631
FXUS63 KTOP 122048
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
344 PM CDT MON MAY 12 2008
DISCUSSION
THE LATEST WATER VAPOR SATELLITE IMAGERY ALONG WITH THE 12Z UPPER
AIR MAPS SHOWED AN INTENSE UPPER LEVEL TROUGH ACROSS THE WEST
CENTRAL CONUS. A BROAD DOWNSTREAM UPPER RIDGE WAS LOCATED ACROSS THE
PLAINS STATES. AN INTENSE UPPER LOW WAS LOCATED OFF OF THE VA/NC
COAST.
THE 18Z SURFACE MAPS SHOWED A DEEPENING LEE SFC TROUGH ACROSS
EASTERN CO...EXTENDING SOUTHWARD ACROSS EASTERN NM AND WESTERN TX.
THE TIGHT PRESSURE GRADIENT ACROSS WESTERN AND CENTRAL KS HAS CAUSED
SOUTH TO SOUTHEAST WIND SPEEDS TO BE IN THE 25 TO 35 MPH RANGE WITH
GUSTS TO 45 MPH. WINDS ACROSS THE CWA HAVE BEEN IN THE 20 TO 25 MPH
RANGE WITH GUSTS TO NEAR 40 MPH. WINDS LATER THIS AFTERNOON COULD
APPROACH WIND ADVISORY CRITERIA ACROSS THE WESTERN CWA...WITH 25 TO
30 MPH AND GUSTS AS HIGH AS 45 MPH.
DEEP GULF MOISTURE WAS ADVECTING NORTHWEST ACROSS SOUTHERN TX. BRO
AND LRD ALREADY HAD DEWPOINTS AROUND 70 DEG F. DEW POINTS FROM NORTH
TX INTO CENTRAL KS WERE IN THE MID 40S.
TONIGHT...THE 5H TROUGH WILL MOVE EAST AND SHEAR OUT A BIT AS THE
NORTHERN SECTION THE 5H TROUGH MOVES EAST INTO THE NORTHERN HIGH
PLAINS. THE SOUTHERN SECTION WILL AMPLIFY AS IT DIGS SOUTHEAST INTO
THE FOUR CORNERS REGION. LOW-LEVEL CAA ACROSS THE NORTHERN HIGH
PLAINS WILL PUSH A COLD FRONT SOUTHEAST ACROSS WESTERN NE INTO
EASTERN CO AND WESTERN KS. A 50KT TO 60KT LLJ WILL DEVELOP ACROSS
CENTRAL AND EASTERN KS AND BEGIN TO TRANSPORT DEEPER MOISTURE NORTH
ACROSS CENTRAL AND EASTERN KS. THE STRONGER WAA/ISENTROPIC WILL
OCCUR TO OUR NORTHEAST ACROSS SOUTHERN NE AND NORTHWEST MO WHERE
THERE COULD BE ISOLATED TO SCATTERED ELEVATED THUNDERSTORMS
DEVELOPING DURING THE EARLY MORNING HOURS OF TUESDAY.
TUESDAY...THE NORTHERN SECTION OF THE 5H TROUGH WILL MOVE EAST
ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST. WHILE THE MORE
INTENSE SOUTHERN SECTION OF THE 5H TROUGH DIGS SOUTHEAST INTO
SOUTHWEST NM. THE SURFACE COLD FRONT SHOULD MOVE SOUTHEAST INTO THE
NORTHWEST COUNTIES OF THE CWA DURING THE EARLY AFTERNOON HOURS. THE
FRONT WILL THEN PUSH SOUTHEAST ACROSS THE CWA DURING THE LATE
AFTERNOON HOURS. AT THE SAME TIME DEEP GULF MOISTURE WILL BE
ADVECTING NORTH AND NORTHEAST FROM CENTRAL OK INTO SOUTH CENTRAL AND
SOUTHEAST KS. THE NAM MODEL SHOWS UPPER 60 TO NEAR 70 DEG F
DEWPOINTS MAKING IT INTO OUR SOUTHEAST COUNTIES AHEAD OF THE COLD
FRONT. THE NAM HAS BEEN A BIT TOO ROBUST WITH DEEP MOISTURE
RETURN...THUS I'M THINKING MID 60 DEWPOINTS MAY REACH AS FAR NORTH
AS THE KS TURNPIKE AHEAD OF THE SURFACE COLD FRONT BY LATE TUESDAY
AFTERNOON. POINT FORECAST SOUNDINGS SHOW AN EML ADVECTING NORTHEAST
ACROSS EASTERN KANSAS DURING THE AFTERNOON HOURS. POINT FORECAST
SOUNDINGS SHOW THE CAP WILL BREAK EAST AND SOUTH OF THE KS TURNPIKE
AHEAD OF THE COLD FRONT AFTER 400 PM. THERE ARE STILL UNCERTAINTIES
IN THE AMOUNT OF OVERALL INSTABILITY THAT WILL DEVELOP AHEAD OF THE
SURFACE COLD FRONT DURING THE AFTERNOON HOURS. THE NAM SHOWS STRATUS
DEVELOPING ACROSS MOST OF THE CWA AND HOLDING THROUGH THE AFTERNOON
HOURS. IF WE RECEIVE NO INSOLATION THIS WOULD DECREASE THE AMOUNT OF
MLCAPE AVAILABLE FOR THUNDERSTORMS AND INCREASE THE CAPPING
INVERSION. THE NAM POINT FCST SOUNDINGS SHOW THAT BREAKS WILL
DEVELOP IN THE STRATUS OVC ACROSS THE SOUTHEAST COUNTIES OF THE CWA
AND ALLOW FOR INSOLATION COMBINED WITH THE DEEPER MOISTURE RETURN
WOULD PROVIDE MLCAPE OF 2,000 TO 3,000 J/KG. MODERATE TO STRONG
VERTICAL WIND SHEAR FROM SFC TO 700MB AHEAD OF THE SFC COLD
FRONT...AND COMBINED WITH THE HIGHER INSTABILITY WILL CREATE A
PRE-STORM ENVIRONMENT FAVORABLE FOR SUPERCELL THUNDERSTORMS. BOTH
THE GFS AND NAM SHOW WINDS VEERING THROUGH THE AFTERNOON AT 850MB
WHICH MAY DECREASE THE POTENTIAL THAT ANY SUPERCELL THUNDERSTORM
WILL PRODUCE TORNADOES...HOWEVER IF THE LOW-LEVEL WINDS ARE BACKED A
BIT MORE TO THE SOUTH THAN MODEL PROGS...THEN ANY SUPERCELL
THUNDERSTORMS WHICH DEVELOPS MAY HAVE A GREATER CHANCE OF SPAWNING
TORNADOES. I THINK THE PRIMARY HAZARD FROM ANY SUPERCELL
THUNDERSTORM DEVELOPING ACROSS THE SOUTHEAST COUNTIES OF THE CWA
TUESDAY AFTERNOON WILL BE LARGE HAIL AND DAMAGING WIND
GUSTS...THOUGH A BRIEF TORNADO CAN NOT BE RULED OUT. ONCE AGAIN THE
BEST CHANCE OF SEVERE THUNDERSTORMS ATTM WILL BE EAST AND SOUTH OF
THE KS TURNPIKE. HOWEVER...IF THE FRONT IS SLOWER AND THE DEEPER
MOISTURE ADVECTS FARTHER NORTHWARD ACROSS THE EASTERN CWA...THE
THREAT FOR SEVERE THUNDERSTORMS WILL INCREASE ACROSS THE EASTERN
COUNTIES OF THE CWA.
THROUGH THE LATE AFTERNOON HOURS THE SCATTERED SUPERCELL
THUNDERSTORMS AHEAD THE COLD FRONT WILL BEGINNING TO CONGEAL INTO A
SQUALL LINE. THIS MAY OCCUR JUST SOUTHEAST OF THE TOP CWA. IF THE
SQUALL LINE DEVELOPS EARLIER ACROSS THE SOUTHEAST COUNTIES THE MAIN
HAZARD WILL BE DAMAGING OUTFLOW WINDS.
HIGHS ON TUESDAY WILL BE DEPENDENT ON CLOUD COVER. IF WE DO SEE
BREAKS IN THE CLOUD COVER AHEAD OF THE FRONT HIGH TEMPERATURES MAY
REACH INTO THE UPPER 70S TO AROUND 80 DEGREES ACROSS THE SOUTHEAST
COUNTIES OF THE CWA. HIGHS BEHIND THE FRONT ACROSS THE WESTERN
COUNTIES OF THE CWA WILL STRUGGLE INTO THE LOWER TO MID 60S.
TUESDAY NIGHT...COLD FRONT WILL BE EXITING THE SOUTHEAST PORTION OF
THE CWA IN THE EVENING...TAKING MOST OF THE CONVECTION WITH IT. WILL
KEEP A SLIGHT CHANCE/CHANCE POPS FOR LINGERING CONVECTION IN THE
EVENING GENERALLY EAST OF HIGHWAY 99. OTHERWISE COLD ADVECTION WILL
BE THE RULE TUESDAY NIGHT AND IT WILL BE DRY DRY OVERNIGHT AND
WEDNESDAY ACROSS THE CWA WITH DECREASING CLOUDS AS NORTHERN STREAM
WAVE MOVES EAST AND DRIER AIR MOVES IN. ALTHOUGH THERE WILL BE MORE
SUN ON WEDNESDAY...THE NORTHEAST/EAST WINDS AND COOLER 850 TEMPS
WILL KEEP HIGHS IN THE UPPER 60S.
AS NEXT NORTHWEST FLOW WAVE DIVES INTO THE NORTHERN ROCKIES
WEDNESDAY...IT WILL HELP EJECT THE CUTOFF LOW IN THE SOUTHWEST U.S.
EAST AND NORTHEAST INTO THE PLAINS. WILL THEREFORE INCREASE POPS
ACROSS MUCH OF THE SOUTHERN AND WESTERN CWA WEDNESDAY NIGHT AND ALSO
INTO THURSDAY...BUT HIGHER QPF POTENTIAL APPEARS WILL FOCUS OVER THE
SOUTHEAST CWA. WITH THE CLOUDS AND PRECIP CHANCES THURSDAY...WILL
LIMIT HIGHS TO ONLY THE MID 60S. HOWEVER IF PRECIP IS MORE
WIDESPREAD...HIGHS MAY BE EVEN COOLER.
AS THE TWO SYSTEMS PHASE OVER THE PLAINS THURSDAY NIGHT AND BEGIN TO
SHIFT EASTWARD...SHOWER CHANCES WILL END ACROSS THE CWA BY FRIDAY
WITH SUBSIDENCE DEVELOPING IN ITS WAKE. THE COOLER HIGHS ON FRIDAY
IN THE 60S WILL BE REPLACED BY THE MID 70S ON SATURDAYS AS EASTERN
TROUGH MOVES EAST OFF THE EASTERN SEABOARD AND ALLOWS FOR A MORE
WESTERLY FLOW ACROSS THE CENTRAL PLAINS. ANOTHER FRONT WILL MOVE
SOUTHWARD ACROSS THE CWA FOR SUNDAY BRINGING SLIGHTLY COOLER
TEMPS...MAINLY ACROSS THE NORTHEAST AREAS BEFORE WARM ADVECTION
BEGINS AGAIN BY MONDAY WITH HIGHS IN THE 70S. WILL KEEP THE WEEKEND
INTO EARLY NEXT WEEK DRY AS CWA REMAINS ON THE EASTERN EDGE OF LARGE
SCALE UPPER RIDGE ACROSS THE WESTERN U.S..
AVIATION
VFR CONDITIONS WILL CONTINUE THROUGH ABOUT 300 AM AT ALL TAF SITES.
SOUTHERLY AND SOUTHEASTERLY SURFACE WINDS OF 18 TO 25 KTS AND GUSTS
OF 35 TO 40KTS WILL SLOWLY DIMINISH AFTER 00Z. AS THE LOW-LEVEL JET
INCREASES THERE MAY BE ENOUGH MIXING TO ALLOW THE WINDS TO GUSTS
THROUGH THE NIGHT. IF WE DECOUPLE LATER THIS EVENING AND WINDS DROP
UNDER 10KTS THERE COULD BE LOW LEVEL WIND SHEAR. BETWEEN 10Z AND 12Z
POINT FORECAST SOUNDINGS SHOW STRATUS CLOUDS DEVELOPING ACROSS THE
TAF SITES. ATTM I KEPT CEILINGS 3,500 FEET WITH SCATTERED STRATUS OF
1,200 TO 1,500 FEET. THERE IS A CHANCE THAT THE LOWER STRATUS MAY
FORM A BKN LAYER BETWEEN 12Z AND 16Z. THE COLD FRONT WILL MOVE EAST
ACROSS THE TAF SITES BETWEEN 19Z AND 22Z AND SHIFT WINDS AROUND TO
THE NORTHWEST AT 20KTS. THERE MAY BE A CHANCE OF SHOWERS AND
THUNDERSTORMS AHEAD OF THE COLD FRONT AT ALL TAF SITES. ATTM THE
SEVERE THUNDERSTORMS SHOULD REMAINS SOUTHEAST OF THE KFOE AND KTOP
TAF SITES.
TOP WATCHES/WARNINGS/ADVISORIES
NONE.
66/63
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