Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 090838

Area Forecast Discussion
National Weather Service Huntsville AL
238 AM CST Fri Dec 9 2016

.NEAR TERM...(Today)
Issued at 238 AM CST Fri Dec 9 2016

Clouds cleared out quickly overnight leaving clear skies over the
local area with a stratus deck pushing to the south in north central
TN. All guidance has this deck diminishing as it encounters the drier
air to the south. At most, it may briefly impact the southern middle
TN counties so will keep skies clear and sunny through the day today.
Even with sunny skies, it will be a tough match for the strong cold
advection. Guidance has been consistent with only raising highs into
the lower to upper 30s. With surface high pressure continuing to
build in, winds will be around 5 mph so wind chill values will be a
few degrees below the temps today.

.SHORT TERM...(Tonight through Sunday Night)
Issued at 238 AM CST Fri Dec 9 2016

Another cold night on tap tonight and it will likely be a few
degrees cooler than Thursday night. Even with the cold advection
lessening, the cold surface/mid level temps remain. Winds will drop
off to light and variable as the surface high finally settles itself
over the TN valley. The light winds with the clear skies will set up
excellent radiational cooling conditions. Guidance is consistent with
lows falling to around 16-22 degrees for lows. At the current time,
dew points aren`t forecast to be much lower than that but wouldn`t be
surprised to see a few locations get a deg or two cooler/drier than

As the surface high pressure shifts off to the east Saturday,
surface winds shift to the east-southeast. Aloft, a mid level
ridging deepens with west-southwesterly winds making a return. Sunny
skies should prevail much of the day helping to push temps into the
middle 40s before high clouds start to stream in from the west. The
warming trend continues through the night aided by increasing clouds
with lows rising into the middle to upper 20s.

On Sunday, an upper trough starts to dig into the upper midwest with
surface cyclogenesis starting to take place over northern Missouri.
Southerly surface winds and southwesterly wind aloft ushers in
warmer and more moist air with highs Sunday in the lower to middle
50s and dew points raising steadily throughout the day.

Could start to see some rain move into NW Alabama by 21z Sunday with
a line of rain showers moving west to east thereafter. There are
still some timing differences with the ECMWF quicker with the
heaviest rain over N. Central AL by 12z while the GFS keeps it
closer to NW Alabama by then. I do think it will be a slightly
slower trend than the ECMWF due to the strong high pressure to the
east and there will be plenty of dry air still at the lower levels
that needs to be overcome before it can rain. Even so, rain should
be mostly overspreading the area by 12z Monday. With the clouds and
rain, lows Sunday night will only drop to the lower 50s.

.LONG TERM...(Monday through Friday)
Issued at 238 CST Fri Dec 9 2016

Monday will start out with a cdfnt, at 12z, approaching the area with
a band of shra along and ahead of the cdfnt. The cdfnt will move
across the TN valley by the late aftn with the shra activity tapering
off according to the GFS. However the ECMWF shows the cdfnt stalling
out somewhere over the TN valley, which would keep the shra lingering
thru much of Monday night. Not sure I buy into the ECMWF solution
attm, but since the blended models are showing a low pop across the
cwa, will keep the low pops for Monday night.

On Tuesday the GFS keeps most of Tuesday mrng/aftn/early evening
dry. However after midnight, the GFS shows return flow/waa across
the cwa which could kick off some sct waa shra.  The ECMWF shows
about the opposite, with sct shra Tuesday mrng thru the evening and
then tapering off after midnight. One thing the models are showing
is that temps are much warmer than last night, especially for
Tuesday night.

Models are showing another cdfnt moving across the TN valley by
Wednesday along with some sct shra, especially Wednesday mrng and
aftn. By Wednesday night and into all of Thursday, models are
showing mainly dry conditions, thanks to a large sfc high across the
region. It also looks like Friday mrng/aftn could be dry, with shra
returning across the cwa by Friday night as an upper disturbance is
progged to affect the TN valley by next weekend.

Bottom line, confidence is still not that great for the extended
fcst with timing/coverage of pcpn. However attm it looks like no
tsra or winter wx is expected thru this time frame. Stay tuned.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1046 PM CST Thu Dec 8 2016

No changes to previous aviation forecast reasoning. Latest IR
satellite data confirms that a plume of subtropical moisture/high-
level cloudiness continues to shift sewd and should clear both
terminals by 09/06Z. Thus, SKC conditions are anticipated until a few
additional high clouds arrive tomorrow aftn. Nw sfc flow in the 7-9
knot range will gradually veer to nne and diminish thru the TAF
period, as center of arctic high pressure builds sewd into the mid-MS
valley region.





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