Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDTX 250749
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
349 AM EDT SAT APR 25 2015

.SHORT TERM...TODAY AND TONIGHT

A RESPECTABLE AMOUNT OF LIGHT RAIN AND VIRGA WAS ABLE TO SPREAD INTO
SOUTHEASTERN MICHIGAN THIS MORNING. THE EARLIER TIMING OF THE
ACTIVITY SUGGESTS THAT PRECIPITATION IS BEING DRIVEN BY SOME
COMBINATION OF FOCUSED CYCLONIC VORTICITY ADVECTION AND MIDLEVEL
SHEARING DEFORMATION. ACCUMULATED RAIN HAS BEEN LIGHT WITH THE
OBSERVATION SITES ONLY REPORTING A COUPLE OF HUNDREDTHS. NUMERICAL
WEATHER OUTPUT MOVING FORWARD HAS THE SHORTWAVE ENERGY PUSHING OUT
OF SEMICH DURING THE NEXT COUPLE OF HOURS WHICH WILL TAKE ONE OF THE
FORCING MECHANISMS COMPLETELY OUT OF THE PICTURE. THAT LEAVES THE
MIDLEVEL SHEARING DEFORMATION AS THE ITEM OF INTEREST FOR THE NEAR
TERM. MODEL DATA SUGGESTS THIS WILL THIN OUT/ERODE SOON WHICH IS
SUPPORTED BY THE REGIONAL Z MOSAIC WITH THE BACK EDGE/SLIGHT
SOUTHWARD DRIFT. THERE IS SOME CONCERN THIS WEAKENING/RESIDUAL
DEFORMATION MAY BE GOOD ENOUGH TO GRIND OUT DRIZZLE. WILL FORGO THE
DRIZZLE MENTION GIVEN THE AMOUNT OF LOW LEVEL DRY AIR THAT EXISTS.
EXPECT THE LIGHT RAIN TO END OR CONSOLIDATE TO THE SOUTH OF THE
STATE DURING THE EARLY MORNING HOURS. THIS HAS SUPPORT IN THE
DETERMINISTIC SOLUTION CONSENSUS AND LATEST ITERATIONS OF THE HRRR.

MODELS THEN SUGGEST IN THE WAKE OF THE PASSING SHORTWAVE THAT LOW TO
MIDLEVEL WIND FIELDS WILL RESPOND MORE AGGRESSIVELY OUT OF THE EAST.
THIS WILL ONLY RESTABLISH THE DRY EASTERLY FEED INTO THE CWA. THE
QUESTION FOR THIS AFTERNOON IS WHETHER OR NOT THERE WILL BE A
SECONDARY NORTHWARD SURGE IN PRECIPITATION ACTIVITY BETWEEN 18-00Z.
THE ONLY REAL POTENTIAL SEEMS TO BE TIED TO THE OVERALL INTEGRITY OF
THE MIDLEVEL CYCLONIC CIRCULATION THAT WILL RELEASE ACROSS
INDIANA/OHIO. THE RECENT TREND IN MODEL DATA IS FOR A MUCH WEAKER
CIRCULATION...ONE THAT IS COMPLETELY SUPPRESSED TO THE SOUTH.
THUS...NOT EXPECTATION FOR MUCH WAVE RESPONSE...OR MIDLEVEL SYSTEM
RELATIVE ISENTROPIC ASCENT. WILL LEAVE A LOW CHANCE IN THE FORECAST
FOR SOUTH AND WEST OF DETROIT...BUT THIS IS TO COVER WHAT MAY BE
SOME VIRGA ON THE RADAR LATER THIS AFTERNOON. THE EASTERLY WINDS
WILL KEEP A CHILL IN THE AIR...BETTER DESCRIPTION IS PROBABLY
OFFERED BY THE WIND CHILLS VALUES. WIND CHILLS ARE NOT EXPECTED TO
CLIMB OUT OF THE 40S IN MANY AREAS.

THE NEXT SURFACE RIDGE WILL EXPAND INTO THE STATE TONIGHT. EXPECTING
THE SURFACE WIND FIELD TO RESPOND UNIFORMLY OUT OF THE NORTH. THIS
WILL CLEAR SKIES OUT RAPIDLY DURING THE LATE AFTERNOON AND EVENING
HOURS. GEOSTROPHIC FLOW IS ENOUGH TO SUPPORT A CONTINUED LIGHT
BREEZE TONIGHT...TEMPERING THE TEMPERATURE FALL RESPONSE. EXPECT
LOWS TO SETTLE AT/JUST BELOW THE FREEZING MARK IN MANY LOCATIONS.

&&

.LONG TERM...SUNDAY THROUGH FRIDAY

MID LEVEL HEIGHTS WILL FALL ACROSS THE ERN GREAT LAKES DURING THE
LATER HALF OF THE WEEKEND. THIS WILL OCCUR AS NUMEROUS SHORT WAVE
IMPULSES ROTATE AROUND THE NORTHERN AND EASTERN PERIPHERY OF THE
QUASI STATIONARY UPPER LOW NOW OVER MAINE. THE NET RESULT WILL BE AN
ELONGATION OF THE UPPER LOW INTO THE ERN GREAT LAKES. THIS WILL
FORCE THE SFC HIGH NOW OVER NRN ONTARIO TO BUILD SOUTH INTO THE
UPPER MS VALLEY/WRN GREAT LAKES SUN INTO MONDAY...WHICH WILL SUSTAIN
A NORTHERLY WIND FLOW ACROSS SE MI. SATELLITE DATA SHOWS A GOOD
DEGREE OF MOISTURE NOW ROTATING ACROSS THE NORTHERN EDGE OF THIS
UPPER LOW...WHICH IS FORECAST TO ADVANCE INTO SE MI ON SUNDAY AND
LIKELY PERSIST WELL INTO MONDAY. DESPITE THE INHERENT UNCERTAINTY IN
TIMING THE INDIVIDUAL SHORT WAVE IMPULSES...THE 00Z MODEL SUITE ARE
IN REASONABLE AGREEMENT IN SHOWING THE STRONGEST OF THESE SHORT
WAVES SLIDING FROM NORTH TO SOUTH ACROSS SRN LOWER MI SUNDAY NIGHT.
THE CORRESPONDING STEEPENING OF MID LEVEL LAPSE RATES AND INCREASE
IN DEEP COLUMN MOISTURE WILL WARRANT ADDING A CHANCE OF SHOWERS SUN
NIGHT. OTHERWISE...THE NORTHERLY FLOW AND EXPECTED CLOUD COVER WILL
KEEP HIGH TEMPS SUN AND MON CONFINED TO THE 50S WITH COOLER READINGS
DOWNWIND OF LAKE HURON IN THE THUMB.

MID LEVEL RIDGING WILL EXPAND ACROSS THE REGION ON TUESDAY. FULL
INSOLATION AND BUILDING HEIGHTS WILL SUPPORT A MODEST WARMING TEND
HEADING INTO AT LEAST MIDWEEK. THE MEDIUM RANGE MODEL SUITE HAVE
BEEN EXHIBITING RATHER POOR RUN TO RUN CONTINUITY WITH RESPECT TO
TIMING AND DEGREE OF AMPLIFICATION OF SHORT WAVE ENERGY DROPPING OUT
OF CENTRAL CANADA DURING THE LATER HALF OF THE WEEK. IF THIS WAVE
AMPLIFIES INTO A LONGER WAVELENGTH TROUGH OVER ERN CANADA OR THE
GREAT LAKES LATE NEXT WEEK...THIS WILL TEMPER THE WARMING TREND A
BIT. IN LIGHT OF THE UNCERTAINTY...FORECAST TEMPS LATE IN THE WEEK
WILL BE NEAR SEASONAL NORMS.

&&

.MARINE...

NORTH TO NORTHEAST WINDS WILL INCREASE DURING THE DAY AS LOW
PRESSURE TRACKS ACROSS THE OHIO VALLEY AND SURFACE HIGH PRESSURE
HOLDS STEADY ACROSS THE NORTHERN GREAT LAKES. NORTHEAST WINDS MAY
GET A LITTLE GUSTY AT TIMES ON SAGINAW BAY. THE NORTH-NORTHEAST
WINDS WILL PERSIST INTO SUNDAY AS THE HIGH BUILDS INTO THE WESTERN
GREAT LAKES. WINDS AND WAVES WILL THEN SLOWLY DECREASE MONDAY INTO
TUESDAY AS THE HIGH EXPANDS ACROSS LOWER MI AND INTO THE ERN GREAT
LAKES.

&&

.AVIATION...ISSUED 1209 AM EDT SAT APR 25 2015

AREA OF SHOWERS CONTINUES TO STRUGGLE WITH VERY DRY AIR IN PLACE
BELOW 10KFT OR SO. EVEN SO...SOME MOISTURE IS MAKING IT TO THE
GROUND TO THE SOUTHWEST OF THE TERMINALS LATE THIS EVENING. FGEN
WILL PERSIST OVERNIGHT AND UPSTREAM RADAR RETURNS SUGGEST THERE MAY
BE ENOUGH MOISTURE TO BRING A PERIOD OF -SHRAS/SPRINKLES INTO THE
INTERSTATE 94 TAFS OVERNIGHT. CONDITIONS SHOULD REMAIN VFR. SHRAS
WILL FOCUS GRADUALLY SOUTH ON SATURDAY AND WILL JUST MAINTAIN A MID
BKN-OVC DECK ATTM WHICH WILL SCATTER OUT LATE IN THE FORECAST AS
EAST TO NORTHEAST FLOW BACKS TO THE NORTH SATURDAY NIGHT.

FOR DTW...EXPANDING PRECIPITATION SHIELD ASSOCIATED WITH SHORTWAVE
TO THE WEST WILL MOST LIKELY BRING A PERIOD OF -SHRAS OVERNIGHT. VFR
CONDITIONS SHOULD PREVAIL AND CIGS WILL MOST LIKELY REMAIN ABOVE
5KFT AND VSBYS SHOULD NOT BE RESTRICTED MUCH GIVEN THE CURRENT LEVEL
OF DRY AIR IN THE LOWER ATMOSPHERE.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

SHORT TERM...CB
LONG TERM....SC
MARINE.......SC
AVIATION.....DG


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.