Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 080537
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1237 AM EST MON FEB 8 2016

.SYNOPSIS...
HIGH PRESSURE EXITS TONIGHT. COLD FRONT MONDAY. UNSETTLED/COLDER
TUESDAY AND WEDNESDAY UNDER LARGE MID/UPPER LEVEL LOW...WITH
ROUNDS OF SNOW SHOWERS THAT LINGER THROUGH MUCH OF THE WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
1230 AM UPDATE...
NOTHING EARTH SHATTERING IN TERMS OF CHANGES YET...BUT STILL IN
THE MIDDLE OF THE FORECAST PACKAGE.

PREVIOUS DISCUSSION... UPPER LOW DIGS DOWN FROM THE UPPER MIDWEST
TONIGHT WITH AN ASSOCIATED SURFACE LOW AND TRAILING COLD FRONT.
COLD FRONT PASSES THE REGION TOMORROW BRINGING RAIN AND SNOW
SHOWERS WITH IT. PRECIPITATION WILL ENTER THE OHIO VALLEY AROUND
DAYBREAK AND SPREAD EASTWARD FROM THERE. FORECAST CONFIDENCE IS
FAIRLY HIGH ON THE TIMING OF FROPA BUT STILL SOME UNCERTAINTY WITH
REGARD TO P-TYPES. CURRENT THINKING IS THAT BEFORE THE FRONT
ARRIVES MOST OF THE REGION SHOULD BE ABOVE FREEZING...HOWEVER AS
HEAVIEST PRECIP MOVES OVERHEAD WET-BULBING IN AREA OF GREATEST
FORCING COULD DROP SURFACE TEMPERATURES ENOUGH FOR A QUICK BURST
OF WET SNOW TO OCCUR IN THE LOWLANDS. THIS WILL LIKELY ONLY BE
WITH THE HEAVIEST BAND OF PRECIPITATION AND AFTER THE BEST FORCING
MOVES THROUGH...EXPECTING JUST PLAIN RAIN SHOWERS OUTSIDE OF THE
HIGHER TERRAIN. AS FAR AS ACCUMULATION GOES THROUGH 00Z
TUESDAY...IT LOOKS LIKE 1 TO 2 INCHES WILL BE POSSIBLE IN THE
MOUNTAINS AND GENERALLY A HALF INCH OR LESS IN THE LOWLANDS.

DUE TO THE UNCERTAINTY WITH BOUNDARY LAYERS TEMPERATURES...ON-
COMING SHIFTS WILL JUST HAVE TO MONITOR HOW THE EVENT UNFOLDS AND
AN SPS FOR A BRIEF PERIOD OF HEAVY SNOW TOMORROW MORNING COULD BE
POSSIBLE.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
DEEP L/W TROUGH OVER THE ERN U.S. THIS ENTIRE PERIOD SPELLS BELOW
NORMAL TEMPERATURES AND SNOW SHOWERS.

THE PARTY BEGINS RIGHT AT THE START OF THE PERIOD MON NT...WITH
COLD ADVECTION OVERSPREADING THE AREA FROM SW TO NE...BEHIND A NW
TO SE ORIENTED SFC LOW PRESSURE TROUGH EXTENDING FROM THE ERN
GREAT LAKES TO THE DELMARVA PENINSULA BY 12Z TUE. OUTSIDE
WIDESPREAD UPSLOPE SNOW SHOWERS...MODELS DEPICT A LAKE MI
TRAJECTORY COMING ACROSS THE NRN TIER OF THE FCST AREA MON NT INTO
TUE...ENHANCING LOWLAND SNOW AMOUNTS THERE VS. AREAS FARTHER S.

BEYOND THAT...TOUGH TO TIME THE SMALLER SCALE FEATURES ROTATING
AROUND THE EVOLVING UPPER LOW NEARBY TO THE N...BUT IT LOOKS LIKE
THE GENERAL TRAJECTORIES MAY NOT CHANGE MUCH. WITH H85
TEMPERATURES DROPPING INTO THE TEENS BELOW ZERO C TUE AND SLOWLY
DROPPING FURTHER BEYOND THAT...DENDRITIC CRYSTAL GROWTH IS
FAVORED...RESULTING IN HIGH SNOW TO LIQUID RATIOS.

FOR STARTERS...SNOW TOTALS FOR MON NT THROUGH TUE ARE CLOSE TO 12
HOUR ADVISORY CRITERIA BUT 3-5 INCHES SHORT OF WARNING CRITERIA ON
A COUNTY AVERAGE BASIS THROUGHOUT THE FCST AREA. THUS NOT
INTRODUCING ANY HEADLINES AT THIS TIME ALTHOUGH IT IS PLAUSIBLE
ADVISORIES WILL BE NEEDED FOR THAT PERIOD...AND THEN TUE NT INTO
WED LOOK TO BE NEARLY AS SNOWY WITH THE UPPER LEVEL LOW AND L/W
TROUGH AXIS STILL OVER THE UPPER AND MIDDLE OHIO VALLEYS. THE LAKE
MI TRAJECTORY INTO NRN PORTIONS OF THE FCST AREA MAY STILL BE
THERE OR MAY BE BECOMING REESTABLISHED WED AFTERNOON.

TEMPERATURES WERE LOWER THAN GUIDANCE BUT GENERALLY STAYED CLOSE
TO PREVIOUS PACKAGE AND RAW GUIDANCE IN THIS ANOMALOUS PNA
PATTERN...PERHAPS JUST SLOWING DOWN THE COOLING A BIT MON NT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
STILL EXPECTING SCT SNOW SHOWERS OVER THE AREA WEDNESDAY NIGHT.
STREAMLINE ANALYSIS AND HYSPLIT BACKWARDS TRAJECTORY PARCELS ALONG
WITH OMEGA/RH IN THE DENDRITIC GROWTH ZONE DO INDICATE SOME
ENHANCEMENT FROM LAKE MICHIGAN FOR A TIME IN THE EVENING...AFFECTING
SE OH AND ESPECIALLY N WV. THIS IS ENHANCED FURTHER WITH A SUBTLE
VORT MAX ROUNDING THE BASE OF THE UPPER TROF.
SO...HAVE KEPT SOME FAIRLY HEALTHY POPS OVER THE N DURING THE NIGHT.
HOWEVER...EXPECT THIS TO BE A LOW QPF/HIGH POP SCENARIO WITH
GREATEST ACCUMULATIONS WEDNESDAY NIGHT OVER THE N WV MOUNTAINS WHERE
AN INCH OR TWO OF ADDITIONAL SNOW MAY FALL. THURSDAY MORNING WILL
FEATURE SOME LINGERING SNOW SHOWERS AND FLURRIES...PRIMARILY WITHIN
ANY LAKE MICHIGAN PLUME AS SHOWN ON GFS. H85 THERMAL TROF LINGERS IN
THE VICINITY SO HARD TO SEE MUCH IN THE WAY OF IMPROVEMENT WITH THE
EROSION OF THE STRATOCU AND ANY TEMPERATURE MODERATION.

WE FINALLY GET SOME WAA GOING THURSDAY NIGHT WHICH SHOULD BE ENOUGH
FOR SOME CLEARING AREAWIDE. AT THE SURFACE HIGH PRESSURE WILL BE
BUILDING IN WHICH WILL MAKE FOR A VERY COLD NIGHT SHOULD WE INDEED
LOSE THE CLOUDS AMID A FRESH SNOW PACK. SOME BELOW ZERO READINGS ARE
POSSIBLE IN THE IN THE TYPICAL COLD SPOTS OF THE MOUNTAIN VALLEYS.
CONFIDENCE BEGINS TO DECREASE HEADING INTO THE WEEKEND. THE GLOBAL
MODELS ARE HAVING SOME ISSUES RESOLVING FEATURES AND THE OVERALL
MEAN TROF OVER THE EASTERN CONUS. THUS HAVE STAYED CLOSE TO WPC
WHICH FAVORED A COLDER ECMWF SOLUTION FOR THE WEEKEND AMID ANOTHER
ARCTIC HAMMER DROP. NO BIG SYSTEM IS ENVISIONED OVER THE WEEKEND
THOUGH.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
EXPECTING OVERALL DETERIORATING AVIATION CONDITIONS THROUGH THE
TAF PERIOD...WITH A STRONG COLD FRONT PASSING THROUGH
TODAY...BRINGING RAIN CHANGING TO SNOW...LOWERING CEILING...AND
VISIBILITIES THAT WILL LIKELY BOUNCE IN AND OUT OF PRECIPITATION.

FOR THE CEILINGS...INTRODUCE MVFR NEAR THE ONSET...BUT HAVE IFR AT
SOME LOCATIONS AS THE LOWEST LEVELS SATURATE IN THE POST FRONTAL
ENVIRONMENT. WITH THE VISIBILITIES...GENERALLY USE MVFR WITH THE
ONSET AND IN RAIN...BUT IFR LIKELY AFTER SEVERAL HOURS OF LIGHT
RAIN...AND ESPECIALLY ONCE THE TRANSITION TO LIGHT SNOW OCCURS.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z TUESDAY...

FORECAST CONFIDENCE...HIGH IN THE DETERIORATING TRENDS...AND MEDIUM
IN THE DETAILS AND TIMING.

ALTERNATE SCENARIOS: TIMING OF IFR WILL VARY. LOW LEVEL SATURATION
MAY REQUIRE EARLIER ONSET OF IFR ONCE THE COLD FRONT PASSES.

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                                                  MON 02/08/16
UTC 1HRLY       03   04   05   06   07   08   09   10   11   12   13   14
EST 1HRLY       22   23   00   01   02   03   04   05   06   07   08   09
CRW CONSISTENCY  H    H    H    H    H    H    H    H    M    M    M    L
HTS CONSISTENCY  H    H    H    H    H    H    H    M    M    L    L    M
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    M    M    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    M    L    L    L
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H

AFTER 06Z TUESDAY...
PERIODS OF IFR CONDITIONS POSSIBLE IN RAIN/SNOW SHOWERS ALL THE
WAY THROUGH WEDNESDAY NIGHT...WITH THE WORST CONDITIONS EXPECTED
TUESDAY MORNING THROUGH WEDNESDAY MORNING.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WINTER WEATHER ADVISORY FROM NOON TODAY TO 1 AM EST TUESDAY
     FOR WVZ046-047.
OH...NONE.
KY...NONE.
VA...NONE.

&&

$$
SYNOPSIS...TRM/JW/30
NEAR TERM...JW/26
SHORT TERM...TRM
LONG TERM...30
AVIATION...26


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