Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 260449

Area Forecast Discussion
National Weather Service Huntsville AL
1148 PM CDT Tue Oct 25 2016

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 814 PM CDT Tue Oct 25 2016

The high pressure system that has been sitting over the area the past
few days will shift east towards the Atlantic Coast tonight into
Wednesday. In response to this and the disturbance over the central
plains, winds become more southerly late tonight and advect moisture
northward into the region. Looking through all of the guidance it
looks like the increase in surface moisture won`t happen in our area
until after sunrise. However, forecast soundings and latest SREF runs
are indicating an increase in moisture between 1000-2000 ft as winds
strengthen and become more southerly shortly before sunrise.

The latest satellite Fog product is showing a low cloud deck
developing over SE GA, which does match up fairly well with the
location on the last few runs of the SREF. Some of this could
approach the area but given the amount of dry air still over the
region and general weak nature of the winds just above the surface,
believe any low cloud deck will probably stop somewhere over east-
central AL and not make it into our area.

But as a previous forecaster would say, The Cirrus Is Near Us. High
clouds ahead of the approaching system will continue to stream into
the area and have made some adjustments to the Sky grids to account
for the increased cloud cover. The current forecast of temps and
dewpoints are in good shape and have made only minor adjustments to
the trends. Expect lows to bottom out in the lower 50s with the
excepting of our sheltered valley locations in NE AL and southern
middle TN where temps in the mid 40s are possible.

.SHORT TERM...(Wednesday through Thursday)
Issued at 127 PM CDT Tue Oct 25 2016

Benign weather will continue through Wednesday as 850 mb high
pressure system will shift into the Carolinas. This will enable a
greater southerly fetch to develop which should increase dew points
and RH values on Wednesday. Highs should once again reach around 80
degrees on Wednesday at most valley locations.

Short range models continue to drop a rather distinct shortwave
southeast toward the region Wednesday Night. This wave outruns a cold
front rather quickly and may limit overall extent of precipitation.
However, there are run to run progs showing low level convergence
and moisture transport in eastern MS and western AL that help to
generate precip development late Wednesday Night into Thursday.
Elevated instability is marginal, but with an increase in dew points
into the 55-60F range, have opted to keep thunderstorms in the
forecast. These should shift southeast of our forecast area on
Thursday afternoon, and probably by late morning in southern TN and
northwest AL. Only modest lapse rates in low to mid levels which
limits CAPE values should keep storms rather ordinary.

.LONG TERM...(Thursday night through Monday)
Issued at 127 PM CDT Tue Oct 25 2016

A surface and upper level high pressure will be in place by Friday.
The departed frontal boundary is forecast to be in place over
southern Alabama and Georgia. Not much difference in air mass behind
the front, since the stronger cold air advection remains in the Mid-
Atlantic and northeastern states.

Temperatures should climb into the upper 70s to around 80 degrees on
Friday based on 850 mb temperatures. Lows will not drop much and
remain in the lower to mid 50s Friday night. Slightly higher 850 mb
temperatures and an upper level ridge on Saturday should allow
temperatures to warm in the 80 to 85 degree range.

By Saturday night, synoptic models are in fairly good agreement that
the upper level ridging weakens significantly. However, it does
remain in place over much of Georgia and Alabama. Could see some
passing clouds at times based on RH fields at various levels (due to
a disturbance well to our north over the Ohio Valley/western Great
Lakes region).

The cold frontal passage may produce winds of 10-15 mph around
daybreak Sunday. Cold air advection will be weak again with this
front. So, just a slight cool down is expected into early next week,
with highs in the upper 70s and lower 80s and lows of 50 to 55.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1148 PM CDT Tue Oct 25 2016

Scattered high clouds will continue to stream into the area over the
next 18 hours. A system currently located over the central U.S. will
approach the area Wednesday evening and with an increase in moisture
expect a SCT deck of clouds to develop between 5-6kft. Cigs will
gradually lower Wednesday night as a front nears the region.

Current models have showers and possibly an isolated thunderstorm
moving through the region just beyond the current TAF period. There
is still some uncertainty in the overall coverage of storms late
Wednesday night into Thursday morning.




NEAR TERM...Stumpf

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