000
FXUS63 KDVN 132335
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
635 PM CDT MON MAY 13 2013

.SYNOPSIS...
ISSUED AT 321 PM CDT MON MAY 13 2013

HIGH PRESSURE RIDGE AT THE SURFACE HAS PUSHED EAST TO THE GREAT
LAKES AND OHIO RIVER VALLEY TODAY WHILE ALOFT...A STRONG WARM
ADVECTION REGIME HAD SET IN UNDER A WEST TO NW FLOW. AREA
RADARS...SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATED A BAND
OF VERY HIGH BASED SHOWERS FROM ABOUT CID NORTH INTO MN AND WI ALONG
AN AXIS OF CONCENTRATED WARM ADVECTION. FALLING FROM NEAR 10000
FT AGL...LITTLE APPEARS TO BE MAKING IT TO THE SURFACE DESPITE
IMPRESSIVE REFLECTIVITY VALUES. 12Z UPPER AIR OBSERVATIONS FROM THIS
MORNING HIGHLIGHTED VERY WARM AIR BUILDING UNDER THE UPPER RIDGE
AXIS FROM THE FOUR CORNERS TO THE CANADIAN PRAIRIES. 850 MB
TEMPERATURES CLIMBED FROM 2 DEG C AT DVN...10 AT OAX...TO 24 DEG
CELSIUS AT RAPID CITY SD.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 321 PM CDT MON MAY 13 2013

MAIN CHALLENGE IS THE NEAR RECORD WARMTH LIKELY TUESDAY AS THE UPPER
LEVEL RIDGE OUT WEST FLATTENS AND SENDS VERY WARM AIR ALOFT
EASTWARD. 12Z MODELS HAD A DECENT INITIALIZATION OF THE 20 PLUS DEG
C ISOTHERMS AT 850 MB OUT WEST...WITH THE EXCEPTION OF NOT BEING
WARM ENOUGH AT KUNR. THE OTHER MAJOR MODEL ISSUE IS THE CONTINUED
MOIST BIAS THAT WORSENS TUESDAY. WHILE THEY APPEARED TO HAVE A
TYPICAL HANDLE ON SURFACE DEWPOINT TRENDS TODAY OVER THE LOCAL AREA
INTO THE CENTRAL AND SOUTHERN PLAINS...MOST HAVE A WIDESPREAD FIELD
OF 55 TO 60 PLUS DEWPOINTS THAT DEVELOP OVER THE AREA DURING DAYTIME
MIXING TUESDAY. WILL CONTINUE TO IGNORE THIS...AND INSTEAD GO CLOSER
TO PERSISTENT PLUS GRADUAL MOISTENING TO REACH COMPROMISE READINGS
IN THE 50S BY LATE TUESDAY AFTERNOON. THIS RESULTS IN AFTERNOON MIN
RH VALUES IN THE 30S.

TONIGHT...ANY SPRINKLES THIS AFTERNOON SHOULD BE OUT OF THE AREA BY
EVENING...OTHERWISE WILL HAVE THIN CI AND LIGHT WINDS. IN THE DRY
AIRMASS...MIN TEMPERATURES FROM THE UPPER 40S NORTHEAST TO MID 50S
SW LOOKS REASONABLE.

TUESDAY...MODEL CONSENSUS HAS 850 MB WARMING TO A RANGE OF 22 TO 24
DEG C OVER THE FORECAST AREA BY 00Z. ACCORDING TO OUR DVN UPPER AIR
CLIMATOLOGY...THIS WOULD BE OVER 2 SIGMA OR ABOVE THE 99TH
PERCENTILE. LOCAL HIGH TEMPERATURE RULES BASED ON THESE
VALUES...WOULD YIELD HIGHS WELL INTO THE 90S...OR POSSIBLY UPPER 80S
IF MIXED DOWN FOLLOWING A MOIST ADIABAT. FORECAST SOUNDINGS CONTINUE
TO FAVOR MORE SHALLOW MIXING...WELL BELOW 850 MB...AND WILL THUS
LEAN TOWARD A MORE CONSERVATIVE HIGH TEMPERATURE RANGE FROM THE MID
80S NORTHEAST TO AROUND 90 CENTRAL AND SOUTHWEST. THIS WOULD BE
BELOW RECORD VALUES AT MOST SITES...LISTED IN THE CLIMATE SECTION
BELOW.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 321 PM CDT MON MAY 13 2013

MOISTURE AVAILABILITY IS THE KEY TO WHETHER OR NOT ANY PRECIPITATION
WILL BE SEEN TUES NIGHT INTO WED MORNING.

INTERNALLY...FORCING/CONVERGENCE IS VERY WEAK WITH THE FRONT.
HOWEVER...THERE IS A WEAK THETA E GRADIENT THAT MOVES INTO THE
NORTHWEST CWFA BY LATE EVENING AND SLOWLY SINKS INTO THE CENTRAL
CWFA BY SUNRISE WEDNESDAY. TAKING ALL THIS INTO ACCOUNT ALONG WITH
LIMITED MOISTURE SUGGESTS LIGHT SHOWERS OR SPRINKLES STARTING LATE
TUESDAY EVENING INTO WEDNESDAY MORNING.

BY WED AFTERNOON THE THETA E GRADIENT LIES OVER THE SOUTHERN HALF OF
THE CWFA WITH THETA E LAPSE RATES TURNING NEGATIVE. MOISTURE IS
STILL SOMEWHAT LIMITED BUT DIURNAL HEATING SHOULD ALLOW SHOWERS AND
SOME THUNDERSTORMS TO DEVELOP OVER ROUGHLY THE SOUTHERN HALF OF THE
CWFA WEDNESDAY AFTERNOON.

CONVECTION THAT DEVELOPS WED AFTERNOON WILL LINGER INTO THE EVENING.
A THETA E GRADIENT REMAINS ACROSS ROUGHLY THE SOUTHERN HALF OF THE
CWFA. THIS FEATURE COMBINED WITH WEAK CONVERGENCE FROM THE FRONT
SHOULD KEEP SHOWERS AND SOME THUNDERSTORMS GOING THROUGH SUNRISE.

ON THURSDAY THE WEAK BOUNDARY REMAINS ALONG THE SOUTHERN BORDER OF
THE CWFA AS A WEAK HIGH PASSES ACROSS WISCONSIN. THE VERY WEAK
CONVERGENCE COMBINED WITH THE STILL PRESENT THETA E GRADIENT SHOULD
MAINTAIN OR ALLOW NEW SHOWERS AND SOME THUNDERSTORMS TO DEVELOP
ACROSS THE SOUTHWEST 40 PERCENT OF THE CWFA.

THURSDAY NIGHT ON...
THE MODEL CONSENSUS CONTINUES TO INDICATE A MORE ACTIVE WX PATTERN
WILL DEVELOP FROM THURS NIGHT THROUGH EARLY NEXT WEEK. ALTHOUGH
STILL WEAK...THE INTERNAL SIGNALS FROM THE MODELS SUGGEST THE
POTENTIAL FOR ORGANIZED THUNDERSTORMS CLUSTERS TO DEVELOP ACROSS THE
MIDWEST. THUS NON LINEAR PROCESSES WILL BE DRIVING THE SENSIBLE WX.
THERE WILL BE PERIODS OF DRY WX FROM THURS NIGHT THROUGH NEXT MONDAY
BUT TIMING THEM IS NOT POSSIBLE ATTM.

THE MODEL CONSENSUS HAS SCHC/CHC POPS THURS NIGHT THROUGH SATURDAY
WITH CHC/LIKELY POPS SATURDAY NIGHT THROUGH SUNDAY NIGHT. THERE ARE
DIFFERENCES AMONG THE MODELS BUT THEY APPEAR TO BE CONVERGING ON
ANOTHER FRONT MOVING THROUGH THE AREA OVER THE WEEKEND THUS
JUSTIFYING HIGHER POPS. ON MONDAY THE MODEL CONSENSUS HAS SCHC/CHC
POPS.

TEMPERATURES THURS NIGHT THROUGH SUNDAY SHOULD AVERAGE A LITTLE
ABOVE NORMAL. ONCE THE COLD FRONT PASSES THROUGH OVER THE WEEKEND...
TEMPERATURES SHOULD DROP TO AROUND NORMAL FOR MONDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 631 PM CDT MON MAY 13 2013

CONDITIONS WILL REMAIN VFR THROUGH TUESDAY AFTERNOON. A COLD FRONT
WILL BE APPROACHING THE AREA BY LATE TOMORROW AFTERNOON. SOUTH
WINDS AROUND 10KTS WILL PERSIST AHEAD OF THE FRONT TONIGHT AND
TUESDAY MORNING. SOUTH WINDS WILL INCREASE DURING THE AFTERNOON
WITH GUSTS OF 20 TO 25KTS EXPECTED AFTER 18Z AT KDBQ AND KCID.

&&

.CLIMATE...
ISSUED AT 321 PM CDT MON MAY 13 2013

RECORD HIGHS FOR MAY 14...

MOLINE.........93 IN 2007
CEDAR RAPIDS...93 IN 1932
DUBUQUE........92 IN 1932
BURLINGTON.....92 IN 1932

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...08
AVIATION...DLF