FXUS63 KTOP 081142
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
542 AM CST TUE DEC 8 2009
.UPDATE...
UPDATED FOR 12Z AVIATION.
&&
.DISCUSSION...
SEE PREVIOUS DISCUSSION.
&&
.AVIATION...
WINTER STORM CONTINUES OVER THE FORECAST AREA. BRIEF BREAK IN THE
MODERATE SNOW FOR TOP/FOE UNTIL 14Z THEN MODERATE SNOW MOVES BACK
IN WITH LIFR CONDITIONS THROUGH MUCH OF THE DAY TODAY. WINDS
SWITCH AROUND TO THE NORTHWEST BEHIND THE DEPARTING STORM THIS
EVENING...AND WILL CAUSE BLOWING SNOW IN STRONG WINDS OF 15 TO
25KTS WITH HIGHER GUSTS. 67
&&
.PREV DISCUSSION... /ISSUED 343 AM CST TUE DEC 8 2009/
DISCUSSION...
STRONG WINTER STORM ALREADY AFFECTING THE AREA BY LATE MONDAY
EVENING. 100M 500MB HEIGHT FALLS AT VANDENBURG AFB WITH UPPER TROF
COMING ASHORE WITH 140KT JET STREAK BEHIND IT. MEANWHILE 850MB TEMPS
IN THE CENTRAL CONUS RANGE FROM -16C AT LBF TO 8C AT LZK. WARM AIR
ADVECTION BRINGING LIGHT TO MODERATE SNOWS TO MUCH OF THE
AREA...WITH SOME LOCATIONS ALREADY RECEIVING 3 PLUS INCHES. RADAR
IMAGERY IN THE TX PANHANDLE AREA SHOWING INCREASING RETURNS SINCE
09Z.
STILL HAVE SEVERAL HOURS OF ISENTROPIC LIFT TO GO BEFORE STRONG
UPPER FORCING VIA PROGGED 150M 500MB HEIGHT FALLS COME IN THIS
AFTERNOON. MOISTURE VALUES STILL QUITE HIGH WITH 3-4 G/KG SPECIFIC
HUMIDITIES AS THE TROF NEARS...THOUGH RELATIVE LACK OF PRECIP IN
SOUTHERN AREAS SHOWS THE MAIN PRECIP TYPE AND AMOUNT ISSUE. MID
LEVELS WILL LIKELY STRUGGLE TO SATURATE PERSISTENTLY UNTIL
AFTERNOON HERE...WITH SOUTHERLY FLOW SEVERAL THOUSAND FEET DEEP
BRINGING SOME ABOVE FREEZING AIR IN AROUND 850MB. ADVISORY STILL
SEEMS IN ORDER HERE. TIMING OF THE HEAVIER SNOWS TO THE NORTH IS
THE MAIN QUESTION THERE WITH ONGOING SNOW MORE SUBSTANTIAL THAN
EARLIER EXPECTED...WITH SOME HINTS OF BANDING EVIDENT ON RADAR AND
MODEL CROSS SECTIONS. BELIEVE MODELS ARE TOO PERSISTENT WITH
HIGHER QPF AMOUNTS INTO EVENING NEARLY COINCIDENT WITH UPPER TROF
AXIS...SO STILL THINK HEAVIER RATES WILL OCCUR FROM MID MORNING
THROUGH LATE AFTERNOON. SIGNIFICANT SNOWS WILL ONLY BE REPLACED BY
INCREASING WINDS AS VERY STRONG PRESSURE GRADIENT FOLLOWS THE
SURFACE LOW AND VERY COLD AIR SURGES IN. THIS WILL BRING A BLOWING
SNOW CONCERN...THOUGH GUSTINESS OF WINDS DONT APPEAR TO SUPPORT
BLIZZARD HEADLINES AS 925-850MB SPEEDS ARENT AS IMPRESSIVE. WILL
NEED TO MONITOR SPECIFIC LEVELS OF TEMPS AND WINDS FOR POSSIBLE
WIND CHILL ADVISORY NECESSITIES BOTH WEDNESDAY MORNING AND
WEDNESDAY NIGHT/THURSDAY MORNING.
FORECAST CHANGES BEYOND WEDNESDAY NIGHT WERE MINOR...THOUGH DID DROP
TEMPS THURSDAY NIGHT AS WELL WITH WEAK WINDS AND FEW CLOUDS.
65
AVIATION...
IFR VISBY/CIGS CURRENTLY EXIST AT ALL TAF SITES AS LIGHT SNOW HAS
OVERSPREAD REGION. ANTICIPATE SNOW TO CONTINUE OVERNIGHT INTO
MORNING WITH MAINLY IFR CONDITIONS CONTINUING. LIFR TO VLIFR IS
EXPECTED BY MID MORNING INTO THE EARLY EVENING AS MODERATE TO
OCCASIONALLY HEAVY SNOW DEVELOPS ACROSS TAF SITES.
BLAIR
&&
.TOP WATCHES/WARNINGS/ADVISORIES...WINTER STORM WARNING UNTIL 6 AM WEDNESDAY FOR KSZ008-KSZ009-
KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026-
KSZ034-KSZ035-KSZ036-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-KSZ055.
WINTER WEATHER ADVISORY UNTIL 6 AM WEDNESDAY FOR KSZ056-KSZ058-
KSZ059.
&&
$$
