FXUS63 KDVN 130752 CCA
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
252 AM CDT TUE MAY 13 2008

.SYNOPSIS...
WARM ADVECTION IS QUITE PRONOUNCED THIS MORNING ACROSS THE MIDWEST
AS SOUTHEASTERLY WINDS AT THE SURFACE HAVE INCREASED. WINDS ALOFT
ARE VERY STRONG...WITH A LLJ SOUTH WIND OF 40 TO 50 KTS JUST OFF THE
SURFACE. A COLD FRONT IS POSITIONED NEAR THE MISSOURI RIVER...AND
SHOULD MAKE SLOW PROGRESS ACROSS IOWA TODAY.  THIS FRONT WILL BE THE
FOCUS FOR SHOWER AND THUNDERSTORM ACTIVITY THROUGH TONIGHT.

&&

.SHORT TERM...TODAY AND TONIGHT...
MID CLOUDS HAVE FORMED WITHIN THE LLJ FLOW...AND MAY LINGER THROUGH
THE MORNING AS LIFT INCREASES AND MOISTURE VALUES RESPOND TO THE
ADVECTION AHEAD OF THE COLD FRONT. HIGHS TODAY WILL BE LIMITED BY
THESE CLOUDS...AND WILL STAY NEAR THE COOLER MAV GUIDANCE IN THE
UPPER 60S TO LOWER 70S.  THE TIMING...AND UPPER SUPPORT FOR THIS
COLD FRONT SUGGESTS LIKELY POPS ARE NEEDED FOR LATE AFTERNOON
WEST...AND EVENING IN THE EASTERN 2/3RDS. HOWEVER...SURFACE CAPES
WILL BE LACKING...AND MOISTURE VALUES ARE LESS THAN IDEAL...BUT NOT
POOR. MODELS DO INDICATE CATEGORICAL COVERAGE IN POPS...BUT SINCE
THIS IS NOT A SLAM DUNK IN ALL VARIABLES...WILL LEAVE OUR HIGH END
LIKELY POPS GOING. THE SOUTH MAY SEE STRONG ENOUGH UPDRAFTS AND
UNSTABLE ENOUGH LOW LEVELS FOR SOME BRIEF SEVERE WINDS AND MARGINAL
HAIL. SPC CONTINUES A SLIGHT RISK SOUTH OF INTERSTATE 80. IN
ALL...RAINFALL SHOULD BE GENERALLY 0.25 OR LESS...BUT WHERE STORMS
ARE ORGANIZED...A HALF TO 0.75 IS QUITE POSSIBLE. THIS IS MOST
LIKELY OVER THE SOUTHEAST 1/2 OF THE CWA.

TONIGHT AFTER THE FRONT MOVES EAST...DRY CONDITIONS AND SOME
CLEARING ARE FORECAST. THIS SHOULD HELP PULL LOWS DOWN INTO THE MID
TO UPPER 40S NORTHWEST...AND LOWER 50S SOUTHEAST.

..ERVIN..

.LONG TERM...WEDNESDAY THROUGH MONDAY...
PLEASANT DAY EXPECTED ON WEDNESDAY FOLLOWING THE COLD FRONTAL
PASSAGE OF TUESDAY NIGHT. HIGH PRESSURE BUILDS INTO THE REGION WITH
SKIES BECOMING SUNNY AND MAXIMUM TEMPERATURES IN THE 60S.

THURSDAY THROUGH MONDAY...PATTERN CHANGE THIS PERIOD WITH RIDGE WEST
AND TROUGH EAST. RATHER COMPLICATED FORECAST WITH THE POSITIONING
AND INTENSITY OF DEEPENING TROUGH IN THE EAST PLAYING A BIG ROLE. A
SHIFT EITHER DIRECTION EAST OR WEST WOULD WRECK HAVOC ON TEMPERATURE
AND PRECIPITATION FORECASTS FOR OUR REGION. OPERATIONAL MODELS
INCONSISTENT ON TIMING OF SHORT WAVES IN THE NORTHWEST FLOW AND
SUBSEQUENT CHANCES OF INSTABILITY SHOWERS. THEREFORE LOW FORECAST
CONFIDENCE IN THIS TYPE OF PATTERN. FOR THIS REASON HAVE KEPT ONLY
SLIGHT CHANCES FOR SHOWERS DURING THIS PERIOD. HOWEVER...GFS/ECMWF
SEEM TO HAVE LATCHED ON TO SATURDAY BEING THE WARMEST DAY OF THE
BUNCH WITH 850 MB TEMPERATURES OF AT LEAST +10. THERFORE HAVE RAISED
MAXIMUM TEMPERATURES INTO THE 70S FOLLOWED BY COOLER TEMPERATURES
AGAIN SUNDAY AND MONDAY. HUNG MY HAT ON THE MEX GUIDANCE FOR NOW.

..HAASE..

&&

.AVIATION...
VFR CONDITIONS WILL CONTINUE THROUGH 15Z TODAY...WITH OCCASIONAL
LLWS IN THE LOWEST 1500FT AGL WHERE LIGHT SOUTHEAST WINDS ABRUPTLY
INCREASE TO 40 OR 50KTS FROM THE SOUTH. OTHERWISE VFR CONDITIONS
EXPECTED AFTER 15Z TODAY UNTIL A COLD FRONT ARRIVES...WITH A PERIOD
OF SHOWERS AND THUNDERSTORMS...ESPECIALLY AT THE MLI AND BRL SITES.
BY 04Z...ALL SITES WILL BE CONSISTENTLY VFR ONCE AGAIN BEHIND THE
COLD FRONT.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

ERVIN/HAASE