Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200031
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
731 PM CDT SUN APR 19 2015

.SYNOPSIS...
ISSUED AT 317 PM CDT SUN APR 19 2015

STRIP OF ONLY THIN CLOUD COVER AND SUNSHINE THAT HAS PERSISTED
SINCE THIS MORNING OVER EASTERN IA INTO NW IL...BETWEEN THE
DEFORMATION ZONE OF THE LOW LIFTING UP INTO SOUTHERN IL...AND THE
APPROACHING UPPER TROUGH...HAS ALLOWED TEMPERATURES TO WARM INTO
THE MID AND UPPER 70S. KDVN 88D SHOWED A BROAD SHIELD OF LIGHT TO
MODERATE RAIN ADVANCING NW OUT OF CENTRAL IL WITH DEVELOPING
SHOWERS IN THE INCREASINGLY UNSTABLE AIR MASS ALONG THE MS RIVER
SOUTH OF THE QUAD CITIES. A SEPARATE AREA OF DEVELOPING STRONGER
THUNDERSTORMS OVER S CENTRAL IA INTO NE MO...LIFTING SLOWLY
N-NE...WAS ASSOCIATED WITH A LOBE OF VORTICITY LIFTING NORTHEAST
ACROSS MO AHEAD OF THE BASED OF THE LONGWAVE UPPER TROUGH
EXTENDING FROM ND TO OK. AT 19Z...MSAS INDICATED THE PRIMARY
SURFACE LOW OVER SOUTHERN IL WITH A SECONDARY WEAKER LOW OVER FAR
SE IA AHEAD OF THE MO SHORTWAVE. A STRONG COLD FRONT WAS NOT FAR
TO THE WEST...EXTENDING FROM THE KMSP AREA THROUGH CENTRAL IA INTO
EASTERN OK. STRONG NW WINDS AND COLD AIR ADVECTION TRAILED THIS
FRONT...WITH AFTERNOON TEMPERATURES IN THE ONLY 40S AND 50S
ACROSS THE PLAINS FROM ND TO KS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 317 PM CDT SUN APR 19 2015

INITIAL CHALLENGE IS RAIN AND THUNDERSTORMS TONIGHT...THEN POTENTIAL
STRONG WINDS AND MUCH COOLER WEATHER TO FOLLOW MONDAY.

THE TWO FEATURES DESCRIBED IN THE SYNOPSIS WILL LIKELY CONVERGE
ALONG THE MS RIVER INTO E CENTRAL IA BY EARLY THIS EVENING TO
FINALLY BRING RAINFALL TO AREAS THAT HAVE BEEN LEFT OUT OF THIS
EVENT SO FAR. HAVE INCREASED THE POTENTIAL FOR THUNDERSTORMS IN
THE LATE AFTERNOON AND EARLY EVENING AS THE STORMS APPROACHING
FROM THE SW WERE FORMING ALONG AN AREA OF 1000 MUCAPE...WHICH
WILL LIKELY CONTINUE TO EXPAND NE WITH THE MID LEVEL
FEATURE...WARMING LOW LEVELS...AND RISING DEW POINTS. AN AXIS OF 4
PLUS MB PRESSURE FALLS FROM EASTERN IA INTO CENTRAL LAKE MI ALSO
SUPPORTS THIS EVOLUTION. AT THIS TIME...THE GREATEST THREAT FROM
THESE STORMS AS THEY MOVE INTO SE IA APPEARS TO BE HEAVY DOWNPOURS
DUE TO THE SLOW MOVEMENT AND POSSIBLY SMALL HAIL...INITIALLY LIMITED
BY HIGH FREEZING LEVELS AND A LACK OF SHEAR.

A SEPARATE AXIS OF SIMILAR MAGNITUDE PRESSURE FALLS OVER E CENTRAL
IL INTO INDIANA BACKS THE MODEL TRENDS SHOWING THE THE MAIN SURFACE
LOW ADVANCING NORTHEAST TOWARD SW LOWER MI TONIGHT AS THE UPPER
TROUGH OVER THE PLAINS MIGRATES EASTWARD. THIS WILL EVENTUALLY
EVOLVE THE PRECIPITATION INTO A MORE STRATIFORM LIGHT RAINFALL OVER
THE FORECAST AREA BY LATE EVENING...WHICH WILL ADVANCE EAST WITH THE
DEPARTING SURFACE LOW MONDAY MORNING. THIS PROCESS WILL DRIVE THE
COLD FRONT EASTWARD...CROSSING THE MS RIVER AROUND MIDNIGHT AND
EXITING TO THE EAST BY 3 AM...BRINGING STRONG W-NW WINDS AND
FALLING TEMPERATURES. LOW TEMPERATURES...OCCURRING AROUND 7 TO 8
AM WERE KEPT CLOSE TO THE PREVIOUS FORECAST FROM THE LOWER 40S
NORTHWEST TO THE UPPER 40S SOUTHEAST.

MONDAY...SCATTERED TO LIKELY POPS ARE CONTINUED IN THE EAST IN THE
MORNING...WITH THE MAIN STORY BEING STRONG WINDS AND COOLER
TEMPERATURES. DEEP MIXING IN THE TIGHT PRESSURE GRADIENT WILL RESULT
IN SUSTAINED WINDS FROM 20 TO 25 MPH WITH GUSTS FROM 30 TO 35
LIKELY...OR JUST BELOW ADVISORY CRITERIA. FORECAST SOUNDINGS
INDICATE MIXING TO TO NEAR 700 MB...WHICH WOULD EASILY SUPPORT
HIGHS IN THE UPPER 50S TO LOWER 60S. WILL CARRY A SLIGHT CHANCE
FOR SHOWERS OVER THE NORTH AND NW LATE...WHERE INCOMING MID LEVEL
MOISTURE SHOWN BY MAINLY THE WRF MAY LEAD TO SOME HIGH BASED
SHOWERS.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 317 PM CDT SUN APR 19 2015

AN UPPER LEVEL RIDGE WILL CONTINUE TO BUILD ALONG THE ROCKY
MOUNTAINS AS A SECOND RIDGE CONTINUES TO BUILD OVER THE NORTHERN
CANADIAN MARITIMES. IN BETWEEN THESE TWO RIDGES A CLOSED UPPER LOW
WILL REMAIN NEARLY STATIONARY OVER THE EASTERN GREAT LAKES/ONTARIO
UNTIL LATE IN THE WEEK. TUESDAY WILL CONTINUE TO BE WINDY WITH
NORTHWEST WINDS GUSTING TO 30+ MPH DUE TO A TIGHT PRESSURE
GRADIENT...STRONG COLD ADVECTION AND DEEP MIXING. ON TUESDAY THERE
IS ALSO A CHANCE OF SCATTERED SHOWERS ALONG AND NORTH OF THE HIGHWAY
20 CORRIDOR WITH STEEP MID LEVEL LAPSE RATES AND COLD 850 MILLIBAR
TEMPERATURES NEAR OR SLIGHTLY BELOW ZERO. DAYTIME HIGH TEMPERATURES
ALL WEEK WILL BE IN THE MID 50S NORTH TO AROUND 60 SOUTH WITH
OVERNIGHT LOWS IN THE LOW 30S NORTH TO AROUND 40 SOUTH. THERE IS THE
POTENTIAL FOR FROST AND POSSIBLY FREEZING TEMPERATURES ON THURSDAY
OR FRIDAY MORNINGS AS THE CENTER OF HIGH PRESSURE SETTLES OVER THE
UPPER MIDWEST. 850 MILLIBAR TEMPERATURES AT THIS TIME WILL WILL BE
AROUND -5 DEGREES CENTIGRADE. WIDE SPREAD 20S ARE POSSIBLE IF THERE
IS ANY EXTENDED PERIOD OF CLEAR SKIES AND LIGHT WINDS. LONG RANGE
MODELS SHOW PRECIPITATION CHANCES RETURN NEXT WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 656 PM CDT SUN APR 19 2015

COMPLEX STORM SYSTEM PROGRESSING ACROSS THE MIDWEST IS PRODUCING
WIDESPREAD RAIN AND ISOLATED THUNDERSTORMS THIS EVENING WITH IFR-
MVFR CIGS AND VSBYS. THE SYSTEM SHOULD EXIT THE REGION TOMORROW
MORNING...BUT BEFORE IT DOES SO...AN ASSOCIATED COLD FRONT WILL
PUSH THROUGH THE AREA THIS EVENING SHIFTING WINDS TO NORTHWEST.
GUSTS THROUGH TOMORROW WILL REACH AND POSSIBLY EXCEED 25-30 KTS.
WHILE VFR CONDITIONS ARE ON TAP TOMORROW...SCATTERED AFTERNOON
INSTABILITY SHOWERS COULD DEVELOP CAUSING LOCALIZED MVFR VSBYS.

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...KUHL
AVIATION...WOLF





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