Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 181628
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1128 AM CDT SAT APR 18 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.UPDATE...
ISSUED AT 407 AM CDT SAT APR 18 2015

AFTER FURTHER COORDINATION WITH ARX AND THE DNR...WILL ISSUE A RED
FLAG WARNING FOR WOOD COUNTY. THE COMBO OF HUMIDITIES FALLING NEAR
20 PCT THIS AFTERNOON...MAX TEMPS IN THE 60S...WIND SPEEDS OF 10
TO 20 MPH...AND DRY FUELS WILL LEAD TO A CRITICAL FIRE WEATHER DAY
THERE. THIS RED FLAG WARNING WILL TARGET THE PINE COUNTRY OF
CENTRAL WISCONSIN.

ADDITIONALLY...THE COLD FRONT HAS JUST PASSED OVER GREEN BAY.
WINDS HAVE SHIFTED TO THE NORTH AND ARE GUSTING TO 22 KNOTS AT THE
GRB AIRPORT. SOME GUSTS UP TO 25 KNOTS OVER THE BAY ARE ALSO OCCURRING.
&&

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 330 AM CDT SAT APR 18 2015

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A FAIRLY
POTENT COLD FRONT DROPPING SOUTH OVER FAR N-C WISCONSIN AND THE
CENTRAL UPPER PENINSULA.  NORTH WINDS BEHIND THE FRONT COMBINED WITH
IMPRESSIVE PRESSURE RISES ARE CONTRIBUTING TO WIND GUSTS OVER 30 KTS
OVER LAKE SUPERIOR.  AS THE FRONT MOVES ACROSS NORTHERN WISCONSIN
EARLY THIS MORNING...EXPECT NORTH WINDS TO STRENGTHEN AND BECOME
GUSTY FOR PERIOD.  ELSEWHERE...UPPER LEVEL LOW PRESSURE CONTINUES TO
SPIN OVER THE CENTRAL ROCKIES AND PRODUCE SHOWERS AND THUNDERSTORMS
ACROSS THE CENTRAL GREAT PLAINS.  FORECAST CONCERNS INCLUDE FIRE
WEATHER PARAMETERS TODAY...AND PRECIP CHANCES ON SUNDAY.

TODAY...THE DRY COLD FRONT WILL DROP SOUTH ACROSS THE REST OF
NORTHERN WISCONSIN EARLY THIS MORNING AND CENTRAL WISCONSIN BY
MID-MORNING.  BEHIND THE FRONT...THE MODELS ARE STILL DEPICTING VERY
DRY AIR TO MOVE INTO NORTH-CENTRAL TO EAST-CENTRAL WISCONSIN TODAY.
THOUGH NORTHEAST WINDS OFF LAKE MICHIGAN WILL HELP MODERATE THE DRY
AIR OVER EASTERN WISCONSIN...MODEST WIND SPEEDS SHOULD BE ABLE TO TAP INTO
THIS VERY DRY AIR JUST ABOVE THE INVERSION...AROUND 900MB.  SO WAS
AGGRESSIVE IN DROPPING HUMIDITIES TODAY...WHICH SHOULD FALL INTO THE
TEENS OVER N-C WISCONSIN AND TO AROUND 25 PCT OVER CENTRAL
WISCONSIN.  EAST WINDS WILL ALSO BE APPROACHING CRITICALLY SUSTAINED
SPEEDS OVER CENTRAL WISCONSIN THIS AFTERNOON.  STILL WAITING FOR A
FINAL DECISION FROM THE DNR CONCERNING A RED FLAG WARNING...WHICH SHOULD
HAVE BY 5 AM.  OTHERWISE...WILL SEE A SUNNY AND COOLER DAY.  HIGHS
IN THE LOW TO MID 60S AWAY FROM LAKE MICHIGAN.

TONIGHT...CLOUDS WILL BE ON THE INCREASE AS THE CENTRAL ROCKIES
UPPER LOW MOVES ACROSS THE CENTRAL PLAINS...WHILE A NORTHERN STREAM
WAVE DIGS OVER THE NORTHERN PLAINS.  AS CLOUDS THICKEN AND
LOWER...WINDS BELOW 900MB WILL REMAIN OUT OF THE SOUTHEAST AND
CONTINUE TO ADVECT VERY DRY AIR OVER THE REGION. THIS DRY AIR WILL
HAVE TO BE OVERCOME...AND THIS MAY NOT OCCUR UNTIL LATE IN THE NIGHT
OVER THE WEST.  WILL MODIFY PRECIP CHANCES SLIGHTLY TO REFLECT THIS.
LOWS RANGING FROM THE MID 30S NORTH TO THE MID 40S SOUTHWEST.

SUNDAY...MID-LEVEL HEIGHT FALLS WILL CONTINUE TO ADVANCE INTO THE
WESTERN GREAT LAKES.  ONE AREA OF LOW PRESSURE WILL MOVE INTO
WESTERN WISCONSIN DURING THE AFTERNOON...WHILE A SOUTHERN STREAM LOW
SWINGS NE TOWARDS THE SOUTHERN TIP OF LAKE MICHIGAN.  FORCING WILL
IMPROVE THROUGH THE DAY AHEAD OF THESE FEATURES...THOUGH THE LEAD BAND OF
LIGHT RAIN MAY DECAY DURING THE MORNING AS A RESULT OF THE DRY LOW
LEVEL FLOW.  THEN A SECOND ROUND OF PRECIP MAY TRY TO MOVE INTO THE
AREA WITH THE APPROACHING LOW PRESSURE SYSTEMS.  TEMPS ARE DIFFICULT
BECAUSE OF THE PRECIP POTENTIAL...AMPLE CLOUD COVER...AND EAST
WINDS.  HAVE DROPPED TEMPS SOME SINCE TEMPS DO NOT TYPICALLY RISE
WELL WHEN THERE IS CLOUD COVER AND EAST WINDS.  PRECIP WILL ALSO
LIKELY HOLD TEMPS BACK OVER CENTRAL AND NORTH-CENTRAL WISCONSIN.  SO
WENT WITH HIGHS RANGING FROM THE MID 50S NORTH TO LOW 60S SOUTH.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 330 AM CDT SAT APR 18 2015

500MB TROUGH WILL EVOLVE INTO A CLOSED UPPER LOW OVER THE WESTERN
GREAT LAKES REGION EARLY NEXT WEEK...THEN MEANDER ACROSS EASTERN
CANADA AND THE GREAT LAKES REGION THROUGH THE END OF NEXT WEEK.
THIS WILL LEAD TO COOL AND UNSETTLED CONDITIONS...ALONG WITH A
CHANCE OF SNOW LATE AT NIGHT AND EARLY MORNING HOURS.

RAINFALL TOTALS STILL PROBLEMATIC SUNDAY NIGHT AS TWO SEPARATE
SYSTEMS WILL BRING RAIN TO THE AREA. NORTHERN STREAM SYSTEM WILL
BRING RAIN TO THE WESTERN HALF OF THE STATE...MEANWHILE A FAIRLY
POTENT LOW PRESSURE SYSTEM WILL MOVE NORTHEAST INTO THE GREAT
LAKES REGION SUNDAY NIGHT. STILL A LOT OF QUESTIONS ON TRACK OF
SYSTEM DUE TO CLOSING UPPER LOW NORTHWEST OF THE STATE. MODEL QPF
WOULD SUGGEST THAT MUCH NEEDED RAIN WOULD FALL ACROSS THE REGION.
MAIN QUESTION IS WHERE AXIS OF HEAVIER RAIN WOULD FALL. MODEL
RUN TO RUN CONTINUITY HAS NOT BEEN CONSISTENT...THUS LOW CONFIDENCE
IN THE RAINFALL AMOUNT FORECAST. MONDAY IS NOT MUCH CLEARER AS SOME
OF THE MODELS BRING DRY SLOT ACROSS THE AREA WITH A SIGNIFICANT DOWNWARD
TREND IN RAINFALL AMOUNTS. THE ECMWF/CANADIAN DO NOT SHARE THIS TREND
WITH THE WRF/GFS...THUS WILL KEEP SCATTERED DEPICTION/WORDING IN
THE FORECAST.

AS UPPER LOW CLOSES MONDAY NIGHT THROUGH WEDNESDAY...COOL CYCLONIC FLOW
AND WEAK DISTURBANCES MOVING THROUGH THE MEAN FLOW WILL BRING
CHANCES OF RAIN AND SNOW SHOWERS DEPENDING ON LOCATION AND TIMING
OF THE DAY. AT SOME POINT...THERE COULD BE A MINOR ACCUMULATION OF
SNOW ACROSS THE NORTH. SOME MODERATION IN TEMPERATURES IS EXPECTED BY
THE END OF THE WEEK AS THE UPPER LOW GRADUALLY SHIFTS EAST OF THE AREA.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1102 AM CDT SAT APR 18 2015

VFR CONDITIONS EXPECTED THROUGH THIS AFTERNOON. GUSTY ENE WINDS TO
CONTINUE BEFORE DIMINISHING THIS EVENING...WITH THE GUSTIEST WINDS
IN EASTERN TAF SITES.

DRY CONDITIONS WILL HOLD THROUGH THE NIGHT...WITH INCREASING VFR
CLOUD COVER FROM SW TO NE THROUGH THE NIGHT. LLWS THROUGH ABOUT
1500FT WILL DEVELOP AFTER MIDNIGHT...AND THEN DIMINISH SUNDAY
MORNING AS WINDS MIX AGAIN.

VFR CIGS WILL STICK AROUND SUNDAY...WITH RAIN SHOWERS POSSIBLE IN
NORTH-CENTRAL WISCONSIN AFTER DAYBREAK AS A LOW PRESSURE SYSTEM
LIFTS TO THE NORTH AND WEST OF THE STATE...WITH ONLY VERY LIGHT
RAIN AND PCPN EXPECTED. EASTERN TAF SITES SHOULD STAY DRY UNTIL AT
LEAST MIDDAY IF NOT MOST OF SUNDAY.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR WIZ035.
&&

$$

UPDATE.........MPC
SHORT TERM.....MPC
LONG TERM......ECKBERG
AVIATION.......ALLEN





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