FXUS61 KRLX 250320
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1020 PM EST THU DEC 24 2009
.SYNOPSIS...
SANDWICHED BETWEEN LOW PRESSURE TO THE WEST AND HIGH PRESSURE TO THE
NORTHEAST. INCREASING WINDS OVERNIGHT AND CONTINUE ON CHRISTMAS
DAY. COLDER AIR GRADUALLY MOVES IN OVER THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
UPDATE...TWEAKED THE POPS FOR THE INCOMING RAIN. DIFFICULT TO
JUDGE DUE TO THE DRY MID AND LOW LEVELS. WATCHING BKW TEMPERATURE
CAREFULLY AS IT SLOWLY DROPS...AND THINKING -FZRA IS STILL A
POSSIBILITY AS EVAPORATIVE COOLING TAKES HOLD WITH RAIN MOVING IN.
PREVIOUS DISCUSSION...EVEN THOUGH STORM TO OUR WEST NOT DEEPENING
MUCH...THE GRADIENT BETWEEN IT AND THE HIGH PRESSURE OVER NORTHERN
ONTARIO AND QUEBEC HAS SOME IMPRESSIVE WINDS IN THE LOW LEVELS
ABOVE THE GROUND. 70 TO 80 KNOTS AT 850 MBS BY 09Z. WITH STABLE
SOUNDINGS THINKING MOST OF THESE MOMENTUM WILL STAY ALOFT...BUT
STILL HAVE SOME 40 TO 50 KNOT WIND GUSTS OVER THE WIND ADVISORY
AREA...OR OUR MOUNTAINOUS TERRAIN.
HAVE THE WINDS INCREASING THIS EVENING...SO WIND ADVISORY STARTS AT
6 PM AND CONTINUES INTO CHRISTMAS DAY.
WITH THE STRONG UPSLOPE SE WINDS...I DO NOT UNDERSTAND WHY MOS
TEMPERATURE GUIDANCE IS SO MILD FOR PLACES LIKE BKW LATE TONIGHT.
I CAN SEE TEMPERATURES RISING IN THE WESTERN LOWLANDS. BUT WE WERE
HOLDING SOME POCKETS OF TEMPERATURES AT FREEZING THROUGH ABOUT 12Z
OR 13Z IN THE SOUTHERN WV MOUNTAIN COUNTIES...AND UNTIL LATE MORNING
IN EASTERN RANDOLPH AND POCAHONTAS COUNTY. SO THE FREEZING RAIN
ADVISORY IS FROM 1 AM TO NOON.
HAVE A NONDIURNAL TEMPERATURE TRACE OVERNIGHT...WITH READING
DROPPING THIS EVENING...THEN RISING OVERNIGHT...EXCEPT WHERE RAIN
BEGINS IN THE UPSLOPE AREAS.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
AS THE STRONG LOW PRESSURE MOVE FROM THE CENTRAL PLAINS INTO THE
GREAT LAKES REGION...AN OCCLUDED FRONT WILL SWEEP ACROSS THE OH
VALLEY INTO WV ON FRIDAY. HAVE CATEGORICAL POPS SPREADING FROM
SOUTHWEST TO NORTHEAST FRI MORNING...AND EXITING MOST PARTS OF THE
NORTHEAST MOUNTAINS DURING THE LATE AFTERNOON EARLY EVENING HOURS.
A SECONDARY LOW PRESSURE DEVELOPS ACROSS THE SOUTHEASTERN STATES AND
MOVES ACROSS VA INTO SATURDAY...KEEPING LINGERING PCPN ACROSS THE
HIGHER ELEVATIONS OF THE NORTHEAST MOUNTAINS THROUGH EARLY SATURDAY.
MODELS ARE IN AGREEMENT OF A DRY SLOT PROVIDING DRIER AND COOLER
CONDITIONS FOR SATURDAY INTO EARLY SUNDAY. THEREFORE...KEPT THESE
PERIODS DRY UNTIL SUNDAY MORNING WHEN LIGHT SNOW FROM THE BACK OF
THE PARENT LOW PRESSURE FINALLY REACHES THE NORTHWEST SECTIONS...AS
THE LOW PULLS NORTHEAST INTO EASTERN CANADA.
FOR FRIDAY...SOME DIFFERENCES WERE NOTED IN H850 TEMPS AMONG MODELS
PERHAPS DUE TO SLIGHTLY TIMING DIFFERENCES OF THE ONSET OF REAL
COLD/DRY AIR ALOFT. HOWEVER...WITH A STRONG SOUTHEAST FLOW AT H850
NEAR 80 KNOTS PER THE NAM/GFS...70 KNOTS PER THE GEM/ECMWF...AND 50
KNOTS PER UKMET...FIGURED A GOOD DEAL OF WARM ADVECTION WILL TAKE
PLACE. THEREFORE...WENT ABOVE NORMAL TEMPS...AND WARMER THAN ALL
GUIDANCE ...BRINGING SFC TEMPS INTO THE LOWER 50S OR A BIT HIGHER
ACROSS THE LOWLANDS...AND INTO THE MID 40S HIGHER ELEVATIONS.
ABOVE NORMAL TEMPS WERE FIGURED FOR FRIDAY NIGHT...A DEGREE OR TWO
WARMER THAN THE GMOS. MAX TEMPS WILL LIKELY BE FORECAST EVEN HIGHER
AS WE GET CLOSER TO FRIDAY.
BEHIND THE BACK SIDE OF THE LOW...GFS/ECMWF H850 TEMPERATURES GETS
INTO THE MINUS 11C...WHILE THE UKMET BRINGS EVEN COLDER TEMPS INTO
THE MINUS MINUS 17 ALL UNDER NORTHWEST TO WEST FLOW. DESPITE THE
AFOREMENTIONED COLD ADVECTION...SOME CLEARING ARE EXPECTED ALONG THE
DRY SLOT PROVIDING SOME HEATING TO THE LOWLANDS ON SATURDAY.
..AND SOME RADIATIONAL COOLING ON SAT NIGHT BRINGING TEMPS INTO THE
MID 20S LOWLANDS....RANDING INTO THE MID TEENS NORTHEAST MOUNTAINS.
BELOW NORMAL TEMPS ARE EXPECTED AT MOST PLACES REMAINING AT OR BELOW
FREEZING FOR SUNDAY AND SUN NIGHT.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
UPPER LEVEL LOW AND ASSOCIATED FORCING FOR PRECIPITATION WILL
PUSH EAST OF REGION MONDAY. HOWEVER....NORTHWEST UPSLOPE SNOW WILL
CONTINUE INTO TUESDAY...BEFORE HIGH PRESSURE BUILDS IN.
ANOTHER SYSTEM WILL THEN BEGIN TO APPROACH THE REGION...WITH
PRECIPITATION CHANCES BEGINNING WEDNESDAY...AND THEN CONTINUING
THROUGH THURSDAY.
MODELS SUGGEST AN SURFACE AREA OF LOW PRESSURE WILL MOVE FROM THE
NORTHERN GULF OF MEXICO INTO THE ATLANTIC OCEAN THURSDAY...WITH
THE STORM EXPECTED TO INTENSIFY AS IT MOVES UP THE EAST COAST NEW
YEARS DAY.
HPC TEMPERATURE GUIDANCE WAS GENERALLY USED...WITH SOME TWEAKS TO
REFLECT THE LATEST ENSEMBLE GUIDANCE.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
CONTINUING WITH THE MAIN ISSUE BEING THE LLWS THAT WILL DEVELOP
AFTER 06Z TONIGHT IN INCREASING SOUTHEAST FLOW ABOVE THE BOUNDARY
LAYER. INCLUDED LLWS AT CRW...BKW...AND EKN...BUT THINK THIS WILL
BE MORE OF A MOUNTAINOUS TERRAIN ISSUE THAT ACROSS THE LOWLANDS.
COULD SEE WIND SHEAR OF 50KTS...ESPECIALLY ACROSS THE SOUTHERN
HIGHLANDS. WHILE LLWS WIND SHEAR THRESHOLDS ARE NOT MET ACROSS THE
BULK OF THE LOWLANDS...THERE WILL BE SIGNIFICANT WIND SPEED
DIFFERENCES WITH HEIGHT IN THE LOW LEVELS OF THE ATMOSPHERE.
SURFACE WIND GUSTS ACROSS THE MOUNTAINS COULD REACH 40KTS...WITH
THE LOWLANDS AROUND 25KTS.
CEILINGS GRADUALLY LOWER...AND WILL TAKE SOME TIME TO DO SO...WITH
THE MAJORITY OF THE CEILING FORECAST REMAINING VFR...AND BECOMING
MVFR LATE BEHIND THE COLD FRONT. MVFR VISIBILITIES POSSIBLE IN
RAIN PRIOR TO FRONTAL PASSAGE.
PRECIPITATION COULD BEGIN AS FREEZING RAIN IN THE MOUNTAINS...AND
ESPECIALLY THE MOUNTAIN VALLEYS AS SOME COLD AIR REMAINS TRAPPED
BEFORE TEMPERATURES BEGIN RISING OVERNIGHT AGAIN. OTHERWISE...RAIN
WILL DEPART AFTER 18Z-21Z.
AFTER 00Z SATURDAY...
IFR POSSIBLE IN LIGHT SNOW SUNDAY NIGHT.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 4 PM EST FRIDAY FOR WVZ033>038-046-047.
FREEZING RAIN ADVISORY UNTIL NOON EST FRIDAY FOR WVZ035-036-
046-047.
OH...NONE.
KY...NONE.
VA...WIND ADVISORY UNTIL 4 PM EST FRIDAY FOR VAZ003-004.
&&
$$
SYNOPSIS...KTB/JSH/ARJ
NEAR TERM...26/KTB
SHORT TERM...AAR
LONG TERM...JSH
AVIATION...26
