SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION...CORRECTED
NWS DETROIT/PONTIAC MI
AFDDTX 325 PM EST MON JAN 14 2002
PRECIPITATION...MAINLY SNOW /WITH ACCUMULATIONS IN THE 1/2 TO 1 INCH
RANGE/...AHEAD OF WARM FRONT HAS NOW PULLED NORTHEAST OF THE CWA.
NOT ONLY HAS PRECIPITATION ENDED...BUT DRY /CLEAR/ SLOT IS NOW
MOVING ACROSS SOUTHERN HALF OF CWA...HELPING TO BOOST TEMPERATURES
WELL INTO THE 40S.
AVN/ETA ARE IN EXCELLENT AGREEMENT ON TRACKING LOW FROM NEAR MKG THIS
EVENING TO OFF THE THUMB COAST AROUND MIDNIGHT...AS WEAKENING 850MB
LOW TRANSITS NORTHERN LOWER. ANOTHER BOUT OF PRECIPITATION IS ON TAP
FOR THE CWA AS OCCLUDED FRONT ASSOCIATED WITH LOW ROTATES THROUGH
THE REGION THIS EVENING. MESOETA SHOWS BRIEF...BUT INTENSE...BOUT OF
DYNAMICS ASSOCIATED WITH THE OCCLUSION INCLUDING 850MB FGEN...AND
SURFACE CONVERGENCE YIELDING IMPRESSIVE UVVS. A LOOK AT EPV
TIME-HEIGHT CROSS SECTIONS HINTS AT POTENTIAL FOR CSI ACROSS
SOUTHERN CWA THIS EVENING. ALTHOUGH MESOETA POINTS TO BETTER
OCCLUDED DYNAMICS AFFECTING SOUTHERN-MOST CWA...KLOT RADAR SHOWS
PRECIP SHIELD ASSOCIATED WITH EVOLVING OCCLUDED FRONT TRACKING TO
THE NORTHEAST. WILL CARRY CATEGORICAL POPS FOR ALL ZONES NORTH OF
DTW...AND LIKELY THERE. PRECIP TYPE WILL ONLY BE A PROBLEM IN THE
FAR NORTH. FURTHER SOUTH...A WEDGE OF WARM AIR ACCOMPANYING
OCCLUSION WILL KEEP PRECIP LIQUID FOR THE MOST PART...EXCEPT FOR A
BRIEF PERIOD AT END. A LOOK AT ACARS DATA ON FLIGHTS INTO DTW SHOWS
FREEZING LEVEL AT 19Z ABOUT 3K FEET...IN REASONABLY GOOD AGREEMENT
WITH MESOETA SOUNDINGS. TRACK OF LOW WOULD PUT BAX/MBS ON THE COLD
SIDE OF THE LOW...AT LEAST AT THE SURFACE. MODELS SUGGEST WEDGE OF
WARM AIR ALOFT WILL SLIDE ACROSS THIS REGION THIS EVENING. IN
ADDITION...RAIN FALLING JUST TO THE NORTH OF THE LOW NOW IN WI.
DEPTH OF THE WARM AIR WILL BE PROBLEMATIC HERE...WITH MAX
TEMPERATURE WITHIN THE WARM LAYER REACHING TO 1.5C OR SO. THIS
THERMAL PROFILE LIKELY TO SUPPORT A MIX OF PRECIPITATION. PRECIP
COULD CHANGE BRIEFLY TO SNOW ALL ZONES BEFORE TAPERING TO FLURRIES
OVERNIGHT. ANTICIPATE LITTLE OR NO ACCUMULATION.
AS LOW PULLS EAST TOMORROW COLDER AIR WILL PUSH INTO THE REGION.
DEEP MOISTURE...CYCLONIC FLOW...AND INVERSION HEIGHTS TO AROUND 6K
FEET POINT TO SCATTERED SNOW SHOWERS. DO NOT EXPECT MUCH FROM THIS
THOUGH...AS AIR/LAKE DELTA T/S REACH ONLY MARGINALLY CRITICAL
LEVELS...AND LATER IN THE DAY AT THAT.
SHALLOW BUT HIGH LOW LEVEL RH PROGGED ON TUESDAY NIGHT KEEPING SKIES
CLOUDY AND TEMPERATURES SLIGHTLY HIGHER THAN MAV/FWC NUMBERS WOULD
INDICATE.
LOW PRESSURE APPROACHES CWA WEDNESDAY AND PER AVN CROSSES CWA
WEDNESDAY NIGHT. ALTHOUGH MAX POPS APPROACH LIKELY CATEGORY FOR
WEDNESDAY...ETA QPF FIELDS ON THE LEAN SIDE. FOR NOW WILL MAINTAIN
CHANCE POPS FOR WEDNESDAY AND WEDNESDAY NIGHT.
EXTENDED...
DEEP POLAR VORTEX WILL MEANDER ABOUT NORTHERN HUDSON BAY THROUGH THE
PERIOD. IN RESPONSE TO THE VORTEX...A MEAN BROAD TROUGH WILL BE IN
PLACE ACROSS THE EASTERN HALF OF THE U.S. THROUGH THE EXTENDED...
ALLOWING FOR THE OCCASIONAL TRANSITORY SHORT WAVE RIDGE. THIS UPPER
AIR PATTERN WILL BRING A RETURN TO NEAR TO SLIGHTLY BELOW NORMAL
TEMPERATURES THROUGH THE EXTENDED. SOUTHEAST LOWER MICHIGAN WILL BE
BETWEEN THE MAIN STORM TRACK ACROSS CENTRAL CANADA...AND A
SECONDARY...WEAKER TRACK ACROSS THE SOUTHEAST U.S. WITH NO MAJOR
STORMS IN SIGHT FOR THE REGION...THE MAIN PRECIPITATION MAKER WILL
BE FRONTAL PASSAGES...WHICH WILL TEND TO KEEP PRECIP TOTALS ON THE
LIGHT SIDE. THERMAL CONSIDERATIONS SUGGEST ANY PRECIPITATION THAT
DOES FALL WILL BE SNOW.
.DTX...NONE.
...CORRECTED TO ADD EXTENDED DISCUSSION...
OKEEFE
SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
AFDDTX 318 PM EST MON JAN 14 2002
PRECIPITATION...MAINLY SNOW /WITH ACCUMULATIONS IN THE 1/2 TO 1 INCH
RANGE/...AHEAD OF WARM FRONT HAS NOW PULLED NORTHEAST OF THE CWA.
NOT ONLY HAS PRECIPITATION ENDED...BUT DRY /CLEAR/ SLOT IS NOW
MOVING ACROSS SOUTHERN HALF OF CWA...HELPING TO BOOST TEMPERATURES
WELL INTO THE 40S.
AVN/ETA ARE IN EXCELLENT AGREEMENT ON TRACKING LOW FROM NEAR MKG THIS
EVENING TO OFF THE THUMB COAST AROUND MIDNIGHT...AS WEAKENING 850MB
LOW TRANSITS NORTHERN LOWER. ANOTHER BOUT OF PRECIPITATION IS ON TAP
FOR THE CWA AS OCCLUDED FRONT ASSOCIATED WITH LOW ROTATES THROUGH
THE REGION THIS EVENING. MESOETA SHOWS BRIEF...BUT INTENSE...BOUT OF
DYNAMICS ASSOCIATED WITH THE OCCLUSION INCLUDING 850MB FGEN...AND
SURFACE CONVERGENCE YIELDING IMPRESSIVE UVVS. A LOOK AT EPV
TIME-HEIGHT CROSS SECTIONS HINTS AT POTENTIAL FOR CSI ACROSS
SOUTHERN CWA THIS EVENING. ALTHOUGH MESOETA POINTS TO BETTER
OCCLUDED DYNAMICS AFFECTING SOUTHERN-MOST CWA...KLOT RADAR SHOWS
PRECIP SHIELD ASSOCIATED WITH EVOLVING OCCLUDED FRONT TRACKING TO
THE NORTHEAST. WILL CARRY CATEGORICAL POPS FOR ALL ZONES NORTH OF
DTW...AND LIKELY THERE. PRECIP TYPE WILL ONLY BE A PROBLEM IN THE
FAR NORTH. FURTHER SOUTH...A WEDGE OF WARM AIR ACCOMPANYING
OCCLUSION WILL KEEP PRECIP LIQUID FOR THE MOST PART...EXCEPT FOR A
BRIEF PERIOD AT END. A LOOK AT ACARS DATA ON FLIGHTS INTO DTW SHOWS
FREEZING LEVEL AT 19Z ABOUT 3K FEET...IN REASONABLY GOOD AGREEMENT
WITH MESOETA SOUNDINGS. TRACK OF LOW WOULD PUT BAX/MBS ON THE COLD
SIDE OF THE LOW...AT LEAST AT THE SURFACE. MODELS SUGGEST WEDGE OF
WARM AIR ALOFT WILL SLIDE ACROSS THIS REGION THIS EVENING. IN
ADDITION...RAIN FALLING JUST TO THE NORTH OF THE LOW NOW IN WI.
DEPTH OF THE WARM AIR WILL BE PROBLEMATIC HERE...WITH MAX
TEMPERATURE WITHIN THE WARM LAYER REACHING TO 1.5C OR SO. THIS
THERMAL PROFILE LIKELY TO SUPPORT A MIX OF PRECIPITATION. PRECIP
COULD CHANGE BRIEFLY TO SNOW ALL ZONES BEFORE TAPERING TO FLURRIES
OVERNIGHT. ANTICIPATE LITTLE OR NO ACCUMULATION.
AS LOW PULLS EAST TOMORROW COLDER AIR WILL PUSH INTO THE REGION.
DEEP MOISTURE...CYCLONIC FLOW...AND INVERSION HEIGHTS TO AROUND 6K
FEET POINT TO SCATTERED SNOW SHOWERS. DO NOT EXPECT MUCH FROM THIS
THOUGH...AS AIR/LAKE DELTA T/S REACH ONLY MARGINALLY CRITICAL
LEVELS...AND LATER IN THE DAY AT THAT.
SHALLOW BUT HIGH LOW LEVEL RH PROGGED ON TUESDAY NIGHT KEEPING SKIES
CLOUDY AND TEMPERATURES SLIGHTLY HIGHER THAN MAV/FWC NUMBERS WOULD
INDICATE.
LOW PRESSURE APPROACHES CWA WEDNESDAY AND PER AVN CROSSES CWA
WEDNESDAY NIGHT. ALTHOUGH MAX POPS APPROACH LIKELY CATEGORY FOR
WEDNESDAY...ETA QPF FIELDS ON THE LEAN SIDE. FOR NOW WILL MAINTAIN
CHANCE POPS FOR WEDNESDAY AND WEDNESDAY NIGHT.
.DTX...NONE.
OKEEFE