000
FXUS63 KDVN 180431
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1131 PM CDT FRI MAY 17 2013

.SYNOPSIS...
ISSUED AT 256 PM CDT FRI MAY 17 2013

500 MB ANALYSIS SHOWS WEAK RIDGING OVER THE CENTRAL US WITH A LOW
MOVING INTO THE OHIO VALLEY...AND A SHORT WAVE CROSSING IOWA.  AT
THE SURFACE LOW PRESSURE IS CENTERED OVER SE WY WITH A STATIONARY
FRONT EXTENDING ACROSS NORTHERN IOWA AND ILLINOIS.  BOUNDARY WAS
REINFORCED BY OUTFLOW FROM THUNDERSTORMS TO THE NORTH OVER MN AND
WI OVERNIGHT AND WARM SOUTHERLY WINDS TO ITS SOUTH. GULF IS WIDE
OPEN WITH DEW POINTS IN THE 60S IN THE WARM SECTOR.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 256 PM CDT FRI MAY 17 2013

ON THE RADAR THIS AFTERNOON...SCATTERED DIURNAL THUNDERSTORMS HAVE
DEVELOPED IN THE WARM SECTOR OVER NORTHERN ILLINOIS IN THE VICINITY
OF THE SURFACE BOUNDARY.  MEANWHILE...A SECOND AREA OF STORMS OVER
NORTH CENTRAL AND CENTRAL IOWA HAS DEVELOPED WITH THE SUPPORT OF THE
PASSING SHORT WAVE.  BOTH OF THESE AREAS ARE EXPECTED TO WEAKEN AND
DISSIPATE WITH LOSS OF DAYTIME HEATING AFTER 00Z. TONIGHT THE FRONT
IS PROGGED TO MOVE LITTLE...THEN PUSH NORTHWARD SATURDAY AND BEGIN
TO WASH OUT. WITH THE CWFA FIRMLY ENTRENCHED IN THE WARM SECTOR...
TEMPERATURES SATURDAY WILL RISE TO NEAR TODAYS HIGHS.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 256 PM CDT FRI MAY 17 2013

SUNDAY AFTERNOON AND EVENING CONTINUE TO LOOK ACTIVE ACROSS THE
PLAINS AND MID MISSISSIPPI VALLEY AS A NEGATIVELY TILTED TROF LIFTS
FROM THE SOUTHERN PLAINS INTO THE MID/UPPER MISSISSIPPI VALLEY BY
MONDAY MORNING.

PRIOR TO SUNDAYS EVENT...THE UPPER TROF WILL BE LOCATED OVER THE
ROCKIES WITH A SURFACE TROF/FRONT OVER THE CENTRAL AND NORTHERN
PLAINS.  MODELS SUGGEST AN MCS WILL DEVELOP OVER THE CENTRAL PLAINS
AHEAD OF THE SURFACE BOUNDARY IN RESPONSE TO THE LLJ STRENGTHENING
TO 40 TO 50KTS SATURDAY EVENING.  THE FAVORED AREA FOR MCS
DEVELOPMENT LOOKS TO BE EASTERN NE WITH THE COMPLEX LIFTING
NORTHEAST POSSIBLY BRUSHING THE NORTHWESTERN CWFA EARLY SUNDAY
MORNING.

FOR SUNDAY AND SUNDAY NIGHT MODELS ARE IN AGREEMENT THAT THE BEST
UPPER FORCING WILL LIFT NORTH THROUGH THE AREA SUNDAY EVENING. AT
THE SAME TIME A SURFACE LOW MOVES NORTH THROUGH EASTERN NE/WESTERN
IA DRAGGING THE WARM FRONT NORTH THROUGH THE AREA.  WITH THE
LOW/UPPER LEVEL FORCING PHASED  THE BIG QUESTION WILL BE THE AMOUNT
OF INSTABILITY THE SYSTEM HAS TO WORK WITH.  AT THIS POINT EXPECT
TEMPERATURES TO BE IN THE THE MID 80S OVER MOST OF THE AREA BY LATE
AFTERNOON WITH ANY DEBRIS CLOUDS FROM THE OVERNIGHT MCS MIXING OUT
EARLY IN THE DAY.  THE NAM/GFS LOOK TOO MOIST WITH THEIR LOW TO MID
70 SURFACE DEW POINTS SUNDAY AFTERNOON. THE ECMWF/S MID OR UPPER 60S
LOOK MORE REASONABLE.  THESE TEMPS/DEW POINTS SHOULD SUPPORT LATE
AFTERNOON/EARLY EVENING CAPES AROUND 2000J/KG OVER EASTERN IA.
GIVEN THE FORCING AND 30 TO 50 KTS DEEP LAYER SHEAR OVER THE
AREA...SEVERE STORMS STILL LOOK PROBABLE WITH HAIL AND DAMAGING WINDS
THE MAIN THREATS.  ISOLATED TORNADOES CAN/T BE RULED OUT ESPECIALLY
IN THE SOUTH DURING THE EVENING AS THE WARM FRONT MOVES THROUGH.
P/W/S WILL BE IN THE 1.5 TO 2.0 INCH RANGE SO ANY STRONG STORMS WILL
PRODUCE LOCALLY HEAVY RAINS.

THE UPPER TROF CLOSES OFF AND THE SYSTEM  OCCLUDES AND STALLS JUST
NORTH OF THE FORECAST AREA MONDAY THROUGH WEDNESDAY OR THURSDAY.
THIS WILL KEEP OF THREAT OF SHOWERS AND THUNDERSTORMS OVER THE
AREA...ALTHOUGH ORGANIZED STRONG OR SEVERE CONVECTION DOES NOT LOOK
LIKELY.  BY FRIDAY MODELS MOVE THE UPPER TROF EAST AS RIDGING BUILDS
OVER THE PLAINS AND A SURFACE HIGH MOVES INTO THE WESTERN GREAT
LAKES.  WITH THIS SYNOPTIC PATTERN COOL NORTHEAST WINDS OFF THE
LAKES COULD GET THE MEMORIAL DAY WEEKEND OFF TO A COOL...DRY START.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1129 PM CDT FRI MAY 17 2013

SOUTHEASTERLY WINDS AROUND 5 TO 10 KTS WILL CONTINUE THROUGH
LATE SATURDAY EVENING...AS A WARM FRONT LIFTS INTO WISCONSIN. CONDITIONS
WILL BE VFR WITH CIGS ABOVE 12KFT PRIMARY. LATER TONIGHT...AFTER
08Z...SOME MVFR FOG IS EXPECTED.  AFTER 13Z SATURDAY...A RETURN
TO VFR WEATHER WITH PARTLY CLOUDY SKIES AND LIGHT SOUTHEAST WINDS.
THIS VFR WEATHER SHOULD PERSIST THROUGH THE REMAINDER OF THE
PERIOD. THERE WILL BE A THREAT FOR A SHOWER AFTER 06Z SUNDAY IN IOWA.
ERVIN

&&

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

$$

SYNOPSIS...DMD
SHORT TERM...DMD
LONG TERM...DLF
AVIATION...ERVIN