Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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666
FXUS63 KDVN 170454
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1154 PM CDT SAT MAY 16 2015

.UPDATE...
ISSUED AT 952 PM CDT SAT MAY 16 2015

IMPRESSIVE BROKEN LINE OF STRONG THUNDERSTORMS REACHED FROM
CENTRAL MN THROUGH WESTERN IA...S-SW ACROSS THE CENTRAL PLAINS
INTO W TX THIS EVENING. OVER THE LOCAL AREA...THE LARGELY PULSE
TYPE STORMS DISSIPATED BEFORE SUNSET. MORE STABLE AIR OVER THE
LOCAL AREA...LACK OF DEEP SHEAR...AND UPPER LEVEL SUPPORT AIMING
MORE AT NW MO INTO WESTERN IA THROUGH MUCH OF TONIGHT SHOULD KEEP
THESE STORMS WELL TO THE WEST. INDIVIDUAL STORMS IN THE LINE IN
WESTERN IA WERE MOVING N-NE...WHILE THE NW MO CLUSTER WAS TRENDING
A BIT MORE NORTHEASTWARD AND MAY BE THE FIRST TO REACH INTO OUR
FAR SW ZONES LATE TONIGHT...LIKELY IN A DISSIPATING MODE AS IT
MOVES AWAY FROM BETTER FORCING.

HAVE UPDATED THE FORECAST TO REMOVE POPS THROUGH THE REST OF THIS
EVENING...THEN KEPT THE TREND OF LOW END POPS INCREASING TOWARD
SUNRISE ACROSS THE WEST AS THE UPPER DIVERGENCE...MID LEVEL
SHORTWAVE AND DEEPER SHEAR BEGIN TO ADVANCE TOWARD THE REGION
ALLOWING WHAT SHOULD BE A DISSIPATING STORM COMPLEX TO ADVANCE
EASTWARD. OTHERWISE...STILL LOOKS TO BE A RATHER HUMID NIGHT WITH
DEWPOINTS IN THE MID 60S HOLDING MINS IN THE MID TO UPPER 60S.
WITH THE WARM FRONT NOW NORTH OF THE AREA...A MORE UNIFORM
SOUTHEAST WIND FIELD AROUND 10 TO 15 MPH...ALONG WITH ADVANCING
HIGH CLOUDS FROM THE PLAINS CONVECTION SHOULD RESULT IN LITTLE
RADIATIONAL COOLING...AND PROVIDE ENOUGH MIXING TO LIMIT ANY FOG
OR STRATUS FORMATION.

&&

.SYNOPSIS...
ISSUED AT 339 PM CDT SAT MAY 16 2015

SCATTERED SHOWERS AND A FEW WEAK STORMS FOUND ACROSS CWA THIS
AFTERNOON IN WARM...MOIST UNCAPPED ATMOSPHERE AND AHEAD OF
WEAK DISTURBANCE LIFTING NORTHWARD ACROSS MISSOURI. EFFECTIVE
BULK SHEAR QUITE MINIMAL LESS THAN 25 KTS SUPPORTING OF THE
LESS ORGANIZED PULSE TYPE CONVECTION. MORE ORGANIZED STORMS
AND ATTENDANT SEVERE WEATHER RISK BEING FOUND IN THE PLAINS
AHEAD OF LARGE UPPER TROUGH OVER THE ROCKIES.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 339 PM CDT SAT MAY 16 2015

UPPER LEVEL TROUGH OVER THE ROCKIES IS FORECAST TO LIFT INTO THE
UPPER MIDWEST BY SUNDAY EVENING TAKING ON AN INCREASINGLY
NEGATIVE TILT. THIS WILL SEND A MODIFIED DRY LINE AND COLD FRONT
THROUGH CWA SUNDAY AFTERNOON AND NIGHT ACCOMPANIED BY CHANCE OF
STORMS AND POTENTIAL FOR A FEW SEVERE STORMS.

THIS EVENING... EXPECT SCATTERED SHOWERS AND A FEW STORMS TO DIMINISH
WITH SUNSET AND LOSS OF HEATING. STORMS ORGANIZING INTO SEVERAL
CLUSTERS IN THE PLAINS TO SHIFT E/NE BUT WILL BE DECAYING/WEAKENING
WITH TIME AS THEY MOVE AWAY FROM BETTER FORCING... BUT MAY SEE
SOME REMNANTS MOVE INTO CWA ESPECIALLY WEST OF THE MISSISSIPPI
OVERNIGHT/EARLY SUNDAY MORNING. LOWS TONIGHT MUGGY AND MAINLY IN
THE LOWER TO MIDDLE 60S.

CONDITIONAL SEVERE WEATHER RISK ON TAP FOR SUNDAY AFTERNOON INTO
EVENING AHEAD OF OCCLUDING/FILLING LOW. DEEP SURFACE LOW WILL
BE MOVING OVER NORTHWEST MN SUNDAY AFTERNOON WITH OCCLUDING FRONT
APPROACHING EASTERN IA. STRONG DEEP LAYER SHEAR WITH 0-6KM OF
40-45+ KTS AIDED BY CYCLONICALLY CURVED JET FROM MID MISSISSIPPI
VALLEY INTO GREAT LAKES. TEMPS IN THE 80S AND DEWPTS IN THE
MID/UPPER 60S SHOULD YIELD MODERATE INSTABILITY WITH MLCAPES OF
1000-2000 J/KG. BOTH INGREDIENTS MORE THAN AMPLE FOR SEVERE
WEATHER... BUT THE WILD CARD WILL BE HOW MUCH IF ANY REDEVELOPMENT
OCCURS SUNDAY AFTERNOON WITH OCCLUDING SYSTEM AND LESS FORCING
WITH WASHING OUT OF LOW LEVEL CONVERGENCE. SEVERAL HI-RES
CONVECTIVE ALLOWING MODELS SHOW LIMITED DEVELOPMENT OVER CWA WITH
INCREASING COVERAGE TO OUR EAST WHERE BETTER LOW LEVEL CONVERGENCE
PROGGED. ANY STORMS THAT DO DEVELOP WILL HAVE POTENTIAL TO
BECOME SEVERE GIVEN STRONG SHEAR WITH MAIN RISK DAMAGING WINDS
AND HAIL. HIGHS SUNDAY MAINLY AROUND 80 TO MID 80S WITH GUSTY
SOUTHERLY WINDS 15 TO 30 MPH.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 339 PM CDT SAT MAY 16 2015

MAIN FORECAST CONCERN FOR THE LONG TERM FORECAST ARE THREE PERIOD OF
PRECIPITATION.  THE FIRST WILL BE ONGOING AT THE BEGINNING OF THE
PERIOD...THE SECOND DURING THE MIDWEEK AND THE LAST AT THE END OF
THE PERIOD.  WITH COOLER AIR SURGING INTO THE AREA...IT APPEARS THE
ONLY DECENT CHANCE OF THUNDER WILL BE SUNDAY NIGHT...THE REST OF THE
PRECIP APPEARS TO BE RAIN AT THIS TIME.

GUIDANCE HAS TRENDED TO A SLOWER FROPA THROUGH THE AREA.  THE
CHANCE FOR CONVECTION SUNDAY EVENING HAS INCREASED AS A RESULT OF
THIS.  DEEP LAYER SHEAR REMAINS IMPRESSIVE FROM 00Z TO
06Z...INSTABILITY WILL BE WANING BUT WILL RANGE FROM 800 J/KG TO
1500 J/KG FROM DVN TO THE EASTERN ZONES.  IF STORMS CAN DEVELOP
THERE IS NO DOUBT THAT THE ENVIRONMENT CAN SUPPORT AND MAINTAIN
STRONG TO SEVERE THUNDERSTORMS THROUGH THE FIRST 6 HOURS OF THE
EXTENDED FORECAST.  LIKE THE SHORT TERM FORECASTER...I HAVE CONCERNS
WITH FORCING AND WILL LEAVE SEVERE OUT OF THE GRIDS AT THIS TIME.

THE COLD FRONT WILL SLOWLY SAG THROUGH THE AREA ON MONDAY.  THIS
WILL LEAD TO HIGH TEMPERATURES CLOSE TO 80 IN THE FAR EAST...I
WOULD NOT  BE SURPRISED TO SEE TEMPS DROP BEHIND THE FRONT TO
COOLER THAN FORECAST HIGHS MONDAY AFTERNOON. TEMPS DURING THE
FIRST PART OF THE WEEK WILL BE LOWER THAN AVERAGE. ANOTHER SYSTEM
APPROACHES THE AREA FROM THE SOUTH AND WEST. AT THIS TIME CAPE
LOOKS TO BE NON EXISTENT...SO WENT WITH STRAIGHT SHOWERS.

ONCE THIS SYSTEM MOVES THROUGH THE AREA...TEMPERATURES WILL REBOUND.
HOWEVER WITH LOW DEWPOINTS IT APPEARS THAT MIDWEEK THROUGH THE END
OF THE WEEK WILL BE PLEASANT. MOISTURE DOES NOT APPEAR TO RETURN
UNTIL THE WEEKEND.  CAPE ALSO INCREASES AND SUGGESTS THAT ISOLATED
THUNDERSTORMS WILL BE POSSIBLE AT THE END OF THE PERIOD WITH THE
NEXT SYSTEM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1153 PM CDT SAT MAY 16 2015

THE DISSIPATING REMNANTS FROM A LINE OF STRONG THUNDERSTORMS
ADVANCING FROM THE PLAINS WILL LIKELY MOVE INTO THE EASTERN IOWA
TERMINALS AS LIGHT RAIN WITH MVFR CONDITIONS DUE TO STRATUS AND
FOG TOWARD MORNING. BEYOND...THE FORECAST REMAINS LOW CONFIDENCE
WITH RESPECT TO THE POTENTIAL FOR STRONG TO SEVERE STORMS AS AN
UPPER LEVEL TROUGH MOVES THROUGH LATER IN THE DAY. FOR NOW...THIS
POTENTIAL IS LIMITED TO HIGHER CONFIDENCE CHANCE FOR SHOWERS IN
THE LATE MORNING OR EARLY AFTERNOON. GUSTY SOUTH WINDS WILL
GRADUALLY VEER TO MORE SOUTHWEST TOWARD SUNDAY EVENING WITH
PREVAILING VFR CONDITIONS.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...05
SHORT TERM...05
LONG TERM...GIBBS
AVIATION...SHEETS



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