Flood Potential Outlook
Issued by NWS Jacksonville, FL

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Probabilistic Hydrologic Outlook
National Weather Service Jacksonville FL
925 AM EST Thu Mar 01 2018

...Spring Flood Potential Outlook...

...FLOOD RISK IS NEAR NORMAL FOR SOUTHEAST GEORGIA AND
NORTHEAST FLORIDA...

...Near Normal Potential for river flooding in Southeast Georgia and
Northeast Florida this Spring...

...Existing Conditions...

In the Altamaha, Satilla and Alapaha Basins...
Long term rainfall signals since October 1st have overall shown
generally drier than normal conditions with rainfall deficits as
high as 4 to 8 inches below normal. Although some recent rainfall
since January 1st has improved stream flows across the basins with
near normal conditions reported for the late February time frame.
The lack of significant rainfall signal this spring and Equal
Chances outlook of precipitation for March, April and May from the
Climate Prediction Center still leads to near normal potential for
river flooding this spring.

In the Upper Suwannee and St Marys Basins...
Rainfall since October 1st has be slightly below normal to near
normal with rainfall deficits of 2 to 4 inches. Stream flows were
running near normal for this time of year, with slightly higher flow
on the St Marys than the Upper Suwannee River Basins.

In the Santa Fe Basin...
Rainfall since October 1st has been near normal across the basin, but
this is following an extremely high amount of rainfall last summer
and during the tropical season which brought record high stages to
portions of the basin. Brief flooding appeared in upper portions of
the basin early in February but stream flows have returned to near
normal levels for late February. The outlook is for higher chances
of below normal rainfall through the spring months will lead to near
normal river flooding potential despite the wet conditions over the
past year.

In the Black Creek Basin...
Rainfall since October 1st has been slightly above normal, a
continuation of the extreme wet conditions last summer and tropical
season. This has led to above normal stream flows through much of
the winter months that have just trended back down towards normal at
the end of February. The outlook is for higher chances of below
normal rainfall through the spring months will lead to near normal
river flooding potential despite the wet conditions over the past
year.

...Long Term Precipitation Outlook...

The three month precipitation outlook for March, April and May,
indicates equal chances for above normal, normal, and below normal
rainfall across Southeast Georgia, while slightly higher chances of
below normal precipitation are expected across Northeast Florida.
The one month outlook for March has been recently updated to reflect
similar forecast conditions as the three month outlook. Typically,
April and May are drier months across the region, and in the absence
of significant rains in the month of March, river flooding becomes
less likely after mid-April as fewer storm systems impact the region.

...Spring Flood Outlook Summary...
With the fading La Nina event in the Pacific becoming neutral
conditions this spring it lowers the amount of predictability of
spring precipitation amounts. Thus lowers the amount of confidence
in the spring flood outlook, this combined with the equal chances
forecast of spring precipitation in an area that has received below
normal rainfall across Southeast Georgia, and the slightly higher
than normal chances of below normal precipitation across Northeast
Florida, an area that has received above normal rainfall over the
past year. These forecasts have a mixed signal with current
conditions, therefore a forecast of normal spring flooding potential
is expected for both Southeast Georgia and Northeast Florida.
Another added factor that may limit flood potential is the recent
warm February temperatures have made trees and vegetation to come
out of winter dormancy much earlier increasing evapotranspiration
rates and minimizing runoff.

$$

HESS



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