809
FXUS64 KOUN 201533
AFDOUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
1033 AM CDT TUE MAY 20 2008
UPDATE
SHOWER ACTIVITY...INCLUDING MAINLY VIRGA... CONTINUES TO DECREASE THIS
MORNING... AND SHOULD BE GONE BY EARLY AFTERNOON. UPDATED FORECAST
TO REFLECT WEAKENING TREND OF THIS ACTIVITY. ALSO BUMPED UP
NORTHEAST WINDS FOR TODAY AS MIXING HAS RESULTED IN GUSTS OVER 20
MPH. ALSO MODIFIED CLOUD GRIDS TO BETTER CAPTURE EXISTING COVERAGE
AND EXPECTED DECREASE DURING THE AFTERNOON.
PREV DISCUSSION
/ISSUED 430 AM CDT TUE MAY 20 2008/
DISCUSSION...
THE RELEASE OF WEAKLY UNSTABLE AIR CONTINUES ACROSS A BROAD AREA
INCLUDING NORTHERN OKLAHOMA THIS MORNING IN ASSOCIATION WITH
SUSTAINED FRONTOGENESIS OCCURRING WITHIN A DEEP BAROCLINIC ZONE.
THESE CONDITIONS SHOULD TRANSLATE SOUTHWARD THIS MORNING WHILE
SLOWLY WEAKENING TOWARD MIDDAY.
BEYOND TODAY...WE HAVE CONTINUED USING THE GFS...WHICH IS IN GOOD
AGREEMENT WITH THE LATEST GFS ENSEMBLE MEAN...AND CONSIDERED THE
MODEL OF CHOICE. THIS APPROACH FAVORS A SLIGHT CHANCE OF
THUNDERSTORMS ONCE AGAIN TUESDAY NIGHT AS STRONG VEERING OF LOW/MID
LEVEL FLOW OCCURS WITH ONSET OF THE LOW LEVEL JET. MODEL FORECAST
SOUNDINGS SHOW 700 MB CAPES AVERAGING 150-500 J/KG. NOT WORTHY OF
SEVERE DESCRIPTIONS IN THE HWO. HOWEVER...SOME MINOR IMPACT WITH
LIGHTNING AND GUSTY WINDS MAY OCCUR.
WEDNESDAY STILL APPEARS MOSTLY A TRANSITION DAY...WITH THE MID/UPPER
LEVEL RIDGE/CAP BUILDING WHILE AT THE SAME TIME...MOISTURE SLOWLY
INCREASES AND A DRYLINE DEVELOPS. GIVEN THE LIKELY CAP STRENGTH AND
ONLY PRELIMINARY ARRIVAL OF BETTER MOISTURE...MOST IF NOT ALL STORMS
ON WEDNESDAY SHOULD BE NORTHWEST OF THE AREA.
BY THURSDAY...OUR CONCEPTUAL MODEL USES A MEAN MODEL SOLUTION THAT
HAS THE SUBTROPICAL JET EXTENDING FROM NEW MEXICO INTO COLORADO
WHICH THEN PERPETUATES THE LEE ROCKIES SURFACE LOW AND A DRYLINE
OVER THE TEXAS PANHANDLE. THE UPPER LEVEL WIND PATTERN FAVORS
SHORTWAVE TROUGH EVOLUTION AND SUBSEQUENT MOVEMENT INTO COLORADO
WITH THE CAP DIFFICULT TO OVERCOME ALONG THE DRYLINE INTO WEST
TEXAS. AGREE WITH THE SPC DAY 3 OUTLOOK THAT COVERS THE POSSIBILITY
OF ISOLATED TO WIDELY SCATTERED CONVECTION FORMING LATE IN THE DAY
NEAR THE WESTERN OKLAHOMA BORDER. THE OUTLOOK WILL BE CONDITIONAL
HOWEVER...GIVEN THE CAP WITH MU/MLCAPE VALUES AND STORM DEPTH SHEAR
MORE THAN ADEQUATE FOR SUPERCELLS.
A SIMILAR SCENARIO MAY HOLD TRUE FOR FRIDAY...EXCEPT THERE IS A
SLOW TREND IN THE MEDIUM RANGE MODELS FOR THE UPPER LOW TO BEGIN
BREAKING APART WITH ONE PIECE MOVING TOWARD THE HIGH PLAINS OF
WYOMING WHILE THE LEFTOVERS OVER THE SOUTHWEST U.S. RETROGRADE. THE
RESULT MAY BE WEAKER MID/UPPER LEVEL FLOW OVER OKLAHOMA/NORTH TEXAS
AND A MORE DIFFUSE AND MORE WESTWARD-ORIENTED DRYLINE.
THE SAME MODEL TRENDS CONTINUE SATURDAY THROUGH NEXT MONDAY WITH THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE STRENGTHENING AS THE WEST
COAST UPPER LOW SLOWLY WEAKENS. ACCOMPANYING THUNDERSTORM CHANCES
FOR ALL OF THESE DAYS ARE WORTH MENTIONING BUT LOW...WITH HOT AND
HUMID CONDITIONS MOST LIKELY PREVAILING.
PRELIMINARY POINT TEMPS/POPS
OKLAHOMA CITY OK 86 57 83 67 / 20 20 20 10
HOBART OK 87 59 87 70 / 10 20 20 10
WICHITA FALLS TX 90 63 89 70 / 20 10 10 10
GAGE OK 82 56 84 65 / 20 20 20 10
PONCA CITY OK 83 54 85 68 / 20 20 20 10
DURANT OK 86 60 83 69 / 20 20 20 10
OUN WATCHES/WARNINGS/ADVISORIES
OK...NONE.
TX...NONE.
32/25
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