH A DEEP LAYER WILL PROVIDE LARGE HELICITY
VALUES LATE THIS AFTERNOON INTO THIS EVENING. THERE IS A LOW
CHANCE THERE COULD BE ENHANCED DIRECTIONAL SHEAR AS THE WARM FRONT
CROSSES. FOR NOW WILL LEAVE OUT ANY THUNDER.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 345 AM EDT SUNDAY...

THE NEW WEEK STARTS OFF WITH OUR REGION IN A WARM AND MOIST AIRMASS. AS
TEMPERATURES RISE WELL INTO THE 70S ON MONDAY THE ATMOSPHERE WILL
DESTABILIZE AHEAD OF THE APPROACHING COLD FRONT AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP. THE DYNAMIC ENVIRONMENT SUPPORTS THE CHANCE FOR
SOME SEVERE STORMS AND THE SPC SLIGHT RISK LOOKS TO BE ON TARGET ACROSS
OUR AREA WITH THE POTENTIAL FOR SVR WEATHER INCREASING EASTWARD WHERE
INSTABILITY WILL BE GREATER. IT WILL ALSO BE QUITE BREEZY WITH
EFFICIENT DOWNWARD MOMENTUM TRANSFER IN A WELL MIXED BOUNDARY LAYER.
THE FRONT SHOULD BE CLEARING THE EASTERN ZONES EARLY MONDAY EVENING.
COLDER AIR WORKING IN ON NW WINDS BEHIND THE FRONT WILL COMBINE WITH
LOW LEVEL MOISTURE TO GENERATE SOME UPSLOPE SHOWERS ACROSS THE FAR
WESTERN SLOPES MONDAY NIGHT.

A BROAD CLOSED UPPER LOW BUILDING IN OVER THE NORTHEAST US WILL THEN
KEEP COOL...BREEZY...AND UNSETTLED WEATHER CONDITIONS ACROSS THE REGION
THROUGH MIDWEEK. TUESDAY LOOKS TO BE THE BEST CHANCE FOR A BREAK IN THE
ACTION AS ANY LINGERING SHOWERS ACROSS THE FAR WEST DISSIPATE BY EARLY
MORNING. BY WEDNESDAY THE NEXT COLD FRONT WILL BE ROTATING IN FROM THE
WEST WITH A CHANCE FOR SHOWERS AND MAYBE SOME THUNDER ESPECIALLY WEST
OF THE BLUE RIDGE. TEMPERATURES TUESDAY AND WEDNESDAY WILL BE RUNNING
AT OR SLIGHTLY BELOW NORMAL WITH UPPER 50S/LOWER 60S WEST OF THE BLUE
RIDGE AND MID 60S TO AROUND 70 EAST.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
AS OF 350 PM EDT SATURDAY...

MODELS IN BETTER AGREEMENT TODAY ON A DEEP AND BROAD UPPER LOW
CENTERED ACROSS THE EASTERN GREAT LAKES DOMINATING THE WEATHER
THROUGH MOST OF THE REMAINDER OF THE WORK WEEK. THIS WILL LEAVE
UNSETTLED CONDITIONS ACROSS THE MOUNTAINS...SOMEWHAT LESS SO ACROSS THE
PIEDMONT. FOLLOWING THIS DISTURBANCE COMES THE BONAFIDE COLDER AIR
WHICH PROMISES TO PUSH 850MB TEMPS DOWN TO 0C OR BELOW FOR MUCH OF THE
REMAINDER OF THE WEEK ACROSS THE NORTHERN AREAS. THE UPPER TROUGH
GRADUALLY SHIFTS MORE TOWARD THE MID-ATLANTIC LATE IN THE
PERIOD...STRENGTHENING THE NORTHWEST FLOW ACROSS THE REGION...AND
ALLOWING 850MB TEMPS TO BOTTOM OUT ACROSS THE NORTH AROUND -5C BY
SATURDAY. THIS PATTERN WILL CONTINUE TO RESULT IN A SIGNIFICANT
TEMPERATURE DIFFERENCE FROM THE WESTERN MOUNTAINS WITH CLOUDS AND
VARIABLE CLOUDS/SCATTERED SHOWERS AND MORE SUNNY/DOWNSLOPE NORTHWEST
FLOW ACROSS THE PIEDMONT. OVERALL...TEMPERATURES SHOULD AVERAGE BELOW
NORMAL THROUGH THE PERIOD...PERHAPS MUCH BELOW IN THE WEST. MEXMOS
SHOWS SEVERAL DAYS WITH HIGHS ONLY IN THE 50S/60S WEST AND LOWS IN THE
UPPER 30S TO LOWER 40S. WIND AND CLOUDS SHOULD PREVENT ANY FROST/FREEZE
CONCERN AT THIS POINT.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
AS OF 745 AM EDT SUNDAY...

RAIN HAD ADVANCED INTO SOUTHWEST VIRGINIA AND WESTERN NORTH
CAROLINA THIS MORNING WITH CEILINGS LOWERING IN ADVANCE OF THE
RAIN. RAIN WILL BEGIN AT KBLF AROUND THE 12Z START OF THE TAF TIME
AND BY 16Z/NOON AT THE OTHER TAF SITES.

A STRONG SOUTHEAST LOW LEVEL JET WILL CONTINUE TO INCREASE TODAY
AND TONIGHT WHICH WILL BRING WIND GUSTS AS HIGH AS 30 KTS TODAY.
WITH A WEDGE OF HIGH PRESSURE IN PLACE ALONG AND EAST OF THE BLUE
RIDGE...AFTER SUNSET THESE STRONG WINDS ARE NOT EXPECTED TO REACH
THE SURFACE. HAVE LLWS IN THE KDAN...KLWB AND KBCB TAFS AFTER
00Z/8PM.

A STRONG UPSLOPE FLOW WILL TRANSPORT ABUNDANT MOISTURE INTO THE
REGION NORTH OF A STATIONARY FRONT TODAY. CEILINGS WILL LOWER TO
IFR BY THIS AFTERNOON AND WILL REMAIN LOW OVERNIGHT.

EXTENDED AVIATION...

A COLD FRONT APPROACHES LATER MONDAY WITH SOME STORMS POSSIBLE
AHEAD OF AND ALONG THE FRONT...ESPECIALLY EAST OF THE BLUE RIDGE.
THIS IS LIKELY TO KEEP PERIODS OF MVFR AND BRIEF IFR IN STORMS
UNTIL THE FRONT CLEARS THE REGION MONDAY EVENING.

VFR RETURNS LATER MONDAY NIGHT AND TUESDAY WITH HIGH
PRESSURE BUILDING IN BEHIND THE FRONT WITH A DRIER AIRMASS.

THEN THE NEXT CHANCE OF MVFR CONDITIONS AND PRECIPITATION WILL BE
IN THE MOUNTAINS ON WEDNESDAY AND THURSDAY.

&&

.HYDROLOGY...
AS OF 430 AM EDT SUNDAY...

HAVE EXPANDED THE FLOOD WATCH FOR MORE OF THE SOUTHERN BLUE RIDGE
AND FOR THE BLUE RIDGE AND ADJACENT EASTERN COUNTIES NORTH OF OF
ROANOKE. BUFKIT SOUNDINGS SHOWED A DEEP LAYER FROM THE SURFACE
THROUGH MID LEVELS OF THE ATMOSPHERE WITH SOUTHEAST WINDS...THAT
WILL BE INCREASING TO AROUND 50 KNOTS THIS AFTERNOON AND EVENING.
PRECIPITABLE WATER VALUES JUST ABOVE 1.5 INCHES WILL BE ADVECTED
INTO THE FORECAST AREA. THE STRONGEST LIFT AND HIGHEST RAINFALL
AMOUNTS WILL BE FROM 18Z/2PM THROUGH 06Z/2AM SO HAVE ADDED HEAVY
RAIN TO THE FORECAST ALONG THE BLUE RIDGE FOR THIS TIME FRAME.

TOTAL RAINFALL AMOUNTS WILL RANGE FROM 1 TO 3 INCHES THROUGH
12Z/8AM MONDAY. FLASH FLOOD GUIDANCE VALUES WERE ROUGHLY 1.5 TO
2.5 INCHES FOR 3 HOURS. SO THIS AMOUNT OF RAINFALL HAS THE
POTENTIAL TO PRODUCE FLOODING ON SMALL STREAMS AND CREEKS.

PROBABILISTIC GUIDANCE FOR MAINSTEM RIVERS SUGGESTS A SMALL
POSSIBILITY FOR MINOR FLOODING ALONG THE DAN RIVER AND NEW RIVER.
HOWEVER...THE IS HIGHLY DEPENDENT ON THE AMOUNT OF RAINFALL
THROUGH MONDAY MORNING.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FLOOD WATCH THROUGH THIS EVENING FOR VAZ009-012>017-032.
     FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT
     FOR VAZ022>024-033>035.
NC...FLOOD WATCH THROUGH THIS EVENING FOR NCZ001>003-018>020.
WV...NONE.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/KK
SHORT TERM...MBS
LONG TERM...RAB
AVIATION...AMS/PC
HYDROLOGY...AMS


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