000
FXUS63 KSGF 220048
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
748 PM CDT TUE MAY 21 2013

.MESOSCALE DISCUSSION...
ISSUED AT 747 PM CDT TUE MAY 21 2013

FORECAST UPDATED TO ACCOUNT FOR RADAR AND NEAR TERM TRENDS.

CONVECTIVE ACTIVITY TO OUR SOUTH ACROSS ARKANSAS AND INTO
TENNESSEE AND MISSISSIPPI CONTINUES TO DOMINATE WITH ONLY A WANING
SHIELD OF LIGHT SHOWERS CLIPPING SOUTHERN MISSOURI. HAVE CUT POPS
ACROSS MUCH OF THE AREA FOR THE REST OF THIS EVENING AND
TONIGHT...FOCUSING HIGHER CHANCE VALUES FROM BRANSON TO SALEM. IN
ADDITION...INSTABILITY HAS COME DOWN CONSIDERABLY OVER THE PAST
FEW HOURS. HAVE DEEMPHASIZED THE PROSPECTS FOR THUNDER AND WILL
REMOVE ANY MENTION OF STRONG/SEVERE CONVECTION.

NOT COMPLETELY OUT OF THE WOODS RAINFALL WISE OVERNIGHT AS THE
MAIN UPPER LEVEL LOW/VORT MAX PUSHES EAST OUT OF CENTRAL OKLAHOMA.
WILL BE WATCHING FOR ANY DEVELOPING RADAR RETURNS TO OUR SOUTHWEST
AND SOUTH AND REFINE THE FORECAST FURTHER IF NEEDED.

AN INTERESTING FEATURE THAT HAS POPPED UP IN THE PAST HOUR OR SO
IS A CONCENTRATED AREA OF SURFACE PRESSURE FALLS ACROSS NORTHEAST
OKLAHOMA. AHEAD OF THIS FEATURE...WINDS ARE GUSTY OUT OF THE
SOUTHEAST AND BEHIND THE FEATURE WINDS ARE JUST AS GUSTY OUT OF
THE NORTHWEST. SUSTAINED WIND SPEEDS OF 20 TO 25 MPH WILL BE
COMMON WITH FREQUENT GUSTS IN EXCESS OF 30 MPH EXPECTED UNTIL THIS
MESOLOW BEGINS TO WEAKEN/MOVE EAST.

&&

.SHORT TERM...(THIS AFTERNOON THROUGH WEDNESDAY)
ISSUED AT 245 PM CDT TUE MAY 21 2013

TWO AREAS OF SHOWERS AND THUNDERSTORMS ARE LOCATED TO THE SOUTH OF
THE AREA WITH ONE AREA PUSHING INTO EASTERN ARKANSAS AND ANOTHER
PUSHING INTO EASTERN OKLAHOMA. SHOWERS WITH A FEW RUMBLES OF
THUNDER ARE CLIPPING FAR SOUTHERN MISSOURI WITH THIS ACTIVITY
EARLY THIS AFTERNOON. CLOUD COVER FROM THE CONVECTION TO THE SOUTH
HAS OVERSPREAD THE REGION. THIS IS LIMITING HEATING WITH
TEMPERATURES IN THE LOWER 60S TO THE LOWER 70S. THE AREA WAS ALSO
WORKED OVER FROM THE STORMS THAT OCCURRED MONDAY EVENING AND
DEWPOINTS ARE CURRENTLY IN THE LOWER 60S EARLY THIS AFTERNOON. AS
A RESULT OF THESE...INSTABILITY IS MUCH LOWER THAN IT HAS BEEN
THE LAST SEVERAL DAYS.

A COLD FRONT CURRENTLY EXTENDS ACROSS GENERALLY ALONG THE
INTERSTATE 44 CORRIDOR. THERE IS ENOUGH INSTABILITY TO EXPECT
SHOWER AND THUNDERSTORM DEVELOPMENT TO INCREASE AHEAD OF THE FRONT
LATER THIS AFTERNOON INTO THIS EVENING ALONG AND SOUTH OF THE
FRONT. NOT EXPECTING WIDESPREAD SEVERE WEATHER DUE TO THE WEAKER
INSTABILITY BUT THERE COULD BE A FEW STRONG TO MARGINALLY SEVERE
STORMS THAT MAY BE ABLE TO DEVELOP ACROSS SOUTH CENTRAL MISSOURI.
THE MAIN SEVERE POTENTIAL WILL REMAIN TO THE SOUTH AND EAST OF THE
AREA. THE MAIN RISK WITH ANY STRONGER STORMS THAT CAN DEVELOP WILL
BE HAIL TO THE SIZE OF QUARTERS AND WIND GUSTS OF 45 TO 60 MPH.THE
FRONT WILL SLOWLY SAG TO THE SOUTHEAST THIS EVENING INTO THE
OVERNIGHT HOURS WITH THE CONVECTION ENDING FROM WEST TO EAST
TONIGHT. A DRIER AIRMASS WILL BUILD INTO THE AREA WEDNESDAY WITH
HIGHS WARMING INTO THE LOW TO MID 70S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 245 PM CDT TUE MAY 21 2013

WEDNESDAY NIGHT THROUGH FRIDAY NIGHT:

A BROAD UPPER LEVEL VORTEX OVER NORTHEASTERN IOWA WEDNESDAY EVENING
OPENS INTO A TROUGH AS IT TRACKS EASTWARD TOWARD THE APPALACHIAN RIDGE
BY FRIDAY MORNING. MEANWHILE...UPPER LEVEL RIDGING OVER THE EASTERN
SLOPE OF THE ROCKIES BUILDS SHARPLY NORTHWARD AS IT SHIFTS EASTWARD
WITH ITS AXIS EXTENDING NORTHWARD FROM TEXAS TO FAR SOUTHERN CANADA
BR FRIDAY MORNING.

AT THE SURFACE...HIGH PRESSURE OVER THE PRAIRIE PROVINCES AND THE
NORTHERN HIGH PLAINS WEDNESDAY NIGHT WILL BUILD SOUTHEASTWARD AND
EXPAND INTO THE CENTRAL GREAT LAKES...CENTRAL MISSISSIPPI AND OHIO
VALLEYS ON FRIDAY. A NORTHEAST...THEN EASTERLY FLOW ON THE
SOUTHWESTERN SIDE OF THIS RIDGE WILL KEEP THE CWA UNDER FAIR SKIES
AND NORMAL TO JUST SLIGHTLY COOLER THAN NORMAL TEMPERATURES FOR
LATER MAY WITH HIGHS IN THE LOWER TO MID 70S AND LOWS GENERALLY IN
THE 50S.

FRIDAY NIGHT THROUGH TUESDAY:

PREVIOUSLY MENTIONED UPPER LEVEL RIDGING OVER THE PLAINS STATES
SHIFT VERY SLOWLY EASTWARD ALIGNING ON A LOUISIANA TO MINNESOTA AXIS
BY MONDAY MORNING...LOSING AMPLIFICATION SOMEWHAT AS WELL. AT THIS
TIME THE ECMWF TENDS TO FLATTEN THE RIDGE MORE AGGRESSIVELY THAN THE
GFS BUT BOTH MODELS DO DEPICT A SERIES OF WEAK BUT PROGRESSIVE
DISTURBANCES (RIDGE RUNNERS) TRANSITING THE RIDGE FROM SATURDAY INTO
MONDAY. THIS PATTERN WILL KICK OFF INTERMITTENT PERIODS OF SHOWER
ACTIVITY THIS WEEKEND INTO MONDAY. EXPECT TOTAL QPF VALUES TO RANGE
FROM ONE HALF TO THREE QUARTERS OF AN INCH FOR THE ENTIRE SATURDAY
THROUGH MONDAY PERIOD WITH THE HIGHEST VALUES OVER WESTERN MISSOURI
AND FAR SOUTHEASTERN KANSAS AS LOW LEVEL GULF MOISTURE FLOW...CAPE
VALUES AND ANY ISENTROPIC UPGLIDE VALUES ARE STRONGEST IN THESE
AREAS.

TOOK A LOOK AT SEVERE WEATHER POTENTIAL FOR THIS WEEKEND AND BELIEVE
WHILE WE HAVE A CHANCE FOR SOME CONVECTIVE ACTIVITY...SEVERE
WEATHER IS NOT LIKELY. PARTICULARLY...UPPER LEVEL AND DYNAMIC
SUPPORT IS WEAK AS THE UPPER RIDGE...ALTHOUGH WEAKER...IS THE
DOMINANT FEATURE AND ANY SHOT WAVE ACTIVITY IS RATHER WEAK. BOTH
MOST UNSTABLE AND SURFACE COMPUTED CAPE VALUES ARE
AMPLE...GENERALLY IN THE 1500J/KG TO 2500J/KG RANGE...BUT ZERO TO
SIX KM BULK SHEAR VALUES GENERALLY REMAIN WEAK...IN THE 20 TO 30
KT RANGE.

SOME RE-AMPLIFICATION OF THE UPPER RIDGE WILL TAKE PLACE ON TUESDAY
AS THE RIDGE AXIS REMAINS JUST TO THE EAST OF THE MISSISSIPPI
VALLEY. THIS WILL HELP TO SUPPRESS MOST SHOWER ACTIVITY ON
TUESDAY. AT THE SURFACE...HIGH PRESSURE WILL CONTINUE TO TRACK
EASTWARD TOWARD THE EASTERN SEABOARD ON TUESDAY...PLACING THE CWA IN
A STEADY AND WARMING SOUTHWESTERLY FLOW LATE MONDAY INTO TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 747 PM CDT TUE MAY 21 2013

AS DISCUSSED IN THE MESOSCALE DISCUSSION ABOVE...A MESOLOW WILL
ALTER WIND SPEEDS AND DIRECTIONS FOR THE NEXT FEW HOURS. SEE THE
TEXT ABOVE FOR MORE DETAILS. OTHERWISE...VFR CONDITIONS ARE
EXPECTED FOR MOST OF THE NEXT 24 HOURS. IF SKIES CAN CLEAR LATE
TONIGHT...THERE WILL BE A RISK FOR LOCALIZED GROUND FOG...HOWEVER
CONFIDENCE IN THIS SCENARIO IS LOW AT THIS TIME. WEST WINDS WILL
BE GUSTY ON WEDNESDAY WITH A FEW PASSING HIGH CLOUDS.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$

MESOSCALE...GAGAN
SHORT TERM...WISE
LONG TERM...COLUCCI
AVIATION...GAGAN