Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 232033
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
333 PM CDT WED APR 23 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 332 PM CDT WED APR 23 2014

CONFIDENCE LEVEL IN THE FORECAST BEYOND ABOUT 06Z TONIGHT IS
RATHER LOW. THE 12Z GRB SOUNDING WAS DRY BELOW 250MB AND MPX WAS
DRY BELOW 750MB...SO THE APPROACHING AREA OF SHOWERS WAS HAVING A
TOUGH TIME MAKING MUCH EASTWARD PROGRESS. HAVE THE SHOWERS MOVING
INTO CENTRAL WISCONSIN 00Z-06Z INTO ALL BUT THE FAR NORTHEAST PART
OF THE STATE 06Z-12Z. PRECIPITATION TYPE IN THE NORTHERN PART OF
THE FORECAST AREA IS QUESTIONABLE WITH SURFACE TEMPERATURES
FORECAST TO REMAIN ABOVE FREEZING DURING THE NIGHT. WPC GUIDANCE
WAS SHOWING AN AREA OF AT LEAST 2 INCHES OF ACCUMULATION ALONG THE
UPPER MICHIGAN BORDER BUT HAVE GONE WITH RAIN AND SNOW WORDING IN
THE NORTH WITH UP TO AN INCH OF NEW SNOW THERE THROUGH THURSDAY
MORNING. MOS 3-HOURLY TEMPERATURES WELL ABOVE FREEZING SHOULD KEEP
PRECIPITATION MOSTLY IN LIQUID FORM. OTHERWISE...HAVE A SLIGHT
CHANCE FOR THUNDER GOING ON THURSDAY...THOUGH COULD NOT FIND ANY
CAPE OR STEEP MID LEVEL LAPSE RATES AND SPC DAY 2 DOES NOT INCLUDE
ANY OF WISCONSIN. CANNOT REALLY RULE OUT THUNDER WITH 40 TO 50
KNOT 850MB JET AND ADJACENT GRIDS HAVE IT MENTIONED TO THE
WEST...SOUTH AND EAST.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 332 PM CDT WED APR 23 2014

FLOW TO BECOME STRONGLY AMPLIFIED THIS WEEKEND AS A STRONG UPPER
TROF DIGS TOWARD THE CENTRAL ROCKIES AND UPPER RIDGING OCCURS
DOWNSTREAM OVER CENTRAL NORTH AMERICA. THIS UPPER TROF IS EXPECTED TO
CLOSE OFF INTO AN UPPER LOW OVER THE CENTRAL PLAINS AND SLOWLY DRIFT
EAST TOWARD THE MID-MS VALLEY EARLY NEXT WEEK. ISSUES CONTINUE
BETWEEN MODEL RUNS WITH HOW FAR NORTH LOW WILL TRACK. AT THIS TIME
SOME CONSENSUS SEEN IN A FURTHER SOUTH TRACK THROUGH FIRST HALF OF
THE WEEK...WITH DRY SURFACE HIGH TO THE NORTH KEEPING CONDITIONS
DRY AT LEAST THROUGH WEEKEND. HAVE TRENDED TOWARDS GFS ENSEMBLE
MEAN FOR LATER PERIODS. THOUGH CONFIDENCE LOW AS MODEL SPREAD
QUITE SIGNIFICANT OVER WI BY WED.

IN THE NEAR TERM...THE NEGATIVELY-TILTED TROF TO CONTINUE TO LIFT
NORTHEAST THROUGH STATE AT BEGINNING OF THIS PERIOD...WITH COLD
FRONT MOVING THROUGH STATE THURSDAY NIGHT. GOOD UPPER DYNAMICS
WITH COUPLED JET FEATURE TO LEAD TO SIG PCPN INTO THE EVENING
HOURS. MODEL SOUNDINGS SUGGEST RAIN THROUGH MIDNIGHT...THEN A
SWITCH TO SOME SNOW NORTH HALF AFTER MIDNIGHT. BY TIME TEMP
PROFILES FAVORABLE FOR SNOW...MUCH OF MOISTURE NORTH OF CWA...ONLY
CARRYING AND INCH OR TWO ATTM.

THE UPPER TROF/LOW IS FCST TO SLOWLY DRIFT ACROSS THE NORTHERN
GREAT LAKES ON FRI KEEPING CYCLONIC FLOW ACROSS WI. MODELS SHOWING
SIG COLD AIR ALOFT AND INSTABILITY FOR MUCH OF FRI FOR THOUGHTS OF
SCATTERED SHOWERS FOR MUCH OF THE DAY.

TEMPERATURES FOR THIS PERIOD TO CONTINUE THEIR BELOW NORMAL TREND.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 113 PM CDT WED APR 23 2014

HIGH CLOUDS COVERED THE AREA AT MIDDAY AND MID LEVEL
CLOUDS CONTINUED TO PUSH IN FROM THE WEST. EXPECT VFR CONDITIONS
TO PREVAIL THROUGH AT LEAST 06Z. THE 12Z NAM AND 00Z EC PRETTY
MUCH KEPT THE FORECAST AREA DRY TODAY AND STILL HAD THE FAR
NORTHEAST CORNER OF THE STATE DRY AT 12Z THURSDAY. BUFKIT TIME
SECTIONS FROM MODELS THAT BROUGHT PRECIPITATION IN SOONER SHOWED
QUITE A BIT OF LOW LEVEL DRY AIR WHEN THEY HAD PRECIPITATION FORECAST SO
NOT CONVINCED THERE WILL BE MUCH HAPPENING DURING THE EVENING.
KEPT VFR CONDITIONS THROUGH AT LEAST 07Z WITH SOME TEMPO MVFR CIGS
WITH LIGHT PRECIPITATION...THEN MVFR PREVAILING AROUND 12Z. THE GRB
SOUNDING FROM THIS MORNING WAS DRY FROM ABOUT 250MB TO THE
SURFACE AND MPX WAS DRY BELOW ABOUT 750MB. THUS...HAVE GONE WITH
THE SLOWER ONSET OF PRECIPITATION ACROSS THE AREA FROM SOUTHWEST TO
NORTHEAST. LOW CONFIDENCE IN PRECIPITATION TYPE FORECAST ACROSS THE NORTH
LATE TONIGHT INTO THURSDAY DUE TO MODEL DIFFERENCES. HAVE USED
RAIN AND SNOW FOR RHI TAF BUT KEPT RAIN AT THE OTHER TAF SITES.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MG
LONG TERM......TE
AVIATION.......MG






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