FXUS61 KRLX 151040
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
540 AM EST TUE DEC 15 2009
.SYNOPSIS...
BLUSTERY WILL FALLING TEMPERATURES TODAY. MUCH COLDER TONIGHT.
UPSLOPE SNOW SHOWERS IN NORTHERN MOUNTAINS TONIGHT. HIGH PRESSURE
WITH COLD TEMPERATURES WEDNESDAY INTO THURSDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
FRONT SLIPPING FAIRLY QUICKLY THROUGH CWA...NOW LYING ALONG A ROUGH
EKN/BKW/LNP LINE. TRUE COLDER AIR LAGS A FEW HOURS BEHIND
FRONT...AND WE HAVE YET TO SEE THE REAL TEMPERATURE DROP. THE MAX
TEMPERATURE FOR TODAY WILL BE THE TEMPERATURE AT 12Z...SOMETIMES
SURPRISINGLY TRICKY TO NAIL. ELECTED TO FOLLOW CLOSE TO LAV NUMBERS
FOR HOURLY TEMPS. ENDED UP WITH MAX VALUES AT/ABOVE THE WARMER
MAV...WHICH SEEMS TO MAKE SENSE GIVEN CURRENT TRENDS. TEMPERATURES
WILL BE FALLING INTO THE 30S DURING THE DAY. STRONG COLD ADVECTION
WILL ALLOW 20-25 KNOT WINDS TO MIX DOWN TO THE SURFACE THIS
AFTERNOON.
MOISTURE DEPTH BEHIND FRONT IS NOT THE BEST...MOSTLY FROM H850
BELOW. STILL...IT REMAINS TRAPPED BELOW INVERSION ALOFT...SO CLOUDS
WILL REMAIN ENTRENCHED TODAY. COLD ADVECTION-INDUCED SHOWERS SHOULD
BE LIMITED MAINLY TO THE MOUNTAINS...WHICH WILL SEE THE TYPICAL
POSTFRONTAL UPSLOPE KICK BY MIDDAY. EXPECT MOSTLY LIQUID UNTIL
ABOUT 18Z...UNTIL SUBZERO H850 TEMPERATURES ARRIVE AND CAUSE THE
CHANGEOVER TO SNOW. THESE WILL CONTINUE THROUGH THE NIGHT...SLOWLY
DECREASING IN COVERAGE...WITH ONLY FLURRIES REMAINING BY 12Z AS
MOISTURE NEARLY DISAPPEARS AND THERMAL TROUGH PASSES. EXPECTING
SNOW AMOUNTS TO BE LIGHT WITHOUT IDEAL CRYSTAL GROWTH...GENERALLY
AROUND AN INCH OR SO ON THE HIGHER PEAKS. MILDLY CONCERNED THAT WE
MAY SEE FREEZING DRIZZLE IN SOME NORTHERN MOUNTAIN LOCATIONS...AS
PRESENCE OF ICE CRYSTALS IN CLOUD LAYER IS QUESTIONABLE AT TIMES.
LEAVING THIS OUT FOR NOW BUT WILL ALERT DAY SHIFT TO POSSIBILITY.
WEST OF THE MOUNTAINS...SIMPLY HAVE A DECREASING CLOUD TREND WITH
INVERSION BREAKING OVERNIGHT AND ALLOW MOISTURE TO BE SCOURED OUT.
USED BIAS-CORRECTED SREF FOR LOW TEMP BASIS...WHICH IS CLOSE TO A
MET/MAV BLEND.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
A RELATIVELY TRANQUIL PERIOD...BEFORE THE UNSETTLED WINTRY WEATHER
ARRIVES THIS WEEKEND. WITH ONLY VERY SHALLOW MOISTURE LEFT ON
FORECAST SOUNDINGS FOR WEDNESDAY MORNING...ONLY MENTIONED SOME
SCATTERED MOUNTAIN FLURRIES IN SCT TO BKN CLOUDS. THE 850 MB
THERMAL TROF STILL APPEARS TO BE BY 12Z WEDNESDAY...WITH ABOUT MINUS
10C ACROSS OUR N.
IN THE BAROCLINIC ZONE...SOME PATCHES OF MID DECK CLOUDS MAY STREAK
DOWN FROM THE NW OVERNIGHT WEDNESDAY NIGHT AND THURSDAY...TO AFFECT
TEMPERATURES...BUT WE SHOULD REMAIN DRY. FIGURE ON TEMPERATURES
MODERATING A FEW DEGREES THURSDAY AFTERNOON AND AGAIN FRIDAY. A
STRONG 850 TEMPERATURE PACKING/GRADIENT SHOULD EXIST SW TO NE ACROSS
OUR FORECAST AREA BOTH THURSDAY AND FRIDAY...MAKING EXACT POINT
TEMPERATURES VALUES "FUN" TO FORECAST.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MINOR CHANGES IN THE LONG RANGE TO INCLUDE AT LEAST CHANCE POPS IN
A MORE EXTENDED TIME FRAME OVER THE WEEKEND...SINCE 20 POPS DO NOT
GET MENTIONED IN OUR CRWZFPRLX. THIS COMPLEX PATTERN WILL BE
REEVALUATE...AS USUAL...DURING OUR DAY SHIFT.
HI/LO CONFIDENCE FCST. RELATIVELY HIGH CONFIDENCE IN PNA PATTERN
WITH HIGH LATITUDE BLOCK TO BRING ABOUT BELOW NORMAL TEMPERATURES
FOR THE WEEKEND INTO CHRISTMAS WEEK. LOW CONFIDENCE IN THE DETAILS
WITH VARIOUS SHORT WAVES MOVING THROUGH THE FLOW.
PERIOD BEGINS WITH WEAK HIGH PRESSURE IN PLACE UNDERNEATH WNW FLOW
ALOFT. UPPER LEVEL VORTEX CENTER PROGGED TO BE NEAR THE MOUTH OF
THE SAINT LAWRENCE RIVER VALLEY AT THE START OF THE PERIOD
RETROGRADES WWD INTO THE GREAT LAKES AREA UNDERNEATH THE HIGH
LATITUDE BLOCK OVER THE WEEKEND...AND THEN S AND THEN LATER IN THE
WEEKEND AND INTO EARLY NEXT WEEK. MODEL DIFFERENCES SHOW UP IN THE
EXACT TRACK OF THIS UPPER FEATURE WITH THE ECMWF AMONG THE MODELS
BRINGING IT FARTHEST S AT LEAST WITH ONE OF WHAT BECOMES A THREE
CENTER FEATURE.
BELOW TO MUCH BELOW NORMAL TEMPERATURES ARE STRONGLY SUGGESTED BY
ALL OF THESE SOLUTIONS WHILE TIMING AND INTENSITY OF PRECIPITATION
VARY. ECMWF IS ONLY MODEL AT THIS TIME SHOWING A SYNOPTIC SCALE
STRATIFORM PRECIPITATION EVENT PER PHASING WHILE OTHER GUIDANCE
SUGGESTS UPSLOPE EVENTS AMPLIFIED SOMEWHAT BY COLD ADVECTION AND
UPPER LEVEL SUPPORT. WENT WITH HPC/GFS SOLUTION WHICH DOES NOT
SINGLE OUT ANY ONE STRONGER SYSTEM FROM THE OTHERS.
USED THE FOLLOWING SCHEMES FOR TEMPERATURES WHICH ARE MOSTLY A BLEND
OF HPC...GFS...MEX...MOSGUIDE AND EVEN THE PREVIOUS FCST IN SOME
CASES...AS DETAILED BELOW...
MAX
FRI - PREV
SAT - GFS40/HPC
SUN - ADJMEX/HPC THEN AT LEAST 2 LOWER THAN SAT
MON - GFS40/ECMWF/HPC
(TUE - GFS40/ECMWF)
MIN
FRI - GFS40/ECMWF/HPC/PREV
SAT - GFS40/MOSG/HPC/PREV
SUN - GFS40/MOSG/HPC/PREV
MON - GFS40/MOSG/HPC/PREV
TUE - GFS40/ADJMEX/MOSG/ECMWF
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
COLD FRONT NOW IN MOUNTAINS...WITH FALLING TEMPERATURES BEHIND IT.
NOT MUCH MOISTURE TO WORK WITH...SO FORESEE MAINLY MOUNTAIN SHOWERS
DURING THE DAY. EXPECT RAIN CHANGING TO SNOW AFTER 18Z ON THE
PEAKS...THEN AFTER 21Z IN THE VALLEYS. GENERALLY MVFR CIGS AREAWIDE
DURING THE DAY. WINDS WILL PICK BY BY LATE MORNING...WITH 15-20 KNOT
GUSTS OUT OF THE WEST/NORTHWEST. SLOW IMPROVEMENT AFTER 00Z WITH CIGS
ACHIEVING VFR LEVELS IN ALL BUT THE NORTHERN MOUNTAINS DURING THE
NIGHT. SNOW SHOWERS MAY BRIEFLY TOUCH IFR VISIBILITY AT LOCATIONS
SUCH AS EKN AND W22...BUT CHANCES TOO LOW TO INCLUDE IN TAFS.
AFTER 12Z WEDNESDAY...
NO IFR WEATHER EXPECTED AT THIS TIME.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...KTB/TRM
AVIATION...CL
