Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 272027
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
227 PM CST FRI FEB 27 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 226 PM CST FRI FEB 27 2015

LARGE COLD DRY SURFACE HIGH PRESSURE SYSTEM DRIFTING OVER THE
GREAT LAKES AND MID MISSISSIPPI REGION AND EVENTUALLY THE OHIO
VALLEY REGION WILL DOMINATE THE WEATHER THROUGH SATURDAY.

A FEW WIND GUSTS APPROACHING 20 MPH SHOWED UP THIS AFTERNOON AS
SURFACE TEMPERATURES APPROACHED THE STEEP LOW LEVEL DRY ADIABATIC
LAPSE RATE. WINDS WILL CALM DOWN AND DECOUPLE AGAIN TONIGHT TO
PRODUCE SIMILAR OVERNIGHT LOWS. WILL USE A HEALTHY BLEND OF
PERSISTENCE FOR TONIGHTS LOWS WITH PARTS OF NORTH CENTRAL
WISCONSIN LIKELY FALLING WELL INTO THE 20 TO 30 BELOW ZERO RANGE.

MAX TEMPERATURES FOR SATURDAY MAY RISE A FEW DEGREES ABOVE
TODAY/S HIGHS BUT WILL BE DEALING WITH A COLD START AGAIN AND
INITIALLY THE AIR MASS WILL BE RECYCLING MORE COLD AIR AROUND THE
DEPARTING HIGH.

MID TO HIGH CLOUDS WILL BE ON THE INCREASE FROM WEST TO EAST LATER
SATURDAY.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 226 PM CST FRI FEB 27 2015

HIGHLY-AMPLIFIED FLOW CONSISTING PRIMARILY OF A STRONG ERN PACIFIC
UPR RDG AND A POSITIVE-TILTED UPR TROF STRETCHING FROM HUDSON BAY
TO THE SW CONUS TO PERSIST INTO THE MIDDLE OF NEXT WEEK. THE RDG
IS FCST TO WEAKEN LATE NEXT WEEK AND THIS WL ALLOW THE TROF TO
MOVE EAST ACROSS THE REST OF THE CONUS. THIS PATTERN CHANGE WL
BRING A FLATTER FLOW TO THE CONUS BY NEXT WEEKEND AND AT LEAST
BRING TEMPS CLOSER TO NORMAL. PCPN CHCS TO BE FOCUSED SUNDAY/
SUNDAY NGT WITH SHORTWAVE ENERGY EJECTED FROM THE SW CONUS UPR
TROF AND THEN MON NGT THRU TUE NGT WITH A BIGGER SYSTEM THAT WL
BRING ACCUMULATING SNOW TO THE REGION. TEMPS WL WARM-UP EARLY NEXT
WEEK...COOL DOWN MID-WEEK AND THEN START BACK UP TOWARD NEXT
WEEKEND.

THE FIRST PIECE OF SHORTWAVE ENERGY TO EJECT E-NE OUT OF THE SW
CONUS UPR TROF IS FCST TO REACH THE MID-MS VALLEY/OHIO RIVER
VALLEY SAT NGT. BROAD LOW-LEVEL WAA AND GULF MOISTURE WL LIFT NWD
FROM THE SRN PLAINS AND POOL ALONG A QUASI-STNRY BOUNDARY
STRETCHED FROM THE SRN ROCKIES E-NE TO THE OHIO RIVER. ALL THE
FOCUS APPEARS TO BE CONTAINED WELL TO OUR SOUTH AND THE MODELS DO
NOT BRING ANY MEASURABLE PCPN TO NE WI. HAVE CONTINUED TO DOWNPLAY
POPS SAT NGT AND FOCUS MORE ON TEMPS AS CLOUDS GRADUALLY THICKEN
OVRNGT. WE COULD EASILY SEE TEMPS BOTTOM OUT IN THE SINGLE DIGITS
ABOVE ZERO AROUND MIDNGT AND THEN HAVE READINGS EITHER HOLD STEADY
OR RISE A FEW DEGS TOWARD DAYBREAK.

THIS SHORTWAVE ENERGY WL CONT TO TRACK E-NE TOWARD THE ERN GREAT
LAKES/APPALACHIANS ON SUNDAY. MEANWHILE...A NRN STREAM SHORTWAVE
TROF IS EXPECTED TO MOVE E-SE INTO THE WRN GREAT LAKES...PRECEDED
BY A CDFNT. THERE MAY BE SOME INTERACTION BETWEEN ALL THESE
WEATHER FEATURES TO AT LEAST BRING A SMALL CHC OF LIGHT SNOW TO NE
WI DURING THE DAY. ANY SNOW ACCUMULATIONS WOULD BE VERY LIGHT WITH
AMOUNTS OF LESS THAN AN INCH EXPECTED. MAX TEMPS TO RANGE FROM THE
LWR TO MID 20S NORTH...MID TO UPR 20S SOUTH.

THE NRN STREAM SHORTWAVE TROF ZIPS ACROSS THE GREAT LAKES SUNDAY
EVENING AND WL SWING THE WINDS AROUND TO THE W-NW. WEAK CAA TO
PUSH INTO WI WITH 8H TEMPS FALLING TO AROUND -14C...SO WL HAVE TO
KEEP AN EYE ON POSSIBLE LAKE EFFECT ACROSS N-CNTRL WI. AT THIS
POINT...AM NOT TOO CONCERNED AS THERE ARE MORE NEGATIVES THAN
POSITIVES FOR SNOW DEVELOPMENT (ICE-COVERED LAKE...NOT OVERLY
COLD...SFC HI BUILDING INTO WI). MIN TEMPS TO RANGE FROM ZERO TO 5
ABOVE N-CNTRL...10 TO 15 ABOVE ALONG LAKE MI. THE SFC HI MOVES
ACROSS SRN SECTIONS OF THE GREAT LAKES ON MON WITH WINDS BACKING
FROM W-NW TO S-SW DURING THE DAY. INCREASING SOUTHERLY WINDS
ACROSS THE CNTRL CONUS WL ALREADY BEGIN TO PULLL GULF MOISTURE NWD
AND WE COULD SEE HI CLOUDS ARRIVING MON AFTERNOON. MAX TEMPS TO
MAINLY BE IN THE MID 20S.

THE MAIN SHOW STILL LOOKS TO BEGIN MON NGT AS A LARGE PART OF THE
SW CONUS UPR TROF BREAKS AWAY AND MOVES NE INTO THE CNTRL CONUS.
THIS SHORTWAVE TROF WL HELP DEVELOP LEE-SIDE CYCLOGENESIS OVER THE
CNTRL HI PLAINS. AS THIS OCCURS...A 40-50 KT SW LOW-LEVEL JET WL
CRANK UP AND QUICKLY PULL ADDITIONAL GULF MOISTURE NWD TOWARD WI.
MODELS VARY ON HOW FAST THIS MOISTURE WL OVERSPREAD WI WITH THE
GEM THE FASTEST AND THE ECMWF THE SLOWEST. THE AIR MASS OVER WI
INITIALLY WL BE DRY SO IT WL TAKE A LITTLE TIME TO SATURATE.
THEREFORE...FAVOR A SLOWER APPROACH TO THE PCPN (SOMETHING BETWEEN
THE GFS AND ECMWF) AND FOCUS POPS MAINLY AFTER MIDNGT. TUE APPEARS
TO BE THE MAIN PERIOD FOR PCPN OVER NE WI AS A SFC LOW TRACKS E-NE
TOWARD SRN SECTIONS OF THE GREAT LAKES BY 00Z WED. THIS TRACK
WOULD BE FAR ENUF TO OUR SOUTH TO KEEP ANY MIXED PCPN OUT OF THE
FCST AREA WITH THERMAL PROFILES INDICATING ALL SNOW. THIS SYSTEM
DOES APPEAR TO HAVE THE INGREDIENTS NECESSARY (GOOD WAA...STRONG
Q-G/FRONTOGENETICAL FORCING AND A 160 KT JET OVERHEAD FOR
ADDITIONAL LIFT) TO BRING ACCUMULATING SNOW TO THE ENTIRE FCST
AREA. THIS EVENT IS STILL FOUR DAYS AWAY...THUS PLENTY OF TIME FOR
CHANGES TO OCCUR. SOMEONE IS GOING TO SEE A GOOD AMOUNT OF SNOW...
SO PEOPLE WITH TRAVEL PLANS NEXT TUE WL WANT TO KEEP ABREAST OF
THE LATEST FORECASTS/POSSIBLE HEADLINES TO COME. THE MEAN W-SW
FLOW ALOFT WL BRING MILDER AIR INTO WI ON TUE WITH MAX TEMPS IN
THE MID TO UPR 20S NORTH...AROUND 30 DEGS SOUTH.

THE SYSTEM IS PROGGED TO PULL AWAY FROM WI TUE NGT...THUS
ACCUMULATING SNOW SHOULD BEGIN TO TAPER OFF LATER AT NGT. AN ISSUE
THAT NEEDS TO BE ADDRESSED WL BE THE GUSTY NW WINDS BEHIND THE
SYSTEM THAT WL NOT ONLY BRING BLOWING/DRIFTING OF THE NEW SNOW TO
NE WI...BUT ALSO USHER IN THE BEGINNING OF ANOTHER BLAST OF VERY
COLD AIR FROM CANADA. THESE CONDITIONS WL CARRY OVER INTO WED WITH
LITTLE IN THE WAY OF A TEMPERATURE RECOVERY. MAX TEMPS TO BE 10 TO
15 DEGS BELOW NORMAL (TEENS TO AROUND 20 DEGS) WITH WIND CHILLS
ONCE AGAIN FLIRTING WITH ZERO. LAKE EFFECT SNOW SHWRS ARE POSSIBLE
OVER N-CNTRL WI...HOWEVER TRAJS ARE NOT PERFECT AND THERE IS
LITTLE OPEN WATER OVER LAKE SUPERIOR.

THIS LATEST ARCTIC INTRUSION SHOULD NOT LAST LONG AS THE ERN
PACIFIC UPR RDG BREAKS DOWN AND ALLOWS A PACIFIC AIR MASS TO
OVERSPREAD THE CONUS. WED NGT/THU TO BE THE COLDEST PERIOD (20
DEGS BELOW NORMAL) BEFORE MILDER CONDITIONS ARRIVE. WE WL HAVE TO
WATCH A CLIPPER SYSTEM APPROACH WI ON FRI WHICH MIGHT TRY AND
GENERATE A LITTLE PCPN.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1143 AM CST FRI FEB 27 2015

FOR THE AFTERNOON HOURS...GUSTY WEST WINDS WILL MIX
DOWN TO THE SURFACE AT TIMES BUT WILL DIMINISH BY THIS EVENING.
OTHERWISE ARCTIC HIGH PRESSURE SLIDING OVER THE MID SECTION OF
THE COUNTRY WILL PROVIDE VFR CONDITIONS TODAY THROUGH SATURDAY.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......AK
AVIATION.......TDH






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