Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 182056
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
356 PM CDT MON JUL 18 2016

.TONIGHT AND TUESDAY...Forecast Confidence High.

Light winds, clear skies, and small dewpoint depressions overnight
will lead to patchy fog across portions of south central and
southeast WI early Tuesday morning. Dense fog is possible in river
valleys and low lying areas. The main thing that could hinder fog
development is any cirrus blow-off from convection that could track
through Iowa overnight.

I went lower than the model consensus blend for min temps tonight,
in the lower to mid 60s. There is no temperature advection going on
tonight and plenty of opportunity for strong radiational cooling
with weak flow in the lowest 5000 feet. Any high clouds could limit
our cooling though, especially toward the IL border.

Tuesday will be very similar to today- dry weather, light winds,
plenty of sunshine, and highs in the mid to upper 80s. The lake
breeze will develop a little earlier than today, so expect the
lakeshore to be just a bit cooler.

.TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...Forecast Confidence
Medium

Jet max drops southeast across the western Great Lakes Tuesday night
into Wednesday ahead of building mid-upper level ridging. 700 mb WAA
brings increasing RH/omega into at least far western WI around 06Z
Wednesday and the western half by 12Z Wednesday. Focus of the
southerly low-level jet is toward northern Minnesota at the
start...with the jet weakening as it heels over to the southwest.

Expecting an MCS to develop to the west and move through the CWA
Wednesday morning. PW values top out around 2 inches so could be a
prolific rain-maker.

Shower and thunderstorm chances continue per low-layer Q-vector
convergence and 850-700 mb frontogenetic response to low-level flow,
though weakened, as it persists through the day Wednesday. Will see
precipitation chances lower from west to east Wednesday night as
warm cap moves across.

.THURSDAY through Friday...Forecast Confidence High

Upper ridge pushes the upper jet stream north to the U.S./Canadian
border as 850 mb thermal ridge settles over srn WI with 23C to 26C
temps in place by 00Z Friday. Have issued an Excessive Heat Watch
for most of the CWA for Thursday through Friday as the hot and humid
airmass will produce heat index values between 105 and 107 for all
but the northeast counties. Those counties will most likely reach
heat advisory criteria.

Could see a chance for for showers and storms in the east Thursday
from an overnight MCS running the warm front as it lifts north
through the state. Most models take the warm front well north of the
CWA but the ECMWF keeps a boundary...either residual outflow
boundary or the warm front...close enough to brush the northern CWA
with showers/storms. Will keep a slight chance in for Thursday
evening.

.LONG TERM...Friday night through Monday...Forecast Confidence
Medium.

500 mb ridge begins to flatten with a short wave trough
approaching in zonal flow. Shower and thunderstorm chances end by
06Z Saturday on the 12Z ECMWF which is much quicker with the short wave
dropping the surface cold front south through the state while the
GFS hangs the front across the central part of the state keeping
shower chances north and then brings an MCS across northern
Wisconsin Friday night with later arrival of the short wave
trough and associated surface wave. ECMWF then brings another wave
across Saturday night and Sunday while GFS is basically dry. Consensus
blend keeps slight chance PoPs through this period which will be
followed until a clearer solution is presented. Will be dry
Sunday night and Monday.

After another muggy day Saturday, temperatures drop back closer to
normal for the rest of the extended.

&&

.AVIATION/00Z TAFS/...

VFR conditions expected for the forecast period with few-sct cumulus
once again Tuesday. Patchy fog possible late tonight due to light
boundary layer winds. River valleys and low lying areas will be
susceptible to dense fog.

&&

.MARINE...

Light winds will continue through Tuesday. Look for increasing
southerly winds Tuesday night through Thursday as warm air and
moisture stream into the region.

&&

.MKX Watches/Warnings/Advisories...
WI...EXCESSIVE HEAT WATCH from Thursday afternoon through Friday
     evening for WIZ046-047-056>058-062>072.

LM...None.
&&

$$

TONIGHT/Tuesday AND AVIATION/MARINE...MRC
Tuesday NIGHT THROUGH Monday...REM



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