Area Forecast Discussion
Issued by NWS Charleston, WV

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678
FXUS61 KRLX 080239
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
939 PM EST SUN FEB 7 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 MONDAY NIGHT/...
930 PM UPDATE...OPTED TO KEEP A MORE PREDOMINATELY RAIN MIXTURE
ON MONDAY MORNING IN THE LOWLANDS...BASED ON LATEST GUIDANCE WHICH
KEEPS A FAIRLY DEEP WARM LAYER BELOW 850 MB. HIGHER TERRAIN
SHOULD SEE AN INCREASE IN SNOW WHICH COULD BE HEAVY AT TIMES AND
THUS DECIDED TO GO WITH A WINTER WEATHER ADVISORY.

THERE IS QUITE A BIT OF UNCERTAINTY IN THE MONDAY AFTERNOON PRECIP
LOCATIONS/AMOUNTS AS AN UGLY MESS OF UPPER LEVEL FEATURES ROTATE
AROUND AN UPPER LOW. ADVISORIES MAY NEED TO BE EXTENDED IN TIME
AND IN AREA AS DETAILS BECOME MORE APPARENT. SPOTTY QPF MAXIMUMS
HINT AT CSI AS COLD AIR FUNNELS IN AND THE DENDRITIC GROWTH ZONE
BEGINS TO NOSE INTO THE MOUNTAINOUS AREAS.

PREVIOUS DISCUSION FOLLOWS...
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 /TUESDAY 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 /02Z MONDAY THROUGH FRIDAY/...
CLOUDS WILL BE ON THE INCREASE TONIGHT AS COLD FRONT APPROACHES
THE AREA FROM THE WEST. RAIN OR SNOW SHOWERS WILL ENTER THE OHIO
VALLEY BY DAYBREAK AND SPREAD EASTWARD THROUGH THE DAY. MVFR WITH
INCREASING CHANCES OF IFR. ALL TERMINALS WILL LIKELY STAY BELOW
VFR CONDITIONS THROUGH THE REMAINDER OF THE PERIOD.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z TUESDAY...

FORECAST CONFIDENCE...MEDIUM.

ALTERNATE SCENARIOS: TEMPERATURES MAY BE COOL ENOUGH TO HAVE IFR
SNOW.

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
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EST 1HRLY       19   20   21   22   23   00   01   02   03   04   05   06
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    M    M
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
EKN CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
PKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H

AFTER 00Z TUESDAY...
MVFR TO PERIODS OF IFR CONDITIONS POSSIBLE IN RAIN/SNOW SHOWERS
ALL THE WAY INTO WEDNESDAY...WITH THE WORST CONDITIONS EXPECTED
TUESDAY MORNING THROUGH WEDNESDAY MORNING.

&&

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

&&

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



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