000
FXUS63 KTOP 230515
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1114 PM CST WED FEB 22 2012

...AVIATION UPDATE...

.DISCUSSION...
SEE PREV DISCUSSION.

&&

.AVIATION...
RADAR WOULD SUGGEST THAT THERE IS A NARROW BAND OF FRONTOGENESIS
ALONG WITH SOME QG FORCING THAT HAS ALLOWED THE LIGHT RAIN TO
DEVELOP OVER THE AREA. RUC AND NAM PROGS SUGGEST THAT THIS WILL
STICK AROUND A FEW MORE HOURS...THOUGHT CONDITIONS SHOULD REMAIN VFR
THROUGH THE DAY. THERE IS SOME INDICATION OF WRAP AROUND LOW LEVEL
MOISTURE MOVING IN AROUND 00Z FRI. THINK THIS SHOULD REMAIN ABOVE 3
KFT. MODELS ARE COMING IN WITH A STRONGER PRESSURE GRADIENT.
THEREFORE HAVE INCREASED WINDS AND GUSTS FOR THE DAY THURSDAY.

WOLTERS

&&

.PREV DISCUSSION... /316 PM CST WED FEB 22 2012/
THROUGH THURSDAY...A WARM AFTERNOON WAS UNDERWAY ON WEDNESDAY WITH
HIGHS EXPECTED TO TOP OUT IN THE UPPER 50S TO MIDDLE 60S ACROSS THE
AREA UNDER FAST WEST NORTHWESTERLY FLOW ALOFT AND A WESTERLY BREEZE
AT THE SURFACE. THERE WERE SOME MID AND HIGH CLOUDS IN THE
AREA...WITH MORE AMPLE CLOUD COVER OVER WESTERN NEBRASKA IN ADVANCE
OF AN INCOMING SHORT WAVE TROUGH. IT APPEARS THAT SOME LIGHT PRECIP
MAY SPREAD DOWNSTREAM OUT OF WESTERN NEBRASKA THIS EVENING AS THE
TROUGH ENTERS THE PLAINS...BUT WITH FAIRLY DRY AIR IN THE LOW TO MID
LEVELS IT SHOULD BE DIFFICULT FOR ANYTHING MORE THAN PERHAPS A FEW
SPRINKLES TO FALL ACROSS THE LOCAL FORECAST AREA. TEMPERATURES WILL
STAY QUITE WARM THROUGH THE EVENING AND EARLY MORNING HOURS AS A
BREEZE WILL KEEP THE BOUNDARY LAYER MIXED AND HIGH CLOUDS SHOULD
INSULATE A BIT. HOWEVER...AS THE TROUGH CROSSES THE PLAINS...A
STRONG COLD FRONT WILL MOVE INTO THE AREA AFTER MIDNIGHT AND CROSS
THE ENTIRE FORECAST AREA BY SUNRISE. TEMPERATURES BEHIND THE FRONT
WILL DROP OFF...SO WHILE MOST OF THE NIGHT WILL BE WARM...TEMPS WILL
DROP QUICKLY AS THE FRONT PASSES.

THE POST FRONTAL AIRMASS ON THURSDAY WILL BE A WINDY ONE. EXPECT
DEEP MIXING TO AT LEAST 800 HPA...AND PERHAPS HIGHER BY LATE
AFTERNOON. THIS WILL ALLOW STRONG WINDS TO MIX TO THE SURFACE...
SUPPORTED BY PERIODS OF STRONG DOWNWARD MOTION THROUGH A
UNIDIRECTIONAL WIND FIELD IN THE WAKE OF THE UPPER TROUGH. HAVE
ISSUED A WIND ADVISORY FOR NORTHWESTERN PARTS OF THE FORECAST AREA
WHERE CONFIDENCE IS HIGHEST IN SUSTAINED WINDS GREATER THAN 30 MPH.
THERE IS A BIT OF UNCERTAINTY REGARDING HOW WINDY IT WILL GET ACROSS
THE REMAINDER OF THE AREA...BUT THE POTENTIAL AT LEAST EXISTS FOR
THE ADVISORY TO BE EXPANDED WITH GUST POTENTIAL IN THE 45 TO 50 MPH
RANGE IF FULL MIXING POTENTIAL IS REACHED. THE WAVE IS STRONG...BUT
EXPECT LITTLE MORE THAN A FEW SPRINKLES ON FRIDAY OWING TO DRY AIR.
TEMPS WILL WARM INTO THE UPPER 40S AND LOWER 50S AS THE WARM START
TO THE MORNING AND DEEP MIXING MITIGATES A BIT OF THE COLD
ADVECTION. THE DEEP MIXING AND DRY ADVECTION PRESENTS A DIFFICULT
FIRE WEATHER FORECAST AS WELL. AT THE CURRENT TIME EXPECT MIN RH
VALUES TO APPROACH 30 PERCENT...BUT THAT MAY BE CONSERVATIVE
DEPENDING ON JUST HOW DEEP THE BOUNDARY LAYER MIXES...AND IS ALSO
HIGHLY DEPENDENT ON HIGH TEMPS.

BARJENBRUCH

THURSDAY NIGHT AND FRIDAY...UPPER TROUGH AND ASSOCIATED SURFACE
LOW TRACKS INTO THE MID MISSISSIPPI VALLEY THURSDAY NIGHT. ALL
MODELS HAVE SOME SORT OF WRAPAROUND LIGHT SNOW TO THE NORTH AND
NORTHWEST OF SURFACE LOW AND THIS COULD BRUSH EXTREME NORTHEAST KS
THURSDAY EVENING. HOWEVER...WITH MAIN DYNAMICS AND ISENTROPIC LIFT
TO THE NORTH OF KS...HAVE LITTLE CONFIDENCE OF ANYTHING REALLY
FALLING OUT OF THE SKY DURING THAT BRIEF WINDOW. NORTHEAST FLOW
CONTINUES TRANSPORTING COOL AIR INTO EASTERN KS ON FRIDAY WITH HIGHS
ONLY IN THE LOWER TO MID 40S.

SURFACE HIGH PRESSURE RIDGE THEN MOVES ACROSS THE PLAINS FRIDAY
NIGHT WITH CLEAR SKIES EXPECTED. AS THE RIDGE TRAVERSES EAST ON
FRIDAY NIGHT AND SATURDAY...LOW PRESSURE DEVELOPS IN THE NORTHERN
AND CENTRAL HIGH PLAINS AS STRONG MID AND UPPER JET IMPINGES ON
THE ROCKIES. SIGNIFICANT PRESSURE GRADIENT SETS UP BETWEEN THESE
WEATHER SYSTEMS AND THIS SHOULD WARM TEMPS UP ON SATURDAY WITH
STRONG SOUTHERLY WINDS. MIXING WILL ALSO KEEP TEMPERATURES
RELATIVELY MILD SATURDAY NIGHT...IN THE MID TO UPPER 30S.

UPPER TROUGH AND INTENSE LOW THEN MOVE INTO THE UPPER MIDWEST
SUNDAY. ALL LONG RANGE MODELS KEEP STRONGEST LIFT WELL TO NORTH OF
EASTERN KS AND HAVE KEPT SUNDAY DRY AS A RESULT. 12Z GEM AND ECMWF
ATTEMPT TO DEVELOP SHOWERS ALONG TRAILING COLD FRONT IN EC KS
SUNDAY EVENING. THEN RIDGE OF HIGH PRESSURE PUSHES INTO THE AREA
FROM THE NORTHWEST FOR LATE SUNDAY NIGHT AND MONDAY.

DETAILS THEN GET FUZZY ON MONDAY NIGHT AND TUESDAY INTO TUESDAY
NIGHT. LAST COUPLE RUNS OF GFS AND ECMWF BRING SYSTEM ACROSS DURING
THAT TIME FRAME...BUT DIFFER IN ONSET TIMING AND LOCATION OF WARM
SECTOR. MORE NORTHERN AND INTENSE 12Z GFS WOULD GIVE CHANCE OF
THUNDERSTORMS AND MUCH HIGHER TEMPERATURES TUESDAY WHEREAS LATEST
ECMWF KEEPS LOW WELL TO SOUTH AND SNOW MORE LIKELY. HAVE GONE WITH
A COMPROMISE AT THIS TIME. WOULD EXPECT MODELS TO BECOME MORE
CONSISTENT WITH EACH OTHER ON THIS SYSTEM WHEN UPPER JET/TROUGH
MAKES IT TO THE COAST THIS WEEKEND AND GETS SAMPLED.

RIGHT NOW THE TIMING OF THAT SYSTEM WOULD KEEP THE DAYTIME HOURS ON
WEDNESDAY DRY...AND HAVE GONE WITH THAT SCENARIO.

PHILLIPS

&&

.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

NWS TOP Office Area Forecast Discussion