Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 220448 AAB
AFDDVN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1148 PM CDT TUE APR 21 2015

.SYNOPSIS...
ISSUED AT 319 PM CDT TUE APR 21 2015

ANOTHER WINDY AND COOL AFTERNOON ACROSS THE REGION COURTESY OF THE
TIGHT PRESSURE GRADIENT AROUND A SLOW MOVING...NEARLY STACKED...LOW
PRESSURE SYSTEM OVER SOUTHEAST ONTARIO. WEST WINDS WERE SUSTAINED
FROM 30 TO 35 MPH WITH OCCASIONAL GUSTS OVER 50 MPH THIS AFTERNOON
ALONG AND NORTH OF I-80 WITH SLIGHTLY LOWER SPEEDS OF 20 TO 30 MPH
WITH GUSTS INTO THE 30S OVER SE IA...NE MO AND W CENTRAL IL. COLD
AIR ALOFT HAS RESULTED IN SCATTERED TO BROKEN STRATO CU...WHICH HAS
BEEN THICKEST ACROSS THE NORTH. TEMPERATURES HAVE REACHED ONLY THE
UPPER 40S NORTH...WHILE 50S COVERED EASTERN IA INTO W CENTRAL
IL...WITH A FEW LOWER 60S IN THE FAR SOUTH. AREA RADARS SHOWED
ELEVATED RETURNS DEVELOPING IN WESTERN IA AND NE NEB AHEAD OF A WEAK
MID LEVEL IMPULSE EMBEDDED IN THE TIGHT CYCLONIC FLOW ALOFT.

&&

.UPDATE...
ISSUED AT 619 PM CDT TUE APR 21 2015

WINDS ARE STARTING TO DIE DOWN HERE. PLAN ON EXPIRING THE WIND
ADVISORY AT THE TOP OF THE HOUR. OTHERWISE...NO SIG CHANGES TO THE
FORECAST...JUST HAD TO ADJUST THE TRENDS ON THE TEMPS AND
DEWPOINTS. AS THE PREVIOUS SHIFT INDICATED...DO NOT THINK THAT
THERE WILL BE A THREAT OF FROST TONIGHT WITH THE WINDS STAYING UP.
COULD SEE A FREEZE THOUGH NORTH OF HIGHWAY 30.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 319 PM CDT TUE APR 21 2015

MUCH LIKE LAST NIGHT...STRONG WINDS WILL UNDERGO A DIURNAL WEAKENING
TREND AND THERE WILL BE A POTENTIAL FOR SCATTERED SHOWERS OVER
ESPECIALLY THE SOUTH EARLY. WEDNESDAY...WINDY AND COOL CONDITIONS
WILL RESUME...BUT WINDS SHOULD BE CONSIDERABLY LIGHTER THAN TODAY AS
THE LOW TO THE NORTHEAST BEGINS TO WEAKEN AND SHIFT EASTWARD.

ON-GOING STRONG WINDS WILL GRADUALLY DIMINISH AND WILL KEEP THE
CURRENT WIND ADVISORY IN PLACE OVER THE NE HALF OF THE FORECAST
AREA. WINDS SHOULD DROP BELOW ADVISORY CRITERIA BY THE 00Z
EXPIRATION TIME.

TONIGHT...WILL KEEP SLIGHT TO LOW END CHANCE
POPS GOING OVER THE SOUTH AS MID LEVEL FORCING INCREASES AHEAD OF
THE ADVANCING MID LEVEL IMPULSE AND INTERACTS WITH THE DAYTIME
HEATING/MID STEEP MID LEVEL LAPSE. THESE HAVE THE POTENTIAL FOR
QUICK BURSTS OF A FEW HUNDREDTHS OF AN INCH RAINFALL BEFORE
DISSIPATING AND MOVING OUT BY MID EVENING. OVERNIGHT...DRY AIR AND
MIXING IN WEST TO TO NW WINDS THAT SHOULD REMAIN SUSTAINED FORM 10
TO 15 MPH WILL LIKELY PREVENT ANY SIGNIFICANT FROST...DESPITE
TEMPERATURES DROPPING INTO THE LOWER TO MID 30S. A LIGHT FREEZE IS
LIKELY ALONG THE NORTH OF THE HIGHWAY 30 CORRIDOR.

WEDNESDAY...NORTHWEST WINDS WILL PICKUP INCREASE TO AGAIN TO AT
LEAST 15 TO 25 MPH WITH GUSTS INTO THE 30S BY LATE MORNING AND
AFTERNOON IN DEEP MIXING. MIXING TO NEARLY 700 MB IN THE EVEN
COLDER AIRMASS ALOFT WILL BE NEEDED TO WARM TEMPERATURES INTO THE
50S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 319 PM CDT TUE APR 21 2015

TEMPERATURES
AND POSSIBLE FROST WILL LEAD OFF THE EXTENDED WEDNESDAY NIGHT
FOLLOWED BY A SLOW MODERATING TREND...INTO A WETTER REGIME FOR LATE
WEEK/WEEKEND.

WINDS WILL SUBSIDE UNDER 15 MPH WEDNESDAY NIGHT...BUT WITH COLD
ALOFT AND THE HIGH PRESSURE RIDGE REMAINING JUST WEST OF THE
CWA...WE SHOULD NOT TOTALLY DECOUPLE THROUGH THE NIGHT. IN ANY
CASE...LOWS IN THE UPPER 20S NORTHEAST TO MID 30S SOUTHWEST LOOK ON
TARGET...AND WITH LIGHTER WINDS THAN THE PAST 2 NIGHTS...SOME PATCHY
FROST DOES APPEAR LIKELY. AN ADVISORY IS CERTAINLY POSSIBLE...BUT
GIVEN OUR CURRENT ADVISORY FOR WIND...WE WILL NOT ISSUE ONE AT THIS
TIME.

MODELS IN THE EXTENDED REMAIN FOCUSED ON A SLOWLY PROGRESSING DEEP
TROF...OVER THE MIDWEST FROM FRIDAY THROUGH SUNDAY. WHILE THERE HAD
BEEN SIGNIFICANT DISCREPANCY OF THE NORTHWARD EXTENT ON THE 00Z
MODEL SUITE...THE 12Z SUITE IS NOW IN MUCH BETTER AGREEMENT IN
BRINING RAIN AND RAIN SHOWERS OVER AT LEAST THE SOUTHERN 2/3RDS OF
IOWA AND ILLINOIS FRIDAY PM THROUGH SATURDAY NIGHT. WHETHER THIS
SYSTEM LINGERS THROUGH SUNDAY IS STILL A POSSIBILITY...BUT MOST
SOLUTIONS SHOW THE WAVE DROPPING EAST AND SOUTHEAST BY THAT TIME.
THE ECMWF REMAINS THE MOST BULLISH...WITH AROUND 0.5 TO 1.0 INCH
OF RAIN FORECAST. THE GFS DOES SHOW CONVECTION...AND THAT DOES
SEEM UNLIKELY GIVEN A LARGE COOL AIRMASS OVER THE MIDWEST AND
GREAT LAKES. A STRATIFORM RAIN IS MOST LIKELY. THIS STRATIFORM
SCENARIO DOES SUPPORT HIGHER POPS...AND WILL INTRODUCE LIKELY POPS
NOW FOR FRIDAY NIGHT. SHOULD THE ECWMF BE CORRECT...SATURDAY ALSO
WOULD NEED WIDESPREAD POPS.

WITH THE RAIN POTENTIAL GROWING FOR FRIDAY AND
SATURDAY...TEMPERATURES WILL BE HELD TO THE LOWER TO MID 50S FOR
HIGHS. SHOULD WE GET INTO A CONSISTENT ALL DAY RAIN...40S ARE NOT
OUT OF THE QUESTION WITH COOL EAST WINDS.   AFTER THIS SYSTEM
EXITS...MILDER AIR APPEARS LIKELY FOR SUNDAY THROUGH TUESDAY...WITH
A LOW CHANCE FOR RAIN EARLY NEXT WEEK. THIS IS DUE TO A MODEL
BLEND...INCLUDING 00Z ECMWF/12Z GFS WHICH SHOW ANOTHER WAVE TOWARDS
MONDAY.

ERVIN

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1143 PM CDT TUE APR 21 2015

VFR CONDITIONS WILL DOMINATE THE TAF PERIOD. WINDS WILL BECOME A
PROBLEM ONCE AGAIN WEDNESDAY. AT THIS TIME THE WINDS WILL BE LOWER
THAN TUESDAY...HOWEVER COULD STILL SEE SOME GUSTS AT OR JUST BELOW
30 KTS. PRESSURE GRADIENT RESPONSIBLE FOR THE WINDS WILL WEAKEN
WEDNESDAY AND LEAD TO LOWER WIND SPEEDS AFTER 00Z THURSDAY.

&&

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

$$

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



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