Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 211517
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1114 AM EDT TUE APR 21 2015

.SYNOPSIS...
COOLER AIR TAKING OVER IN THE WAKE OF A COLD FRONT...WILL BE
REINFORCED BY ANOTHER COLD FRONT WEDNESDAY.  HIGH PRESSURE CROSSES
FRIDAY.  LOW PRESSURE TRACKS SOUTH OF THE AREA THIS WEEKEND.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
SLOWED DOWN THE ARRIVAL OF POPS THIS AFTERNOON AND EVENING BASED ON
LATEST MODEL TRENDS.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH FRIDAY/...
COLD FRONT ENTERS AREA RIGHT AT THE START OF THE PERIOD.  THIS FRONT
IS DRIVEN BY AN UPPER LEVEL S/W TROUGH AXIS ROTATING AROUND THE BASE
OF A LARGE UPPER LEVEL LOW N OF THE GREAT LAKES.  THE UPPER LOW
DOMINATES THE WEATHER FOR THE GREAT LAKES AND NE CONUS THROUGHOUT
THE PERIOD AND EVEN BEYOND...AS IT MEANDERS AND DUMBBELLS TO THE
CANADIAN MARITIMES.

THE FRONT...EXTENDING SWWD FROM A SFC LOW TRACKING ENEWD INTO
PA...WILL TRAVERSE THE FCST AREA DURING THE MORNING AND EARLY
AFTERNOON HOURS WED.  EXTENDED LIKELY POPS DOWN TO THE TUG FORK WED
MORNING BASED ON THE FRONTAL CONVERGENCE AND SWD EXTENT OF UPPER
DYNAMICS.  FRONTAL TIMING AND INFLOW AHEAD OF IT SUGGESTS JUST
ENOUGH INSTABILITY FOR THE POSSIBILITY OF THUNDER IN THE MOUNTAINS
DURING MIDDAY AND EARLY AFTERNOON...JUST BEFORE THE FRONT CROSSES.
ANY THUNDERSTORM CAN BE STRONG GIVEN THE FAST FLOW...AND A LOW
FREEZING LEVEL COULD LEAD TO SMALL HAIL...BUT FAST MOVEMENT AND PW
VALUES OF 3/4 OF AN INCH OR LESS WILL PRECLUDE ANY WATER PROBLEMS.

W FLOW PREVAILS FOLLOWING THE FRONT THROUGH THU NT BEFORE HIGH
PRESSURE BUILDS IN ON FRI.  COLD ADVECTION UPSLOPE SHOWERS IN THE
WAKE OF THE COLD FRONT SHOULD WANE BY THU MORNING AS THE COLD
ADVECTION CUTS OFF.  HOWEVER...WRAP AROUND MOISTURE WILL LEAD TO
CONSIDERABLE STRATOCU ATOP THE MIXING LAYER ACROSS THE N THU.

USED NAM / MET FOR TEMPERATURES WED.  TEMPERATURES CAN PEAK AHEAD OF
THE FRONT IN THE MORNING AND AGAIN IN THE SUNSHINE IN THE AFTERNOON
ESPECIALLY E OF THE OHIO RIVER.  USED ALLBLEND FOR HIGHS THU AND THE
PREVIOUS FCST FOR HIGHS FRI WAS CLOSE TO THE LATEST GUIDANCE AND
ACCEPTED.  BLENDED IN BIAS CORRECTED MAV FOR LOWS AT OR BELOW
PREVIOUS THU MORNING...AND THE MEX FOR LOWER LOWS FRI MORNING.  THIS
LEADS TO A TOUCH OF FROST THU MORNING AND A MORE WIDESPREAD FROST
FRI MORNING...FOR THE MIDDLE OHIO VALLEY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
STILL A FAST WNW STEERING FLOW AROUND THE LARGE CIRCULATION OVER
EASTERN CANADA AND NEW ENGLAND.  SO TEMPERATURES WELL BELOW NORMAL
THRU PERIOD FOR LATE APRIL.  FOCAL POINT WILL BE CHECKING WITH
PARTNERS...ON WHEN TO START UP THE FROST/FREEZE PROGRAM.

MAIN DILEMMA IS THE POPS FOR SATURDAY.  TREND TODAY WAS TO INCREASE
POPS FOR CENTRAL AND SOUTHERN COUNTIES ON SATURDAY...BUT STILL
DIFFICULT TO DETERMINE HOW FAR NORTH TO INCREASE POPS.  HAVE
INCREASED THE CHANCE POPS INTO THE LIKELY POP RANGE OVER
SOUTHERN WV AND SW VA FOR SATURDAY.

COLD AIR LINGERS THROUGH MONDAY.  COULD NOT RULE OUT SOME FLAKES
OVER TALL WV MOUNTAINS...ESPECIALLY BY DAY 7 NIGHT/MONDAY NIGHT.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
MAINLY VFR CONDITIONS FOR THE PERIOD. WESTERLY WINDS WILL INCREASE IN
STRENGTH TODAY HOWEVER...WITH GUSTS GENERALLY IN THE 20 KTS RANGE
DEVELOPING AFTER 15Z...AND LASTING THROUGH AROUND 03Z...PARTICULARLY
ACROSS SOUTHEAST OHIO...WHERE GUSTS OF 30-40 KTS WILL BE POSSIBLE.

A COLD FRONT WILL SAG SOUTH ACROSS THE REGION TONIGHT...WITH -SHRA
DEVELOPING AS IT DOES SO...GENERALLY AFTER 00Z. EXPECT BRIEF MVFR
CONDITIONS IN -SHRA...MAINLY AFTER 09Z.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z WEDNESDAY...

FORECAST CONFIDENCE: HIGH.

ALTERNATE SCENARIOS: WIND GUSTS ON TUESDAY COULD BE STRONGER THAN
CURRENTLY FORECAST. MORE WIDESPREAD MVFR MAY DEVELOP IN -SHRA THAN
CURRENTLY FORECAST.

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.

UTC 1HRLY       11   12   13   14   15   16   17   18   19   20   21   22
EDT 1HRLY       07   08   09   10   11   12   13   14   15   16   17   18
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
BKW CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    H
EKN CONSISTENCY  M    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    H    H    H    H    H    H    H    H    H    H    H

AFTER 12Z WEDNESDAY...
NO WIDESPREAD IFR CONDITIONS EXPECTED AT THIS TIME.

&&

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

&&

$$
SYNOPSIS...TRM/SL
NEAR TERM...RPY
SHORT TERM...TRM
LONG TERM...KTB
AVIATION...SL









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